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.
California red scale is a citrus pest found throughout California, except in Coachella Valley, where an eradication program is in place. These insects may be tiny, but California red scale is a serious pest of citrus trees.
Like other armored scale insects, California red scale (Aonidiella aurantii) have piercing, filamentous mouthparts that are inserted into stems, fruit, and leaves, and suck life-giving sap from your tree. These particular scale insects prefer lemons, limes, Valencia and Navel oranges.
Red scale lifecycle
You will probably never see a tiny, flying male red scale. They only live for about 6 hours and have only one purpose. The females, however, attach themselves to your citrus trees, where they feed on your tree and give birth to 100 to 150 crawlers. Two or three crawlers are born every day to each female. These crawlers leave to their own feeding site. They can also be blown to nearby trees by the wind, or move from place to place by catching a ride on a bird in a practice known as phoresy - though I don’t know if they do it on purpose. Once they settle on a new location, both males and females begin to grow a waxy dome over themselves. Male covers are more elongated, while female covers are more round. Females molt two more times, while males molt under their first dome four times before taking to the air.
Damage caused by California red scale
Chlorosis, twig and branch dieback, fruit loss, and, in severe cases, tree death can all result from California red scale infestations. This damage most commonly occurs at the end of summer, when trees are water stressed and scale populations are at their peak.
How to control California red scale
Scale insects are naturally protected from pesticides. And California red scale has developed a resistance to many insecticides, so, unless you are a commercial farmer or city government, you do not have access to chemicals powerful enough to kill off California red scale. [And would you really want to spray that stuff on your food?] Keeping your trees healthy with regular, deep summer irrigation will reduce water stress. And avoiding the use of broad spectrum insecticides will allow natural predators to do their thing against scale populations. Parasitic wasps and several varieties of lady beetles can provide significant control of scale insects.
Because ants, dust, and poor air flow all make it more difficult for these beneficial predators to find and catch their prey, be sure to prune for good air flow, wrap tree trunks with sticky barriers to block ants, and give your trees an occasional rinse with the hose during the dustier parts of summer. In winter, apply dormant oils.
The next time you go water your citrus trees, take a closer look to see if California red scale has made an appearance.
Beans are easy to grow, they help improve soil structure, and they add nitrogen to the soil. They can also become infected with bean yellow mosaic.
There are three different bean mosaic diseases that occur here in California: bean common mosaic, cucumber mosaic, and bean yellow mosaic. These are all viral diseases that cause downward cupping and wrinkling of leaves, especially as leaves get older, along with the telltale mosaic pattern. Bean leaves that develop a bright yellow mosaic pattern may be infected with the bean yellow mosaic virus. There are several strains of bean yellow mosaic (BYM). In addition to beans, bean yellow mosaic can infect peas, peanuts, soybeans, black locust, and fenugreek.
Bean yellow mosaic symptoms
You can differentiate between bean yellow and the other mosaic infections because bean yellow has a yellow mosaic, rather than a light or dark green mosaic. Bean yellow mosaic also exhibits as bright yellow spots on leaves. Plants infected at an early stage of development can become severely stunted and should be removed from the garden and tossed in the trash.
Bean yellow mosaic lifecycle
The bean yellow mosaic pathogen is called, very unimaginatively, bean yellow mosaic virus, or BYMV, for short. This poorly named virus commonly overwinters in legume crops, such as fava beans, alfalfa, clovers, and vetch, as well as in certain weeds and gladiolus. The virus moves from plant to plant in aphids. When an aphid feeds on an infected plant, it becomes a carrier, transporting the disease to every plant it feeds on from that point forward.
Since resistant cultivars are not yet available, these tips may help prevent bean yellow mosaic in your garden:
Finally, if you see an infected plant, trash it.
Onions, chives, and garlic plants with pink roots are not happy.
This disease rarely causes significant problems in garlic, but it can shrink your onion and chive harvest by quite a bit.
The pink root pathogen
Pink root is caused by a fungi called Phoma terrestris. Phoma terrestris is nearly always present in the soil and it pretty much lasts forever. Normally, it causes no serious problems. If your onion plants are weakened by drought, insufficient or excessive fertilizer, water stress, insect feeding, compacted soil, or any number of other less than ideal circumstances, your onions may become susceptible. This pathogen thrives in temperatures between 75° and 85°F and can be moved around the garden by splashing rain or water, and on tools.
Symptoms of pink root
Aside from the obviously pink roots, plants infected with this fungal disease also exhibit roots that darken to red, purple, and, eventually, black. These roots shrivel up and die. These discolorations may move up into the bulb. This infection leads to stunting, but it rarely kills the plant. This disease looks a lot like fusarium wilt.
Preventing and controlling pink root
Keeping plants healthy and employing crop rotation are the two best ways to avoid pink root from causing too many problems. A note on crop rotation: do not follow a cereal crop with onions, as it creates conditions that promote this particular pathogen. Severe infestations can be eliminated with soil solarization, but that’s a pretty drastic measure for the home gardener.
If you see pink, purple, or black shriveled roots on your onions, try growing them in a different area, in fresh soil, and be sure to feed, weed, and water them properly, and protect them from insects, to ensure that they stay healthy enough to protect themselves.
If the lower limbs on your almond tree are turning brown, you have a problem.
While it is normal for the leaves on lower limbs to turn yellow because of being shaded by the limbs and leaves above, lower limb dieback (LLDB) goes much farther and can result in the death of your tree. LLDB first appeared in 2005. Scientists do not yet know what causes this condition, but learning how to avoid it can save your trees.
Symptoms of lower limb dieback
This disease normally appears in late April or May, on trees that are 7 or 8 years old. It starts out with the leaves on lower limbs yellowing, and then turning brown. Eventually, the entire branch becomes girdled by cankers and dies, right up to where it attaches to larger, scaffold branches, or the trunk. If you scrape the bark off of an affected limb, you will see brown spots in the wood. [Sorry, but I couldn't find an image I could use.]
Some almond varieties are more susceptible to lower limb dieback than others. Padre almonds are the most likely to get this disease, with Butte being a close second. Almond varieties that show some resistance to lower limb dieback include Aldrich, Carmel, Fritz, Mission, NePlus Ultra, Nonpareil, Sonora, and Wood Colony. If you are shopping for an almond bare root tree, you might consider one of these more resilient varieties.
Preventing lower limb dieback
While research is currently underway, it is believed that overly wet soil, low light levels, and root exposure to herbicides or excessive fertilizer may weaken trees, making them vulnerable to whatever it is that causes this problem. This is just the opposite of shade tree decline, in which severe drought slowly kills a mature tree, with the early symptoms being a lack of leaf cover in the upper canopy, or crown, of the tree.
Lower limb dieback occurs most often in years with a cool, wet spring, followed by high temperatures. Soil compaction and low infiltration rates are also believed to play a role in lower leaf dieback. Trees with hull rot also appear to be more likely to develop this condition. In this case, fumaric acid and other toxins are believed to accumulate in larger branches when multiple spurs are infected. In this weakened state, these trees are also more likely to be infected by fungal opportunists, such as Botryosphaeria dothidea and Phomopsis amygdali. Phomopsis amygdali causes the stoma to stay open, desiccating the tree. Botryosphaeria dothidea causes cankers on a wide variety of plants.
Keeping your trees healthy is the best way to prevent lower limb dieback. This means proper irrigation, reasonable applications of fertilizer (only after a soil test shows a need for it), and control of scale insects, which may play a role in the spread of this disease. Fixed copper, sulfur, and fungicide treatments have not been shown to be effective.
If you love your trees (or your blueberries), be on the lookout for Asian longhorned beetles.
Native to China, Japan, and Korea, these invasive, wood boring beetles love to hitch overseas rides on wood-related packing materials: shavings, pallets, that sort of thing. In 1996, an infestation of Asian longhorned beetles (Anoplophora glabripennis) was discovered in Brooklyn. Two years later, a second sighting occurred in Chicago. Then, they were found in New York, New Jersey, and Illinois, where they are responsible for the removal of thousands of trees. These pests have already cost state and federal government (our tax dollars) over $168 million and that number looks to rise exponentially, now that they have expanded their range into California and Washington.
The potential economic impact was first estimated to be more than $41 billion. That number has increased to nearly $700 billion, and that’s before you factor in the damage to breakfast morale when the northeast’s sugar maples are attacked! Eradication efforts got into affect each time these invasive pests are found, sometimes successfully, sometimes not. The U.S. Customs Department is working hard to halt the importation of these pests. Eradication in the U.S. is still possible, but it’s an uphill battle. And they need our help.
Asian longhorned beetle identification
Asian longhorned beetles (ALBs), also known as starry sky or sky beetles, are easy to identify. Approximately one inch wide and and an inch-and-a-half long, they are shiny black with 20 white spots on each wing cover, and they feature an impressive set of black and white banded antennae. They have long, whitish-blue feet and large mandibles. Larvae are large and cream colored.
Adult female beetles chew pits into wood and then deposit their eggs into those pits, one at a time. She can lay up to 90 eggs in just a few weeks.
When the eggs hatch, larvae tunnel deep into the tree (where they are safe from predators and pesticides), leaving behind a trail of frass. Deep within the tree, the larvae go through several instars before entering a pupal stage.
As adults, they tunnel out of the tree, leaving 3/8-inch exit holes along trunks and branches. Piles of frass can be seen at the base of infected trees and in branch crotches. Branch dieback and leaf wilting are early signs of infestation. The egg sites and larval feeding make the trees susceptible to many other pests and diseases, as well as more vulnerable to damage from heavy winds. Sap is often seen oozing from wounds. This larval tunneling causes extensive damage and girdling, making the wood unusable and eventually killing the tree. Infested trees must be removed and destroyed by trained professionals. Do not attempt this yourself.
Trees susceptible to ALB
Many popular hardwood trees are vulnerable to ALB infestation. These trees include alder, ash, beech, birch, boxelder, elm, hackberry, hornbeam, horse chestnut, mimosa, planes, poplar, sycamore, and willow. And blueberries! And members of the Prunus family, which includes apricots, peaches, nectarines, cherries, and almonds! We do not yet know what the impact will be on California’s native hardwood trees.
Experts predict that this pest could cause more damage than gypsy moths, Dutch elm disease, and chestnut blight combined, destroyed millions of acres of trees across the country, in parks, along streets, in backyards, and in agriculture. Dead and dying trees are more likely to cause fires and they are unable to support the biodiversity that keeps a region healthy. If you consider all the wood-based products we use every day, ALB could cause many prices to increase significantly. All because of an insect.
If you see it, catch it! Report it!
If you see an Asian longhorned beetle, catch it. Period. Just do it. They don't bite or sting. While they can fly, they don’t do it very well and only for short distances. You can do this.
Your efforts could save millions of trees and billions of dollars. Seriously.
Put your captive in a glass jar [they chew through trees, remember?] and place it in the freezer. Be sure to label the jar with where you found it (GPS position, if possible), the date you found it, and your contact information. These reports are critical if we are to protect our trees. Using this information, experts can create quarantine zones and implement eradication programs most effectively.
If you live in California, call the CDFA hotline at 1-800-491-1899. In fact, put the number in your phone now, so you’ll have it if you ever need it. I did. If you live outside of California, report it to your state’s Department of Agriculture. Together, we can save millions of trees.
Pierce’s disease is becoming a major threat to grape vines.
The bacteria responsible for Pierce’s disease, Xylella fastidiosa, was first seen on grapes in Southern California in the late 1800’s, when it was called Anaheim vine disease. By the 1930’s and 1940’s, it had spread to California’s Central Valley. By the late 1990’s, the disease had spread to several California counties. This increase is believed to be, in part, a result of warmer temperatures allowing more of the bacteria to survive the winter. According to CABI, Pierce’s disease is now found throughout the Americas, and in Italy, Iran, and Taiwan.
Pierce’s disease is carried by sap-feeding insects. Most commonly, this means sharpshooters, such as blue-green and glassy-winged sharpshooters. [Did you know that sharpshooters can consume hundreds, or even thousands, of times their body weight in sap in their short lives?] Spittlebugs have also been found to carry this disease. Whichever insect is chewing on your grape vines, they inject the bacteria into the vine’s vascular bundle as they feed, making them a disease vector. These bacterium then live and reproduce in the xylem, clogging the flow of nutrients and water through the plant.
Pierce’s disease can occur on a large number of weedy and ornamental crops, such as wild grape, California blackberry, periwinkle, stinging nettle, eucalyptus, live oaks, blue elderberry, and mugwort. These plants are not affected by the bacteria that cause disease in grapes. But they do provide a transitionary location for the insects that carry the disease to your garden.
Symptoms of Pierce’s disease
Infected plants exhibit leaf scorching and stunting. These symptoms start out as slightly yellow or red leaf margins (edges) of white or red grape varieties, respectively. Concentric areas of infected leaves may dry up. You may also see ‘matchstick’ petioles, ‘green islands’ on mature brown stems, raisined clusters of fruit, and dieback. These symptoms do not normally appear until spring, after temperatures are above 65°F.
There is no cure for Pierce’s disease. In some cases, the disease will disappear on its own and we don’t yet know how or why. It seems to be a function of temperature, the timing of the initial infection, and the variety of plant being infected. Generally speaking, a late season infection, one that occurs after June 1st, has a 95% chance of recovery. Water stressed plants are more likely to succumb to the infection. If a plant becomes infected early in the season, the bacteria have time to become firmly established. Once that happens, you will ultimately have to remove the vine completely.
Pierce’s disease control and prevention
This disease triangle consists of the host plant, the feeding insect carrier, and the disease-causing bacteria. Break the connection between any one of those three and you can reduce the chances of disease. The easiest ways to prevent Pierce’s disease is to keep host weeds out of the area and treat for the sap-sucking insect pests. Since insect-eating birds, such as bluebirds, along with several predatory insects, love to eat sharpshooters, keep your garden welcoming to these natural helpers.
Monitor your plants for signs of Pierce’s disease so that you can act quickly, reducing the spread of the disease. Most of the vector insects are low fliers, so physical barriers can be used to quarantine potentially infected plants. During the dormant season, remove any vines that have been infected for more than one year. They will not recover and they will spread the disease to other plants as vector insects feed on them and then move to nearby plants for more feeding.
Moles are creatures of darkness. They almost never leave their tunnels. Often falsely blamed for plant damage, moles are primarily insect eaters.
Differences between moles and pocket gophers
Many people assume that moles and voles (also known as pocket gophers) are related. They are not. Voles are plant eating rodents, while moles are primarily insect-eating members of the Scapanus species, more closely related to shrews. Crescent-shaped mounds with closed holes indicate the presence of pocket gophers. Pocket gopher populations can lead to girdled trees, slope erosion, and dead plants. Moles, on the other hand, have round mounds which may have open or closed holes, and long surface ridges from their shallow tunnels are often visible. Moles normally feed on worms, grubs, insects, and other invertebrates. Moles will occasionally eat mice, shrews, and nuts. Your average mole will eat 40 pounds of insects each year.
Moles are rather funny looking. They have stubby, hairless tails, cylindrical bodies (usually 5 to 7 inches long), pointed snouts, and short, webbed hands and feet. They don’t see very well because their eyes are covered with skin, and you can’t see their ears. Mole fur, however, is quite thick and velvety, and moleskin is the stuff of hiking blister legends. There are 42 mole species worldwide, 7 of which live in North America, and 4 species found in California:
Moles like their privacy. Unless it’s the breeding season, you will only find one mole per tunnel system. Moles have one litter each year, usually with 3 or 4 young, in spring.
Moles create an extensive system of both deep and shallow tunnels. The deeper tunnels are their permanent housing, with separate rooms for food storage, sleeping, and rearing young. Tunnels are usually 2 inches in diameter and found 8 to 12 inches below the soil surface. The shallow tunnels are for hunting out grubs, worms, centipedes, and other soil dwelling creatures. It is the shallow tunnels that cause most of the problems associated with moles. As they burrow under the surface of the soil, looking for their supper, moles often dislodge smaller plants and expose root systems to the air, drying them out. If you want a lawn that looks like a putting green, moles are not your friends.
If you cannot tolerate moles in your garden or landscape, trapping will be necessary. While there are dozens of repellants, scaring devices, home remedies, and plants that claim to offend moles, research has not shown that any of these methods actually work. The only exception is castor oil solutions, which have been shown effective on eastern moles. Flooding tunnels wastes water and does not rid an area of moles. [They’ve dealt with floods for far longer than we have been gardening.]
Trapping always works. Underground harpoon traps and scissor-jaw traps are the most effective methods. Of course, this means dealing with a dead mole and a messy trap. Some new mole baits are showing limited effectiveness, but then you have to worry about children, pets, and local wildlife also suffering a horrible death. Plus, if your landscape was appealing to a mole before, it probably will be again, to a different mole. If you have valuable plants that need protection against moles, you can install a hardware cloth barrier 2-feet into the ground, with a 6-inch lip bent at a 90° angle away from the plant to thwart mole digging.
Moles are fascinating creatures. Some of the more interesting mole facts include:
If you can tolerate moles, they actually provide many benefits to the garden and landscape.
Did you know that mole saliva contains toxins that paralyze earthworms? Researchers have found underground storage spaces filled with thousands of paralyzed earthworms, for later eating.
Now you know.
Kuno scale is a pest of plum and other stone fruits.
Like other soft scale, kuno scale (Eulecanium kunoensis) is a sap-sucking insect that hides under a dome-shaped protective barrier. Unlike armored scales, which can be separated from their dome, kuno and other soft scales are attached to their dome.
Kuno scale lifecycle
Eggs hatch under their mother in spring. These first instar nymphs are called ‘crawlers’ because they crawl away from her and find a place to feed on leaves throughout the summer, going through multiple instars as they feed. In fall, mature nymphs find a hiding place on twigs just before leaf fall. These nymphs overwinter on twigs and reach adulthood in spring, just in time to lay more eggs.
Kuno scale damage
As a sap-sucking insect, Kuno scale sucks phloem sap from twigs and leaves. While it prefers plum trees, Kuno scale can also be found on peach, cherry, nectarine, apricot, and almond, as well as rose, walnut, and pyracantha. These pests can populate an area so quickly, that it can seem as though they appeared overnight. Plants may appear water stressed. Heavy infestations can lead to twig dieback and premature leaf drop. Also, Kuno scale produces a lot of honeydew (sugary poop). Honeydew is the perfect growth medium for sooty mold. It also attracts ants, which will protect and farm Kuno scale. If you see ant trails on your plum tree, make a point of finding out where they are going in your tree.
Kuno scale control
Since ants protect Kuno scale from natural predators, blocking ants from getting up in your trees is the easiest control measure. To do this, simply wrap the tree trunk with a sticky barrier. You can also apply horticultural oil to twigs and the ends of branches just as buds are swelling, in spring. You can also try drenching the undersides of leaves in early summer, but this is tricky, because it’s not a good idea to spray dormant plum or walnut trees with oil, especially during periods of drought.
And, let’s face it, spraying the underside of leaves is a royal pain.
What happened? Yesterday, your plants looked lovely. Today, several leaves are rolled up, looking like green cigars. What did this, is it a problem, and what can you do?
Physiological causes of leafroll
Leafroll (or leaf roll) can indicate environmental problems, such as water stress, too much nitrogen, drought, excessive heat, root damage, severe pruning, overspray, or transplant shock. Moderate upward cupping is usually first seen in lower leaves, spreading inward and upward, as the cupping progresses into a full blown leafroll. Leaves affected by these physiological conditions will thicken and become leathery as the plant tries to protect itself. This response is common to members of the nightshade family. Luckily, it has very little impact on fruit production or quality of tomato, eggplant, or pepper plants.
Leafroll is also a family of viral diseases that can infect many different plant species. These viruses enter plant tissue as their insect carriers feed. These carriers are normally aphids, mealybugs, and soft scale insects. The leafroll virus can also be spread through infected scion wood. Once infected, vascular bundles become clogged as the viruses reproduce in the nutrient-rich phloem. This reduces water and nutrient flow within the plant, causing stunting, delayed maturity, reduced crop size, chlorosis, necrosis, leaf curling, and leafroll.
There are three major types of leafroll that warrant concern:
Because these viruses can spread rapidly, over relatively great distances, close monitoring and control are in everyone’s best interest. Once a plant is infected with one of the leafroll viruses, it should be removed and destroyed. There is no cure or treatment. When shopping for plants, choose resistant varieties, and be sure to control carrier pests, to reduce the likelihood of leafroll affecting your garden.
Cottony cushion scale inspires a certain measure of fascination. One look at these intricate insects, and you’re sure to want to learn more.
Cottony cushion scale (Icerya purchasi) are soft scale insects. Like other scale insects, their lifecycle touches on the bizarre. But before we get started, take a look at this photo and see if you can figure out what, exactly, is insect and what might be something else.
Cottony cushion scale lifecycle
Cottony cushion scale insects start out as eggs. The eggs hatch out into crawlers. First stage (instar) crawlers are red, with black legs and antennae. These newlings make their way to nearby leaf veins, where they will begin producing their telltale white, cottony secretion. As they grow, these tiny pests will shed their outgrown skins (molt) and grow a bigger protective coating. Second instar crawlers make their way to twigs and leaves. Third instars prefer branches. Adults are usually found on branches and tree trunks.
Nearly every cottony cushion scale insect you see will be female, and they tend to form colonies. The males have red wings, but are really too small to see. Females can produce young with or without the help of a male. She will lay 600 to 800 eggs. Before she does, she will carry them around in a white, fluted sac that can be 2 or 3 times the length of her body. Most people mistake this egg sac for the insect’s body. Did you?
Damage caused by cottony cushion scale
Scale insects feed by inserting tiny, straw-like structures into bark, leaves, or fruit. One attached, they will suck the sugary juices out of fruit, or mainline sap directly from the xylem. This high sugar diet results in the insects pooping out honeydew, an equally sweet, high nutrient discharge that ants and fungi just love. Heavy infestations can lead to overall stress and loss of vigor, branch dieback, and defoliation of affected areas. Very often, it is the presence of sooty mold and heavy ant traffic that will first cue you to the presence of scale insects.
How to control cottony cushion scale
Natural predators do a much better job of controlling these pests than we do. Specifically, the vedalia beetle (Rodolia cardinalis) and the parasitic fly (Cryptochaetum iceryae) feed only on this particular pest and nothing else. Normally, these two beneficial insects are all that is needed to control a cottony cushion scale infestation. Unfortunately, dust, ants, and insecticides can interrupt that assistance.
'Ants will actively protect and farm scale insects. You can remove that protection by attaching sticky barriers around the trunks of trees. Chemical controls are not generally effective against cottony cushion scale insects (regardless of what they say on the label).
Take a look at your trees on a regular basis to see if cottony cushion or other scale insects have set up shop in your garden or foodscape.
With a name like bottom rot, you just know it isn’t going to end well.
Bottom rot is a fungal disease of lettuce and other leaf vegetables, caused by the Rhizoctonia solani fungi. This is the same fungi that causes damping off disease. These fungi live in the soil and are a big problem in warm, moist conditions.
Plants affected by bottom rot
In addition to lettuce, bottom rot can wipe out your Chinese cabbage, escarole, broccoli, radish, collards, Brussels sprouts, cauliflower, and turnip crops. The Rhizoctonia solani fungus also attacks potatoes, onions, beans, and corn.
Symptoms of bottom rot
At first, all you may see is some wilting of outer leaves. Closer inspection will show reddish-brown, sunken lesions on the midribs of leaves that are touching the soil. Brown or white fungal tissue may be visible and lesions may discharge a light brown ooze. Leaf spots and brown lumpy bits may also be present on the plant and in nearby soil. The fungus grows inward, toward the center of the head or body of the plant. The damaged plant tissue then becomes susceptible to other soft rots, causing total collapse of the plant.
Controlling bottom rot
Fungicides are ineffective against bottom rot, so prevention is your only course pf action. These tips will help protect your leafy bottoms:
As with all bottoms, keep them dry and they will be happy.
Earworms. Those songs that get caught in our mind and play over and over and over… These are not those earworms, but they can be just as annoying.
You don’t grow corn, you say? Don’t think that your garden plants are off the hook, just yet. The larval form of the corn earworm (Helicoverpa zea) goes by several names, such as cotton bollworm and tomato fruitworm. Tomato?!!? Yes, this is the dreaded tomato fruitworm. And these innocuous-looking moths can migrate as far as 400 km (or nearly 250 miles) to get at many favorite garden plants, including melon, beans, spinach, soybeans, peas, okra, squash, and sweet potato.
Corn earworm description
Adult moths are a little more than an inch across, and pale tan to light brown. The front wings can have various markings, and the hind wings are dirty white with a dark grey band at the tip. These moths are often found early in the worming, crawling in the lawn, as they get warm enough to start moving. [If seen, stomp on them!]
Eggs are spherical and slightly flattened, with ribbed lines running from end to end. They look a lot like cabbage looper eggs.
Larva start out a creamy white color, with a dark head. They have distinct, sparse hairs (tubercles) with dark spots. As the larva feed, the color changes to greenish-yellow to nearly black, depending on the food supply. Fine white lines can be seen along the body. The hairs and the spots remain. On some individuals, stubby bristles or spines can be seen with a hand lens.
Corn earworm lifecycle
Tiny pale green eggs turn creamy white, and then yellowish or grey. They are laid singly on upper and lower surfaces of leaves, leaf hairs, and on corn silk. They develop a reddish-brown ring within 24 hours. Eggs darken in color just before hatching, usually less than 72 hours after being laid. Larvae go through 4 to 6 instars, or developmental stages, all the while feeding heavily. In fact, corn earworm larvae are a brutal bunch. In addition to attacking your tomatoes, they will also attack and feed on other insets, especially butterfly and moth larvae, including their own kind. After 12 to 16 days, the larvae enter a pupal stage. If the soil is moist enough and temperatures are warm enough, an adult moth will emerge to begin the cycle again. A single adult female corn earworm moth can lay up to 2,500 eggs in her lifetime.
Corn earworm damage
Adult moths feed on nectar and pollen, but they are not the problem. It is the larval stage that causes all the damage. Being polyphagous, corn earworm larva eat many different things. And you won’t even know they are there until it is too late, unless you look very closely. The larvae feed inside the fruit, so it’s not until you cut into it or take a bite that the pest is discovered. Yuck! Also, larvae may move from fruit to fruit, leaving behind a wake of squishy, watery digested insides filled with frass and shed skins.
Controlling corn earworms
Protected within fruit, corn earworms are tough to get rid of. Making matters worse, these pests have developed a resistance to our chemical arsenal. This means that integrated pest management must be used instead. Integrated pest management (IPM) is an approach that uses many sustainable methods to provide the least amount of damage. IPM practices that reduce the damage caused by corn earworms include:
*Egg parasitism appears as tiny holes in the shell, and the eggs are often flatter than normal. This is because parasites have laid their eggs in the corn earworm eggs, and the parasite babies eat the moth larva.
Farmers also use commercially available parasites and deep ploughing to combat the corn earworm, but these methods are not relevant to the home gardener. The parasites (Trichogramma pretiosum) are not available over-the-counter, and deep ploughing damages the soil microorganisms that help our plants thrive.
Monitoring plants regularly for signs of eggs of young larvae can help you protect your tomato, corn and other garden plants.
Did you know that plants use the saliva of their attackers to figure out which defense chemicals to produce?
Young sunflowers track the sun across the sky, reaching new heights with every passing day - except, sometimes they don’t. Sometimes, a small injury can become infected and a black rot spreads around the base of the flower, finally engulfing it in a black goo that dries and hardens into a smelly shadow of what might have been. What causes this, and can it be prevented?
Head rot, also known as pin rot, is a disease of sunflowers, lettuce, and broccoli, caused by the Pectobacterium carotovorum, subsp. carotovorum and P. atrosepticum bacteria.
Symptoms of bacterial head rot
The first symptom of bacterial head rot is nothing more than a small, brown, greasy or water soaked looking area on the surface of a cluster of unopened flowers or leaves. These lesions are usually seen at the sight of mechanical injury caused by bird and insect feeding, hail, or falling twigs. Bacteria enter the damaged tissue and that’s where the infection begins.
Affected areas turn from brown to black as the infection spreads into surrounding plant tissue. There is a distinctly bad smell, similar to rotten potatoes, but it is rare for secondary fungal growths to occur when head rot is present. If the bad smell is absent and other bacterial and fungal infections are present, the infection is more likely to be caused by Alternaria fungi.
Bacterial head rot prevention and control
Cool winter and spring temperatures combined with prolonged periods of rain, fog, and dew provide the perfect medium for bacterial head rot pathogens. This means good air circulation between plants can go a long way toward preventing this disease. That’s a good thing, because chemical sprays and other treatments have not been consistently effective in preventing bacterial head rot.
The best way to prevent this problem in your garden is to start with resistant cultivars, such as broccoli with dome-shaped heads, space plants properly, and avoid overhead watering.
Whether you call them June beetles, Junebugs, or May beetles, these small, reddish-brown, clumsy flyers can be annoying. They get their name because of when they emerge. In the Bay Area, these pests come out in June. Other places get them in May, hence the difference.
Adult Junebugs feed on leaves. They fly in from weedy areas to feed at night. During the day, they tend to hunker down in a shady spot or burrow into the soil until dusk. The damage they cause is similar to Fuller rose beetles, earwigs, and snails. Grasshoppers and caterpillars may also cause similar damage. The only way to be sure is to catch them in the act.
The more insidious damage occurs underground as Junebug grubs feed on the roots of your lawn, especially ryegrass and bluegrass. Symptoms of infestation include brown, dying patches. If things get really bad, you can actually roll up patches of turf because it is no longer attached to the ground! Large numbers of Junebugs can defoliate a young tree in a matter of days. This is especially true for avocado trees, which may need to be protected with netting.
Commercial growers use blacklight traps when Junebug infestations cause too much damage. This is not recommended for home growers because the trap may attract more Junebugs than it captures. Heavy infestations are treated with an application of entomopathogenic nematodes. For the most part, home gardeners can’t do anything besides hand pick them whenever they are seen. Junebugs really are clumsy flyers, so it’s not hard to catch them. They are attracted to lights at night and often bump into windows and screens. When I catch them, I feed them to my chickens, who are very happy to help with Junebug control.
If you have children, you can always gift them a butterfly net and offer a bounty on every Junebug they catch!
Lack of vigor or sudden death by the phytophthora root and crown rot is nearly always caused by too much water.
The name is from the Greek phytón (plant) and phthorá (destruction), so the name Phytophthora means the plant-destroyer. There are different types of Phytophthora that attack different host plants.
What is Phytophthora root and crown rot?
Phytophthora [fie-TOF-ther-uh ] is a family of water molds, called oomycetes. Oomycetes fall somewhere between fungi and algae in the web of life. There are many different types of Phytophthora molds. They generally attack stems and roots. Stem damage normally occurs at or just above the crown, where the stem meets the roots, at the soil line, though it can also occur elsewhere on a plant. These molds cause many different plant diseases, including sudden oak death, potato blight, damping-off disease, and crown rot. Phytophthora root and crown rot, in particular, can kill a tree or shrub if the soil remains wet for too long, or when planted too deeply. [Moist soil around the trunk is never a good idea.]
Nearly all fruit and nut trees, including cherries and kiwifruit, are susceptible to Phytophthora root and crown rot. But so are alfalfa, and members of the nightshade and cabbage families. This means tomatoes, eggplant, and potatoes are vulnerable, as are kale, cauliflower, Brussels sprouts, broccoli, kohlrabi, horseradish, cabbage, collards, turnips, rutabagas, radishes, bok choy, and mustard. And all because of too much water.
Symptoms of Phytophthora root and crown rot
Plants affected by Phytophthora root and crown rot look drought stressed. This is particularly unfortunate because the natural response is to provide more water - the last thing you want to do when Phytophthora is present. Symptoms normally start in just one branch or area of the tree or shrub before spreading to the rest of the plant. Leaves may turn purple or reddish. Sudden wilting and plant death may occur when the basal stem or crown are attacked, or the mold may attack the root system, causing plants to linger poorly for years before dying.
Symptoms can vary greatly, depending on the type and age of plant, the plant’s genetic resistance to infection and overall health, as well as soil temperatures and moisture levels, but you will probably see darkened areas of the bark around the crown and upper roots of infected plants. You may also see dark sap or gum oozing from damaged areas. Using a sharp knife, you can cut away an area of bark. Infected trees will show reddish brown streaks or patches. Water-soaked areas on roots may also be visible. If you also see white threads between the bark and the inner layer, or around the roots, the infection is from Armillaria root rot, rather than Phytophthora.
Preventing Phytophthora root and crown rot infestation
Proper water management is the best way to prevent and control Phytophthora root and crown rot. Never allow standing water to remain around tree and shrub trunks. Also, don’t let sprinklers hit tree trunks. These other tips can help you manage Phytophthora in your garden or landscape:
You may be able to maintain an infected plant, with proper irrigation and good cultural practices, but it will never be the same. Phytophthora can stay in the soil for many years, so prevention is far easier than control.
NOTE: One new-to-us variety, Phytophthora tentaculata, is on the Dept. of Agriculture’s watch list. If it appears in your garden or landscape, please contact your local Cooperative Extension Office right away. They may have helpful advice that will protect your plants, and they need to know how far this disease is spreading.
If older leaves on cucumber, melon, or squash are turning yellow and leathery, the plants may be infected with cucurbit aphid-borne yellows.
This viral disease is transmitted by the cucurbit aphid-borne yellows luteovirus (CABYV). Luteoviruses are a genus of viruses that use plants as hosts, and are transmitted by aphids.
Symptoms of aphid borne yellow virus
Early symptoms are chlorotic (yellow) areas on lower leaves. These spots expand to include the entire leaf, leaving the larger veins bright green. The affected areas become leathery and brittle. Stunting and fruit drop are common as the plant struggles. Before genetic testing, this condition was attributed to plant aging (senescence), nutrient deficiencies, or other diseases, such as cucurbit yellow stunting disorder.
How the disease is spread
As the name suggests, this disease is spread by aphids. As aphids pierce plant tissue to feed on sap in the xylem, they infect the plants they eat. Once infected, the aphid will continue to spread the disease as it feeds. This disease can also be spread to lettuces, beets, and several weeds.
Controlling cucurbit aphid borne yellows
There is no way to control the virus, but you can reduce the presence of aphids in your garden with these tips:
Infected plants should be removed and destroyed, to prevent the disease from spreading to nearby plants.
Crawlers with no legs, a species with no males, and broody females who keep thousands of eggs warm and safe - what are these garden pests? Citricola scale.
Native to Japan and southern China, citricola scale is currently found in California, Arizona, and Maryland, and in several other countries. Also known as grey citrus scale, citricola scale (Coccus pseudomagnoliarum) can be found feeding on citrus and pomegranate twigs in spring and early summer, and immature scale insects can be found feeding on the underside of leaves in late summer and fall. In addition to feeding on pomegranate, lemon, lime, orange, and grapefruit, these sap-sucking pests also feed on elm, bay laurel, hackberry, and oleander.
Citricola scale lifecycle
There are only female citricola scale insects. They reproduce asexually (parthenogenesis). Each female can produce between 1,000 and 5,000 eggs during the summer. She will keep her eggs safe under her body until they hatch out in to crawlers, usually from June through August. That may sound like a crazy broody season, but citricola scale eggs hatch after only 2 or 3 days. The babies that come out of those eggs are called crawlers. The name crawlers sounds a little misleading because they don’t look as though they could do anything. But they do. These crawlers move to a good feeding site, attach themselves, becoming sessile (fixed), and feed until they molt into second instar nymphs, usually around November. These nymphs produce a lot of honeydew and are often protected and farmed by ants.
Citricola scale description
Citricola scale start out as a yellow, oval egg. First instar crawlers are oval, flat, and nearly translucent. Sometimes they are yellowish-green to brown. Second instars are mottled brown. Citricola scale adults are one-quarter of an inch long, grey, oval, and flat. Well, slightly convex, but flat enough. They can be difficult to see because they start taking on the color of the twig to which they are attached. Citricola scale are often confused with brown soft scale.
Citricola scale or brown soft scale?
Citricola scale tends to have only one or two generations each year, while brown soft scale can have multiple generations going at any one time. This means that citricola scale insects you see will nearly always be at the same life stage, while brown soft scale specimens may be at any life stage. Also, adult citricola insects are grey, while brown soft scale adults are brown or yellow.
Damage caused by citricola scale
Underneath those tiny domes of protection, citricola scale attach themselves to stems and leaves of citrus and pomegranate. They pierce the surface to reach the phloem, to siphon away valuable nutrients and sugary sap, weakening the tree. And they poop. This poop, called honeydew, contains a lot of sugar, and it creates the perfect growing medium for sooty mold fungus. Sooty mold blocks photosynthesis, further reducing your tree’s vigor. Citricola scale can reduce flowering and fruit production. During heavy infestations, twigs can be killed by citricola scale.
How to control citricola scale
Regularly monitoring citrus and pomegranate trees for these pests is your first line of defense. If you notice ant trails or sooty mold, take a closer look at twigs and leaves for signs of scale. Since ants protect these pests, you can eliminate that protection, making the citricola scale more vulnerable, by wrapping the tree’s trunk with a sticky barrier. Also, there are naturally occurring parasitic wasps that will control citricola scale insects (as long as you do not apply broad spectrum pesticides). Applying dormant oil in winter can also help reduce citricola scale populations.
Research has shown that 40% of citricola scale in San Joaquin Valley are resistant to organophosphates. It is believed that there is also a cross-resistance to malathion and carbaryl. This looks to be yet another example of chemical pesticides actually making the pests stronger, as we add more poisons to the environment and our food chain.
Bottom line, to control citricola scale on your pomegranate and citrus trees, inspect twigs very closely in April through June, and then look at the underside of leaves in late July. These pests can then be flicked off the leaf or stem with your fingernail.
Relatively new to the United States, the European pepper moth is poised to cause significant damage to gardens and commercial agriculture.
Each time an invasive plant or pest is brought into an area, there’s no telling what might happen. Resident predators or local diseases may make short work of the interloper. Then again, the insurgent may find a rich, predator-free environment perfectly suited to a population explosion. We don’t know, yet, which way things will go for the European pepper moth, but it’s probably a good idea to know what we’re up against, just in case.
Plants damaged by European pepper moths
It’s difficult to get excited about something that hasn’t directly caused damage in your garden, so here’s the list of just some of the plants harmed by the pepper moth:
If that list doesn’t get your attention, I don’t know what will. Also on the list of favorite foods are roses, African daisies, azaleas, orchids, and many other flowers and ornamentals.
Damage caused by pepper moths
The moths themselves don’t cause any harm to plants. Like other moths and butterflies, it is the larval stage, or caterpillar, that feeds voraciously on leaves, roots, buds, fruit, and flowers. Pepper moth caterpillars may girdle young seedlings, causing what looks like damping off disease. Later larval instars may burrow into stems unnoticed, until the the stem collapses. Leaf damage starts out looking crescent-shaped, similar to damage by the Fuller rose beetle, or round, but the entire leaf ends up being eaten. Feeding is normally seen in the lower leaves, then moving up the plant until it is completed defoliated. Feeding on the roots can interfere with a plant’s overall health and vigor and feeding on buds, flowers, and fruit, well, there goes your crop. So, what does the European pepper moth look like?
Pepper moth identification and lifecycle
Also known as the European marsh pyralid, adult pepper moths (Duponchelia fovealis) have a wingspan of approximately three-quarters of an inch wide and a body less than half an inch long. The forewings are grayish-brown with two distinct yellowish-white transverse lines. The outermost line has a “finger” that points backwards.
At rest, the pepper moth holds its wings out to either side in a triangular shape. The head, body, and antennae are olive brown, and the abdomen features cream-colored rings. Legs are pale brown. Both sexes have long abdomens, but the male’s is unusually long, and he holds his curved upwards at rest.
Pepper moth eggs are really tiny (1/50 of an inch). The eggs start out whitish green or pale yellow, which turn pink, then red, as they mature. Just before hatching, the egg turns brown. Eggs are laid singly or in batches on the underside of leaves, normally near the leaf veins. Eggs can also be found on stems, at the crown, in the soil, on the tops of leaves, and even on greenhouse walls and furnishings.
Caterpillars start out salmon pink with a black head, and a line of grey and brown spots along each side. Some sections may feature a double row of dots. Using a hand lens, you can see a hair emerging from each spot. Just behind the head, you can also see a hard plate, which is the same color as the head. As they grow, the pink turns a dirty white color that can range from pure white to pale or even dark brown, depending on which of your garden plants they are eating.
These caterpillars can grow to over an inch long. Just before pupating, they may lose their spots. Pepper moth caterpillars create a cocoon out of soil, frass, and webbing. The cocoon can be 1/2 to 3/4 of an inch long.
A single female pepper moth can lay up to 200 eggs. Under optimal conditions (temperatures around 68°F), those eggs can hatch in 4 to 9 days. Over the next 3 or 4 weeks, the caterpillars feed ravenously. Then, pupation takes 1 or 2 weeks. Adult moths live to mate and procreate for a week or two and the whole process beings again. In greenhouse environments, 8 or 9 generations a year can occur. That ends up being a lot of pepper moths! In areas like California, where cold winters rarely occur, this pest could prove to be devastating.
These moths have an unusual flight pattern - both males and females fly fast and low, with their abdomens curved upwards. You may see individual moths, or they may swarm. Pepper moth caterpillars are photophobic, which means they do not like light. If you shine a flashlight on a pepper moth caterpillar, it will become agitated, moving rapidly side to side.
How the pepper moth got here
Pepper moths have been present in Europe for a very long time. In 1984, it became a greenhouse pest in Europe and Canada for the cut flower, vegetable, and aquatic plant industries. It is believed to have been spread globally through infested plants from those products. [Yet another example of why it is so important to quarantine new plants!] By 1988, the pepper moth had developed a taste for strawberries. In 2004, the pepper moth was found on begonia plants in San Diego, CA. It was again detected in 2010. By 2011, the European pepper moth had been found in seventeen California counties, as well as in fourteen other states. Departments of Agriculture in each of these states is monitoring for this pest. If you think you see one, please try to capture it and report it to your local County Extension Office.
Native to Europe, the pepper moth moth prefers fresh and saltwater marshes. You might think, since you don’t have a marsh in your garden, that your plants are safe. But most of us have a creek, reservoir, or some other body of water nearby, and a pepper moth can fly up to 62 miles.
Also, check the debris (detritus) that falls from container plants and around the base of the containers for signs of eggs or pupae. You can also lightly brush the soil around potentially infested plants for signs of pupae and cocoons.
How to control European pepper moths
At this point, the best biological controls are to spray Bacillus thuringiensis (Bt) or beneficial nematodes (Heterorhabditis bacteriophora and Steinernema spp.). Rove beetles seem to enjoy feeding on pepper moth eggs and caterpillars, and certain predatory mites and wasps also parasitize these pests, so avoid using broad-spectrum pesticides. Since pepper moths prefer moist, hidden areas, keeping your garden tidy and free of overly moist areas can reduce the chance of perpetuating the species in your neck of the woods.
Again, because this is a relatively new pest, with the potential for significant long term damage, if you see one, please report it. If you live in California, you can call 1-800-491-1899. If you live elsewhere, contact your local Department of Agriculture for reporting instructions. Knowing where this pest is can help in its eradication, which is really good news for your tomatoes, basil, figs, and cucumbers!
You can grow a surprising amount of food in your own yard. Ask me how!