Fig trees can be stately and highly productive, but fig mosaic can take a toll on your fig tree. Fig mosaic is a complex of several, as yet unidentified, viral diseases that all infect Ficus subspecies.
Fig mosaic symptoms
Yellow leaf mosaic patterns are a common symptom of fig mosaic. These patterns are brighter yellow toward the center of each spot, fading to light yellow before reaching the healthy green leaf tissue. As the condition progresses, a rust-colored band appears around the edge of each mosaic spot. Leaves may also be deformed. Infected fruit shows mild mosaic patterning but may be smaller and less abundant than on healthy trees. Most often, fig mosaic causes early fruit drop, all but eliminating your crop.
How fig mosaic is spread
Fig mosaic is spread by eriophyid mites, particularly fig mites. As the mites feed, the virus is transmitted through their saliva. Fig mosaic can also be spread by grafting and cuttings.
Fig mosaic management
Tree infected with fig mosaic should be removed. Trees take time to grow, so having to remove an infected tree is best avoided. Begin by only installing disease-free tree and planting them at the proper depth, giving them the irrigation and food they need to stay healthy. Monitor your fig trees for sign of mite feeding. You will need a 20x hand lens to see these tiny sap-suckers. Fig mite feeding is usually seen around bud scales and young leaves and it often causes a faint russetting. Twig stunting and leaf drop may also occur.
Sulfur treatments and horticultural oils have been shown to control fig mites.
Go take a look at your fig tree to see if mites might be present. If they are, get rid of them so that you can enjoy many years of sweet, delicious figs.
Beetles among your squashes and melons is never a good thing, especially when they carry the squash mosaic virus.
Squash mosaic is second only to cucumber mosaic in damage to cucurbits caused by disease. There are two strains of squash mosaic, strain 1 affects melons most often, while strain 2 prefers squash. In either case, your crop will be lumpy, discolored, and significantly reduced, but still edible.
Crops vulnerable to squash mosaic
All cucurbits are susceptible to squash mosaic. This includes your zucchini and other summer squashes, melons, gourds, cucumbers, and pumpkins. Watermelons, however, are not susceptible to squash mosaic. Some legumes and umbellifers can also become infected with squash mosaic.
Squash mosaic symptoms
Squash mosaic causes a dark green mottling or mosaic pattern on leaves, as well as blistering, yellowing (chlorosis), leaf hardening and distortion, and vein clearing. Vein clearing is a common symptom of viral disease and it refers to the way leaf veins become almost translucent while the rest of the leaf remains green.
Squash mosaic carriers
Unlike other mosaic diseases, squash mosaic is not spread by aphids. Instead, striped and spotted cucumber beetles, leaf beetles, and 28-spotted ladybird beetles are the most common vectors of squash mosaic. Many other beetles are also capable of hosting the virus. As these insects feed, their saliva transfers the virus to the plant. This is why it is so important to remove infected plants right away.
Squash mosaic controls
In addition to removing infected plants, beetle control is important in the prevention of squash mosaic. And beetles can be tough to control. The virus can stay viable inside a beetle for up to 20 days, so it is worth the effort. A single beetle can infect dozens of plants in that time frame. To control beetles, handpicking is always an option, if you are quick enough. You can also use neem oil to kill beetle eggs. Encouraging beneficial predators, such as ladybugs, mantids, and solider bugs, in the garden with fresh water, insectary plants, and little or no chemical use is probably the easiest method of keeping beetle populations within reasonable limits.
Squash mosaic can also be carried on melon seeds, so be sure to get clean, disease-resistant seeds from a reputable supplier (and not that melon from the grocery store).
Certain chenopod weeds, including lambsquarters, goosefoot, Russian thistle, and kochia, provide overwintering sites, so keep these weeds away from your cucurbits.
As with many other viruses, tools, clothing, and other surfaces can also become carriers. To prevent the spread of this disease, sanitize tools regularly and avoid working around plants while they are wet.
Warty zucchinis with skinny leaves may mean the zucchini yellow mosaic virus has infected your plants.
No garden would be complete without the versatile, fast-growing zucchini. A favorite in stir-fry, breads, and the ever popular chocolate zucchini cake, zucchini can be very productive plant, as long as it stays healthy.
Zucchini yellow mosaic symptoms
Whitened leaf veins, mottled, abnormally small leaves with alternating light and dark areas, and deformed, warty fruit are all signs of zucchini yellow mosaic. These are also symptoms of watermelon mosaic and papaya ringspot virus, two viral diseases that often occur at the same time as zucchini yellow mosaic. Watermelon mosaic infections tend to include blistered leaves, while zucchini yellow mosaic has the added symptom of leaf lobes becoming long and narrow, creating a ‘shoestring’ or ferny appearance.
Zucchini yellow mosaic host plants
In addition to infecting zucchini, zucchini yellow mosaic also infects other members of the cucurbit family, including melons, squash, pumpkins, some gourds, cucumbers, cantaloupe, and watermelon. The disease is transmitted by aphids.
Zucchini yellow mosaic management
As anyone who gardens knows, controlling aphids is difficult. These pests seem to appear overnight, in huge numbers. And all it takes is one aphid to get the whole process started. Unfortunately, insecticides are rarely useful in managing zucchini yellow mosaic, because the disease has often been transmitted before you even know the aphids are there. Reflective mulches can be used to discourage aphids, just be sure to remove the reflective material before it gets too hot. Row covers can also be used to reduce access to susceptible plants.
This disease can also be spread on infected garden tools and seeds, so be sure to sanitize your tools regularly and get your seeds from a reputable source (and not that zucchini from the grocery store).
Infected plants should be destroyed and replaced with resistant cultivars.
Since this virus is only viable for a few hours within their aphid carriers, creating a physical barrier of tall, non-host plants around your cucurbits can be enough to prevent the aphids from getting to the plants while the virus is still active.
Speckled, mottled, or otherwise deformed leaves and fruit usually indicate a mosaic disease.
Mosaic diseases are caused by a variety of viruses that can infect the majority of your garden plants. Since these diseases are difficult or impossible to treat, recognizing and removing infected plants right away can help prevent the disease from spreading.
Symptoms of mosaic diseases
The classic mottled appearance of infected leaves is only one symptom of mosaic disease. Leaf cupping, blistering, stunting, crinkling, and other distortions are also common symptoms of mosaic disease. Stems may be shortened, creating a bushy appearance to vines.
Plants infected early in the growing season rarely produce fruit. Interestingly, plants infected later in the season retain their healthy, earlier growth and fruit production, while future growth is distorted. Fruit may also show the same mottling and other distortions seen on leaves. Warty bumps are common.
Plants that host mosaic diseases
It would be easier to list plants that are not affected by mosaic disease. Plants commonly infected with mosaic diseases include:
Common mosaic diseases
While there are dozens (hundreds?) of mosaic diseases, some of the more common varieties include:
Mosaic disease management
Generally speaking, mosaic diseases are not curable. Infected plants should be removed. This means that prevention is a far better course of action.
Depending on the specific virus, it may be carried in to your garden on seeds or tools, or by aphids, dryberry mites, and any number of other sap-sucking pests. Removing weeds that could provide overwintering sites, creating physical barriers with row covers and walls of non-host plants, and regularly sanitizing your tools goes a long way toward preventing mosaic disease from taking hold in your garden, as does buying clean, disease-resistant seeds and plants from reputable suppliers.
While mosaic diseases make plants look funny, the fruit of infected plants is still safe to eat. The viruses responsible for mosaic diseases are not harmful to people.
Growing your own corn makes a dramatic statement in the garden. Reaching 10 to 12 feet in height, modern corn plants grow in tandem with other giants, such as sunflowers and hollyhocks. Unless they become infected with corn stunt.
Corn stunt does not mean ears of corn will suddenly start doing gymnastics over the fence into your neighbor’s yard. Instead, this bacterial disease will infect the phloem of corn plants, reducing them in size and all but eliminating kernel production.
Corn stunt disease complex
Some people see corn stunt as a single disease, while others see it as one part of a complex of three disease, the other two being maize bushy stunt mycoplasma and maize rayado fino virus (MRFV). Yet others include maize chlorotic dwarf virus in the corn stunt complex. Any combination of these diseases can be devastating to your corn crop.
Corn stunt symptoms
Healthy corn plants produce one or two ears of corn, depending on whether they are early or late maturing varieties, respectively. Plants infected with corn stunt are significantly shorter than normal, often only 5 feet tall, and may produce 6 or 7 ears. That may sound great, but it’s not. These ears are small and they do not fill properly, meaning there ends up being a lot of empty spaces. The kernels that do develop are not well attached, in a condition known as “loose tooth ears”. Infected plants will also exhibit pale yellow new leaves at the top. As these leaves mature, they tend to turn reddish.
How corn stunt spreads
Corn stunt is caused by Spiroplasma kunkeliiI, which is carried by leafhoppers. Corn leafhoppers (Dalbulus maidis), in particular, carry this disease with them, spreading it as they feed.
Corn stunt management
You can prevent corn stunt by using reflective mulches that deter leafhoppers. Planting your corn as early as possible in the growing season has been shown to reduce the impact of corn stunt infections. Apparently, the first generation of emerging bacterium are not as effective at spreading the disease as those that occur later in the season. Insecticides are generally not effective.
You don't have to grow corn to have a reason to worry about seed corn maggots.
Seed corn maggots mostly feed on decaying organic material, but sometimes they feed on the roots and seeds of over 50 different garden plants. Also known as the bean seed fly, seed corn maggots may be tiny, but they can ruin several of your crops.
Seed corn maggot description
Seed corn maggots (Delia platura) are small, dark grey flies with grey wings, black legs, three stripes on the back, and scattered bristles. Less than 1/4” long, seed corn maggot adults looks nearly identical to onion maggot flies. White or off-white larvae are legless and have rounded tails and pointed heads. Pupal cases are brown and hard and look like skinny footballs.
Seed corn maggot damage
Seed corn maggots often feed on the seeds of corn, peas, beans, and soybeans but they do not always kill the embryos within the seeds. When those seeds germinate, they are spindly and rarely make it to maturity, wasting valuable resources. Other crops commonly attacked by seed corn maggots include cucumbers, melons, onions, peppers, and potatoes.
Seed corn maggots may tunnel into the stems and roots of many different garden plants and feed on spinach leaves, often providing points of entry for other pests and diseases.
Seed corn maggot lifecycle
Adult flies emerge in spring and begin feeding on nectar and honeydew. After mating, females lay an average of 270 eggs in the soil, near the surface. One week later, larvae emerge and begin feeding. One to three weeks later, larvae move back into the soil where they pupate for one to three weeks, or over the winter.
How to control corn seed maggots
The key to controlling corn seed maggots is in the soil. While I am a proponent of no-dig gardening, repeated appearances of corn seed maggots warrants disturbing the top 2 or 3 inches of soil on a regular basis during the spring and summer months. Research is being conducted on the possibility of beneficial fungi being used to control these pests, but it is not currently an option.
As is nearly always the case, prevention is far easier. You can reduce the odds of seed corn maggots attacking your crops by waiting for the weather to warm up before planting, and spacing plants properly. Anything that slows germination or initial seedling growth makes it easier for seed corn maggots.
With the 4th of July right around the corner, watermelons are a common sight. But watermelon mosaic is something I hope you never see.
Watermelon mosaic (WMV) is a viral disease that can also infect cantaloupes, squash, and other cucurbits, along with some legumes, such as peas and alfalfa, and chenopods. Infected watermelons look like they have ring worm.
There are two different watermelon mosaic viruses: WMV1 and WMV 2. While these are two distinctly different viruses, we are going to throw them together for the sake of this discussion.
Symptoms of watermelon mosaic
Symptoms of watermelon mosaic virus vary by host, but the first sign of infection is light discolorations in the leaves. This irregular chlorosis is usually seen along leaf edges (margins) and along veins. Leaves may also be smaller than normal, deformed, blistered, or wrinkled. That wrinkling is called rugosity. Finally, infected fruit develops a mottled appearance. The mottling looks like light-colored rings just under the skin. Warty growths may also appear. Fruit production is significantly reduced.
How to prevent watermelon mosaic
Spread predominantly by aphids and occasionally leaf miners, watermelon mosaic virus can also be carried on garden tools and clothing, so sanitize your tools regularly. The virus is only able to survive inside aphids for a few hours, so creating physical distance between potential carriers of the virus can also reduce infection. Crop rotation and removing infected plants can break this disease triangle.
Weeds, such as lambsquarters, cheeseweed, goosefoot, and Russian thistle, can act as vectors for this disease, so keep them away from your watermelon and other susceptible plants.
Horticultural oil spray can also interrupt transmission of this virus, but may cause problems of its own.
Insecticides are not effective because the disease is transmitted before the chemicals can kill the carrier. You can use reflective mulches under susceptible plants to repel aphids. If you use reflective mulch, be sure to remove it before the summer sun uses it to cook your plants.
If you grow currants, you should know about currant sawflies.
Currants make delicious jellies, pies, sauces, and even wine, but currant sawfly larvae can completely strip the leaves from your currant plants in only a few days.
Also known as imported currantworms and common gooseberry sawflies, these pests feed on gooseberries and other members of the Ribes family. Native to Europe, this pest is now found throughout North America.
Currant sawfly identification
If you see chewed holes in the leaves of your currant bushes, take a closer look. There are several pests that can cause this damage. It may be currant borers (Synanthedon tipuliformis), currant spanworms (Itame ribearia), the Epochra ribearia maggot, gooseberry fruitworms (Zophodia convolutella), or currant sawflies (Nematus ribesii). Sawflies tend to feed in groups, while those other pests do not.
Like other sawflies, adult currant sawflies look like a cross between a wasp and a fly. The larvae grow to 3” in length, but their coloration makes them difficult to see. They start out green with black heads. As they grow, they develop yellowish ends and black spots.
Currant sawfly lifecycle
Adult currant sawflies lay tiny, oval white eggs on the underside of leaves and there can be three generations each year. The first brood emerges after the first leaves appear in spring, the second occurs in early summer, and a third generation may occur, weather permitting. In each generation, feeding is very heavy and rapid.
To make matters worse, feeding often begins on the lower, inner reaches of the shrub, so you may not even notice the damage right away. Be sure to inspect plants regularly for signs of feeding and look on the underside of leaves for eggs.
How to control currant sawflies
Before you take any drastic measures, you need to know that the larval stages of currant sawflies look a lot like little green caterpillars. The distinction is important because control measures are different for moth and sawfly larvae. Take a closer look. If you have one, grab a hand lens or magnifying glass. If if you see 6 or more pairs of hookless legs, it’s a sawfly. Caterpillars have tiny hooks on their stubby legs and they usually have only 3 pairs of prolegs.
You can treat moth larvae infestations with Bacillus thuringiensis (Bt). That treatment will not work against sawflies. Commercial growers spray plants with Malathion as soon as currant sawflies appear. Your best choice for controlling currant sawflies is to spray infested plants with insecticidal soap and handpick currantworms as they are seen.
Yellow spots on leaves may indicate Septoria leaf spot.
This fungal disease is very destructive and it affects celery, chicory, cucumber, and other cucurbits, along with asters, carnations, chrysanthemums, verbena, and various trees and shrubs. Septoria leaf spot is one of the most destructive tomato diseases I know.
Like other leaf spot diseases, Septoria reduces photosynthesis and the flow of important nutrients through the vascular bundles, leaving plants to wither and die.
Warm, wet weather is all this fungi needs to set up housekeeping in your garden. And remember, that wetness can be caused by poorly placed sprinklers, leaky hoses, and overhead watering, just as easily as the weather. Temperatures between 60°F and 80°F are ideal for fungal growth. Knowing what to look for can help you protect your plants.
Types of Septoria
Septoria is a family of fungi. Different subspecies affect different plants. The most common types of Septoria, followed by their host plants and symptoms, include:
Symptoms are first seen in older leaves. The disease spreads upward into newer growth. As the spots spread, leaves turn yellow, die, and fall off. This leaf loss reduces plant vigor and increases the chance of fruit being damaged by sunburn. Severe infections can result in complete defoliation.
Septoria leaf spot lifecycle
Septoria fungi travel on the wind and in rain, so it’s something you need to monitor for regularly. Spores come into contact with host plants and send out thready hyphae, which enter plants through cracks and injury sites. Spores overwinter in the soil and on infected plant debris.
How to control Septoria leaf spot
As with many other diseases, prevention is far easier than treating. These tips will help prevent Septoria leaf spot in your garden:
If Septoria leaf spot is seen, remove infected leaves right away and throw them in the trash. Also, sanitize any tools that may have come into contact with infected plants and avoid working around plants when they are wet.
While it might be cute to picture a fly buzzing around with a tiny saw, there is nothing to love about sawflies.
Sawflies get their name because their ovipositor (egg-laying organ) is shaped like a saw and used to cut notches into plants for egg-laying.
Sawfly larvae may look like caterpillars or slugs, but these pests are in the same order as bees, wasps, and ants, and are closely related to woodwasps and horntails. You can tell the difference between sawfly larvae and caterpillars by counting their legs. Caterpillars usually have five or fewer prolegs on their abdomen, while sawfly larvae, such as the California pear sawfly, have 7 or 8 pairs of prolegs on their abdomen and 3 more pair on the thorax.
With over 8,000 sawfly species, spread out over 800 genera, there is a wide variety of coloration and body type in the world of sawflies. As a group, their soft bodies are stubby and only slightly wasp-like, and they tend to be weak flyers. The ovipositor is often mistaken for a stinger, though sawflies cannot sting. Some sawfly larvae, however, are known to puke up a noxious liquid that would-be predators find distasteful, while other sawfly species raise their rear ends up, cobra-fashion, weaving back and forth a warning.
Some of the more common sawfly species include:
Adult sawflies only live for one week, during which time they mate and females lay 30 to 90 eggs. Eggs are tan, oval or kidney-shaped, and look like tiny blisters on the upper surfaces of leaves. In 2 - 8 weeks, depending on temperatures, those eggs hatch and then go through 5 or 6 larval stages, depending on the species, before heading to the soil, en masse, to pupate. Some sawfly species use webspinning and leafrolling to protect their young, while others spin cocoons. The entire process can take 2 years. It is during the larval stages when sawflies do the most damage.
Sawflies are defoliators, which means they strip the leaves from several garden plants. Species tend to be host-specific. Rose sawflies attack roses, pine sawflies attack pine trees, and so on. Plants vulnerable to sawfly feeding include apple, cherry, peach, pear, plum, and quince trees, along with most cane fruits.
Larvae often feed in large groups, for added protection. Damage caused by larval forms of sawflies include leafmining, defoliation, skeletonizing, galls, and notching of leaves.
Generally speaking, handpicking is your best method of controlling sawfly larvae. You can feed them to your chickens for a tasty protein treat, or bag them and toss them in the trash. While Bacillus thuringiensis (Bt) can be used to control moth and butterfly larvae, it is not effective against sawfly larvae.
Insecticides can be used against sawflies, but sawfly larvae are a popular food for many native birds, including partridges, black grouse, corn buntings, and chestnut-backed chickadees. Shrews, lizards and frogs also enjoy snacking on these pests, along with several predatory wasps, including ichneumon and braconid wasps.
You can attract these garden helpers by providing fresh water, growing a variety of insectary plants and plants that provide pollen and nectar, and avoiding the use of broad spectrum pesticides and herbicides.
Blue-green sharpshooters are sap-sucking, disease-carrying cousins of leafhoppers. Native to California, blue-green sharpshooters (Graphocephala atropunctata) have only recently become serious pests.
As blue-green sharpshooters feed, they inject plants with a bacteria that causes Pierce’s disease.
Pierce’s disease primarily affects grapes, but it can also appear on alfalfa, almond, avocado, blackberry, citrus, elderberry, and olive. The bacteria that cause Pierce’s disease block the flow of water and nutrients through the xylem, causing scorching, stunting, bleaching, leaf stippling, “matchstick” petioles, ‘green islands’ on stems, raisined grapes, defoliation and dieback. But symptoms do not always appear in the year the plant is infected. This results in many more plants becoming infected as sharpshooters move from plant to plant as they feed. Plants infected the previous year often exhibit delayed or absent budbreak. Plants infected early in the growing season are more likely to look as though they have recovered, even though they haven’t.
There is no cure for Pierce’s disease and infected plants usually die within 1 to 3 years. Other diseases caused by the same bacteria include almond leaf scorch, oleander leaf scorch, and olive leaf scorch. These bacteria can also be carried by spittlebugs and glassy-winged sharpshooters.
Outbreaks of Pierce’s disease have been growing dramatically. This is believed to be due to warmer temperatures allowing vectors, such as blue-green sharpshooters, and the bacteria they carry, to live through the winter.
Blue-green sharpshooter description
Unlike glassy-winged sharpshooters, which average 1/2” in length, blue-green sharpshooters are much smaller and easy to miss. As far as pests go, the blue-green sharpshooter is quite colorful. From a distance, it simply looks like a wedge-shaped green insect. If you look closely, with a hand lens, you suddenly see striking bright blue to green wings, thorax, and head, with a yellow abdomen and legs. There are sometimes red, yellow, or green markings. You may also be able to see red drops of sap attached to their legs.
Blue-green sharpshooter lifecycle
Until recently, only one generation of blue-green sharpshooter appeared each year. Rising temperatures and stressed predator insects are making multiple generations possible. Most sharpshooters overwinter near creeks, becoming active in spring. Eggs are laid just after budbreak. As surrounding vegetation begins to dry up, concentrations of sharpshooters in gardens, vineyards, and orchards increases. Sharpshooters go through complete metamorphosis, frequently leaving pale discarded exoskeletons behind on the underside of leaves. Nymphs and adults feed on nutrient-rich sap throughout the summer, moving back into nearby weeds and vegetation at the end of summer.
Blue-green sharpshooters use vocalization to communicate and to find a mate. Males have 3 distinct calls: a complex mating call, a gulping call, and a chirping call. Females have a call they use to respond to males’ mating calls. The pair sings a type of duet before mating, which is all very nice, but they still spread disease. Because there is no cure for Pierce’s disease, interrupting the disease cycle is the only way to prevent plant loss.
Controlling blue-green sharpshooters
The first step to controlling blue-green sharpshooters is to make sure they are present. This is done with yellow sticky sheets. Sharpshooters are most commonly found in locations with abundant soil moisture and some shade. Unshaded, dry areas and areas of deep shade are less likely habitats for sharpshooters.
You can reduce the chance of infection of Pierce’s disease with these tips:
Famers have found that installing bluebird boxes goes a long way toward reducing blue-green sharpshooter populations. Insecticides aimed at sharpshooters are only marginally effective, while insecticidal soap and horticultural oil provide some control.
Since people first started growing plants for food, we have been battling the pests that eat, damage, or infect those plants.
Initially, those battles were hand-to-hand combat. Pests were removed by hand, chased away, and puzzled over. Then came the age of ‘better living through chemistry’, when powerful concoctions were sprayed willy-nilly, threatening entire species. Now, the pendulum has swung in a new, more balanced direction. That direction is called integrated pest management.
Integrated pest management (IPM) is a program of science-based pest controls with the minimal disruption of natural cycles and least harm to other organisms. Integrated pest management was made a national policy in the U.S. by President Nixon in 1972.
What are pests?
Your younger brother or sister may have been a pest when you were kids, but garden pests never outgrow the potential to cause damage. Garden pests include any organism that can harm or hinder the plants we want to grow. Using this definition, a pest can be disease-carrying bacteria, viruses, or fungi, a plant-eating insect or animal, a competitive weed, destructive soil nematodes, or a neighbor’s cat that thinks your carrot patch is its litter box.
What is IPM?
IPM takes a long view on reducing the negative impact of pests in ways that are sustainable and responsible. An integrated pest management plan has six basic tenets:
Rather than relying on a single method of control, IPM combines these tenets, in the order presented, to reduce the negative impacts associated with killing off pretty much anything. Rather than spraying chemical pesticides and insecticides on your food plants and into the soil and water table, you can work your way through these sustainable practices for surprisingly effective control of most garden pests.
Monitoring for pests
The first step in an IPM program is monitoring. Monitoring involves more than simply looking for bugs. Monitoring for problems begins by arming yourself with factual information about your soil and microclimate. This means sending out a sample for a soil test. Test results will let you know which nutrients are at acceptable, toxic, of deficient levels, along with soil pH, soil organic matter levels, and base saturations. It also means noting sun and wind exposure levels at various locations in your yard, the likelihood of frost damage, drainage problems, and preexisting pest problems. Each of these conditions play powerful roles in keeping plants healthy enough to defend themselves against pests.
After collecting all that information, go outside and start looking for pests. You don’t know what you are up against without looking. You can use pheromone traps and yellow sticky sheets to help collect information of what costs are present. As you see pests, learn to identify them and then read up on them. Learn enough about them to counteract the damage they do without causing undo damage of your own. This is where things like trap crops come in handy.
The next step is to decide just how much damage you are comfortable with. Wiping out entire species is generally not a good plan. Evolution takes time and the balances that are created can be delicate and easily thrown out of whack. Allowing tolerable levels of pests to be present provides food for beneficial insects which will help you fight the battle against those and others pests.
Cultural practices are the way you manage your garden. Do you use overhead watering, which can encourage fungal disease, or do you use soaker hoses? Pruning for proper air flow and good structure go a long way toward pest control. There are several good cultural practices that help your plants stay healthy:
The third plan of action is mechanical controls. Row covers, tree cages, tomato cages, netting, sticky barriers, brassica collars, mulch, shade cloth, tree supports, trellising, and fencing are common mechanical controls that help plants stay healthy. This stage of pest control also includes trapping, hand picking, and soil solarization. Cold frames, greenhouses, and hoophouses also provide mechanical controls that reduce pest damage by making life harder for the pests.
There is an army of beneficial insects ready to help you control pests naturally, if you will only get out of their way. Instead of using chemical pesticides and insecticides, which can kill off beneficial predators and parasites, install insectary plants and provide water to create a welcome habitat for the natural enemies of the pests in your landscape.
Other biological controls include the release of sterile insects (generally performed by government agencies and universities) and introducing other natural predators periodically. Unfortunately, buying ladybugs and other predators rarely works as well as you might hope. They generally don’t stick around. Creating a welcoming environment is far more effective.
Chemical pesticides are used as a last resort. Pesticides should be selected as appropriate for the specific pest being controlled and used in ways to avoid affecting non target organisms.
Whichever chemical controls you use, it is important to switch things up periodically to prevent the likelihood of pest resistance. Pest resistance occurs when an organism develops an immunity toward a treatment, making it necessary to use ever-stronger poisons against them. Insects and pathogens evolve much faster than we do, so there is a limit to what we can tolerate.
Finally, after monitoring the situation and deciding which pests can be tolerated, using good cultural, mechanical, biological controls, and applying only necessary chemical controls, be sure to assess the situation, to make sure the problem is being corrected. If it isn’t, you need to go back and learn more about the pest(s) causing the problem to develop a new plan of action.
Generally speaking, pests appear seasonally and on specific crops. Knowing when to look and where to look can give you a jump-start on controlling the pests that damage your garden plants.
You can help the scientific community by participating in citizen science projects, such s the Big Bug Hunt, where you report insect sightings as you see them. This helps researchers develop better predictions about when pests are likely to appear in your area.
Western grape rootworms are leaf beetles that eat the leaves of grapes, roses, and fireweed in spring and summer. If that weren’t bad enough, their offspring are found underground, chewing up the root system. The combined effect can be devastating.
Western grape rootworm description
These beetles are very small, averaging only 1/7” in length. This works out to 4 or 5 beetles standing end-to-end across a dime.
Unlike their more tan-colored cousins, western grape rootworms are usually black or reddish-brown with dull gray, yellow, or white hairs, and orangish-red antennae. Larvae are 1/4-inch long, C-shaped white grubs. These grubs have 3 pairs of prolegs, a reddish brown head, and black or brown mouthparts. Eggs are laid in clusters on old wood under loose bark.
Male western grape rootworm beetles rub their legs together to attract females, the same way crickets and grasshoppers do each summer.
Damage caused by western grape rootworms
These beetles cut slit-like holes in leaves, shredding them to tatters. The leaves then dry up and die, reducing photosynthesis and food for the plant. Adult beetles may also be found feeding on berries, petioles, and the bark of new shoots. Underground, western grape rootworm larvae feed extensively on the root system and can cause considerable damage.
Controlling western grape rootworms
Since larvae spend most of their year 2-feet underground, control is generally only possible during spring, when larvae and adult beetles move to the surface. Monitor plants for signs of beetle feeding and handpick whenever possible. You can also use sticky barriers to capture beetles moving up and down the trunk.
If you see a tiny beetle playing ‘possum, don’t be fooled. The western grape rootworm beetle uses that trick to avoid being eaten, often falling off a leaf, stiff-legged.
With a name like Asian jumping worms, you might expect colorful, flamboyant gymnastics moving gleefully through the soil, helping your plants grow.
Okay, that was a stretch. And you’d be mostly wrong.
I say mostly because, while not colorful, these worms really can move. Also known as snake worms, crazy worms, and Alabama jumpers, Asian jumping worms writhe violently when disturbed. They can even drop their tail when threatened.
Sadly, instead of helping plants grow, these voracious feeders strip an area of nutrients, destroying the top soil layer, and leaving desolation in their wake. This interrupts thousands of years of evolution and nutrient cycling, threatens biodiversity, and increases erosion.
The invasives mixed bag
Before we get into the Asian jumping worm story, let me remind you that our beloved European nightcrawlers and honey bees are also non-native species. Sometimes invasives can be a good thing. This is not one of those times.
As with many other situations involving invasive anything, the problem lies in imbalances. North American forests and farmlands have evolved, over thousands of years, to use surface plant litter as slow-release food and secure habitat for countless microorganisms, insects, reptiles, amphibians, and other life forms. Asian jumping worms eliminate that layer and they do it very quickly.
What are jumping worms?
Our more sedate earthworms tend to be reddish brown with a raised white or grey partial band part way down the body. That band is called the clitellum. Asian jumping worms, which can range from 3 to 7” long, are grey to dark brown, with a smooth the clitellum that goes all the way around and is closer to the head end.
Also, while shiny, jumping worms do not produce the slime seen on many earthworms. Regardless of how you feel about that slime, it is very useful in creating soil aggregates that allow for the healthy movement of air, water, microorganisms, and roots through the soil. Jumping worms also tend to be more rigid than our squishy earthworms.
There are three species of Asian jumping worm: Amynthas agrestis, A. tokioensis and Metaphire hilgendorfi, with A. agrestis being the most commonly seen. Native to Southeast Asia, jumping worms are believed to have been brought to North America in potted plants, bagged soil, or nursery stock, though we don’t know exactly when or how.
Asian jumping worms have moved quickly westward, in worm terms, over the past 10 years and are now found in Oregon. As you can imagine, these continued movements are not just worms traveling on their own. Asian jumping worms end up in plants, mulch, and soil, on shoes and equipment, in agricultural produce, and in batches of fishing bait. They get transported by us, one gets loose, the problem spreads. It’s easy to do because these jumping worms spend their winters as tiny, pinhead size cocoons, filled with eggs, they reach adulthood twice as fast as our familiar earthworms and red wigglers, reproduce more rapidly, and are more aggressive. They can also thrive in higher densities and eat a wider variety of foods.
The real problem with Asian jumping worms is where and how fast they feed.
Damage caused by Asian jumping worms
Asian jumping worms are too efficient. That may sound like a good thing, but too much of a good thing can be a bad thing. Let me explain.
As earthworms feed on fungi and bacteria that grow on decomposing organic material, they burrow into the soil, excreting castings that are filled with broken down plant and animal material, churning the soil and improving soil structure, soil health, water retention, drainage, and nutrient cycling. Everybody’s happy. Plants and organisms grow. Life goes on.
Asian jumping worms are eating machines, quickly devouring all of the surface material in an area and leaving behind a trail of low-nutrient crumbles prone to serious erosion. Research has shown that jumping worm castes are different from those of other worms. Instead of the soft, brown, crumbly bits of plant food and soil amendment we associate with earthworm castings, Asian jumping worm castings look more like a pile of coffee grounds.
Asian jumping worms process nutrients so rapidly that their feeding releases nutrients faster than plants can absorb them, causing the nutrients to be washed, blown, or leached away. These castings contain important plant nutrients, such as potassium and calcium, and they tend to contain higher levels of heavy metals, such as iron and aluminum. When those crumbles are eroded away, those nutrients are lost. As a result, Asian jumping worm feeding quickly converts healthy, loamy soil in to granular, more sandy soil that tends to be hydrophobic, which means water runs off instead of sticking around long enough for plants to absorb. These invasive worms also push nutrients so deeply into the soil subsurface that many shallow-rooted plants cannot reach those important nutrients, leaving them to starve.
What can you do about jumping worms?
In a word, be diligent. Asian jumping worms generally cannot survive freezing winters, but anything less than that and they can become a serious problem in your yard. You can help prevent the spread of these invasive worms with these handy tips:
Bottom line, earthworms create topsoil while Asian jumping worms destroy it. Of course, that’s an oversimplification, but I want you to understand how important it is that these pests are kept in check.
If you suspect the presences of Asian jumping worms in your garden, conduct a mustard test using these steps:
Basil’s fragrant leaves make it a garden favorite, but there is a new disease on the horizon: basil downy mildew. And warm, moist conditions are all basil downy mildew needs to set up housekeeping on your basil plants.
First seen in Africa, in the 1930’s, basil downy mildew (Peronospora belbahrii) came to the U.S. in 2004 on infected seeds from Italy. By 2008, it had made its way to California and is now a global problem for everyone who enjoys basil and pesto.
Like other downy mildews, basil downy mildew is caused by tiny, algae-like microbes called oomycetes. Oomycetes parasitize vascular plants to complete their life cycle. They do this by collecting on the underside of leaves. From there, these tiny one-celled creatures send out threads that enter the leaf through the stoma and begin propagating. Since the oomycetes cannot pass beyond leaf veins, the damage from each infection is usually contained between leaf veins.
New spores are then released through the stoma, where they fall to soil, waiting to be splashed right back up by rain or irrigation water, or caught on the breeze for a ride to a new host plant. The party responsible for basil downy mildew travels on a variety of surfaces to reach your garden. In addition to water and wind, spores can be carried on garden tools, clothing, transplants, and infected seeds.
So how do you know if your basil plants are infected?
Symptoms of basil downy mildew
Unfortunately, the earliest sign of infection, yellowing leaves, looks a lot like nutritional deficiencies. If you see yellowing between the major leaf veins with dark blotchy areas, take a closer look on the underside of those leaves. If you see purple or gray powdery spores, it is probably basil downy mildew. Those spores are reproductive bodies and each infected leaf is a disease factory.
Once a plant is infected, it is too late. Harvest any healthy leaves and bury the plant under soil or in the compost pile to prevent spores from spreading. Generally speaking, these pathogens will not survive in compost or through winter temperatures. We hope. For now, the basil downy mildew pathogen is under California State quarantine, which means infected plants must be destroyed.
Preventing basil downy mildew
To avoid being part of the problem, be sure to buy only certified disease-free seeds and seedlings, place all new plants in quarantine, and monitor plants closely.
Good air circulation goes a long way toward keeping leaves dry. Dry leaves are not hospitable to this disease, so keep irrigation water at ground level. Skip the watering can. Instead, use a soaker hose or drip system that will prevent spores from splashing up onto the underside of leaves.
At the end of the growing season, cut basil plants off at ground level and compost them completely. Do not leave them in place to harbor disease. This helps break the disease triangle and reduces the chance of things starting up again each spring.
Some research is being done on the effectiveness of spraying basil plants with fixed copper as a preventative, but the results are not yet in.
If you think basil downy mildew has appeared in your garden, please notify your local County Extension Office or Department of Agriculture. You can even use the Basil Downy Mildew Reporting Page to add you contribution to science!
What do peaches and potatoes have in common? The green peach aphid.
Considered the world’s worst disease vector among garden plants, green peach aphids (Myzus persicae) love to feed on peach and potato leaves, along with dozens of other garden plants.
Green peach aphid description
Green peach aphids are generally found in colonies of winged and wingless adults and immature nymphs. Green potato aphids look a lot like potato aphids (Macrosiphum euphorbiae). While potato aphids can be seen throughout the plant, green peach aphids prefer hiding on the underside of leaves.
Adults may be bright or pale green, with a dark patch on the back (dorsum). Nymphs are pale green, yellowish, or pale pink. Eggs are elliptical in shape and only 1/50” long. At first, eggs are green or yellow, but they soon turn black, making them nearly impossible to see. Green peach aphids have a rather bizarre lifecycle that is too complex for this venue. You can read an excellent summary about it at the University of Florida website, if you are interested in that sort of thing.
Damage caused by green peach aphids
Green peach aphids often overwinter in the egg stage on stone fruits, particularly on peach and peach hybrids, though apricot and plum are also favored. In spring, these eggs hatch and nymphs begin feeding on buds, flowers, and new stems. A few generations later, which only takes a month or so, winged adults move to summer feeding areas. It would probably be simpler to list the garden plants that do not attract green peach aphids, but you do need to know where to look for these pests.
Summer feeding can occur on artichoke, asparagus, beans, beets, broccoli, Brussels sprouts, cabbage, carrot, cauliflower, cantaloupe, celery, chili peppers, corn, cucumber, fennel, kale, kohlrabi, turnip, eggplant, lettuce, mustard, okra, parsley, parsnip, peas, peppers, potato, pumpkin, radish, spinach, squash, sunflowers, tomatoes, turnips, watercress, and watermelon.
Aphids prefer feeding on tender new growth. This leads to wilting, water-stress, and stunting. It also generates a lot of honeydew (sugary insect poop), which provides the perfect growth medium for sooty mold. Heavy aphid feeding can weaken a plant to the point of death. The bigger problem, as with nearly all aphid species, is that these pests carry diseases. Green peach aphids may infect plants with a variety of viral diseases, including:
If potato leafroll virus appears in your garden, it is a good idea to remove the infected plant, plus three other plants in every direction, to prevent green peach aphids from spreading the disease even further. This is yet another reason why it is so important to plant certified disease-free plants in the first place. These pests are often found in greenhouses, so placing new plants in quarantine can go a long way toward preventing an infestation. They can also travel on the wind, so it's a constant battle.
Green peach aphid management
The best way to control green peach aphids is to hit them in winter. This means removing overwintering sites, such as infested leaves, spent plant debris, and nearby weeds. Malva is a popular winter wonderland for aphids, so keep that weed away from your peach trees and potato plants. Bindweed, lambsquarters, penny cress, pigweed, sowthistle, tumbleweeds, white goosefoot, and rouge members of the nightshade family can also provide overwintering sites for this pest.
As spring and summer come around, however, you can attract and protect beneficial predators, such as lady bugs, lacewings, parasitic wasps, and syrphid flies, by providing fresh water, planting a variety of insectary plants, and avoiding the use of broad spectrum pesticides. Most chemicals designed to kill aphids cause more harm than help by disrupting the lifecycle of many natural predators. There is also a parasitic fungus (Entomophthora aphidis) that attacks aphids, but you can’t do anything about that one.
Early each June, in northern California, green peach aphids migrate into our gardens. You can prevent a full-blown infestation by monitoring plants on a weekly basis and using a damp rag or paper towel to wipe off colonies before they can really start propagating. A single female, hatched in spring, can reach sexual maturity in only 10 days, creating 20 generations in a single year. By the end of summer, this can result in billions of offspring.
Armillaria root rot is a soil borne that attacks the roots and trunks of many fruit and nut trees. It is also the largest living fungi in the world.
In Oregon’s Malheur National Forest, there is a mushroom colony that covers 2.200 acres. That colony is believed to be a single entity, all growing from the same network of fungal mycelium.
By itself, that's impressive. In your tree, it's a deadly fungal disease.
Trees vulnerable to Armillaria root rot
Also known as honey fungus, shoestring fungus, or oak root fungus, Armillaria root rot (Armillaria mellea) is a deadly disease that infects avocado, cherimoya, cherry, chestnuts, conifers, kiwifruit, kumquat, lemons and other citrus, pomegranate, stone pine, and walnuts, along with the mighty oak. If that weren’t bad enough, trees weakened by Armillaria root rot become more susceptible to serious pests, such as Pacific flathead borers.
Armillaria root rot symptoms
Everything starts out looking fine. Your tree is growing nicely and you suspect nothing. Suddenly, you notice downward cupping leaves, chlorosis (yellowing), dieback of upper limbs, and leaf drop. You may also see a variety of mushrooms growing nearby.
Your tree is dying. Young trees die quickly, while older trees make take longer, but the end result is nearly always the same.
Armillaria root rot diagnosis
If your tree shows the above mentioned symptoms, take a closer look at the base of your tree. You may be able to see fan-shaped fungal growth rising up the trunk from the soil level. Use a sharp knife and cut away a section of bark at the base of the tree, so you can see the cambium layer. If you see white fungal threads (mycelia) and can smell a strong mushroom odor, your tree is in serious trouble. If you see reddish brown streaks or patches, or water-soaked areas, the infection is more likely to be Phytophthora root and crown rot, rather than Armillaria, though that isn't any better news for your tree.
If you have easy access to the tree’s roots, cut one open. Infected roots are darker than normal and have a cottony center. You may also see black rhizomorphs, called ‘shoestrings’, on the surface of infected roots.
How Armillaria spreads
As a soil borne disease, Armillaria mycelia can remain viable in the soil for many years. It isn’t until a healthy root comes into contact with infected wood, roots, stumps, or other wood fragments. Then, the fungus enters the healthy tree and begins to populate the cambium layer, eventually killing the tree. Infected nursery stock can also carry this disease, so always quarantine new plants.
Preventing Armillaria root rot
Good drainage, sunburn protection, and proper (not excessive) irrigation can all help protect your trees against Armillaria root rot. Once infection occurs, the tree should be completely removed and the area should only be planted with crops that are not vulnerable to Alternaria root rot.
Dark brown spots on your tomatoes? It’s probably early blight.
Cool spring temperatures and too much rain or other moisture creates the perfect storm for this fungal disease. The early blight fungus (Alternaria solani) is a disease of the nightshade family, which means your potatoes, eggplants, bell peppers, and chili peppers are equally susceptible, as are other plants in the nightshade family, such as petunias and blue potato bushes. If similar lesions are seen later in the season, it is more likely to be late blight, also known as the dreaded potato blight.
Early blight was once a disease found only on the east side of the Rocky Mountains. Sadly, that is no longer the case. The early blight pathogen is now found everywhere host plants have been grown and can result in up to 30% of your potatoes and 79% of your tomato crop ending up in the trash bin.
Early blight symptoms
Small black or brown spots, usually 1/4 to 1/2 inch in diameter, may appear on fruit, leaves, and stems. These spots may have a concentric rings pattern, or bullseye. Fruit spots are dry, sunken areas, most commonly seen near the calyx end of the fruit. [That’s the flower end, as opposed to the stem end.] Spots on leaves feel leathery. Symptoms are seen on older leaves first. Stem lesions do not have the same circular, bullseye pattern.
In some cases, this pathogen can cause collar rot and damping off, which usually kills seedlings. As the disease progresses, leaf loss can significantly reduce fruit production. Honestly, the fruit that is produced doesn’t look particularly appetizing. Infected potatoes either rot in the ground or in storage.
Early blight lifecycle
Fungal spores overwinter in the soil and on infected fruit and plant debris. Rain and overhead irrigation splash spores onto plants, where they begin reproducing. To reduce the chance of early blight in your garden:
Fixed copper or sulfur sprays can provide fungicidal benefits in heavy infestations. Also, healthy plants are less likely to become infected, so feed and water your plants properly, give them enough space to reach full size, and help them avoid physical injuries, which provide entry points for early blight fungal spores.
Two-spotted spider mites can kill off many of your garden plants as temperatures rise and humidity drops. Before a hot, dry summer kicks in, it’s a good idea to know what to look for.
Two-spotted spider mites (Tetranychus urticae) can become a serious threat to your citrus and other fruit trees, most vegetables, and many ornamentals, such as marigolds, roses, and salvia. Beans, blackberries, blueberries, cucumber, eggplant, lettuce, peas, squash, strawberries, and tomatoes are all favorite foods of the two-spotted spider mite.
Two-spotted spider mite description
As arachnids, all mites have two body segments and eight legs. Two-spotted spider mite eggs are round to spherical, but very difficult to see. Instead, you may see the webbing used to protect those eggs. Colorless larvae, which start out with only six legs, go through two developmental stages to reach greenish-yellow, eight-legged adulthood. This transformation can occur in as little as 5 days, and females can lay 120 eggs in their lifetime, so populations can rapidly explode.
An interesting note, unfertilized eggs hatch into males, while fertilized eggs hatch as females. This is called arrhenotoky.
Males are smaller and have narrower bodies and are more active than females. These close cousins to red mites are greenish-yellow to brown, with two dark spots, and they even have a red winter phase, but you probably won’t be able to see them without a hand lens. [Those dark spots are accumulated body wastes, so they are not always visible.] At only 1/50” long, two-spotted spider mites are easier to find by looking at the damage they cause.
Damage caused by two-spotted spider mites
As sap-sucking pests, similar to citrus mealybugs and citrus bud mites, these mites pierce plant cells and remove the contents. Hidden from view by feeding on the underside of leaves, they often go unnoticed until the damage becomes obvious. Mite feeding causes stippling and bleaching. These damaged areas increase, causing bronzing and early leaf drop. If you look at the underside of these leaves, you will often see the cast-off exoskeletons of mites. You may also see extensive webbing over buds, stems and flowers. Extensive feeding can cause stunting and even plant death.
How to manage two-spotted spider mites
Since two-spotted spider mites feed on such a wide range of plants, they are difficult to control. Mites favor feeding on stressed plants, so proper feeding and irrigation can help your plants seem less appealing to these pests. In addition, you can use these tips to reduce problems caused by two-spotted spider mites:
Predatory mites, such as Phytoseiulus persimilis, ladybugs, minute pirate bugs, and lacewings are all beneficial insects that feed on two-spotted spider mites, so keep you yard hospitable to these helpful predators. Mites are developing resistance to most chemical pesticides, but insecticidal soaps are effective against mites, with horticultural oils (not dormant oils) coming in a close second. These treatments are only affective against the mites that come into contact with it, so repeat treatments are often necessary.
If you have a walnut tree, you should know about walnut scale. Even if you don’t, this is still an interesting read.
Walnut scale insects (Quadraspidiotus juglansregiae) have a unique behavior that makes them particularly fascinating. Like other armored scale insects, females protect themselves under round, dome-shaped covers. But walnut scale takes this concept to a whole new level.
Walnut scale lifecycle
Female walnut scale insects lay eggs in spring. These eggs hatch in only 2 or 3 days. Female crawlers move around a little bit, searching for a good spot to set up household. Once a spot is selected, they begin feeding and start building their protective cover.
Male crawlers wander around, looking for a female. When they find one, they huddle up next to her, tucking themselves under the edge of her ‘skirt’, where they excrete their own elongated scale coverings. This often creates a daisy-shaped cluster of scales.
After these groups mate, those females lay the year’s second batch of eggs. These eggs hatch, usually mid- to late summer, and stay in the crawler stage over winter. In spring, females claim real estate and males emerge with wings, which they use to find a female.
Walnut scale description
Walnut scale coverings start out white. This is called the white cap stage. Then they darken to grey or brown within a week or so. If you lift the covering off the central, round female walnut scale, you would see a yellowish body with indented margins. Other scale insects do not share those characteristics.
Damage caused by walnut scale
Like other scale insects, walnut scales use piercing mouthparts to suck plant juices from the cambium layer of twigs and branches. This weakens the tree, leading to branch dieback, cracked bark, and reduced harvest. Walnut scale feeding also increases the likelihood of canker development and fungal diseases caused by Botryosphaeria.
How to control walnut scale
You can’t control them if you don’t know they are present. Make a point of inspecting your trees regularly for signs of infestation and infection. You can apply sticky barriers near walnut scale adults to capture crawlers, as they emerge. There are many beneficial predators that feed on scale insects. Parasitic wasps, twicestabbed lady beetles, and a tiny black beetle that goes by the name Cybocephalus californicus, in particular, love to feed on walnut scales. Commercial growers apply insecticides during dormancy or when crawlers emerge in spring.
Narrow range oils can also be used, but walnut trees are very sensitive to horticultural oils. Do not use oils on walnut during dormancy, or between bud break and shoot elongation. Oil use at these times can harm your tree. Horticultural oil can be used with caution as buds begin to swell and the tree enters the delayed dormant period. If your walnut tree is water stressed or suffering other forms of stress, do not apply oil. Oils should also never be used when temperatures are above 90°F.
Scale infestations are on the rise. This is believed to be the result of several different factors, including reduced numbers of beneficial insects. Keeping your trees healthy makes them less likely to be harmed by pests such as walnut scale.
Now you know.
You can grow a surprising amount of food in your own yard. Ask me how!
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