Four-lined plant bugs are sap suckers. This means they have piercing mouthparts, similar to their cousins, tarnished plant bugs and capsid bugs. Small populations can be ignored, but things can get out of hand. Four-lined plant bugs (Poecilocapsus lineatus) are traditionally found east of the Rocky Mountains, but that can always change. Four-lined plant bug identification Four-lined plant bugs look like small beetles, but they lack the characteristic hardened wing covers. They are greenish-yellow with four distinct black stripes running the length of their wings. The head is orangish-brown, with prominent red eyes, and they average ¼” long or a little more. Newly hatched nymphs are bright red with black wing pads. If you flip one of those nymphs over, you’ll see black spots on the abdomen. As they mature, nymphs turn more orange, and a stripe develops on the wing pads. Damage caused by four-lined plant bugs Adults and nymphs feed on basil, cucumber, currants, gooseberry, lavender, mint, oregano, peppers, and sage. They also suck the vital fluids from several flowers and woody shrubs, including azalea, butterfly bush, dogwood, geraniums, Shasta daisy, and zinnia. As they pierce plant cells and siphon out sugary liquids, dark, round, sunken spots appear. Those spots range from 1/8” to 1/16” in diameter. Those spots may turn black or translucent. After a few weeks, the dead plant tissue falls away, leaving holes in leaves. These holes are commonly mistaken for leaf spot disease. If leaf holes have discolored edges, they are more likely to be bacterial or fungal disease than insect feeding. Distorted growing tips may also occur. Four-lined plant bug lifecycle
Four-lined plant bug nymphs emerge in late spring and start feeding on the upper side of leaves. One month later, they molt and become adults. Those adults continue eating as they look for a mate. Females then cut 2” vertical slits into stems where they lay six or more banana-shaped eggs. Adult feeding continues through mid-summer. The next spring, those eggs hatch, and the cycle continues. Four-lined plant bug management Unless the infestation is severe, you don’t need to do anything about four-lined plant bugs. Monitor your plants for signs of infestation as you work in the garden. Don’t be surprised if one of these pests falls to the ground if you surprise them. They tend to panic that way, even though they can fly. They are also known to try hiding from us behind stems as we pass by. And they move quickly. If four-lined plant bug infestations become troublesome in your landscape, you can reduce their numbers by removing the aboveground portion of host plants in autumn and tossing them in the compost pile. Composting destroys many eggs before they have a chance to hatch. Treat severe nymph infestations with insecticidal soap or neem oil. These treatments aren’t very effective against adults. I have no idea why. Tattered leaves, distorted flowers, and corky fruit may indicate capsid bugs. Capsid bug identification There are several capsid bug species, but they all have one thing in common: a triangle on their back. Capsid bugs can be green or brown and up to ¼” long. They fold their wings over the abdomen. The 2/3 of the wings closest to the body are darker and thicker-looking. The outer third is translucent, showing a diamond-shaped area on the insect’s rear end. Nymphs are pale green and wingless. Some of the more common capsid bug species include:
Capsid bug hosts Capsid bugs feed on many different flowers, including butterfly bush, chrysanthemums, clematis, dahlia, fuchsia, hydrangea, roses, and salvia. They can also be found on apples, beans, and pears. Some capsid bugs are predators. Capsid bug damage Early capsid bug damage is easy to overlook. What starts as several small leaf holes can transform into something that looks like gale force shredding. Leaves growing near shoot tips may also be misshapen with several small, brown-edged holes. Flowers often become distorted. Apples and pears develop corky growths where capsid bugs fed on them during their early development. These bits can be cut off. The rest of the fruit is fine. Capsid bug lifecycle Capsid bugs are true bugs, which means they have mouthparts designed for piercing and sucking. These pests are active in late spring through summer. They lay their eggs in the bark of twigs and branches. Those eggs hatch in spring. Except for the tarnish bug, which overwinters as an adult. Depending on the species, there can be one or two generations each year. Capsid bug management
Minor capsid bug infestations can be ignored. The threat of capsid bug feeding can be reduced by planting resistant cultivars. Capsid bug management starts with monitoring susceptible plants, starting in spring, and removing weeds from around those plants. At the end of the growing season, remove plant debris from around these plants, as well. This eliminates hiding and overwintering places for capsid bugs. Birds and ground beetles eat capsid bugs, so making the garden safe and appealing for them will help. Severe infestations can be treated with summer oils, neem oil, or pyrethrum [not pyrethroids]. It would be nice to think of spotted lanternflies as Asian equivalents to our gentle fireflies of summer evening fun, but that would be a mistake. According to Penn State, lanternflies “could be the most destructive species in 150 years.” Native to China and India, invasive spotted lanternflies (Lycorma delicatula) were first detected in the U.S. in 2014. But it appears they snuck in on shipments of stone, woody plants, firewood, wood products, landscaping materials, and outdoor furniture two or three years before that. [Why in the world we are shipping stones from China is beyond me…] Today, spotted lanternflies occur in several states, and they threaten gardens and farms everywhere. There are also serious concerns about our nation’s forests. Crops vulnerable to spotted lanternflies include apple, cherry, chestnut, grape, hops, nectarine, peach, pear, plum, and walnut. Vulnerable ornamentals include birch, maple, pine, poplar, and rose. Its favorite host is the tree-of-heaven (Ailanthus altissima), also known as Chinese sumac, and varnish tree (because of its stinky odor). There may be more plants at risk. We don’t know yet. What we do know is this—we need to report these pests every time. Let’s learn how. Spotted Lanternfly identification As far as bugs go, spotted lanternflies are rather pretty. They are large, mothlike bugs, approximately one inch long and an inch-and-a-half wide. Adults have a black head and grayish-brown forewings with black spots. The plump abdomen is yellowish with black and white stripes. If you see one in flight, you’ll see that they have red underwings and a white triangle in the middle of the wing. Their hindwings have a brick-and-mortar pattern around the edge of the wings. Spotted lanternfly lifecycle Yellowish-brown eggs are laid in inch-long, rectangular masses on stones, smooth-barked trees, or other vertical surfaces. These egg masses are covered with a gray or yellowish-brown waxy coating and are referred to as egg cases. Each cluster contains 30–50 eggs. In spring, the eggs start to hatch. Wingless nymphs go through several developmental stages, or instars, before reaching adulthood. The first instar is black with white spots. As they develop, red spots become visible. In the final instar, the upper body is red, and you can see red wing pads if you look closely. These spotted lanternfly nymphs crawl or hop to feed on a wider variety of plants than adults. I guess as they mature, their taste buds change. By midsummer, adults are actively seeking mates and wreaking havoc in gardens, fields, and orchards. While lanternflies can fly, they seem to prefer jumping. Eggs are laid starting in autumn and ending as winter arrives. Late season eggs overwinter unseen, and the cycle begins again in spring.
Because this pest is new on the scene, there is a lot we don’t know. While spotted lanternflies have natural enemies in China, that may not be the case elsewhere. At this point, the Pennsylvania Department of Agriculture makes the following recommendations:
There may still be time to eradicate spotted lanternflies from North America, but only if we all keep our eyes open and report any sightings. I can’t stress this enough: if you see a spotted lanternfly, catch it, kill it, and report it to your local County Extension Office or Master Gardeners. Bright yellow, red, or purple leaves may indicate beet western yellows, though this plant disease is not limited to beets or the west. Beet western yellows virus is responsible for significant losses in many global crops. Unfortunately, free-to-use photos are not as readily available. You can search online to see what this disease looks like. Beet western yellows host plants This disease occurs on over 250 plant species, including beets, broccoli, cabbage, canola, cauliflower, chickpeas, endive, escarole, fava beans, lentils, lettuce, mustard, peas, peppers, radish, spinach, sunflowers, tomatoes, turnips, and oilseed rape. Oilseed rape is a member of the cabbage family grown for its oily seeds and as food for livestock. It can also occur on annual phlox, bee’s friend, false flax, and lupine. Weeds that harbor beet western yellows include chickweed, common groundsel, prickly lettuce, little mallow, shepherd’s purse, sowthistles, and pennycress. [Even though it is a weed, pennycress is commonly used to salvage toxic soil through phytoremediation.] Beet western yellows virus symptoms
Symptoms of beet western yellows infection vary depending on the affected species and the virus strain, making diagnosis tricky. Most plants infected with BWYV don’t show any signs at first. Then red, blue, purple, or black discolorations that start at the tips and edges of leaves appear. Eventually, the entire leaf turns bright yellow or orange. Petioles and veins remain green or may be pale. Infected leaves feel thick and brittle, and they may curl upward. Stunting is common, and leaf crinkling may occur. These symptoms look similar to iron or nitrogen deficiencies or chemical overspray. Beet western yellows virus management Aphids spread beet western yellows. Green peach and wheat aphids are the biggest culprits, though other aphid species are involved. So, the best way to prevent and manage beet western yellows is to control aphids and eliminate rouge host plants. Also known as turnip yellows and turnip mild yellows, some cultivars are resistant to this disease. Look for the letters TuYV, BWYV, and TuMYV on plant labels. Buying resistant plants makes your job a lot easier. Avoid planting too early in a season, as this can make plants more vulnerable to beet western yellows. Toss infected plants in the trash. There are no chemical controls for viruses (yet). Asian bean thrips were first seen on US soil in March 2020, in Florida. Native to tropical Asia, this pest now ranges from Japan to Australia. And in March of 2021, it was found in Central America, in Belize. It’s probably only a matter of time until it spreads to our gardens, so let’s see what we’re up against. Asian bean thrips damage Asian bean thrips (Megalurothrips usitatus) suck the sap out of snap bean, cowpea, lima bean, peanut, and soybean plants. And potatoes. They also feed directly on host plants. This feeding usually begins in the flowers. Pods and growing tips become deformed and twisted, with streaks of russeted reddish-brown where thrips feeding has occurred. Heavy infestations can cause stunting, wilting, and poor pod set. In China, Asian bean thrips are responsible for crop losses of 30% to 100%. Asian bean thrips identification
To me, Asian bean thrips look like hoverflies with pointy rear ends. They are very small. You could almost fit 10 females across the face of an American dime. Males are only half that size. Size isn’t the only difference. Females are black, with yellow or white bands. Their wings are banded, too. Males are yellow, with a similar but less defined banding pattern. Both males and females have black antennae with white bands. Larvae start yellow but turn red as they near adulthood. Asian bean thrips lifecycle These pests love warm weather and they can complete their lifecycle in as little as 10 days. Eggs are inserted into flowers, leaves, and pods. After hatching, larvae go through two molts over 2 or 3 days before dropping to the ground to pupate. Pupae seem to prefer moist, sandy soil, so they probably won’t feel welcome on my sun-scorched clay, but I’ll still keep a lookout. Just in case. Adult Asian bean thrips feed on pollen, mate, and lay eggs. If no mate is available, they can reproduce without them. This ability is called parthenogenesis and it is why aphid populations can seem to explode overnight. I can only imagine that Asian bean thrips populations can do the same thing. Asian bean thrips management Since this invasive pest is new to North America, we’re not really sure what we’re up against. Many beneficial insects eat thrips, but we don’t know their efforts will be enough. We’re not even sure if those garden helpers like the taste of Asian bean thrips. All we can do is hope. Actually, we can also remove plant debris once a crop has finished its cycle. Adding that plant material to the compost pile may help reduce hiding places for this new pest. Since thrips, as a group, are known to develop resistance to pesticides rather quickly, chemical sprays are not recommended. My guess is that mechanical control methods, such as diatomaceous earth (DE) and sticky barriers may help. They can’t hurt. If you think you have Asian bean thrips in your garden, try to catch one or take a picture and reach out to your local Master Gardeners, County Extension Office, or Department of Agriculture. Those groups work hard to protect our gardens from invasive pests, and we can help them with any information we might have. Chubby, round peas tearing through your garden without their pods is not pea streak, but it does conjure a cute mental image.
Unfortunately, there isn’t anything cute about pea streak virus (PeSV). Aphids carrying this viral disease spread it as they feed. The virus responsible for pea streak also causes chickpea wilt. Pea streak symptoms Stems of infected plants develop dark brown, gray, or purple longitudinal streaks. These streaks are similar to those caused by alfalfa mosaic and bean yellow mosaic. Infected plants produce deformed pods that have sunken areas. The pods do not fill out, and many leaves wither and die. Dieback starts at the growing tips and moves toward the center of the plant. Pea streak management There are no chemical treatments for pea streak. All you can do for infected plants is remove them and toss them in the trash. You can reduce the likelihood of pea streak in your garden by starting with certified disease-free seeds and seedlings and removing potential hideouts. Aphids infected with the pea streak virus often hide in alfalfa, clover, and other perennial legumes. Bean plants can be surprisingly prolific, and the fresh, crisp beans are a treat. Except sometimes things go wrong. Sometimes, bean plants turn yellow. It is normal to see lower, older leaves turn yellow and fall off. When entire plants start turning yellow, there's a problem. Bean leafroll virus (BLRV) goes by many other names: chickpea stunt virus, pea leafroll virus, legume yellows virus, and pea yellow top virus are just a few. Bean leafroll is a luteovirus infection spread by aphids. And this luteovirus attacks more than just peas and beans. Once found only in peas and beans, bean leafroll has spread to include alfalfa, chickpeas, lentils, soybeans, and many other legumes. It can also occur in clover and vetch. Bean leafroll virus symptoms
Plants infected with bean leafroll turn yellow, and the leaves curl. This chlorosis occurs between the leaf veins. Stunting is common. These symptoms are similar to beet western yellows virus (BWYV) and nutrient stress. Symptoms can vary between species. In addition to these symptoms, these species-specific symptoms may occur:
There can be a 50% to 90% reduction in pod production due to bean leafroll. In some cases, symptoms may appear and then fade away, creating a problem since the plant is still infected, and any aphids that feed on it can then spread the disease to neighboring legumes. Bean leafroll virus management The best way to reduce the chance of bean leafroll from occurring in your garden is to control aphids —easier said than done, I know. While you can dislodge aphids with a strong spray from your garden hose, not all plants take kindly to that treatment. Neem oil and insecticidal soaps are organic methods of aphid control. Removing other host plants, such as burr medic and subterranean clover, can help reduce the spread of this disease. Since aphids and aphid eggs are brought into your landscape on other plants, putting new plants into quarantine is always a good idea. There is no treatment for the bean leafroll virus. Remove infected plants and throw them in the garbage. Watch for resistant varieties being made available. They will have BLRV somewhere on the label. Finally, you can break this disease cycle by rotating your legumes with cereal crops, such as barley, corn, millet, or oats. There are two types of torus in the plant world. One is related to flowers, and the other is a donut-shaped plug that protects plants when they cavitate. Xylem torus The donut-shaped plug variety occurs within the xylem. The xylem is part of the vascular bundle that pulls water from the ground. The torus found within the xylem protects plants from cavitation. Cavitation occurs when the water pressure within the plant is greater than the atmospheric pressure outside the plant. You can hear it happening to trees in summer. It sounds like a large crack. Cavitation causes sap to vaporize, creating embolisms. The torus, held within a pit called the torus-margo structure, acts as a plug. This plug reduces the spread of the embolism. Flowering plant torus The place where a stem meets a flower is called the torus, or receptacle. The torus is the thickened part of a stem from which flowers emerge. Accessory fruits, such as apples and strawberries, grow from the torus. And it is the way you can tell blackberries from raspberries! That mammoth sunflower head? It’s a torus, too. Types of flowers The torus is found at, below, or surrounding a plant’s reproductive organs, depending on the species. Flowers can be hypogynous, perigynous, or epigynous. Don’t let the words scare you off. The -gynous part of these words means it refers to the Lady Parts of your plant. Stamens and petals are below the ovaries (or gynoecium) of hypogynous flowers. They are at the same level in perigynous flowers. The ovary is enclosed in the torus of epigynous flowers, with the petals and other parts above. You can use this information to help identify plants and win at Scrabble. Raspberry or blackberry? Do you know how to tell blackberries and raspberries apart? It’s not the color. There are black raspberries and red blackberries. The only way to tell the difference between blackberries and raspberries is to look at the way the fruit comes away from the torus. If the torus comes with the fruit, it is a blackberry. If the torus breaks away from the fruit, it is a raspberry.
Now you know. I was so inspired by Linda King’s guest post, Gardening With Nature, that I decided to transform my backyard lawn into a meadow, as well. Living in California, the first, most obvious reason for shifting a lawn to anything else is water conservation, but there are several other reasons to let nature take its course. Within reason. For many years I thought California was called the Golden State because of the gold mining. It ends up that the name refers to the hillsides turning a golden brown as everything dies in the scorching heat. My lawn was no exception. My normal summer landscape is green where I water it and brown where I don’t. Until July. By that time, most of the lawn is brown no matter what we do. We made every attempt to make our lawn look like a golf course. In California, that’s pretty unreasonable when you consider how much water a lawn takes. No matter what we did, the scorching summer sun would burn our green grass to a crisp. We watered. We edged and weed-whacked. We mowed. We aerated. We altered the pH and added missing soil amendments after a lab-based soil test told me my soil had no iron and too much of everything else. For 2–4 weeks of the rainy season, we have a beautiful lawn. That’s in February. The rest of the year has been a struggle. After reading Linda’s post, I decided what the heck. We stopped mowing. We stopped edging. We pretty much left it alone. What happened surprised us. Before I tell you what happened, let’s find out more about meadows. What is a meadow? Meadows are open habitats that feature grasses, herbs, and other non-woody plants. There can be occasional trees or shrubs, but the main idea is an open field. Traditionally meadows were used to grow hay for livestock. The word meadow comes to us from the Old English mǣd, which came from the Germanic word for mow. Returning to our open field concept, meadows feature a variety of plants. This means there can be all sorts of flowers, seeds, and vegetation occurring at the same time, changing with the seasons. This makes food and habitat available to many amphibians, birds, insects, and reptiles that see lawns as desolate, unforgiving landscapes. Types of meadows I never gave it much thought before. It ends up that there are different kinds of meadows. They can be agricultural, transitional, perpetual, or urban. Agricultural meadows are those we mentioned earlier that are allowed to grow on their own to produce hay for livestock. Agricultural meadows are similar to pastures except that pastures are grazed during the summer and meadows are not. Transitional meadows are more of the wild and woolly type. They are not mowed or grazed. They are just left to flower and go to seed. Transitional meadows generally do not last long. Perpetual meadows occur naturally in a variety of environments. Alpine, coastal, desert, prairie, and wetlands are the primary types but there are others. Perpetual meadows reach a point of balance, an equilibrium that we can rarely replicate. Which leads us to urban meadows. Urban meadows are the ones we create. Urban meadows are gaining in popularity as we learn more about the importance of biodiversity and least harm to the environment. As honey bee and monarch butterfly populations decline, many other creatures are at risk due to habitat loss. Urban meadows allow pockets of natural habitat to co-exist along with our driveways, air-conditioners, and patio furniture. My meadow I live across the street from a park. This means seeds (and trash) are blowing in all the time. I used to see those seeds as weed sources. Now I recognize that they are the plants that grow in my yard without any help. In less than two weeks, seed heads have started appearing in what used to be my lawn. Goldfinches, Black Phoebes, California Towhees, and other birds I have yet to identify are now visiting my yard regularly. There are more butterflies, lacewings, and hoverflies, too. Hiding under a self-watering container now lives a tiny lizard I affectionately refer to as Little Buddy. Little Buddy is the offspring of an alligator lizard that lives near one of my raised beds. I hope they stay. The grass that was struggling is now 4” tall and still green. It’s even putting out seeds of its own. There are still brown patches but I expect they will be filled with herbaceous plants without any effort on my part at all. That doesn’t mean I’m completely off the hook by having a meadow. Urban meadows may not require watering, fertilizing, mowing, or edging, but you do need to be vigilant about invasive plants, unwanted weeds, such as foxtails, and disease. Instead of a manicured (temporary) lawn, I now have a softer, richer environment that features more variety and takes less work. I’ll probably toss out some native flower seeds just to see what happens. Instead of working my lawn, I can now sit back and enjoy watching my meadow.
Thanks, Linda! Pepper mild mottle virus (PMMoV) and pepper mottle (PepMoV or PeMV) are not the same diseases. The pepper mild mottle virus is related to the tomato mosaic virus. Unlike pepper mottle, pepper mild mottle does not affect eggplant or tomatoes. It is a peppers-only disease (so far). Pepper mild mottle symptoms Like many other diseases, pepper mild mottle causes stunting and chlorosis, or yellowing of the leaves. It also causes distorted and lumpy fruit, leaf curling, and streaking. These symptoms will vary depending on the species and cultivar. Pepper mild mottle management
The virus that causes pepper mild mottle occurs around the world. It is the most abundant RNA virus found, I beg your pardon, in human feces. It ends up that we are the Number One carriers of this disease. Just as livestock manure can carry many pathogens, such as E. coli, our waste can, too. This virus also moves around on our clothing, tools, and skin. There is some suspicion that this virus can also cause disease in people, but more research is needed. Whether it hurts us or not, it can devastate your pepper plants. This pathogen thrives in heat and humidity, making it a common problem in greenhouse environments. The viruses can enter plants through wounds and other damaged areas. This disease is highly contagious in the pepper world. And it remains viable on tools, containers, structures, and plant debris for a long time. Remove any plants infected with pepper mild mottle and throw them in the trash. Do not add them to the compost pile or burn them. These viruses are so rugged that they can travel on smoke! And wash your hands. Commercial growers used to apply methyl bromide as a pre-plant treatment. Most countries have banned that nasty chemical. One Japanese study demonstrated that soil that contains a lot of humus is less likely to harbor the pepper mottle virus, so keep mulching and composting. Crop rotation is a good idea, too. The best way to prevent this problem is to use certified disease-free seeds and seedlings. Pepper mottle affects more than peppers. This viral disease infects eggplants, groundcherries, potatoes, tomatillos, and tomatoes. Especially tomatoes. First identified in an Arizona Tabasco pepper in 1969, pepper mottle is a Potyvirus similar to potato virus (PVY). Pepper mottle now occurs in several states and countries. Also known as chili mottle virus and pepper mottle potyvirus, this is not the same disease as pepper mild mottle.
Pepper mottle symptoms Pepper model symptoms vary by the species infected and the age of the plant at the time of infection. Initially, peppers will show vein clearing, which shifts to dark vein banding, mottling, crinkled leaves, and deformed fruit. Tomatoes have similar leaf and stem symptoms. The fruit ripens unevenly with green, orange, and yellow areas that never fully ripen. Infected plants are stunted and produce significantly less fruit. Diagnosis can be difficult because pepper mottle mimics cucumber mosaic and often occurs as other infections appear. Pepper mottle management Aphids carry the pepper mottle virus. Those aphids are likely to hide out in weeds from the nightshade family. The virus can also be spread mechanically by working with an infected plant and then moving to a healthy plant. To reduce the chance of pepper mottle in your garden, remove Datura and other nightshade weeds and any rouge tomatoes. [I know it’s hard to get rid of volunteer tomato plants. But they often harbor diseases, so add them to the compost pile and focus on the ones you planted on purpose.] Garden tools can carry the virus, so sanitize them between plants whenever the disease is suspected. Bathroom cleaners work well. And control aphid populations as well as you can with horticultural oils and insecticidal soaps. Invest in certified pest- and disease-free plants when shopping for seeds and seedlings. Doing so can save you time and effort later in the growing season and in future years. Some pests and diseases can stick around for a very long time. Look for resistant varieties with PepMoV or PeMV on the plant labels. Yellow, orange, or green shoulders on tomatoes indicate a common, preventable disorder. Yellow shoulder, also known as greenback and green shoulder, appears as discolored areas on the tops of tomatoes. Unfortunately, these discolorations enter the fruit as well. Fruit affected by yellow shoulder tends to be hard and white, not exactly what you expect from a sun-ripened tomato. Despite what everyone says, extreme sunlight is not what causes yellow shoulder, though it will cause sunscald if there isn’t enough leaf cover.
When scientists tried to figure out yellow shoulder, they discovered the red, neatly arranged cells found in healthy tomatoes were smaller and erratic. The chlorophyll in these deformed cells failed to turn red, which is bad news in the world of tomato growers, so they set out to find out what was going on. What causes yellow shoulder? I would love to say that the solution is simple. Most garden gossip says that high heat and too much sunlight cause yellow shoulder, but that is false. Research has demonstrated it takes insufficient potassium, too much magnesium relative to calcium, and a pH above 6.7 to trigger yellow shoulder. Lab-based soil tests can give you this kind of information. Luckily, those tests cost about the same as a large bag of fertilizer and provide a wealth of information. In case you hadn’t noticed, I recommended a soil test every 3-5 years. Now, back to your tomatoes. Preventing yellow shoulder A soil pH of 6.4 to 6.7 can help prevent yellow shoulder. Plants can absorb many more nutrients when the soil pH is between 6.2 and 6.5. And this is probably where the extreme sunlight and heat myth comes in. When plants are too hot or have insufficient water, they become less able to absorb nutrients. blossom end rot works the same way in many cases. There’s probably enough calcium in the soil but not enough water in the plant to move the calcium around. Yellow shoulder also occurs when temperatures get too low for the same reason. Maintaining a magnesium/calcium ratio of 1:6 is good, but 1:4 is ideal. Too much calcium or magnesium in the soil can trigger yellow shoulder. [I bet you never thought gardening included being a chemist! You may want to read up on Mulder’s chart to see how intricately these chemicals interact. It makes me realize high school chemistry class could have been much more interesting than it was.] Ideally, potassium levels of 144 ppm are best at the seedling stage and then 350 ppm as the plant starts fruiting. Since this disorder starts developing as soon as fruit appears, adding amendments later in the season does not help. Researchers are developing tomato cultivars less prone to yellow shoulder, but that takes time. Until then, get your soil tested, water your tomatoes regularly, and aim to keep your soil pH within a healthy range. Whiteflies are common greenhouse pests, but they can cause surprising problems in the garden, as well. Silverleaf whiteflies (Bemisia argentifolli, also B. tabaci biotype B) feed on many garden plants. Alfalfa, beans, broccoli, cabbage, cantaloupe, citrus, eggplant, grapes, lettuce, melons, peppers, potatoes, squash, sweet potatoes, tomatoes, and watermelon are all plants that silverleaf whiteflies use as food. These pests hide and feed on the underside of leaves.
Silverleaf whitefly damage Whiteflies are sapsuckers. They have piercing mouthparts which they insert into leaves and fruit to suck out the sap. This feeding leaves a severe mottling or silvering on the leaves of many plants in the cabbage, squash, and nightshade families. This feeding creates points of entry for diseases such as squash vein yellowing. It also allows whiteflies to “plant” misinformation into their hosts, making life easier for these pests. Whiteflies carry viruses that cause plants to defend themselves against the viruses rather than the whiteflies. As plants defend themselves against the viruses, they release chemicals that tell neighboring plants to protect themselves against the same viruses. This means the plants are too busy to protect themselves against the whiteflies. You will rarely see any feeding damage on the leaves of tomato plants. Instead, the fruit will look very strange. What starts out looking like tomato gray wall evolves into longitudinal green or yellow stripes that never ripen. If you cut the fruit open, you will see that this uneven ripening affects the entire tomato. Squash and other crops will look bleached. Silverleaf whitefly management
If you live in an area with cold winters, the weather should wipe out your silverleaf whitefly problem. Of course, they’ll be back in the spring. If whiteflies are in your garden, you can protect your plants by helping out natural enemies, such as big-eyed bugs, lacewing larvae, and ladybugs. You can also use row covers and crop rotation. Harvesting as soon as crops are ready and applying insecticidal soap or neem oil, as needed, will also help. Whiteflies are resistant to most insecticides. Commercial tomato growers use trap crops to lure silverleaf whiteflies away from their tomato plants. It ends up that squash plants are the trap crop of choice, so you may want to keep your squash plants away from your tomato plants. Cantaloupe and cucumber are also used as trap crops. Another silverleaf whitefly control method is to use an LED-CC trap. Inexpensive LED-CC traps use a green LED light to attract whiteflies to the trap. [I may need to get one of those!] Take a look at the underside of leaves to see if silverleaf and other types of whiteflies are lurking. Are your tomatoes ripening unevenly? When you cut into them, do the walls look gray? It’s probably tomato gray wall. Also known as graywall and blotchy ripening, this disorder occurs when environmental conditions are less than ideal. Tomato gray wall symptoms
While the rest of your tomato plant looks fantastic, with sturdy stems and lush leaf growth, tomatoes affected with graywall ripen unevenly with both red and yellow areas. This yellow mottling starts appearing when the fruit is green. As the fruit matures, these areas can turn gray and become sunken. These symptoms are not the same as yellow shoulder. When tomatoes develop yellow or green shoulders, it is from too much heat and sunlight, and symptoms are limited to the upper portions of the fruit. Tomato gray wall can be seen all around the fruit. If you cut open an affected tomato, you will see that the walls of the fruit are gray, yellow, brown, or green. Anything but red. Look closely, and see the vascular tissue has turned dark brown. If the rest of the plant looks affected, it is probably tomato mosaic virus. Tomato gray wall causes Several conditions can cause gray wall in tomatoes. Some you can change, and some you can’t. Extreme heat, fluctuating temperatures, and high humidity can stress plants into responding with gray wall. Overcast skies during hot weather, fog, and excess shade can cause blotchy ripening. Overly wet or compacted soil can also cause tomato graywall. Too much nitrogen, or insufficient potassium or boron, can also cause tomato gray wall. [Have you tested your soil lately?] Scientists also believe some bacteria, fungi, and the tomato mosaic virus may be part of the problem, but they’re still exploring those possibilities. Tomato gray wall prevention You can prevent tomato gray wall by providing good drainage, improving soil structure, planting tomato mosaic-resistant varieties, and feeding your plants appropriately. Gray leaf spot doesn’t exactly live up to its name. Rather than gray spots on leaves, this fungus causes small brown or yellow dead areas that merge to make larger necrotic areas. Gray leaf spot is a fungal disease commonly caused by Stemphylium solani fungi. S. floridanum and S. botryosum may also be involved, but the symptoms are the same. These pathogens favor tomatoes, potatoes, peppers, and other nightshade family plants. Gray leaf spot can also occur on amaranth, broad beans, coriander, peas, sorghum, spinach, and wheat. When seen in the onion family, it is called leaf blight. Gray leaf spot symptoms Older leaves tend to show symptoms of gray leaf spot before new growth. It starts as small spots on both sides of the leaves. Yellow halos may also be visible. As these lesions grow and mature, they become dry and brittle, ultimately causing leaf drop. Some people say these dead areas look gray. To me, they’re brown. [If you have a hand lens, you may see gray fungal growth in the center of areas damaged by gray leaf spot.] Whatever you call it, these infections can lead to secondary infections, creating a domino effect of destruction in your garden. Symptoms of gray leaf spot look a lot like Septoria leaf spot. The only difference is that the damaged areas of gray leaf spot do not have black specks in the middle. Septoria leaf spot infections do have those black specks. Gray leaf spot lifecycle
The fungi responsible for gray leaf spot can travel through the air, in rainwater, and on infected seeds. In areas with high humidity, gray leaf spot can easily take hold on leaf, twig, and stem surfaces. Each infected plant part becomes a new point of infection. Infected leaves can spread the disease to neighboring plants just by touching them. Gray leaf spot prevention Preventing gray leaf spot is a lot easier than dealing with an infection. Start with resistant varieties and certified disease-free seeds and seedlings. Then, space your plants so that they are not touching their neighbors. The gap slows the spread of disease and improves airflow for faster drying times. Avoid overhead watering and water in the morning to give leaves time to dry during the day. Once an infection begins, remove infected leaves to slow the spread of the disease. Just make sure to sanitize your garden tools between every cut. You can use bathroom cleaner. And it’s a good idea to give them (and your hands) a good soap and water washing, drying, and oiling after the ordeal. Throw infected leaves in the trash. Since this pathogen can overwinter in life and plant litter, it is a good idea to clean up at the end of each growing season and practice crop rotation. Commercial growers use fungicides to prevent and manage gray leaf spot. You can help prevent this disease with fixed fixed copper sprays or Bt (Bacillus thuringiensis). These treatments may halt an infection if they are applied early enough. Otherwise, get rid of infected leaves, harvest what you can, and give your tomato plant an umbrella if it loses too many leaves to prevent sunburn Rhizopus soft rot is one of those diseases that can come into your garden from the grocery store. Foods may look perfectly healthy when you bring them home. But you do not see the thousands of bacteria, fungal spores, or viruses that quickly establish themselves in your garden. Some of these pathogens can take years to get rid of. Rhizopus soft rot hosts Also known as black bread mold, Rhizopus soft rot is caused by Rhizopus stolonifer fungi. This fungal disease occurs in sweet potatoes, strawberries, pears, peaches, melons, and mangos. These delicious crops have a high sugar content and are easily damaged. When these fungi appear in damaged almonds, we call it hull rot. Rhizopus soft rot symptoms Tiny wounds or bruises slowly become water-soaked areas. Those areas then turn soft and start to rot. When conditions are right, white thread-like mycelia appear with little black knobs (sporangia) on top. These fungi produce enzymes when they germinate that help them penetrate plant cell walls. Rhizopus soft rot behavior
The fungi that cause Rhizopus soft rot are surprisingly athletic. Like many plants in the garden, they spread rapidly using stolons or runners. These fungal runners can move vertically up walls and tree trunks and horizontally across branches, stems, and soil. These fungi thrive when temperatures are 68°F–86°F and can survive in weather as hot as 140°F. Rhizopus soft rot prevention Once the fruit begins rotting, there isn’t much you can do besides trim out the bad bits and eat the rest. There are several things you can do to prevent Rhizopus soft rot:
If you are growing sweet potatoes, curing them properly after harvesting is the best way to prevent Rhizopus soft rot. Store them at 84°F at 90% humidity for 5 to 7 days, and they should be fine. Are your squashes rotting on the vine? It may be cucurbit wet rot. Cucurbit wet rot is a fungal disease caused by Choanephora cucurbitarum. Also known as Choanephora fruit rot and wet rot, this disease affects members of the melon family, such as pumpkins and cucumbers. Beans, peas, and okra can also be infected. Cucurbit wet rot symptoms Cucurbit wet rot first appears as a soft area on the blossom end of fruit or pods. Those spots can also appear around wounds in the fruit. White fungal growth develops, turning purplish-black and causing the whole fruit to rot. Cucurbit wet rot is often confused with blossom end rot and Rhizopus soft rot.
Cucurbit wet rot management
Like most rots, cucurbit wet rot needs moisture to become a problem. You can prevent it with good drainage and by allowing the soil to dry out between waterings. Fungal spores can travel on the wind, with insects, or in splashing water. While there isn’t anything we can do about the wind, there are things we can do to prevent wet rot:
Infected fruit should be removed and tossed in the garbage. Chocolate tube slime sounded so strange that I had to learn more about it. Like our beloved dog vomit slime mold, chocolate tube slime molds were once classified as a type of fungus. Scientists now include this family in the protists. Amoebas are another type of protist. Slime molds have the bizarre ability to move across materials in their search for food. They do this so efficiently that city planners now use some slime molds to design roads and electrical grid systems. Normally found as individual cells, chocolate tube slimes, also known as pipe cleaner slimes and tree hair, converge into giant communities. Chocolate tube slime (Stemonitis splendens) looks a lot like a sea urchin and is usually found on forest floors feeding on decaying material. They are sometimes found attached to older wooden houses. Chocolate tube slime mold also grows on planter pots but what I find particularly strange is that they can even grow on plants that are alive and green. I recently heard of chocolate tube slime growing on tomato stems. The tomatoes looked fine, they just had little brown tufts growing on them. The sea urchin-like spikes are fruiting reproductive bodies. Fungal spores are released from these tubes. Before they reach the stage, they start as white spikes that are often topped with pink globs of I don’t know what. Those white spikes turn a golden yellow and the globs turn golden yellow. Eventually, these spikes turn chocolate brown. Sometimes they turn a reddish-brown. They can be ½” to ¾” tall or huge.
Since chocolate tube slime molds feed on decaying organic matter, they will not harm your tomatoes or other garden plants. Have you ever seen chocolate tube slime mold in your garden? We’ve already talked about brown marmorated stink bugs, consperse stink bugs, green stinkbugs, red-shouldered stink bugs, rough stinkbugs, say stink bugs, Uhler’s stink bugs, and predatory stink bugs. Today, we’re going to look at brown stinkbugs. Like most stink bugs, brown stink bugs (Euschistus servus) feature the classic shield-shaped body and they smell bad once threatened or stepped on. Found in Central and North America, these pests damage a wide variety of garden plants including alfalfa, beans, buckwheat, corn, millet, okra, peas, pecans, sorghum, soybeans, sunflowers, and walnuts, along with several fruit trees. Brown stink bug description From above, brown stink bugs have a mottled gray to brown back, pointy shoulders, and rust-colored legs with tiny black dots. If you were to flip one over you would see that the underbelly is yellowish, with an orangish area in the middle of the belly. Adults average ½” in length. Eggs are clusters of yellowish-white spheres that start turning pink before they hatch. Nymphs are tiny reddish-brown ladybug-shaped insects. Brown stink bug damage
Brown stink bugs move through the garden as the seasons change. They love to start with peaches and nectarines, causing catfacing and other types of fruit scarring. From there, they move to whatever is nearby and edible. They feed by inserting needle-like mouthparts into fruits, leaves, stems, and seed pods. When they do so, they inject toxic substances into the plant that may slow or halt the further development of that plant part. Over time, the accumulated effects of brown stink bug feeding can be pretty devastating to a crop. They can kill seedlings outright, cause stunting of larger plants, and provide points of entry for several pathogens. Brown stink bug lifecycle Adult brown stink bugs overwinter in dead weeds, under boards, in hedgerows, and in the bark of trees. As soon as temperatures start rising they emerge to start eating, breeding, and reproducing. Each female lays an average of 18 egg masses. Each mass contains 60 eggs or so. There can be as many as four or five generations a year, depending on the weather. Adults are strong flyers so you have to keep a lookout. Brown stink bug management Assassin bugs, green lacewing larvae, some parasitic wasps, and earwigs are also known to feed on stink bugs, so you’ll want to avoid using broad-spectrum insecticides. In fact, most stink bugs are resistant to insecticides and pesticides. Row covers can also be used to protect specific plants and crops against stink bug damage. Your best defense against brown stink bugs is to monitor plants regularly, handpick stink bugs when you see them, and squash any egg or nymph clusters you see. Do your apple leaves have big orange freckles? It may be apple measles. Or it may be Alternaria blotch of apple. This leaf spot disease is also known as Alternaria leaf blotch, cork spot, and storage rot. This isn’t the same thing as apple blotch, though both are fungal diseases of apple trees. Alternaria blotch of apple symptoms Apples infected with Alternaria mali have raised black or brown lesions that are commonly found near the blossom end, though they may appear anywhere on the fruit. Infected fruit does not store well and may turn dry and corky. Most symptoms of this disease are seen in the leaves. Leaves may turn unusual colors, dead areas develop, and yellowing is common. Most often, you will see rust-colored circular spots in late spring or early summer. These spots can merge into large, irregularly-shaped areas. Those spots have light brown centers and purple halos. Eventually, infected leaves die and fall off, reducing photosynthesis and increasing sunburn damage. Green, woody tissue, such as petioles, can also become infected, but this is rare. These symptoms are easily confused with chemical overspray, frog-eye leaf spot, cedar apple rust, and magnesium deficiencies. You can take a sample to your local County Extension Office to find out for sure. Alternaria blotch of apple management
There are already bacteria in the soil (Bacillus cereus) that attack Alternaria mali. The problem pest is red mites. While the connection isn’t fully understood yet, research has shown that high red mite populations correspond to serious damage by Alternaria blotch of apple. European red mites are controlled using delayed dormant horticultural oil. Miticides are not effective against red mites. As always, remove mummies, prune for good airflow, and remove dead leaves from under the tree. Healthy leaves can be composted, while infected leaves belong in the garbage can. Take a closer look at your apple tree. Are there spots on the leaves? What’s your favorite apple? Sooty blotch and flyspeck are two different conditions. They occur together so often that the combined name is now an all-in-one fungal disease. It is also known as apple summer disease. Apple summer disease can affect bananas, blackberries, citrus, crabapple, papaya, pears, persimmons, raspberries, and several other tree and vine crops, along with apples. We will explore the two conditions individually and then learn what we can do about them. Sooty blotch Sooty blotch looks like small gray patches just under the fruit skin. These patches are usually ¼” in diameter or larger. They can merge to cover large areas of the fruit. These smudged areas are hundreds of tiny fungi connected by hyphae. Peltaster fructicola, Geastrumia polystigmatis, and Leptodontium elatius fungi are all responsible for sooty blotch. Flyspeck Zygophiala jamaicensis fungi infect fruit, generating black flecks that look like fly poop on the fruit skin. Those tiny flecks can coalesce into large scabs or blotchy areas. Rub or scratch off these scabs and see normal healthy fruit skin underneath. Sooty blotch and flyspeck (SBFS) work together to create dark blemishes on the fruit. These mycelia can also grow on leaves, stems, and twigs. Summer apple disease lifecycle Scientists are still learning about this disease. We do know that the damage is primarily cosmetic. The fungi live on and in the waxy cuticle and do not enter the fruit. Spores hibernate on ash and willow trees. They also occur in hedgerows, wild brambles, and our beloved edibles. Humidity favors the growth of these fungi. In particular, temperatures between 60°F and 70°F with a relative humidity greater than 96% set the stage for massive fungal growth.
As apples and other fruits mature, they exude a tiny bit of fruit juice through microscopic tears in the skin. Fungal spores land on this juice and use it as food, entering the skin through the tears. Surprisingly, infection with summer apple disease does not lead to fruit decay. But it does reduce storage time. Sooty blotch and flyspeck management Sooty blotch and flyspeck is most likely to occur on lighter-colored, thicker-skinned, slower-to-mature fruit from older trees growing in regions with fog or frequent rain. Hot, dry weather halts the growth of these fungal pathogens. Pruning for good airflow is the best way to prevent sooty blotch and flyspeck disease. Proper fruit thinning will also reduce the chance of this disease, as does removing mummies and keeping the area under trees clear of weeds. Commercial growers spray fungicides to treat summer apple disease along with apple scab. Organic growers spray with cocoa soap or lime sulfur, neither of which I’ve ever heard of. Home growers are finding that sprays of potassium bicarbonate (KHCO3) work well. Do not mistake potassium bicarbonate for baking soda. They are NOT the same thing. Keep your fruit dry to prevent sooty blotch and flyspeck from harming your harvest. Are you seeing spots? Black or brown spots on apples and apple leaves? It may be apple blotch. Apple blotch (Marssonina coronaria, M. mali, Diplocarpon mali) is a fungal disease that attacks apple trees around the world, damaging fruit, causing early defoliation, and weakening trees. Also known as Marssonina blotch, this disease was first seen in Japan in 1907. While it is not the problem it used to be, thanks to the use of Bordeaux mixture, it is still a good idea to know what to look for. [Note: I was unable to find photos of this disease that I could use. Any volunteers?] To muddy the waters just a bit, there is another apple blotch disease. This one is caused by Phyllosticta solitaria fungi. The symptoms and treatments are mostly the same, but there are a few differences. Also, when these two diseases occur, it is not uncommon for other diseases to appear. Sooty blotch and flyspeck is one of those diseases. Alternaria blotch of apple is another. We will get to those another day. Apple blotch symptoms Spotted fruit and early leaf drop are signs something is wrong. Closer inspection of a tree infected with apple blotch will reveal dark green circular areas on the tops of mature leaves. Tiny yellow spots develop within those areas. Those yellow spots get bigger and turn into grayish-brown round lesions (0.2”–0.4” diameter) with black pinhead-sized fruiting fungal bodies called acervuli. As the infection spreads, leaves turn more yellow than green with brown patches. These symptoms usually appear in mid-summer and severe defoliation usually begins two weeks after the first symptoms are seen. These symptoms look a lot like black rot and Alternaria blotch of apple. Fruit is less commonly affected by Marssonina fungi, while fruit infected with Phyllosticta will often display brown spots that can coalesce into large, scabby areas. Fruit infected with apple blotch it’s still edible but I would give it a good wash first.
Apple blotch management Since apple blotch fungi overwinter in leaf litter, you can help prevent this disease by removing fallen leaves from under the tree each autumn. If an infection is suspected, those leaves should be thrown in the garbage. Bordeaux mixture sprays are effective against apple blotch, as are several fungicides. These treatments are usually applied as soon as blossoms fall. Then you need to start counting the hours that tree leaves are wet from rain. After 175 hours, spray again and then spray every 10 to 14 days throughout the growing season. You can help your apple tree healthy with good pruning, sanitation, and regular feeding. This helps your tree protect itself. Lesser appleworm moth larvae burrow into apples—a bad surprise when eating an apple. Native to northeastern North America, these pests of pomes and stone fruits have moved across the U.S. and into Canada. Lesser appleworm moth hosts
Lesser appleworms (Grapholitha prunivora) call members of the rose family home. Hawthorn trees are the primary host of lesser apple worm moths, along with oaks and serviceberry shrubs. Unfortunately, apples and pears (pomes) are also vulnerable, along with stone fruits, such as apricots, cherries, nectarines, peaches, and plums. As such, they are commonly known as plum moths. Lesser appleworm moth identification Adult lesser appleworm moths are only ¼” long. They are dark brown to almost black with white, grayish orange, or brown bands on the forewings. Larvae start out creamy-white with a dark head and only 1/20” long. As they feed and grow, they turn pinkish white and can reach up to 3/8” in length. Lesser appleworm pupa are golden brown and 1/5” long. Eggs are flat, oval, and very tiny (1/40”). These eggs start out white and shiny but they turn yellowish as they mature and you can see a red ring inside. Lesser appleworm moth lifecycle Lesser appleworm moths lay eggs on fruit and leaves. In 7–10 days, they hatch and larvae begin feeding on fruit. Three weeks later they spin cocoons around themselves where they will pupate under bark or on the ground in plant or fruit debris. This cycle continues allowing an average of three generations each summer. Lesser appleworm moth damage Lesser appleworm moth damage looks very similar to codling moth and oriental fruit moth damage, though the tunneling doesn’t usually go as deep. Initial infestations often cause fruit drop. Fruit entry holes are often seen near the calyx, or bud end, of the fruit, so check your fruit before taking a bite. You can use pheromone traps to monitor for these pests, but control measures are generally not needed. Oriental fruit moths are also known as peach moths, but more than your peaches are at risk. Apple, apricot, cherry, nectarine, pear, plum, and quince trees and fruit may become infested by this invasive pest of pome and stone fruits. Originally from China, Oriental fruit moths (Grapholita molesta) are now found throughout much of the world. Oriental fruit moth damage Oriental fruit moth damage starts early in the growing season when newly hatched larvae burrow into leaf axils (where leaves are attached to stems). From there, they tunnel several inches into tender young twigs to feed on sap. This kills the twigs, creating ‘flags’ and can lead to a bushy appearance. As the season progresses, Oriental fruit moth larvae start feeding on the ends of established twigs (terminal growth) and developing fruit. Boring into the fruit, they create the perfect opportunity for brown rot and other fungal diseases. Significant amounts of frass (bug poop) can usually be seen around entry holes. In apple and pear trees, this damages looks similar to codling moth and lesser appleworm damage. Oriental fruit moth identification Adult Oriental fruit moths are gray to grayish-brown with brown markings. They are small moths with 1/4"–1/2” wingspans. Larvae are born white and then turn pink to cream-colored. They have dark heads and grow to 1/2” long. Eggs are white and flat. Oriental fruit moth lifecycle Female Oriental fruit moths lay up to 200 eggs each spring. Those eggs are laid singly on the underside of leaves and on twigs and they hatch as fruit trees begin to blossom. Oriental fruit moths overwinter as larvae in protective cocoons which may be found attached to the host tree or nearby on the ground. There can be up to seven generations each year.
Oriental fruit moth management Checking trees regularly for signs of infestation, starting early in the season, will help keep this pest in check. Pheromone traps can be used to monitor for Oriental fruit moths and disrupt their mating. While commercial growers still rely on broad-spectrum pesticides, home growers can use less destructive insecticides, such as spinosad. Infested plant tissue should be removed and thrown in the garbage. If their sunny yellow flowers and delicious seeds weren’t reason enough to grow sunflowers, it ends up that small stands of sunflowers will attract Macrocentrus ancylivorus, an Oriental fruit moth parasite. These helpers will also parasitize peach twig borers. European corn borers are the larval form of an unassuming tan moth. This invasive pest bores into all parts of corn, millet, and other grain plants, but that’s not all. If corn isn’t available, these pests will also feed on lima beans, peas, peppers, and potatoes. As far as I know, this pest is currently only found East of the Rockies, but that may change as early as tomorrow. You may as well learn about it today, wherever you are. European corn borer identification Known as the European high-flyer, these moths are one inch long with a one-inch wingspan. Females are tan with light brown markings. Males are smaller, with darker markings. If you see an adult at rest you will be able to see the abdomen sticking out from under the wings. European corn borers (Ostrinia nubilalis) can be dark reddish-brown to pinkish gray. They have brown spots on each segment and are just under one-inch long. European corn borer lifecycle European high-flyers lay clusters of whitish-yellow eggs on corn and other host plants, usually on the underside of leaves. Females lay two clusters of eggs each night over 10 days. This translates into 400–600 eggs per adult female. Just before hatching, the eggs become translucent. Then the larvae chew their way to freedom and begin feeding on the host plant. Once they’ve eaten their fill and made a mess of your corn, they enter a pupal state. Inside the chrysalis, larvae transform into adults. In some cases, there may be two pupal stages. I have no idea why. As daylight hours shorten, larvae enter hibernation. The scientific term is diapause. I wonder if that’s a reflection of “die or pause”—hard to say. European corn borer damage As larvae bore into leaves, stalks, and ears, photosynthesis is reduced, nutrient and water transport are slowed, and dozens of points of entry for Fusarium and other pathogens are created. This sets the stage for some very unhealthy, unproductive plants. Symptoms of European corn borer feeding include clumps of what looks like sawdust (it’s bug poop) on top of mature leaves, frass and damage where leaves emerge from the stalk, and a shot-hole type of leaf damage.
European corn borer management While immature corn plants can protect themselves against this pest with an antibiotic substance they create, that protection doesn’t last into adulthood. Commercial corn growers often plant varieties of GMO seed corn that contains a synthetic version of a gene from Bacillus thuringiensis kurstaki, an insecticidal bacteria. For the home gardener, there are other ways to manage European corn borers. For one thing, insidious flower bugs, predatory stink bugs, and Trichogramma wasps all prey upon or parasitize these pests, along with ladybugs and lacewing larvae, so you’ll want to avoid using broad-spectrum pesticides. Beyond that, monitor your corn plants for signs of entry holes. You can also use pheromone traps. You can apply your own Bacillus thuringiensis kurstaki or spinosad to treat severe infestations. |
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