While it might be fun to imagine tiny worms wearing hardhats and utility belts, there's nothing cute about carpenterworms.
Carpenterworms (Prionoxystus robiniae) are the larval form of a common moth, and they love to burrow into apricot and pear trees. They can also be found in many ornamental trees, such as maple, oak, birch, cottonwood, ash, and willow. Once these pests are inside your trees, they can be difficult to evict.
As you can see, this is a robust caterpillar. They can be 1/2 an inch in diameter and 2 to 3 inches long. They have a dark, brownish head and a yellowish white body that is covered with fine hairs. They have sharp, hooked legs on the middle section (thorax) and distinct fleshy legs on the abdomen
Damage caused by carpenterworms
These wood-boring insects live in galleries, feeding on sapwood. Knowing the signs of infestation can help you get a handle on this pest before the damage becomes irreversible. The galleries created by carpenterworm feeding tend to be vertical, except for the entrance. These entrances are often found in branch crotches and in bark crevices. Tunnels are 1/2 an inch in diameter and 6 to 10 inches long. This tunneling creates points of entry for many other pests and diseases. Adult female carpenterworms seem to prefer areas that are already infested for egg laying, which can result in multiple galleries in the same area of the same tree. All that feeding and tunneling can weaken branches, making them more likely to break in strong winds, or when supporting heavy crops. Branches can also become girdled by carpenterworm feeding and tunneling, and die.
Adult carpenterworms are large, mottled grey moths that can have a 3-inch wingspan. Their coloration blends with tree bark and lichen. This camouflage makes them difficult to see. If you are able to catch one and spread out its wings, you wing be able to see if you have a male, with orange hind wings, or a female, with off-white hind wings.
Because adult female carpenter moths cannot fly very far, they tend to lay their eggs near the gallery where they were feeding. Three to six eggs are laid in the crevices near an existing gallery entrance. Upon hatching, the larvae immediate start boring into the sapwood, leaving small, rectangular entrance holes.
As they feed, the larvae will occasionally push sawdust and frass (bug poop) out of the ever-widening entry. The larvae will feed on the sapwood and hardwood until they reach maturity, molting 8 to 31 times over the next 2 to 4 years. Finally, mature pupae wriggle their pudgy selves to the entry hole and create a protective pupal case, which will block the hole until adult moths emerge. In California, this usually occurs May through July. As soon as adults start flying, they mate and the cycle continues.
Signs of carpenterworm infestation
The first sign of carpenterworm infestation is stained areas on the trunk. These stains are a combination of sap, sawdust, and frass. You may also see pupal cases sticking 2/3rds of the way out of the tree. Since the stained areas and branch dieback may also be caused by clearwing moths/currant borers, flatheaded borers, bark beetles, and longhorned borers, it is important to identify the pest before trying to control the problem.
Healthy trees are better able to protect themselves, so start by planting trees in the right location, at the proper depth, with regular fertilization and irrigation.
Because these caterpillars are already protected by the tree, insecticides do not work. There are a couple of specific nematodes, Steinernema feltiae or S. carpocapsae, that have been very successful at controlling carpenterworm larvae. Before you place your order, however, make sure that these are exactly the type of beneficial nematodes you are buying. Any other variety will be ineffective against carpenterworms. And be sure to follow the package directions exactly, or you will have wasted your money.
Small infestations can sometimes be controlled by poking long, sharp, flexible wires into the galleries and skewering the caterpillars. This is tricky because you really can’t see if you killed them or not. The only way to really know is to clear all the frass and other debris away from the area and mark the spot with some paint. Then, check the area every week for signs of frass. If frass and sawdust are seen, you missed and the caterpillar is still alive and busy feeding and burrowing.
Heavy infestations are dangerous and should be left to a professional arborist. This is because tree branches that are compromised this badly are very likely to fall on you. Since none of us are exempt from the laws of physics, and heavy branches can paralyze or kill you, stay away from them, and call an expert.
This winter, take a few minutes each week to inspect your trees for signs of frass and sawdust, or pupal cases, and cut those cute little, hardhat wearing pests off at the knees.
Glass snails, such as this whimsical piece by GlassBorisov, are a delightful way to add art and color to houseplants and your garden.
The same is generally not true of real snails. Yesterday morning, after our first rain of the year, I noticed a snail trail. Snail trails are pretty normal in most gardens, but this one ended with a flat-bodied snail I’d never seen before.
Introducing, the glass-snail family (Oxychilidae). Glass-snails get their name because their shells are translucent. Looking closely at my discovery, I could see the snail body through the shell!
Glass-snails are land snails that breathe air. Unlike marine snails, which breath using a single gill, land snails have evolved a single, simple lung. Most glass-snails are omnivores. They eat everything: live plants, dead plants, dead animals, insects, poop, other slugs and snails (and their eggs), sowbugs, and earthworms.
Sorting out glass snails
Specific characteristics are used when comparing different snail species, including height, width, number of whorls, and the umbilicus. The umbilicus is the snail’s bellybutton. It is the tiny opening at the center of the whorls on the underside of the snail’s shell.
Only three glass snails are found in California, at this time: cellar snails, garlic snails, and Drapernaud’s snail. [I'm not sure if my guest is a cellar or Drapernaud's glass-snail, but I'll keep you posted.]
Cellar glass-snails (Oxychilus cellarius) have shiny, translucent yellowish-brown shells are just under 1/2 an inch wide, 1/6 of an inch tall, with 5-1/2 to 6 whorls. The umbilicus is very narrow. The snail itself is bluish-grey, with small brown freckles and a groove that runs along each side of the foot
The garlic glass-snail (Oxychilus alliarius) gets its Latin name, a twist on the onion family (Allium), because they emit a garlic odor when disturbed. Originally from the Netherlands, Great Britain, Ireland, Poland, and the Czech Republic, the garlic snail has spread its range to include Columbia, Latvia, and California. Garlic snails are reddish or greenish brown, and the snail is blackish blue. The shell is 1/4 of an inch in diameter, a little more than 1/8 of an inch high, with 4 or 4-1/2 slightly convex whorls. The umbilicus is 1/6 of the overall diameter, and the whorls are coiled more narrowly than cellar glass-snails.
Drapernaud’s glass-snail (Oxychilus draparnaudi) is larger than the other glass snails, being slightly more than 1/2 an inch in diameter, and the shell is a waxy yellowish-brown on top and somewhat lighter underneath. The body is a dark blue and grey color. Drapernaud’s glass-snail is carnivorous.
How to control snails
Unless you are enjoying artistic versions of this common pest, managing snails is an ongoing task. It comes as no surprise that these snails’ peak breeding season in the Bay Area is autumn, just before our rainy season begins.
The first step in snail management is to inspect and quarantine new plants. A single snail can lay over 400 eggs. Putting new plants into isolation for a couple of days, with a beer trap nearby, can prevent years of frustration. Once infestation occurs, try to reduce hiding places, such as boards, stones, and other debris. Regularly applying slug and snail bait, and using beer traps, can take a big bite out of the snail population, before they start taking bites out of your plants. Going outside with a flashlight at night, you can catch them feeding - handpick them and feed them to your chickens or dispose of them in the trash.
Did you know that snails have a powerful sense of smell?
Now you know.
Mealybugs have been around for a long time. There is a relatively new, invasive mealybug that may be attacking your grapes.
Traditionally, California grape growers have had to watch for grape mealybugs, obscure mealybugs, and long-tailed mealybugs. These species generally do not cause significant problems, as long as their populations do not get out of hand. They are easy to recognize because of the clusters of grey, soft-bodied females gathering on the underside of leaves and in nooks and crannies. The invasive vine mealybug is another problem altogether.
Vine mealybugs (Planococcus ficus) are native to the Mediterranean areas of North and South Africa and Europe. Vine mealybugs were first seen in California in the mid-1990s and had spread to 17 California counties by 2011. Vine mealybugs are now considered a significant pest of grapes, figs, avocado, apple, bananas, mango, citrus, date palm, and several ornamental plants.
Vine mealybugs are difficult to see because they spend most of their lives protected under the bark, on roots, and around developing buds. Only during spring, when they become active again, can you sometimes see them moving away from the roots and trunk and into the leaf canopy. By summer, vine mealybugs may be found under the bark of first- and second-year canes, among fruit clusters, and under leaves. Sometimes, ants can be seen providing the mealybugs with transportation to their summer feeding grounds.
Vine mealybug description
Vine mealybug females are 1/8 of an inch long, pink, oval-shaped, and covered with a white, mealy wax that also covers filaments (spines) along the sides and posterior end. These filaments are shorter than those seen on other mealybugs, and there are no long tail filaments. Like their cousins, vine mealybugs have a segmented body. Males are tiny, winged, and you’ll probably never see them, unless you have a 30x microscope. They are 0.7 inches long, amber colored, with beaded antennae, one pair of wings, and 4 tail filaments that may stick together. It is important to know which mealybugs you are dealing with. If you see mealybugs, try to collect some and place them in a sealed plastic bag, or in a container of alcohol, and take them to your local County Extension Office for identification. This also helps authorities better understand the spread of this invasive pest.
Vine mealybug lifecycle
In summer, females lay 300 to 700 eggs in the leaves above the fruit in little pouches, called ovisacs. First instar nymphs, called crawlers, are orange and very tiny. During winter, only nymphs are present. They can be found hiding under the bark around the graft union, below the base of spurs, and around pruning wounds. There can be 3 to 7 generations a year.
Damage caused by vine mealybugs
Vine mealybugs are phloem sap suckers that produce significantly more honeydew than native mealybugs. This honeydew attracts protective, disease-carrying ants and creates a growth medium for sooty mold on fruit clusters. These invasive pests can also carry grapevine leafroll viruses and corky bark disease. Vine mealybugs reproduce at a much faster rate than their native cousins.
How to control vine mealybugs
Being an invasive pest, vine mealybugs do not have as a many natural predators as their native cousins. Because vine mealybugs are such a serious threat to California grape growers, parasites of these particular mealybugs have been released in the state. This has helped somewhat, but eradication appears to be impossible at this point. Since these beneficial insects are unavailable to the home grower, the best things you can do to protect your vines is to inspect them regularly, especially during spring, monitor and control ant traffic with sticky barriers, and to quarantine new vines and other plants before installing them. Also, sanitize your tools regularly. Vine mealybugs also feed on burclover, malva, black nightshade, sowthistle and lambsquarters, so controlling these weeds can also help prevent infestation.
Protecting your grapevine from vine mealybugs is an important step toward providing your family with fresh, delicious, organic, homegrown grapes.
You’ve proba-bly never heard of proba bugs. They are another relatively new pest on the California scene. And they love artichokes.
Proba bugs (Proba californica) have been around for some time, but they used to prefer coyote brush. Coyote brush is a common native plant found along highways in agricultural areas of California. At some point (around 1997) a proba bug decided to give artichokes a try. From that moment on, proba bugs have become an increasing threat to artichoke plants. So, what do they look like?
Proba bug description
Adult proba bugs are plain brown and only 0.2 inches long. [That means you could line up 3-1/2 proba bugs across the top of a dime.] Nymphs start out looking like pale yellowish green aphids, except that they move a lot faster than aphids, due to their long legs. During the next to developmental stages (instars) they are reddish-brown, and then they develop light and dark bands on they abdominal area during the final two instars. [I couldn't find any usable photos of proba bug nymphs - sorry!]
Proba bug lifecycle
Proba bugs are active year round (just a lot slower in winter). As temperatures begin to rise, usually in March, they begin feeding and breeding in earnest. Eggs are laid on artichoke petioles (leaf stems) and hatch within 20 to 30 days. Nymphs go through five instars before reaching adulthood.
Damage caused by proba bugs
The damage caused by proba bugs is similar to that of lygus bugs, only proba bugs are more aggressive in their feeding habits. Adults and nymphs feed on young artichoke leaves and at the base of developing buds. They feed by piercing the tissue and injecting a toxin that kills plant cells. As the surrounding leaf tissue continues to grow, these punctured areas turn into brown dead spots that dry and fall off, leaving a shot hole appearance. Feeding on the base of flower buds causes the bud [the part we eat] to turn black. Not very appetizing. This phytotoxin also causes stunting and deformed flower buds. Severely affected leaves will be smaller than normal and chlorotic.
Controlling proba bugs
Until relatively recently, commercial artichoke fields were treated with organophosphates and chlorinated hydrocarbon insecticides. Use of these neurotoxins is being phased out, so proba bugs are becoming more of a problem. Infested fields can lose 20 to 30% of the harvest to proba bugs. Farmers are now removing the coyote brush near their fields and tilling the crop residue under, in a practice called stumping, to help combat this pest.
Natural predators, such as big-eyed bugs, damsel bugs, minute pirate bugs, and spiders all feed on the nymph stage of proba bugs, so avoid using broad spectrum pesticides.
You can help protect your artichoke plant by cutting the plant off at ground level, once flower production is done for the year, and monitoring for signs of infestation in March and April.
It is unusual for a new disease or pathogen to be discovered. It is even more rare when a new disease is found to be caused by a common pest. This is Fusarium dieback, and it can kill your trees.
Fusarium dieback is a fungal disease carried by invasive borers. As borers burrow into trees, they carry three different fungal pathogens with them. These fungi form colonies within a tree’s vascular system, blocking the flow of water and nutrients. Trees infected with Fusarium dieback must be destroyed and disposed of by professional arborists.
Symptoms of Fusarium dieback
Since this disease affects many different types of trees, and is caused by different fungi, it is no wonder that there are different symptoms. Infected avocado trees, for example, will exhibit sawdust-like frass (bug poop), gumming, and sugar volcanoes. Sugar volcanoes are white discharges of sugary sap. On other host trees, you may see dark, greasy looking areas on the bark, withered leaves and stem tips, and the presence of white mycelium under the bark. Mycelia are the vegetative growths of fungi.
As the infestation progresses, perfectly round, tiny borer entry and exit holes may become visible. These holes are only 0.03 inches in diameter, so you have to look very closely, usually just below areas showing symptoms of disease. Eventually, you will start seeing branches die. If you cut into an infected branch, you will see that the wood is discolored, brown or black. If you scrape the bark away from entry or exit holes, you will also see discoloration. After cutting, be sure to disinfect your tools with a 5% bleach solution or bathroom disinfectant, to avoid spreading the disease.
Once Fusarium dieback has infected a tree, the wounds and weakened condition of the tree make it susceptible to many other fungal infections and other diseases.
Originally found in Israel, Fusarium dieback was first seen in Southern California in 2003. The carrier was believed to be the tea shot hole borer, a common pest of tea plants in Sri Lanka. DNA testing, however, showed that this was an entirely new species, now named the polyphagous shot hole borer. By 2010, this borer, and the disease it carries, had become a serious threat to SoCal’s box elder trees, palm trees, black locust, and our beloved avocado trees. In 2015, a second variety of carrier, the Kuroshio shot hole borer, joined the party and started infecting the popular California palms (Washingtonia filifera). It is estimated that this disease now threatens 25% of all the trees lining Southern California’s streets.
To the naked eye, the two species of borer responsible for Fusarium dieback look identical. Female beetles are tiny and black, only 0.07 to 0.1 inches long. Males are brown and even smaller, at only 0.06 inches long. Female beetles can fly and will leave their birthplace to find other host trees to use as nurseries, carrying the disease with them when they go. Males do not fly and generally stay in the tree of their birth. These beetles are most active during summer and fall.
Fusarium dieback hosts
Shot hole borers can be found feeding on and breeding in over 200 species of woody plants. That’s a lot of potential hosts. To date, the disease has been found in more than 130 different host species.
While this disease prefers palms and ornamentals, such as maple, birch, and tulip trees, it is becoming a serious threat to avocados and California live oaks. California bay laurel, carob, chestnut, elderberries, figs, olive, peaches, persimmons, pineapple guava, pistachios, and pomegranate are also vulnerable to Fusarium dieback.
How infection occurs
This disease starts when female beetles bore into tree trunks and branches, creating galleries of tunnels. Within the tunnels, chambers are built for eggs. Female beetles have developed a symbiotic relationship with three different fungi, which they carry around in their mouths, much the way we carry around bacteria in our gut. [The fungal pathogens of Fusarium dieback are Fusarium euwallaceae, Graphium euwallaceae and Paracremonium pembeum, if you enjoy the Latin.]
The fungi that set up housekeeping within the tree end up being food for the newly hatched beetle larvae. By eating the fungi, the larvae then become carriers of the disease. These fungal colonies develop very rapidly, once they are inside a tree, and there is no known treatment at this time. Complicating matters even more, not all infected trees will show signs of infection. Some infected trees simply serve as breeding grounds, without showing any signs of disease, and we don’t yet know why.
Healthy trees are far better able to protect themselves against borers. This means selecting plants appropriate to your microclimate, irrigating and fertilizing them properly, and providing healthy soil. Also, monitor your trees regularly.
Currently, Fusarium dieback is limited to Israel and Southern California. You can see a map of the disease, as it spreads through California, here. [It’s a big file, so it make take some time loading.] While Fusarium dieback has only come as far north as San Luis Obispo, to date, that can change overnight. Research is underway, to try and identify an effective lure that can be used to trap the borers.
If you suspect Fusarium dieback on a tree, please contact your local County Extension Office. Together, we may be able to slow or stop the spread of this disease.
Fire ants are an experience you will never forget.
For me, it happened when I was a child, playing with friends. We sat down on the ground to continue our game, I started feeling something tingly, and then, all of a sudden, my legs were on FIRE!!!! I jumped up and tried to rid myself of the horrible burning sensation, but it was several hours before I was comfortable.
The burning, itching sensation that comes from being bitten by fire ants is not to be ignored. So, how is it that these tiny insects can cause so much pain? And are they a problem where you live?
Types of fire ants
There are three basic types of fire ants (and countless variations) found in the U.S.: native southwestern fire ants, red imported fire ants, and their close cousin, the black imported fire ant. Our domestic fire ants are not as aggressive as their South American cousins, and their stings are not as painful. Red imported fire ants (Solenopsis invicta) and black imported fire ants (S. richteri) are extremely aggressive and their stings can be excruciating. Black imported fire ants are currently only found in the Southeastern U.S., and they are similar enough to their red-headed cousins, that we will be focusing on our biggest problem: the red imported fire ant.
Originally from Argentina, red imported fire ants are believed to have entered the U.S. in the 1930’s, in Alabama. By 1998, these stinging insects had made their way across the country to California. When the imported species meet our domestic fire ants, the home team loses.
Fire ant description
Red imported fire ants look like common ants, only bigger. Females are reddish colored. Males are black. Eggs are white and oval-shaped. Within one week, the egg looks more like a larva and the egg casing falls away. The larvae go through four stages (instars) before they reach adulthood. There are castes within a fire ant colony. The queens are the biggest, and then there are two castes of workers: major and minor. Smaller, minor workers tend to stay indoors and care for the brood, while larger, major workers go outside and forage for food. Major workers are twice the size of minor workers.
Fire ant colonies
Fire ants live in colonies. Since they need water to live, these colonies are generally found near water. Colonies may be found under a sidewalk, near the base of a tree trunk, in electrical equipment, and in and around your home. Colonies in the ground will often mound the soil up 12 to 18 inches. Each colony hosts 100,000 to 500,000 workers and several breeding queens. These queens may live for a few years, while the sterile workers only live a few weeks. If nearby water levels rise, fire ants will build floating islands to protect the colony.
Red imported fire ants have developed symbiotic relationships with insects, such as mealybugs, that produce honeydew. As omnivores, fire ants often eat dead animals and insects, fruit, and seeds. Their favorite food, however, is honey, so protect your hives!
Harm caused by fire ants
Fire ants can ruin more than a child’s game or a picnic. A red imported fire ant colony can make working in the garden nearly impossible. If a fire ant colony feels threatened, it can swarm an area with thousands of angry, stinging insects. These swarms are responsible for killing young livestock, such as rabbits, pigs, and even cattle. [Never restrain an animal or place a playpen near a fire ant colony.] The Stock Island tree snail is believed to have become extinct because of fire ants. Even if nothing in your garden becomes extinct because of fire ants, these pests, along with other ants, can carry diseases that may harm your plants.
Fire ant stings
A single burning, itching sting can capture your attention for about an hour. After that, the sting turns into a blister that will bother you for 3 or 4 hours. This blister transforms into a pustule that resolves in a couple of days. That’s if you’re lucky enough to only get stung once. If you develop an allergic reaction after a fire ant sting, get to the emergency room right away.
If you are not allergic to fire ant stings, wash the area with soap and water and apply a cold compress to reduce the pain and swelling. Antihistamines and topical steroid ointments may also provide some comfort, but nothing will get rid of it completely.
It is estimated that 14 million people are stung by red imported fire ants each year in the U.S., and that many of those people will develop an allergic reaction over time.
How to control fire ants
Luckily, fire ants are susceptible to the same control measures as other ants. Over-the-counter ant bait systems can be placed near the colony. If a severe infestation is present, contact local county pest control agencies by calling the statewide red imported fire ant hotline at 1-888-434-7326.
Apparently, high level conflicts attract one another. As much as 75% of a black widow spider’s diet is, you guessed it, red imported fire ants.
Other fire ant predators include earwigs, dragonflies, beetles, and other ants. To keep these somewhat beneficial insects alive, it is a good idea to avoid using broad spectrum insecticides. Birds and armadillos also find fire ants to be a tasty snack, but the strangest predator, in my opinion, is the fire ant decapitating fly (Pseudacteon obtusus).
These flies lay an egg on the back portion of a fire ant’s head, where the ant cannot reach it. The egg hatches and the larva starts feeding on the ant’s head, until it falls off. The fly larva enters the fallen head and stays there to pupate. [You can’t make this stuff up.]
So, if you see a mound that might be a fire ant colony, be careful!
The guava fruit fly is yet another invasive pest that home gardeners need to be aware of.
You may have driven through an agricultural inspection station on your way into California, at one time or another. These inspection points, along with those at international ports, and at shipping and postal centers, all work together to prevent infestations of foreign pests. This is a lot easier and cheaper than getting rid of them after they start feeding and breeding in a new area, which may not have native predators.
First seen in California in 1986, guava fruit flies are a major pest in Southeast Asia. In 2015, 15 guava fruit flies were found in California; 12 in Los Angeles, and one in Orange, San Mateo, and Santa Clara counties. Since a single female can lay hundreds of eggs that hatch and grow to sexual maturity in an astoundingly short period of time, a single fly is all it takes to trigger the need for extensive eradication programs. You can help in the fight against these pests by knowing what they look like and how they live.
Guava fruit fly hosts and damage
These pests enjoy several host plants other than guava. Common California crops that are threatened by guava fruit flies include black plum, cherry, citrus, peach, and melons. Banana, cashew, coffee, dragon fruit, mango, castor bean, papaya, sandalwood, rose apples, jujubes, bael fruit, sapodilla, and various gourds may also be at risk.
Guava fruit flies damage fruit by laying eggs in it. Females have a pointed ovipositor (egg depositor) that pierces the fruit. This provides points of entry for bacterial, fungal, and viral infections. When the eggs hatch, in as little as two days, maggots tunnel through the fruit, feeding and pooping as they go. None of us wants to bite into that. Maggots shed their skins twice over a two week period, depending on temperature, before dropping to the ground to enter a pupal stage. Within 1 to 2 weeks, adults emerge. Two to five weeks later, females are sexually mature. There are several generations each year.
Guava fruit fly identification
While most fruit flies are quite tiny, the guava fruit fly (Bactrocera correcta) is the same size as the common house fly. There are two major families of fruit fly: Drosophila and Tephritidae. Guava fruit flies are members of the Tephritidae, or peacock fruit fly family. They get that name because of the bright colors they display. It is mostly black, with yellow stripes, with two black spots on its face that can blend into a single band. Wings are clear with a dark line along the edge most of the way around, followed by a second line that continues around to the end of the wing. They look like they have a “T” on their butt, which is actually their abdomen. Research on this pest has only recently begun, so we will have to assume that earlier developmental stages look much like their close cousins, the Oriental fruit fly. This would mean that eggs are white, very small, and tubular, while larvae (maggots) are creamy-white and legless, and pupae are held in a dark, reddish brown cylindrical puparium. [Isn’t that a great word?]
The Northwest guava fruit fly (Anastrepha striata) is yet another invasive pest, but from the Americas, rather than Asia. Close cousins to the Oriental fruit fly, they can all be difficult to tell apart without looking closely.
Admittedly, capturing a fruit fly can be tricky business. After you’ve done it once, however, you will probably do it again. These creatures really are fascinating to look at up close. You will need to use a hand lens or a simple microscope to really see the amazing and colorful details.
If you even remotely suspect that you have a guava fruit fly, please call the Pest Hotline at 1-800-491-1899, or bring it to your local Department of Agriculture office. If guava fruit flies were to take hold in the U.S., crop losses and pesticide use would both skyrocket.
You should always protect your own garden by quarantining new plants, to ensure that they are pest and disease free.
Fusarium crown and foot rot means death for asparagus.
Heavy soil, poor drainage, over-harvesting, and insect feeding all work to create the perfect habitat for this ubiquitous fungi.
Fusarium is a large fungal family that causes several different disease in many garden plants. You may have already heard of Fusarium wilt, but there are several different crown and root diseases caused by these pathogens. One version attacks pumpkins, melons, and other cucurbits. Another group of Fusarium fungi attack asparagus.
Rather than having a single cause, there are three different forms of the Fusarium fungi that cause this fungal disease of asparagus. This trio of Bad Guys go by the names Fusarium oxysporum f. sp. asparagi, F. verticilliodes, and F. proliferatum. [Don’t worry, there won’t be a quiz.] All three fungi colonize the roots and crown, and the first one listed can also infect xylem tissue.
Symptoms of Fusarium crown and foot rot
Asparagus plants infected with the Fusarium fungi decline over time. At first, you may see one or more stunted, bright yellow ferns. This bright yellow coloration is a warning flag that should not be ignored. Wilting is also common. If you look at the crown area, you will see reddish brown discoloration. At this point, it is a good idea to pull the plant up, for closer inspection.
Cut open the crown or below ground area of the plant, to see if sunken brown lesions or reddish flecks are present. Then, look closely at the roots. Infected plants will have reddish brown, elliptical lesions on the storage roots. Feeder roots will probably rotted off completely, though any remaining tendrils will have the same reddish brown discoloration seen elsewhere.
Unfortunately, these fungi can survive in the soil indefinitely, and they are found pretty much everywhere. The disease is often spread as infected soil is moved from place to place on shoes, tools, and equipment. It can also be carried on seeds, which is why choosing reliable seed sources is so important. This disease can occur anywhere underground. Very often, insect feeding creates points of entry for these fungi. Asparagus miners are a common culprit.
Controlling Fusarium crown and foot rot
Environmental conditions that keep plants healthy also improve their ability to prevent these fungi from entering in the first place, so avoid water stress and feed plants regularly with top dressings of aged compost. [Asparagus plants are very heavy feeders.]
Once a plant becomes infected, it should be removed completely, along with nearby soil, and disposed of in the trash. To reduce the chances of the disease taking hold in the first place, your asparagus plants should be rotated every five years and be sure to provide proper drainage.
Remember, perennial asparagus can provide you with many years of delicious spring and autumn spears, so don’t let these pathogens stop you from trying to grow your own!
No, we are not discussing a breakfast cereal.
Frosted scale is a soft scale pest of walnuts. If you have a walnut tree (and why wouldn’t you), scale insect pests can be a major problem. These sap-sucking pests also feed on stone fruits, such as apricot and peach, along with apples, pears, raspberries, grapes, pistachio, roses, laurel, birch, locust, sycamore and elm, spreading disease as they go.
Frosted scale description
Like other scale insects, adult female frosted scale are 1/4 inch, dark brown ovals, with a protective, dome-shaped covering. As the name suggests, frosted scale has a waxy, frost-like coating over its shell. This frosty coating stays in place for a while, but it eventually wears off, leaving behind a brown shell that can remain in place for a year or so.
Frosted scale lifecycle
Nymphs overwinter on twigs. In early spring, these nymphs quickly grow to adult size. By late spring, females lay many eggs, filling the space between their body and their protective shell. After the eggs are laid, the female dies. When the eggs hatch, the nymphs, or crawlers, come out from hiding and begin feeding on the underside of leaves. They will continue feeding until fall, when they molt and move back onto twigs, where they spend the winter. There is one generation each year.
Problems associated with scale feeding
Frosted scale insects feed on the nutrient rich plant juices found in leaves and new twigs. As they feed, these nymphs produce large amounts of honeydew (sugary bug poop), which attracts disease carrying ants, and promotes the growth of sooty mold. Small numbers of frosted scale insects are not a problem. Heavy infestations, however, can suck the vitality from your trees, reducing crop size and quality. Also, as scale insects feed, they create wounds. These wounds make it easier for infections to take hold. One such fungi, Botryosphaeria, can lead to lower limb dieback and other potentially fatal fungal diseases.
Controlling frosted scale
In the world of commercial agriculture, insecticides are recommended if 5 or more nymphs are found per foot of the previous year’s wood. This means grabbing a hand lens and looking very, very closely. In the home garden, beneficial hunters, such as parasitic wasps, will provide the best protection. You can tell that a frosted scale nymph has been parasitized because it will turn black. Parasitized adults will have perforated shells.
You can increase the populations of these tiny, beneficial wasps by avoiding the use of broad spectrum insecticides and pesticides. Dormant oils can be used in winter and early spring to rid your tree of scale insects, but walnut trees are sensitive to horticultural oils and you need to use narrow-range oils to avoid harming the tree.
Scale infestations can sneak up on you. Be sure to take the time every month or so to inspect your trees for signs of infestation.
You may have played with (or been horrified by) potato bugs as a child. The Colorado potato beetle is not that bug. [Those bugs are Jerusalem crickets, which are neither crickets nor from Jerusalem, but we will discuss those pests another day.]
The Colorado potato beetle looks more like a striped cucumber beetle. Unfortunately, the infamous Colorado potato beetle eats more than just potatoes. To make matters worse, this pest has an impressive ability to become resistant to even the harshest chemicals.
History of the Colorado potato beetle
The Colorado potato beetle (Leptinotarsa decemlineata) is also known as the ten-lined potato beetle, ten-striped spearman, or simply the Colorado beetle. First identified in 1824, this pest is native to southwest North America. Initially, this dome-shaped beetle preferred wild members of the nightshade family, but, by 1840, the domesticated potato became its favorite food, followed closely by tomatoes, peppers, and eggplants. Exports of potatoes (and the Colorado potato beetle) to France and Germany inspired the world’s first plant quarantine laws. During the Cold War, the CIA was accused of releasing Colorado potato beetles in Russia, in an effort to threaten the Soviet Union’s food supply. In 2014, to call a pro-Russian separatist of the Ukraine a ‘koloradi’, a nickname given to the invasive Colorado potato beetle, was an insult directed at their similar orange and black stripes. In Hungary, a statue commemorates the arrival of this difficult to control pest.
Colorado potato beetle description
This stubby, round beetle has the same size and shape as a Japanese beetle. It is usually 1/ to 1/2 an inch long and tends to be bright yellow or orange, with five stripes on either side of its wing covers (elytra) and scattered holes (elytral punctures) on its shoulder covers (thorax). Colorado potato beetles are easily confused with their close cousins, false potato beetles. False potato beetles, L. juncta, have stripes, too, but their stripes tend to be white, with light brown center stripes, and their elytral punctures are spaced in an orderly fashion.
Colorado potato beetle lifecycle
Adult females can lay over 500 eggs in one month. These bright yellow or orange, torpedo-shaped eggs are laid in clusters on the underside of leaves. These beetles go through four stages, or instars, on their way to adulthood. Each instar only lasts 2 or 3 days. Eggs hatch after 4 to 15 days, depending on temperature. These larvae have humped backs, are dark reddish brown, with two rows of spots on either side (if you look very closely). They can usually be found near abandoned egg cases. By the time these baby beetles reach their third instar, they are bright red with black heads. These pests will continue feeding and growing until they reach adult size. Then, during the fourth instar, they enter a nonfeeding, prepupal stage. These larvae are a lighter color and they don’t move around very much.
Natural predators, such as ladybugs, pink lady beetles, spiders, ground beetles, lacewings, wasps, damsel bugs, beneficial nematodes, and praying mantids all enjoy feeding on these pests, so avoid using broad spectrum pesticides.
Neem oil and Bt sprays can be used as effective controls. Dusting with diatomaceous earth (DE) has also been shown to be effective.
Black rot may sound like the perfect name for your next Halloween character, but this bacterial disease can wreak havoc on plants in the cabbage family (Brassicaceae).
Popular brassicas, or cole crops, include broccoli, cauliflower, kohlrabi, horseradish, Napa/Chinese cabbage, collards, turnips, rutabagas, Brussels sprouts, watercress, kale, radishes, bok choy, and mustard. Rapeseed (canola) is also a member of this family. And all of these plants are susceptible to black rot, a close cousin to bacterial spot.
Black rot symptoms
The early symptoms of black rot (Xanthomonas campestris pv. campestris) don’t look like anything serious. You will see some chlorosis (yellowing) along leaf edges (margins), and some V-shaped lesions pointing toward the center of the plant. Then, those lesions may dry up and fall away, lulling you into thinking the problem has resolved itself.
Instead, black rot bacteria have gained a foothold in the phloem and xylem of your cabbage. As they populate and block these important vascular tissues, wilting and dieback occur.
If you cut an infected stem longitudinally, you will be able to see blackening of the vascular tissue. [Just be sure to disinfect your cutting tool afterwards, so that you don’t spread the disease to other plants.]
Managing black rot in the garden
Since this disease is most likely to occur in warm, humid weather, planting your cole crops after any chance of Indian summer has passed can help prevent it from occurring. The moisture left behind from overhead watering can also create the perfect conditions for black rot to take hold, so water your cabbages at ground level. There are some resistant varieties available, so shop for those if you have had problems with black rot in the past. Also, it’s a good idea to use crop rotation with cabbages and cauliflower in particular, as these two crops are the most likely to be affected. Since this bacteria can survive on cruciferous weeds, be sure to keep your cabbage patch weed free.
Glyphosate is an herbicide. It is the active ingredient in RoundUp and other popular broadleaf weed and grass killers. And recent scientific research has shown us that glyphosate may be killing honey bees along with plants.
Before we begin learning about this litigious herbicide, let me tell you from the gate that I do not use it, in any form. I practice sustainable, integrated pest management (IPM) and organic gardening. This is a heated topic and I want you to be aware of where I stand.
The chemistry of glyphosate
Glyphosate is a broad-spectrum, systemic herbicide, which means it is absorbed by and kills the plants it touches. It does this by blocking an enzyme pathway, called the shikimic acid pathway. [It gets this unique name from the Japanese shikimi flower, in which the process was first identified, back in the 1800s.] The shikimic acid, or shikimate, pathway is a 7-step metabolic process that synthesizes folates and amino acids necessary for plant survival. Herein lies the problem. The shikimic pathway is also used by algae, bacteria, fungi, protozoa, and others. When the shikimate pathway in any of these organisms is blocked, they die.
Glyphosate in the environment
More that 700,000 tons of glyphosate are produced each year, making it the world’s most used pesticide. As a substance, glyphosate molecules bind tightly to soil. While this means they are less likely to end up in ground water as, say, motor oil, it can cause a different type of pollution. Depending on soil type and weather conditions, glyphosate can be found in the soil 6 months after being applied. Soil bacteria break down glyphosate, but I have to wonder about the chemicals those bacteria poop out afterward. Maybe it’s just me. Some studies have found that carrots and lettuce plants absorb glyphosate long after the area was treated. Compounding the problem, many glyphosate products also contain other toxic ingredients.
Glyphosate and GMOs
Glyphosate use walks hand-in-hand with genetically modified plant development. GMOs are designed to be resistant to glyphosate and other weed-killing chemicals, making it possible to grow more food for our ever-increasing global population. It certainly has its appeal. It’s so simple - just aim, squirt, and you’re done. No more weeds. But at what cost?
Glyphosate and overspray
If you (or your neighbor) use a glyphosate product, you need to be aware of the overspray risk. Since none of us is perfect, and breezes do happen, these chemicals can be carried on the wind to places where they are not welcome. That delicate, well loved exotic, handed down from your great-grandmother, is just as vulnerable to death by glyphosate as the dandelions. Also, since glyphosate products kill all the plants it touches, indiscriminately, many plants important to local biodiversity are being lost. We do not yet know the full extent of that domino effect.
Glyphosate and bees
Beekeepers have long suspected that glyphosate is, at least partly, responsible for the recent decline in global bee populations. [Did you know that China now must hand-pollinate their apple and pear trees because there are not enough bees?] New research from the University of Texas at Austin shows that glyphosate kills some of the beneficial bacteria found in a honey bee’s gut, making the bees more susceptible to infection. [Maybe we need to start feeding our bees some type of probiotic? I’m guessing.]
Glyphosate first came on the market in 1974. It provided an easy way to kill weeds with just a squirt. Glyphosate is used in agriculture and forestry, and to control aquatic plants. It is sprayed along railroad tracks, between orchard trees, and in public parks. According to the National Pesticide Information Center, there is a sodium salt form of glyphosate that is used to regulate plant growth and ripen fruit. So, it’s very useful and convenient. There are over 750 products on American shelves that contain glyphosate, including RoundUp, Bonide KleenUp Grass and Weed Killer, and Kleeraway Grass & Weed Killer. Tragically, glyphosate is also found in many oat products on grocery store shelves, according to the Environmental Working Group (EWG). The worst offenders the EWG listed include Giant Instant Oatmeal, Back to Nature Classic Granola, Quaker Dinosaur Eggs Oatmeal, and, I hate to say it, Cheerios. I urge you to read through their entire list and shop accordingly. The FDA was/is aware of glyphosate in our foods, but has failed to release its findings to the public. More recently, glyphosate has been linked to the development of Parkinson’s and Alzheimer’s diseases, and may also cause cancer in humans.
As with any herbicide, always follow the package directions EXACTLY and COMPLETELY. This is not a time to be careless. You can harm other plants with overspray, or you expose yourself to dangerous chemicals. This can occur by breathing it in during the application process, eating or smoking after applying it, if you don’t wash your hands, or by touching plants that are still wet from the spray. If exposure occurs, follow the first aid directions on the product label. For more information about risks and treatments, contact the Poison Control Center at 1-800-222-1222. Pets are also susceptible to herbicide poisoning.
Instead of using toxic chemicals to rid your garden and lawn of weeds, be industrious and put out the effort to pull them before they go to seed. While you’re out there, use it as a time to take a closer look at the other plants and the soil, and listen for the birds and insects that share your yard space.
Bottom line, glyphosate makes it possible to grow far more food, at least in the short term, but the long term costs, in my opinion, far outweigh any convenience or benefits it may provide.
Brown marmorated stink bugs have invaded the world!
Okay, so maybe that was a bit melodramatic, but the fact remains: brown marmorated stink bugs have exponentially increased their range and they can be serious garden pests.
The problem with stink bugs
Most stink bug species eat popular fruit and vegetable crops, such as apples, peas, peppers, as corn, raspberries, grapes, tomatoes, pecans, pears, peaches, nectarines, lima beans and other bean plants, blueberries, hazelnuts, and cucumbers. When they feed, stink bugs inject your garden plants with enzymes that break down plant tissue into juices they can suck up. This makes the fruit under the skin tough, and pretty unappealing to us. It also sets the stage for several bacterial, viral, and fungal diseases.
Stink bugs also feed on buds, flowers, leaves, stems, and new bark. Since stink bug populations can grow very quickly, they can cause significant damage. [They also like to overwinter in your home.] To make matters worse, insecticides do not generally work to control stink bug populations. So, what makes the brown marmorated stink bug an even bigger problem than other stink bugs?
The traveling brown marmorated stink bug
Brown marmorated stink bugs are originally from Eastern Asia. They are believed to have first appeared in the U.S., in Pennsylvania, some time between 1996 and 2001. These pests reached the West Coast in 2004, and are now found in over 40 states. While native stink bug populations tend to be controlled naturally by beneficial predators, such as parasitic wasps, this invasive pest has few natural enemies and, as stated earlier, it tends to be unfazed by chemical insecticides. This is why it is so important to be able to tell the difference between native stink bugs and brown marmorated stink bugs.
Brown marmorated stink bug identification
Adult brown marmorated stink bugs are 5/8 inch long and a mottled brown. Like other stink bugs, they have the telltale shield-shaped body. Some characteristics unique to these particular stink bugs include two white bands on the antennae, a blunt face, faint white bands on the legs, and a banded edge around the abdomen. If you are looking really closely (and why wouldn’t you?), you will also see that the thorax (shoulder area) is smooth, and there are dark bands on the tip of the membranous forewings. The folks at UC Davis made an informative video about the differences between brown marmorated stink bugs and more common, native consperse stink bugs.
Brown marmorated stink bug eggs are white to pale green, and barrel shaped. Eggs are normally laid in clusters on the underside of leaves, though I have also seen them laid in lines on bird netting. After hatching, nymphs go through fives developmental stages, or instars, in which they shed their skin, much the way a snake does, as it grows. Nymphs start out only 2.4 mm (less than 1/10 inch), and grow to reach 12 mm (just under 1/2 inch). Early nymphs are brown, with an orange abdomen. Second instars are nearly black, while later instars develop the characteristic mottled brown color. Initially, markings are red, then black, and finally white.
Managing brown marmorated stink bugs
Since insecticides don’t work, and there are few natural predators, what is a gardener to do about brown marmorated stink bugs? First, start by excluding them from your home and other buildings. Caulk openings, seal cracks, and use weatherstripping around air conditioners, doors, and windows. [This can reduce your electric bill, as well!] Next, since stink bugs are attracted to light, turn off unnecessary lights at night. [Another bonus for your utility bill.] In the case of heavy infestations, you can always use a shop vac or a handheld car vacuum to collect the little beasties. The most effective stink bug control is simply handpicking. You can drop stink bugs in a container of water with a couple of drops of dish soap, or feed the pests to your chickens.
Assassin bugs, green lacewing larvae, some parasitic wasps, and earwigs are also known to feed on stink bugs, so avoid using broad spectrum insecticides. Row covers can also be used to protect specific plants and crops against stink bug damage.
Brown marmorated stink bug lifecycle
Each autumn, these pests gather along fences, tree trunks, and buildings. From there, they move to a protected area where they overwinter in a resting stage called facultative diapause. In the spring, these adults become active again and start feeding. Within two weeks, they mate. Soon after, females begin laying the 200 to 500 eggs she will deposit in her lifetime. In the mid-Atlantic states, there are two generations each year. Here, in California, we do not yet know the extent of the brown marmorated stink bug’s reproductive capabilities. It is safe to assume that there will be even more generations here, where winters tend to be mild.
Bacterial leaf scorch is a collection of diseases that can affect a wide variety of plants.
Bacterial leaf scorch (BLS), also known as bacterial leaf spot, is a tricky disease, because it is actually several diseases caused by different strains of a single pathogen. That pathogen, Xylella fastidiosa, causes different diseases in different plants. And sometimes those bacteria strains overlap their feeding habits, making classification and control difficult.
Leaf scorch diseases
Collectively, these diseases caused by Xylella fastidiosa are known as scorch diseases. Blueberries, mulberries, pears, peppers, plums, tomatoes, and even coffee plants can become infected with bacterial leaf scorch. Scorch diseases that go by a different name include:
Oak, sweetgum, oleander, sycamore, gingko, flowering dogwood, silk trees, jacaranda, maple, and elm can also become infected.
Lifecycle of Xylella fastidiosa
This particular bacterium is what’s called a fastidious mollicute, which means it must live within a plant’s xylem to be able to reproduce. The diseases they cause occur because they get so overcrowded that they block the flow of water and nutrients through the xylem.
Not all plants are negatively affected by this bacterium. Clover, blackberry, goldenrod, and many grasses can host this pathogen, acting as a way station without suffering any consequences. Unfortunately, when a sharpshooter feeds on one of these plants and then moves to your garden, trouble can start.
Symptoms of bacterial leaf scorch
Scorch diseases are characterized by the same symptoms you would see as a result of environmental conditions, such as herbicide overspray or too much fertilizer, or other diseases, such as verticillium wilt. Initially, you will see wilting and/or chlorosis. Leaf edges look, well, they look scorched! Then leaves start dropping. Fast. Before you know what happened, the plant dies. Except when it doesn’t, because sometimes it won’t. Scientists are still trying to sort it all out.
The bacteria that cause scorch diseases are carried into your garden by leafhoppers and spittlebugs. Actually, it’s in their saliva. Sharpshooters are the biggest carriers of the disease, as far as we know. These insect pests have a wide host range of their own. As sapsuckers, every bite they take infects the plant on which they are feeding. Because their host range is so large, they are spreading diseases to plants that have never been exposed before, so they have no defenses in place.
There are no known chemical treatments for scorch diseases, so controlling the disease carriers is your best bet. If the disease appears, remove the infected plant completely and put it in the trash.
Mulching and proper irrigation can help your plants protect themselves.
Curly top may sound like a cute little redheaded kid, but it’s really a viral disease of many garden plants.
Curly top host plants
This viral disease can strike beets, beans, ground cherries, peppers, pumpkins, chickpeas, tomatoes, squash, spinach, melons, horseradish, watermelon, and more. Scientists have identified different species of virus that cause similar symptoms. For lack of better ideas, those viruses are called Beet curly top geminivirus (BCTV), Beet mild curly top virus (BMCTV), and Beet severe curly top virus (BSCTV).
Symptoms of curly top
Infected plants exhibit leaves that cup upwards or downwards, depending on the plant variety. These leaves may turn a darker green than normal, or light green to yellow, and they are thicker and more brittle than normal. Puckering and wrinkling are also common. Infected tomato leaves may have veins that look purple.
The internodes (spaces between nodes on a stem) become shortened, causing stunting and dwarfing. These symptoms are more exaggerated when infection occurs while a plant is young, and death is common. Infected older plants often just turn yellow. The telltale symptom of curly top occurs when the top of the plant turns into a rosette or tiny bouquet. If any fruit is present, the skin will be dull, rather than shiny, it will taste bad, and will tend to ripen before it reaches full size.
Curly top virus lifecycle
The virus overwinters in annual and perennial weeds. From there, beet leafhoppers (Circulifer tenellus) carry the disease to your garden plants. Symptoms don’t start to appear until long after the leafhoppers are gone, but they are the disease vector, so controlling leafhoppers goes a long way toward preventing this disease. Unfortunately, insecticides are generally not effective against leafhoppers. Leafhoppers have many natural enemies, so make your garden hospitable to beneficial insects. You can do this by avoiding broad spectrum insecticides, planting a variety of umbellifers, such as dill, carrot, and fennel, and providing a water source.
The symptoms and host plants of curly top look too much like other viral diseases, such as spotted tomato wilt, to be identified by the casual gardener. Laboratory tests are needed to know for sure. In the case of viral disease, it is simpler to yank the plant and toss it in the trash, rather than spreading the infection to other plants.
Plants may not have an active immune system, but that doesn’t mean they just roll over and take whatever hits them. When pathogens strike, plants can respond in two different ways to resist becoming infected: they use pre-existing structures and chemicals, and they can use responses that are induced by the presence of a pathogen.
Just as our skin blocks many pathogens from entry, a plant’s skin, or epidermis, does the same thing. That's why insect feeding and mechanical damage can increase the chance of a disease taking hold - the plant’s first line of defense has been breached. Plant cell walls also block viruses, bacteria, and fungi. Unlike our human immune system, which uses white blood cells to actively hunt down and destroy invaders, plant cells have antimicrobial defenses built right in. These defenses take the form of saponins, glucosides, and antimicrobial proteins. Enzyme inhibitors can also stop some pathogens from feeding on the plant. Plants also have chemicals that can neutralize toxins created by a pathogen. Finally, receptors can recognize a pathogen and alert the plant to take further action.
Inducible plant defenses
Once a pathogen is recognized, cell walls are reinforced and defensive chemicals, such as hydrogen peroxide, as well as antimicrobial enzymes and proteins, are manufactured. In some cases, plants have evolved a behavior called a ‘hypersensitive response’ in which the tissue surrounding an infection is killed off, to block further infection to neighboring cells.
Disease resistant varieties
Rather than treating a disease after it occurs, it is far easier to grow plants that have built-in defenses. This reduces the need for pesticides and fungicides. When shopping for plants, look at the plant label to see if that particular plant is resistant to diseases that tend to appear in your garden. Plant labels use the following codes to designate specific disease resistances:
So, if you see a plant label with the letters, V, F, and N, that means that particular plant is resistant against verticillium wilt, fusarium wilt, and nematodes. This does not mean the plant is guaranteed to not get these diseases, but it does mean the chances are significantly lower.
You can help your plants fight disease by selecting resistant varieties, spacing plants properly, employing crop rotation, and providing adequate water and nutrients. Also, be sure to sanitize your tools regularly, to halt the spread of disease from one plant to another.
There are no aboveground symptoms, but a carrot root fly infestation can ruin your carrot crop, along with several other umbellifers. Carrot root fly (Psila rosae), also known as the carrot rust fly, is a pest found in most temperate regions.
Carrot root fly description and lifecycle
These tiny, fast flying pests are slender, greenish-black metallic flies. Their legs and head are yellow. Carrot rust flies tend to hang out in weeds and undergrowth near carrot fields. After mating, females head for the carrots, where they will lay their tiny, white eggs on the soil surface. Larvae are creamy white, approximately 1/3 of an inch long, and rather stiff, as far as maggots go. Orangish-brown pupal cases can be found in the soil.
In addition to feeding on carrots, carrot root flies also feed on caraway, celery, dill, fennel, parsley, and parsnips. Other plants, such as lettuce, endive, and chicory can serve as host plants in areas where the maggots are already in the soil.
Damage caused by carrot root flies
Like other root maggots, carrot root maggots feed on tiny root hairs and then tunnel along the surface and burrow into the root. These tunnels and burrows are then filled with mushy frass. The initial feeding causes stunting, and tunneling makes it easy for other pathogens to enter, which leads to several different types of rot and other problems.
Carrot root fly control
The best way to protect young plants from carrot root flies is to use row covers as soon as seeds are planted, and to leave the cover in place until it is time to harvest. Some people use window screen panels around raised beds to block this pest, while others use window screen material to create protective cones for individual plants.
There are resistant varieties of carrot, specifically ‘Flyaway’, which claim to thwart these pests, though I can’t vouch for its effectiveness, personally. Research has shown that intercropping alfalfa with carrots and other host plants, or mulching with alfalfa works to reduce carrot root fly infestations. Crop rotation can also be used to interrupt the carrot root fly lifecycle.
Melon flies could end up costing California farmers over $4.5 billion if they ever get a toe-hold in the state.
Melon flies (Bactrocera cucurbitae) are a type of fruit fly. Native to India and Asia, melon flies were first seen in Hawaii in the late 1800’s. They have now become a devastating pest on the Islands. Quarantine stations have worked long and hard to prevent this pest from entering the Continental U.S. The melon fly was first seen in California in 1956, and several other times since, but whenever melon flies are identified stateside, eradication programs immediately go into affect. These programs use pheromones to attract male melon flies. These males are then sterilized and released. This messes up melon fly breeding. So far, this method has been effective. So, why would a gardener care, if the pest isn’t even here? Because maybe it is.
Melon fly host plants
It would probably be easier to list the plants that are not seen as food by melon flies, but it is important to know where to look, and to know what to watch for, so here’s the fruit fly menu of favorites from your garden:
Melon fly description
The size of a house fly, melon flies are mostly orange or yellow and brown with a pale black T-shape on the abdomen and distinct wing patterns. Wings are clear with a large brown spot at the tip and a brown stripe along the back edge and along the base. Melon fly antennae also have an especially long third segment. Melon fly larvae (maggots) are creamy white, without legs, somewhat flattened at the back end. Maggots are less than 1/2 an inch long. Pupae are somewhat smaller than the maggots, held in a protective case that can be dull white or red, or brownish yellow. Eggs are very tiny, white, and somewhat elliptical.
Melon fly lifecycle
A single female melon fly can lay 1,000 eggs. Eggs are laid on young fruit and tender new stems, which will provide food for newly hatched maggots. Eggs that have been laid under the skin of fruits, or in host plant stems, flowers, and exposed roots, will hatch and the feeding damage begins. There are three larval stages, or instars. After feeding continuously, mature maggots drop to the ground, where they burrow into the top inch of soil and enter a pupal stage. There can be 8 to 10 generations a year.
Melon fly damage
During the heat of the day, adult melon flies rest on the shady undersides of leaves. When temperatures are more comfortable, they feed on nectar, decaying fruit, sap, and bird poop. [Keep in mind, as these pests fly from one food source to another, they can be carrying pathogens from the bird poop to your fruit crop.] Tunneling and feeding create points of entry that allow bacterial, fungal, and viral diseases to enter. Generally, the fruit ends up rotten and inedible.
Melon fly control
Unfortunately, there are not any effective controls available to the home gardener. You can certainly rake up the soil under and around potential host plants, to spot, remove, and report any pupal cases you find, and be sure to quarantine new plants. Currently available insecticides have not been found to work against melon flies.
If you think you see a melon fly, please make every effort to capture or kill it. Then call the CA Pest Hotline at 1-800-491-1899, or your local Department of Agriculture, to report it. Only by working together can we protect commercial agriculture and our own gardens from the melon fruit fly. And don’t smuggle fresh fruit or produce across state lines. There’s a lot more at stake than you might think.
White mold, also known as lettuce drop, is a disease that affects far more than just lettuce in your garden.
White mold (Sclerotinia spp.) can remain dormant in the soil for a very long time. It takes a significant amount of cool moisture to wake one of these fungi up from its dormant sleep, but the underside of a head of lettuce, or a cabbage, provides just the sort of humidity needed to trigger an awakening and the ensuing infection. This disease is also known as Sclerotinia stem and crown rot and it is caused by two different fungi, depending on the host plant.
Symptoms of white mold
White mold is seen on outer leaves, lower stems, and pods, in the case of beans. Starting at the base, the mold spreads, causing outer leaves to wilt and fall away from the plant, while remaining attached. Garbanzo beans are particularly likely to become infected in the crown area. Affected plant tissue develops watery lesions as cottony white mycelium form on the surface. Mycelium are the vegetative part of a fungus, made up of threadlike hypha.
Stems may become girdled by the decay. As damaged tissue dies and dries up, it will turn white and looked bleached. Tiny (0.25–0.5 inch), irregularly shaped black flecks, called sclerotia, can be seen on the surface and inside of dead stems. Sclerotia are the resting body of the fungi, made of of a cluster of hyphal threads, and able to remain dormant for a surprisingly long time.
White mold host plants
Along with lettuce and escarole, several members of the nightshade family and the cabbage family are susceptible to white mold. This means that your tomatoes, potatoes, and eggplants, along with Brussels sprouts, mustard greens, broccoli, cauliflower, turnips, radishes, rutabagas, and kale can all become infected. Dried bean plants, alfalfa, other broad-leafed plants, and many weeds can also become infected.
How to avoid white mold in the garden
Since prolonged moisture is needed for this fungus to come among us [sorry, I couldn’t resist], keeping things dry is a good defensive plan. These specific steps can help you avoid a white mold problem in your garden:
As prevalent as white mold is, it’s a good idea to know what to look for ahead of time.
Johnson spot is a fungal disease of rice, wheat, barley, rye, and millet. It also attacks your lawn.
Other names for this disease include rice blast fungus, pitting disease, and ryegrass blast. As a threat to your lawn, Johnson spot can infect kikuyugrass, fescues, rye grasses, and St. Augustine grass.
The fungal pathogen
The fungi that causes Johnson spot is called Magnaporthe grisea (previously known as Pyriculria grisea). Magnaporthe grisea is a highly effective fungus. Spores attach themselves to plant surfaces. They can reproduce both sexually and asexually, and they are prolific. A single spore can complete its reproductive cycle in one week, though it can live for 20 days. Thousands of new spores are generated each night. I don’t know how to calculate the math on all that, but I am certain that those numbers would be overwhelming to a plant. As the fungi perform all that precreation, seed production is reduced and entire leaves are killed.
Johnson spot symptoms
Early signs of fungal infection include white to grayish green spots with dark borders. As they age, the lesions take on a more elliptical shape. These symptoms can be seen on many parts of the plant, including the leaf collar, stems (culms), and flowers (panicles).
How to prevent and control Johnson spot
Moisture is a key ingredient to this fungal growth. If leaves are wet and temperatures are between 77 and 82°F, Johnson spot can quickly take hold. To break this disease triangle, be sure to space plants in such a way that supports good air flow, avoid overhead watering, allow the soil to dry out between waterings (without causing water stress), and only apply the minimum amounts of nitrogen needed by the plants.
Of course, that advice is only partially useful when it comes to lawn care. To help your lawn avoid becoming infected with Johnson spot, water as early in the day as you can. This will allow plants to dry off before evening comes around.
This fungus has developed resistance to chemical treatments, so cultural practices are your only option. These practices include crop rotation, selecting resistant varieties, and disposing of infected plant material in the trash.
Johnson spot is the most significant disease of rice in the world. Experts estimate that this disease destroys enough rice to feed 60 million people every year.
You can grow a surprising amount of food in your own yard. Ask me how!