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 grey to greyish-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.
Moth caterpillars devour garden crops, but they aren’t all bad. In fact, they can also be important pollinators. Let’s see if we can sort out the Good Guys from the troublemakers.
As a child, I always thought that butterflies were colorful and flew in the daytime, while moths were fuzzy and flew only at night. Like everything else, it’s not that simple.
Lepidopterans, as moths and butterflies are called by scientists, are one of the easiest insect orders to recognize. Their name comes to us from Ancient Greek words that mean ‘scale’ and ‘wing’. There are believed to be over 180,000 scale wing species around the world and 160,000 of those are moths. Together, they make up approximately 10% of the known insect world. More than 11,000 moth species call the U.S. home.
Moth or butterfly?
The easiest way to tell if it’s a moth or butterfly is to look at the way they hold their wings while at rest. Generally speaking, moths hold their wings out to either side, while butterflies hold their wings upright, over their back. [butterfly/up – moth/out] You can learn more about the differences between moths and butterflies on my post about them. Did you know that moths have ears and butterflies do not? I didn’t either.
Moths start out as eggs. Those eggs are normally laid in or around plant material. Some eggs are laid in the soil. When those eggs hatch, moth larvae (caterpillars) appear. Those larvae eat a lot. Seriously. It is that feeding that causes all the damage in the garden. Eventually, those caterpillars eat their fill and build cocoons around themselves. Within those cocoons, some pretty amazing changes take place. What started as a squishy, worm-shaped digestive system is transformed into a fuzzy, winged creature of the sky.
Most adult moths only eat nectar. Some moths don’t eat at all. They simply do not have mouthparts and do not live long enough to need food. This nectar-feeding means that moths are important pollinators. In some parts of the world moths are an important food source and some moths give us silk.
Hummingbird moths are an example of a daytime moth that acts as a pollinator. While most of their clearwing cousins are troublemakers, these lovely specimens are a good sign your garden has abundant biodiversity. In most cases, however, moths are not a gardener’s friend. Or rather, their offspring, the caterpillars, are not
Bad moths infest our pantries, closets, and our gardens. They chew holes in flour bags, sweaters, and leaves. Here is a list of the most common garden variety problem moths:
New threats to plant health are occurring all the time. For example, in 2005, a single European pepper moth was found in a shipment of begonias at a San Diego Home Depot. That serious pest is now found in 13 US states and Canada.
*NOTE: If you come across a tomato hornworm covered with tiny white oval protrusions, put it into something it can’t escape from but that will allow those protrusions to hatch and fly away. They are beneficial parasitic wasps
Before you start adding mothballs to your closet (or the garden), you need to know that carcinogenic mothballs are bad for us. You can more safely protect your clothing from common clothes moths (Tineola bisselliella) by bagging it or adding cedar or juniper to your closet. You can use yellow sticky sheets or commercially available moth pheromone traps to take care of Indianmeal moths (Plodia interpunctella). Garden moths are best controlled by natural predators. That list of predators includes amphibians, bats, birds, cats, dogs, lizards, and even rodents. [I have trained one of my dogs to chase imported cabbageworm butterflies out of my garden. It’s fun to watch and sometimes she even catches one.]
Since it is the caterpillars that are causing most of the damage, observation and handpicking are often the best organic controls. Personally, I allow caterpillars to grow large enough to be worth feeding to my chickens. It’s a case of how much one is willing to tolerate.
Lace bugs are not the same thing as lacewings.
There are over 2,000 lace bug species and each one is plant-specific. Most lace bugs spend their entire lives in the same area of the same plant, even though they can fly. And they bite! Apparently, they don’t fly very well because sometimes they fall out of their trees and bite the people they land on. While these bites do sting, they are not dangerous.
Lace bug identification
Lace bugs are very small. You could fit up to 8 or 9 lace bugs end-to-end across a dime, though some species are significantly bigger than that. Lace bugs tend to be tan, brown, or black, depending on the species.
Lace bugs get their name because of their diaphanous fore wings and lacy outgrowths on their thorax. They can be broad or narrow but most lace bug bodies are flattened and the heads are often hidden under a hood-like pronotum.
Damage caused by lace bugs
Lace bugs are host-specific sap suckers. They are most often found on the underside of leaves where they pierce leaf tissue and tap into plant cells to feed on sap. This feeding initially causes small yellow or white spots. Eventually, lace bug feeding leads to leaf silvering or bronzing. It can also provide points of entry for anthracnose.
Heavy infestations can lead to leaf curling, leaf drop, and reduced crop size. These pests frequently feed on young shoots which leads to wilting and twig death. If all that wasn’t bad enough, it ends up that these pests use both the upper and lower decks of their leaves as a toilet, leaving behind black flecks of excrement
Here are just a few lace bug species you may find in your garden:
There are also lace bug species that attack azalea, bamboo, banana, cotton, oak, sycamore, and willow, just to name a few.
Lace bug lifecycle
Lace bugs go through an incomplete metamorphosis that takes them through 4 or 5 instars, depending on the species. Generally speaking, wing pads appear in the second or third instar and continue to develop into adulthood. There may be two to five generations of lace bugs each year, depending on the species and environmental conditions. They may overwinter as eggs, nymphs, or adults.
Oblong lace bug eggs can be yellowish to black. Some species lay their eggs are at an angle, in circular arrangements, on the underside of leaves, similar to whitefly eggs. The only difference is that the eggs are then covered with black, sticky frass (bug poop). Yuck! Other lace bug species insert their eggs into stems and shoots, while some species lay their eggs along the edge, or margin, of nearby leaves or leaf veins. Unlike many other insects, lace bug mothers are protective of their young. When predators appear, Moms fan their wings and approach the threat as only a protective mom can do.
Lace bug management
Small populations of lace bugs are no cause for concern. In fact, their presence attracts many beneficial predators. Simply keep your trees and plants healthy with good drainage, mulch, and proper feeding and irrigation. These pests may overwinter on horsenettle (Solanum carolinense) and common mullein (Verbascum thapsus), so you may want to keep those plants away from your garden.
Assassin bugs, jumping spiders, lacewing larvae, ladybugs, pirate bugs, predaceous mites, predatory thrips, and spined soldier bugs will all help keep lace bug populations under control, so avoid using broad-spectrum pesticides. Severe infestations are best managed with insecticidal soap or narrow-range oil sprays.
Stunting and yellowing leaves may mean your tomato plants are infected with tomato mosaic virus.
Tomato mosaic virus (ToMV) looks and behaves a lot like tobacco mosaic virus (TMV). While both viruses can infect tomatoes and tobacco, the tobacco mosaic virus can also be found on beets, cucumbers, lettuce, and petunias, while tomato mosaic virus spreads to peppers and potatoes, along with apple, cherry, and pear trees.
Tomato mosaic symptoms
Tomato mosaic symptoms can vary greatly, making it difficult to distinguish from other tomato viruses, such as tomato spotted wilt and cucumber mosaic. Along with stunting and chlorosis, other symptoms of tomato mosaic virus include:
This disease is very responsive to temperature. If plants are infected while young, they may not exhibit any symptoms until temperatures are warmer.
Tomato mosaic virus lifecycle
These pathogens can survive in dry soil, leaf litter, and infected root debris for up to two years. Add water and that time is reduced to just one month. While ToMV can be transmitted through infected seeds, it is most often spread by us. The virus gets on our hands, clothes, shoes, and garden tools and we spread it everywhere we go, to every plant we touch or brush against. Like tobacco mosaic, the tomato mosaic virus can even survive the tobacco curing process and is then spread by smokers who haven’t washed their hands before working in the garden.
Tomato mosaic virus management
There are no chemical treatments for tomato mosaic virus. Good cultural practices, such as hand washing, avoiding infected areas, and sanitizing tools can slow the spread of this disease.
Tomato mosaic can also infect lamb’s quarters and pigweed, so keep those particular weeds away from susceptible plants. Installing certified disease-free, resistant varieties is another way to reduce the impact of this disease.
If you suspect tomato mosaic virus in your garden, pull up the affected plant, roots and all, and put it in a plastic bag. Then, contact your local County Extension Office to see if they offer free testing since that’s the only way to know for sure. By identifying the disease early and notifying the Extension Office, they can help you and others in your area protect the remaining plants.
Straightneck squash is, in my opinion, one of the most satisfying crops to grow. Sunny yellow fruits are easy to see for harvesting and their delicate flavor lends them to countless sautés, stir-fries, and salads. A close cousin to yellow crookneck squash and zucchini, these summer squashes are prolific and undemanding.
Straightneck squash plants
Like other bushy squash plants, straightneck varieties produce large, bristled leaves that make them useful when grown together with corn and pole beans in the Three Sisters Method. Stems are tubular and bristled. These plants take up some room, growing to three feet tall and wide aboveground and even wider root systems underground.
These plants produce both male and female flowers. Female flowers have tiny, unfertilized fruits at the base. Male flowers, which tend to come out first, do not have these structures. Since squash are not self-pollinating, bees and other pollinators are needed for a harvestable crop to develop.
How to grow straightneck squash
Squash plants are heavy feeders. Prepare growing areas before planting with lots of nutrient-rich aged compost and manure or fertilizer. Their taproots make them best suited to direct seeding, rather than transplanting. They can be grown in large containers, but prefer the ground.
Once temperatures stay at or above 60°F, seeds can be planted 2” deep and 3 to 4 feet apart, if planting in rows. Another option is to create hills that are 6” to 12” tall and 20” across. In each hill, plant 4 or 5 seeds, spread 3” apart, and keep only the best seedling for each hill, snipping off the others at soil level. In arid regions, you can use inverted hills or shallow areas. This makes watering easier, but it may increase problems with pests and fungal disease.
You can help them stay healthy and productive by top-dressing around plants with aged compost or fish emulsion. Avoid applying extra nitrogen. Nitrogen stimulates leaf growth, not fruit.
Insufficient pollination is a common problem with squash plants. You can overcome this problem by collecting male anthers and touching them to female flowers repeatedly until pollination occurs. Hand-pollinating takes little time and it works very well.
Straightneck squash pests and diseases
This is one case where you have to trust that your straightneck squash plants will produce abundant crops against all odds. There are astounding numbers of pests and diseases that can and will go after your squash plants, and you will still get big harvests.
Those insect attackers include aphids, armyworms, cabbage loopers, crickets and grasshoppers, cucumber beetles, cutworms, darkling beetles, dried fruit beetles, earwigs, false chinch bugs, flea beetles, green peach aphids, leafhoppers, leaf miners, Lygus bugs, melon aphids, melon flies, Mexican fruit flies, mites, nematodes, redhumped caterpillars, seed corn maggots, spider mites, squash bugs, squash ladybugs, squash vine borers, stink bugs, thrips, two-spotted spider mites, whiteflies, and wireworms. If you live in the southeastern U.S., melonworm moths and pickleworms may also be a problem. Deer, rats, squirrels, and other animals will also take a bite out of your straightneck squash crops. Monitor plants for signs of damage and treat as needed.
The disease arena is no less daunting, but you can take most of it with a grain of salt. These plants are, as I’ve said, productive and low-maintenance. Diseases that may occur on your squash include Alternaria leaf blight, angular leafspot, aphid borne yellow virus, ashy stem blight, bacterial leaf blotch, bacterial wilt, bean yellow mosaic, beet yellows virus, belly rot, charcoal rot, cucumber mosaic, cucurbit aphid-borne yellows, cucurbit yellow stunting disorder, curly top, damping off, downy mildews, Fusarium wilt, leaf blight, measles, Phytophthora fruit and crown rot, potyviruses, powdery mildew, septoria leaf spot, squash mosaic virus, sudden wilt, Verticillium wilt, virus decline, and zucchini yellow mosaic. Spacing plants out properly, feeding and irrigating regularly, and checking on your plants every few days should prevent any serious problems.
Environmental conditions can also lead to problems such as bitter fruit and blossom end rot. These problems can often be prevented with regular irrigation. If your squash plants are growing well but there’s no fruit, it may be a molybdenum deficiency. An affordable lab-based soil test can tell you if this is your problem.
Two straightneck squash plants should keep your family supplied all summer. At the end of the season, let one squash grow past the tender stage and save its seeds for next year. Just keep different varieties of summer squash away from each other as cross-pollination can occur.
How many types of summer squash are you growing this year?
Mosquitoes can smell the carbon dioxide you exhale from 150 feet away. They zero in, land ever so lightly, stab you, and suck your blood. In doing so, they may expose you to several fatal diseases, including chikungunya, dengue fever, encephalitis, malaria, yellow fever, West Nile Virus, and Zika virus. They can also carry canine heartworm.
Mosquitoes are responsible for 700 million illnesses and over 1 million deaths around the world each year. In 2016, there were more than 96,000 cases of mosquito-borne disease in the U.S. and California has the highest U.S. number of cases of chikungunya, a viral disease that causes debilitating muscle and joint pain and fever.
Odds are very high that mosquitoes are lurking in your garden. If you search online for “mosquito repelling plants”, you’ll find thousands of lists. With all the claims about mosquito-repelling plants, what’s true, and what’s hype? Let’s find out.
There are many claims made about plants being able to turn away these blood-sucking, disease-carrying pests. Research has shown us that many plants do, in fact, have the ability to repel mosquitoes, but probably not in the way you expect.
Pine, lemongrass, lavender, catnip, scented geranium (aka mosquito plant), jasmine, eucalyptus, chamomile, juniper, rosemary, soybean, olive, Tagetes, violets, sandalwood, thyme, peppermint, lemon, rosewood, turmeric, and sage can all repel mosquitoes. Sort of.
The essential oils contained in those plants are what provide the protection. But adding them to your landscape isn’t going to help, though they may look lovely. The problem is, you’d have to roll around in those plants every 15-30 minutes to be protected from mosquitoes. I don’t know how long your plants could tolerate that sort of treatment.
In fact, both male and female mosquitoes eat nectar, sap, and honeydew. It is only the females who need the protein found in blood for egg-laying.
Many mosquito-repelling products claim to be natural plant extracts. Keep in mind that natural does not always mean safe. Strychnine is natural but it can kill you. Extended exposure to chemically significant essential oils can lead to allergic reactions and skin sensitivities.
Mosquito predators and repellent products
Electronic mosquito repellers do not work. Either do mosquito-repelling wristbands. Bug zappers kill millions of beneficial insects and very few mosquitoes. CO2 traps are mostly ineffective. If you are sitting in one place, clip-on insecticide fans and personal propane vaporizers may provide some protection. And, as much as I enjoy candlelight, citronella candles don’t work much better than regular candles once you get a few feet away, according to a study by NIH.
Crane flies are not the mosquito-eaters we thought they were and bats do not eat as many mosquitoes as is commonly believed. Larger bats eat larger prey and smaller bats don’t seem to have a big impact on mosquito populations. Another common myth claims that setting up a Purple Martin house will reduce mosquito numbers. Local martins will be happy, but it won’t change your mosquito problem. You could always copy the Capuchin monkeys and rub yourself with millipedes, but I don’t recommend it.
Aphids spend their entire lives sucking sap from garden plants and spreading viral diseases, but those lives are fraught with danger.
Aphids are soft-bodied insects with piercing mouthparts. They insert their sharpened straws into plant tissue, where they slurp up copious amounts of sugary sap. They eat so much and so quickly, that much of what they eat simply goes in one end and out the other. This “honeydew” can be contaminated with pathogens and it attracts the attention of protective ants, but aphids have many enemies. We’re not just talking about gardeners here, either. In most cases, aphid killers are either predators or parasites, though there are exceptions.
Parasitoids are insects that lay their eggs in, on, or near host insects. Those hosts end up being the first meals for parasitic larvae. There are many parasitic wasps that bring death to aphids. They do this by laying an egg in every aphid they can. When the eggs hatch, they eat their aphid hosts from the inside out. Gruesome, right?
Eventually, the aphids die and the now-adult wasps fly away. All that’s left behind are dozens of tan or golden aphid husks known as mummies. If you use a hand lens, you may even be able to see wasp exit holes.
The most commonly seen species and their favorite aphids include:
Predators actively hunt and eat aphids. Aphid predators include:
Remember those exceptions I mentioned? One of them is the ichneumon wasp. Adult ichneumon wasps kill their prey outright and then lay eggs in the corpse. It’s a brutal world out there, make no mistake
Many varieties of parasitic wasps and other aphid killers are available for purchase, but you can often attract these garden helpers to your landscape with plants that provide abundant nectar and pollen. Queen Anne’s lace, coreopsis, coneflowers, cosmos, coyote brush, dandelions, dill, goldenrod, sweet alyssum, and sunflowers look lovely and they create a natural welcome mat to insects that see aphids as the perfect meal. Hedgerows also provide beneficial insects with good hiding places.
Brood X is on the brink of clawing their way out the soil after nibbling roots for nearly 20 years. Brood X refers to this year’s cicada event.
I lived in Virginia during an emergence year. It was an experience I’d rather not repeat. While not as bad as the Midwest’s plague of locusts, there were cicadas everywhere. They coated windshields, driveways, and roads. They flew into you, clinging to your clothes and hair. The noise was enough to drive any sane person crazy. And then it was over. Like it never happened, except that there were hollowed out exoskeletons attached to every tree you saw. But finally, it was quiet.
As you may know, I use sticky barriers around the trunks of my fruit and nut trees to thwart crawling insect pests. These barriers also give me a chance to see which insects are out and about, though the sticky sheets hanging in the trees do a much better job of that. This year, I was very surprised to find cicada exoskeletons caught in the barriers protecting my navel citrus tree. I thought cicadas were only on the East Coast, but I was mistaken.
Cicadas are well known on the East Coast for their epic numbers, mind-numbing noise, and littering trees and shrubs with exoskeletons. What I didn’t know is that the West Coast has cicadas, too. And this is the year, coast to coast, when billions of cicadas come out of the ground to mate. Most of them have been underground for 17 years.
Types of cicadas
Cousin to leafhoppers, there are more than 3,000 types of cicadas around the world and more than 170 species in North American that we know of. There are two cicada families: one lives in Australia and the other lives everywhere else except Antarctica. Within that global family there are annual cicadas and periodic cicadas.
Periodic cicadas (Magicicada) are native to North America and they spend most of their lives underground as nymphs. Here, they feed on sap from tree roots. Depending on the species and location, these nymphs emerge at 13- or 17-year cycles in those mind-boggling numbers. Periodical cicadas include M. septendecim, M. cassini and M. septendecula. These synchronized mass emergences make predators less likely to rely exclusively on cicadas as food and the massive numbers ensure the survival of the species.
Most annual cicadas emerge every year, though they can spend up to 9 years underground. Unlike periodic cicadas, the emergence of annual cicadas is not synchronized. Annual cicadas are also known as jarfly or dog-day cicadas because they tend to emerge in mid-summer. In my California landscape, I probably have annual citrus cicadas (Diceroprocta apache), though there are several other cicada species present.
Cicada description and lifecycle
Cicadas are true bugs with large, wide set eyes, clear forewings, and short antennae. They are stocky, substantial bugs that are generally active during the day. While the Malaysian emperor cicada is nearly 3 inches long with a wingspan of up to 8 inches, most cicadas are significantly smaller than that and thank goodness! Most adult cicadas, or imagos, are 1 to 2 inches long with comparably smaller wingspans.
After mating, female cicadas cut slits in the bark of twigs where they lay their eggs. When the eggs hatch, the nymphs are pale and about the size of a grain of rice. They drop to the ground and use their strong front legs to burrow as much as 8 feet into the soil. Here, they will feed on xylem sap from the roots of trees and shrubs. They prefer ash, cypress, maple, oak, and willow, but will feed on other trees, as well. In the final instar, they return to the surface where they shed their skins and emerge as flying adults. Those shed skins are commonly found attached to trees.
If you’ve ever been present for a cicada emergence, you know how incredibly noisy these insects can be. At up to 120 dB, they are the noisiest insects on Earth. They are so loud that they can cause permanent hearing loss when experienced at close range.
Both males and females have membranous structures called tympana that detect sounds. When a male cicada sings, he turns his tympana off so as not to damage his own hearing. [I used to have a neighbor like that. I had to move to a new apartment.]
Male cicadas create all that noise using organs called tymbals found on their abdomen. In some species, both males and females rub their wings over a series of ridges found on the thorax. These bugs have resonating cavities and membranes that amplify the sound. While we can’t tell the difference, it ends up that each male cicada has a unique song composed of modulated clicks that sound, to us, like continuous notes. I have to assume that the female cicadas can tell the difference. To me, they’re just very noisy. I did learn that one of the Australian cicada species does not produce audible sound. Instead, they produce vibrations that are transmitted through whatever tree they are on, which sounds far more civilized to me. And some cicada songs are so high-pitched that we can’ hear them. Another interesting notes about cicada courtship is that different cicada species may be found on the same tree, but that each species uses a different height from which to operate.
Adult cicadas feed on sap from xylem tissue, but they generally do not harm mature trees and shrubs. Newly planted trees and shrubs should be protected with netting during emergence years. In most cases, cicada root feeding is not significantly destructive. Females have been known to lay eggs on asparagus, citrus trees, date palms, and grapevines.
This year’s cicadas are being called Brood X. As temperatures rise, they stop nibbling the roots of your plants and emerge from the soil to mate, lay eggs, and die. Ants, bats, birds, squirrels, spiders, and wasps will all gorge on cicadas this year. While cicadas do not bite or sting, they are also not very bright and may mistake you for a tree and try to feed.
Don’t bother spraying pesticides or insecticides for cicadas. The damage they do is minimal and you would have to use gallons of the toxic stuff to counteract a periodic emergence. If you simply cannot tolerate the noise, use it as an excuse to spend a week in Hawaii.
Cicadas are eaten in many parts of the world. In China, nymphs are deep-fried. Supposedly, they are pretty tasty when dipped in chocolate. I don’t think I’m ready for that just yet. The French onion crickets were about as far as I feel comfortable.
If you have a citrus tree, you may want to take a closer look for signs of purple scale in late spring and early summer, and again in autumn.
Purple scale insects suck the sap from citrus trees and they look like miniature mussels. Also known as mussel scale, orange scale, and comma scale, purple scale (Lepidosaphes beckii) are a type of armored scale that attach to banana, bay laurel, citrus, fig, mango, pear, and stone fruit trees and grapevines. These pests have several ornamental hosts that bear inspection:
Purple scale damage
Like other scale insects, purple scale feed predominantly on leaves and young fruit, but they will attack all parts of a tree. You may see tiny yellow halos on the leaves. Purple scale feeding can weaken branches, disfigure fruit, and reduce productivity. Heavy feeding can lead to defoliation and twig dieback. In extreme cases, the tree can die.
Populations of purple scale are usually low and found mostly in coastal regions, but mild temperatures, high humidity, and overcast skies can provide the conditions needed for a population explosion. You can find these pests in the cooler, shaded areas of trees.
Purple scale identification
Purple scale insects aren’t actually purple. That sure would make them easier to find! Instead, they are dark brown and may have tan edges with a slight purplish tinge.
Male purple scales are smaller and narrower than females. In both cases, you may see a slight bend at the narrow end of the scale. Male purple scales are 1/10” long and females are slightly larger. Male purple scale insects are tiny and they fly around in search of immobile females.
Purple scale lifecycle
Females lay 40 to 80 eggs under their protective covers. After the eggs hatch, crawlers emerge and scuttle to nearby fruit, leaves, and twigs, where they begin forming their own covers. At first, purple scale crawlers are covered with a mass of waxy threads. When they are about half-grown, their purplish-brown covers begins to develop. Once a female attaches herself, she stays put.
Purple scale management
Temperatures above 80°F are hard on purple scale, so their numbers are greatly reduced by the time summer is in full swing. But a second generation may appear in autumn and, in some years, a third generation may occur before winter cold brings them to a halt.
Natural predators, such as parasitic wasps, twicestabbed lady beetles, and Australian lady beetles, take a big bite out of these pests. We can help them do their job by avoiding broad-spectrum pesticides and applying sticky barriers to the trunks of trees. Argentine ants are known to protect scale insects, so sticky barriers remove that protection.
Purple scale prefer dusty conditions, so giving your citrus trees a quick shower with the hose can help.
Rather than steamy backseat interludes, frenching describes the way leaves can become discolored or distorted.
Frenching most commonly occurs in cotton and tobacco, but it may also be seen in citrus, sorrel, squash, and tomatoes. Peppers seem to be exempt from this condition, but no one knows why.
Is frenching a disease?
Well, yes, and no, and maybe. Since frenching is not entirely understood by botanists, its causes are currently referred to as “frenching factors”. These factors include predominantly fungal diseases, insufficient iron, poor drainage, alkaline soils, and temperatures above 95°F. [It sounds like I just described my yard!]
In some cases, frenching is caused by specific bacteria commonly found in the soil (Bacillus cereus, Macrophomina phaseolina), the latter being one cause of damping-off disease. Frenching is also more likely when plants are grown in soil that stays moist during a drought. [I guess this means I should back off on watering my heavy clay soil quite so much in summer…]
How to identify frenching
While there are many ways that leaves can turn the wrong color or take on an abnormal shape, frenching has some consistent characteristics:
*Apical dominance refers to some plants’ natural tendency to have one main shoot that actively inhibits the growth of other shoots.
These symptoms can be mistaken for aster yellows at first, but roots are not affected. This condition, regardless of its cause, starts out as tiny pinheads of chlorosis. New leaves are narrower than normal with wavy edges. As these leaves grow, only the midrib gets longer, pulling the leaves into strap-like shapes that end up looking more like stiff strings than leaves.
Scientists have found that autoclaving soil eliminates the frenching effect, but I’ll bet none of us have that option. There isn’t much we can do about the weather, either, but there are things we can do that will reduce the chance of frenching in our home gardens. Those actions include improving drainage, monitoring and maintaining a good soil pH, and feeding and irrigating plants regularly should do the trick.
Have you seen frenching in your garden? Which plants were affected?
Today, we are learning about the Krebs cycle. Wait! Come back!
The Krebs cycle is how plants get energy from their food. Also known as the citric acid cycle, it won’t tell you how to grow bigger tomatoes or sweeter melons, but understanding the Krebs cycle gives you a better understanding of how plants grow and what they go through to make all those delicious things we eat.
We’ve already discussed the nitrogen cycle, the carbon cycle, and the water cycle. Those cycles describe how things needed by plants become available (and unavailable) as they change forms, moving through the environment.
We’ve also discussed the Calvin cycle, which is part of photosynthesis. In the Calvin cycle, several anaerobic chemical reactions occur that allow plants to transform the carbon from CO2 into sugars. After those sugars are formed, the Krebs cycle begins.
Messrs. Krebs and Johnson
In 1937, a man by the name of Albert Szent-Györgyi was studying pigeon muscles. Stay with me, now! He received a Nobel Prize for his efforts, part of which was discovering several aspects of what later became known as the citric acid cycle. His discoveries were taken further that same year by Hans Adolf Krebs and William Arthur Johnson. [I guess they decided the Johnson cycle didn’t sound as impressive.] Krebs received the Nobel Prize for Physiology in 1953 for that work. [I don’t know why Johnson didn’t. Maybe he was too difficult to work with. I don’t know.] The Krebs cycle is part of the aerobic respiration process plants use to produce usable energy.
Respiration, not what I expected
When I hear “aerobic respiration” I start thinking about increased heart rates and time spent on a treadmill, but that’s not it. Aerobic respiration refers to one way that usable energy is formed. That usable energy is adenosine triphosphate or ADT. ATP is a molecule that carries usable energy around within a cell, taking it wherever it is needed. ADT is created when food (sugar) is burned with oxygen. I don’t know how plants burn anything but I keep getting images of little campfires in plant cells, so that’s kinda fun.
Sugar as plant food
I always thought plants simply drank sugar solution as food, but that’s not exactly how it works. Let’s put our steampunk magnifiers on and see what’s really going.
How plants convert sugar into energy is far more complex and amazing than my little campfire, especially when you think of the scale at which all of this is happening. Plant cells are 10 to 100 micrometers across, depending on the species. This means you could put approximately 180 to 1,800 plant cells across the top of an American dime. [Human and animal cells are even smaller and they do similarly impressive things.] Now back to converting sugar.
To start, you need to know that sugar molecules are relatively large. To use them, plant enzymes go to work, breaking down those acidic glucose molecules into energy and pyruvic acid. That process is called glycolysis. More reactions occur, breaking the remaining bits down into carbon dioxide. As energy is released through these processes, it is moved to other molecules, called electron carriers. Electron carriers are like tiny cargo trucks. They form a chain called the electron transport chain. This transport chain creates ATP. As a side benefit, the processes also create the building blocks of several other molecules, such as amino acids.
For perspective, let’s say that a plant cell is the size of Arizona and the mitochondria are Phoenix. Arizona has a railway system that transports food. All the food comes from Texas and is too big to be packaged. This giant-sized food is taken to Phoenix where it goes through a 9-step process that converts the giant food into snack-sized portions that are small enough to fit on the trains. The trains take the food wherever it is needed. Put simply, that’s the Krebs cycle.
But what does all this have to do with your garden?
The bottom line, healthy plants produce bigger, tastier crops with less effort on our part. They are better able to defend themselves against pests, diseases, and weather extremes. All you have to do is make sure they get the right amount of water regularly and that the soil they are growing in contains the correct range of nutrients.
Have you had your soil tested yet? What did you learn?
The water cycle is a global phenomenon, but something similar is happening in your garden.
In its simplest terms, the water cycle describes how water moves around on the Earth’s surface. It might be moving very slowly as ice in a glacier, whipping around on the wind as a gas, or flowing across the soil surface to water your bean plants. Regardless of its form, the mass of water on Earth stays relatively unchanged. The same is not true of your garden.
Unless you water exclusively from a rain barrel, the water for your garden probably comes from a spigot. If you’ve ever experienced a water main break or a flood, you know just how devastating too much water can be.
Let’s compare the basic aspects of the water cycle from global and gardening perspectives.
The water cycle starts when the sun heats the surface of the planet. Water on the surface is converted to a gas that rises into the atmosphere. The soil of your garden, your driveway and house, and the concrete of your patio also act as heat islands, absorbing the sun’s heat and causing nearby water to evaporate. This is why it’s a good idea to give potted plants sitting on a concrete patio feet that raise them off the surface enough to allow air to flow. This will keep them cooler and reduce the amount of water they need.
Water held within plants is also released. As they perform photosynthesis, gas exchanges must occur. Water is released into the atmosphere as this happens. The combination of evaporation by heat and transpiration by plants is called evapotranspiration.
As water vapor moves around in the atmosphere, the bits of water vapor bump into each other and grab on. Those clusters of water vapor keep getting bigger, condensing into fog, mist, and clouds. If you’ve ever been to Disney World in August, you know exactly what I mean.
Some plants thrive in misty, foggy, humid environments. Others end up with fungal diseases. If humidity is causing problems in your garden, be sure to prune your plants in ways that provide good airflow.
Water falling to the ground is precipitation. Globally, precipitation may mean rain, snow, hail, or sleet. In your garden, that precipitation may be rain, sprinklers, or a garden hose. As precipitation passes through the atmosphere, it collects particles along the way. Those particles are often car fumes, factory pollution, and dust, and those particles reach your soil right along with the water.
Water passing from the surface into the ground is called infiltration. Once the water has been absorbed by the soil, it is known as groundwater or soil moisture. Just because water is in the ground does not mean it is available to plants. Compacted soil has poor infiltration rates. And water does not spread smoothly through the soil in all directions.
A fellow gardener called me with a zucchini problem. Her plant kept wilting, even though she was watering it regularly. I asked her if the water was reaching the roots. The phone was silent for a moment before she replied, saying she thought so. I had her go check. She called me back a few minutes later astounded. Even though she had been laying the hose next to her zucchini plant, the water was all veering away in another direction once it infiltrated the soil. I had her create an irrigation ring around her zucchini and it grew much better.
Speaking of growing well, infiltration is how minerals get in the water that feeds our plants. As water enters the soil, some minerals are caught in solution. That solution is then absorbed by plants to provide both food and water. Now, some plant nutrients are more mobile than others. Immobile nutrients aren’t actually immobile, they just need a lot more water to move around. Blossom end rot is an example of irregular irrigation causing what looks like a nutrient deficiency. Most gardens on the West Coast of the US have abundant calcium, but may not be watered regularly enough. [Of course, a lab-based soil test is the only way you can learn what’s really in your soil.]
Water moving across the land is called runoff. Surface runoff, or urban drool, is wasteful and potentially dangerous. As suburban sprinklers miss their mark and water streets and sidewalks instead of lawns, they also carry oil, excess fertilizer, trash, and pollutants into waterways. Please make sure your sprinklers water where you think they do and adjust them as needed.
As you can see, the water cycle is a series of steps that pass through various filters along the way. I once had a student create a variety of natural filtering systems for a science project. She used rocks, leaves, sand, and soil in separate containers to filter muddy water. Which material do you think did the best job of cleaning the water?
I thought it would be the rocks, but I was wrong.
It was the soil.
In most cases, thrips are pests. Their feeding causes stippling, stunting, and scarring. Some varieties of thrips can even spread tomato spotted wilt and other diseases. But some thrips are predators
These tiny hunters may not look like much to us, but predatory thrips are other thrips’ worst enemy. In fact, predatory thrips control other thrips more effectively than other natural enemies. Mites, spider mites, and whiteflies are in the same boat. Predatory thrips are worth their weight in gold.
These tiny hunters share many traits with their prey. Males are rare and females can produce offspring without mating. Predatory thrips also eat plant material, but they cannot survive without eating meat.
While most thrips congregate in massive numbers, predatory thrips tend to be loners. There are four major species of predatory thrips:
Like other thrips, these insects are vulnerable to broad-spectrum insecticides and pesticides, horticultural oils and insecticidal soaps, so leave them as a last resort. Instead, create a habitat that attracts these and other beneficial insects. Your predatory thrips need food, water, and shelter, like every other living thing. You can buy predatory thrips. Or, you can simply provide a water source and a variety of places to hide, and these garden helpers will find your garden on their own.
Western flower thrips feed on much more than flowers. In fact, this group sucks the sap out of over 250 different plants. They can also bring tomato spotted wilt and other tospoviruses to your garden. And they bite!
Western flower thrips (Frankliniella occidentalis) are native to the Southwestern United States but have spread to several other continents on contaminated plant material. [Yes, Virginia, invasiveness goes in all directions.] In fact, western flower thrips have earned the dubious distinction of being one of the world’s most important agricultural pests. And they have developed a resistance to many insecticides, so don’t bother spraying. Some scientists believe that western flower thrips have become such a problem and experienced such a significant population explosion as a result of genetic mutations caused by the insecticides we used to try to kill them. Oops.
Western flower thrips description
Male thrips of any type are rare. The same is true for this species. If you do see one, you might notice that they are yellowish-white. They are also larger than many other thrips, measuring up to a whopping 0.06 inches (1.4 mm). When male western flower thrips come together, they fight by flicking the tip of their abdomens at each other. Wouldn’t that be a sight?
Western flower thrips lifecycle
Like other thrips, females do not need to be mated to produce offspring. Eggs are laid in unopened buds and under the epidermis layer of leaves, flowers, and fruit, causing discoloration and distortions. When those eggs hatch, hungry, mobile larvae start feeding. They use raspy mouthparts to shred and pierce to get at the sugary sap they crave. When not eating, they hide in tight little spaces where they are difficult to find. After they have eaten their fill, they enter a two-step, non-feeding pupal stage. In some cases, they drop to the ground to pupate. There can be up to 15 generations each year.
Western flower thrips host plants
It would probably be easier to list the garden plants not affected by western flower thrips, but you need to see just how damaging these micro pests can be. Members of the carrot, broccoli, citrus, legume, melon, mint, onion, sage, stone fruit, and tomato families are all susceptible to western flower thrips. So are apples, artichokes, beets, blueberries, figs, grapes, lettuce, pistachios, rye, strawberries, and wheat. See what I mean?
These pests also feed on several native plants and many popular ornamentals, including carnations, chrysanthemum, gladiolas, impatiens, orchids, petunias, roses, and sweet peas. As thrips feed, their saliva damages the surrounding plant tissue. And nymphs feed heavily on newly forming fruit and leaves, causing damage and spreading disease.
But they aren’t all bad. Western flower thrips also feed on certain mites that attack cotton crops. [I still don’t want them in my garden.]
Western flower thrips damage
You may have to look closely to see these pests, but the damage they cause is more visible. As they feed, they leave behind scarring and stippling of petals, leaves, and other plant parts. You may also see distorted growing tips, pimpling of flower petals, or leaf silvering. The damage varies based on where and when the damage occurred. In some cases, you won’t see it until much later. This later damage may include distorted or spotted fruit, which bruises more easily, Fruit splitting may also occur and Western flower thrips are the main vector of tomato spotted wilt.
Being attracted to bright colors, especially blue, white, and yellow, these pests will land on people wearing those colors and bite them. Thrips won’t drink your blood or make you sick, but you might be uncomfortable for a while. And you can use that information to help control these pests.
Blue sticky sheets are very effective at attracting and capturing western flower thrips. Sadly, beneficial hoverflies are also attracted to those blue sticky sheets. You can protect those garden helpers by surrounding the blue sticky sheet with a mesh that will allow the thrips through, but not the hoverflies. Reflective mulches actively discourage western flower thrips and insidious flower bugs are particularly fond of western flower thrips. For dinner.
Names can be misleading. While it’s true that onion thrips feed on onions, they also eat asparagus, beets, broccoli, cabbage, cauliflower, cucumbers, garlic, leeks, melons, potatoes, pumpkins, strawberries, and zucchini, along with several other fruiting and ornamental plants. If that weren’t trouble enough, they can carry serious plant diseases, too.
Also known as potato thrips, tobacco thrips, and cotton seedling thrips, onion thrips (Thrips tabaci) hide in many herbaceous ornamentals, tucked into cramped quarters where they are easy to overlook.
Onion thrips description
Like other thrips, these garden pests are very small. Maxing out at 0.05 inches (1.3 mm), you could fit 13 or 14 of them end-to-end across an American dime. Adult onion thrips can be yellow to dark brown and sometimes black. Most of them are female. Using a hand lens, you can see that their wings have a single, central vein and long hairs. Eggs are white at first but turn orange a few days later, just before hatching. Larvae are also yellow to brown.
Onion thrips lifecycle
Females use an ovipositor to cut into leaf tissues. Then she tucks her eggs in, under the epidermis, of up to 80 leaves. Less than a week later, those eggs hatch and start sucking the sap from those and neighboring leaves. There are two larval stages during which a lot of sap is eaten. Larvae then stop eating and go through prepupal and pupal stages. Adults generally only live for two or three weeks, but they can overwinter in legumes, grains, weeds, and plant debris.
Damage caused by onion thrips
To get at the sap they love, thrips use their raspy, piercing mouthparts to shred and penetrate the surface of predominantly young leaves and flower petals, breaking open plant cells and drinking their fill.
Since they are feeding on young parts that continue to grow, the damaged areas become elongated, silvery streaks. You may also see leaf curling, stippling, scarring, stunting, leaf tip browning, white patches, and smaller crop sizes. On cauliflower, you may see brown streaks on curds. Damaged areas of leaves cannot perform photosynthesis, injured areas lose water faster than normal, and provide points of entry for other pests and diseases, such as bacterial rot. But onion thrips can infect your plants with a variety of diseases simply by feeding.
Onion thrips are vectors (carriers) for Impatiens necrotic spot virus (INSV), Iris yellow spot virus (IYSV), purple blotch, strawberry necrotic shock virus, tobacco streak virus, and tomato spotted wilt virus (TSWV).
Onion thrips management
Onion thrips are easily dislodged with a garden hose, but that won’t fix the problem. There are some cultural practices you can adopt that will help reduce onion thrips problems. First, clean up plant debris at the end of each growing season. When planting, only use certified pest- and disease-free seedlings, seeds, and onion sets. Monitor the areas surrounding your garden for signs of onion thrips and other pests, and remove volunteer plants that may harbor pests and diseases.
Beneficial insects, such as lacewing larvae, pirate bugs, and predatory thrips will help in the fight against onion thrips, so avoid using broad-spectrum pesticides and insecticides.
Since healthy plants are better able to protect themselves against onion thrips, water and feed your plants with that goal in mind and get your soil tested by a lab. You’ll be glad you did.
Bean thrips (Caliothrips fasciatus) were first found in the 1800s on orange leaves, but they prefer eating beans and other legumes. That being said, these California natives are also found on avocado, pear, and walnut trees, in the navels of navel oranges, mandarins, and other citrus, as well as cantaloupes and other melons. They don’t eat all of these plants, but they do like using them for shelter because of how close they are to your legume crops.
Known as California bean thrips and North American bean thrips, these pests are also called citrus thrips, which is incorrect. Citrus thrips (Scirtothrips citri) are another species. These are also not Asian bean thrips (Megalurothrips mucanae), another entirely different species that we will explore another day. While different, these species have a lot in common with our California bean thrips.
Bean thrips identification
Adult bean thrips have dark, greyish-black bodies with white wing bands. The legs have light and dark bands and both genders have fringed wings that they fold over their backs when at rest. Of course, these pests are about the size of any letter on an American penny, so you probably won’t see all that. If you use a hand lens, you can. You would also be able to see that larvae are yellowish to orange. Those larvae are about 1 mm long at their biggest. Eggs are even smaller, at only 0.008 inches. If you could see them, you’d notice that they are banana-shaped.
What you are more likely to see is the tiny black frass (bug poop) deposits which are often found on the top and underside of leaves, in and around citrus navels, and where clusters of fruit touch. You will also see the damage they cause.
Bean thrips damage
Both larvae and adults feed on leaves and growing tips. As they feed, they cause leaves and growing tips to turn brown and distorted. Silvering and premature defoliation can also occur, reducing plant vigor and resulting in sunscald. Bean thrips also feed on immature beans.
Bean thrips lifecycle
Female thrips lay eggs in the leaves and fruit of legumes. Legume fruits are also known as pulses. Pulses are the beans and lentils we enjoy eating. When bean thrips eggs hatch, first and second instar larvae feed heavily on leaves, growing tips, and immature pulses before they fall to the ground and go through two-stage pupation. Winged adults emerge and the cycle starts again. Like most other thrips, mating is not needed for reproduction to occur: unfertilized eggs produce male offspring and fertilized eggs produced females, but there’s more to it than that.
Research has found that females generally only live 20 to 55 days. At the 10-day mark, short-lived females stop producing female offspring. If they happen to live for more than 50 days, they will produce female offspring until the 30-day mark. How does this stuff evolve? And how do they know? It baffles me.
Bean thrips control
Bean thrips are very bad fliers. They can only fly a few feet in a crazy zig-zag or spiral pattern. But they can catch rides on the wind, so you have to monitor plants for signs of thrips during warm and hot weather.
Bean thrips thrive in hot weather and there isn’t anything you can do about that. But there are steps you can take to make your garden less appealing to bean thrips. First, they like to hide out in weeds, such as prickly lettuce (Lactuca serriola) and wild blue indigo (Baptisia australis) so keep weeds, especially those in the legume family, several feet away from your garden beds.
Yellow sticky sheets attract and capture all sorts of thrips and other pests and they are inexpensive. While research has shown that green sticky sheets are more effective at capturing bean thrips in particular than other colors, you’ll probably do fine with the yellow.
So, what’s going on (and under) your plants’ leaves?
Even if you aren’t growing avocados, avocado thrips are pretty fascinating.
[Just a reminder, the word thrips is the same for one thrips or many thrips.]
Avocado thrips (Scirtothrips perseae) are native to Mexico and Guatemala. In 1971, a single female was stopped at the border. By 1996, avocado thrips were found throughout California and Hawaii. By 1999, it was estimated that avocado thrips infested 99% of California’s avocado trees.
Damage caused by avocado thrips
These pests may be tiny, but they can cause significant damage. Thrips populations explode rapidly in spring and autumn, leading to defoliation and premature leaf drop. This, in turn, reduces tree vitality and crop size. The biggest problem with avocado thrips is the scabby, brown scars on the fruit they create. These damaged areas don’t look very nice and they can create points of entry for rot and other diseases and pests.
Avocado thrips identification
These suckers are tiny. At 0.03 inches long (0.7 mm), you could put 23 adult avocado thrips end-to-end across a dime, making them one of the smaller thrips species. If you could see them up close, you would see that adult avocado thrips are straw-colored, with three red spots on the top of their heads, between their eyes. Those dots are called ocelli and they are light-sensitive organs. They also have yellow abdomens with brown stripes, but their bellies may look greenish because of all the chlorophyll they consume. [I was unable to find a free-to-use image of an avocado thrips, but they look enough like chili thrips that that’s what I used above.] Avocado thrips first instar larva are pale whitish-yellow, while second instar larvae are bigger and brighter yellow.
Avocado thrips lifecycle
Avocado thrips have six distinct life stages and adult females can lay eggs whether they have mated or not. Unfertilized eggs produce males and fertilized eggs produce females. How’s that for efficiency?
Eggs are laid on immature leaves and fruit. When they hatch, they begin feeding in the first larval stage. Then they enter a voracious second larval stage, followed by two non-feeding pupal stages. These pupae hide out in cracks and crevices in the bark and on branches, or in leaf litter (duff) under the tree. Flying adults emerge and begin feeding on leaves and fruit as they search for mates and good sites for egg-laying, and the cycle continues.
Avocado thrips management
Scorching summer heat seems to do a number on thrips, but the eggs they lay beforehand are waiting for conditions to improve. You can use yellow sticky sheets, mulch, and natural enemies to battle avocado thrips. Those natural enemies include various green lacewings and a fascinating predatory thrips called Franklinothrips. I can’t make this stuff up, but we will learn more about that pest later this week. Some predatory mites also like to feed on avocado thrips larvae. To help these predators succeed, avoid using spinosad and other insecticides.
Avocado thrips and several other pests are attracted to yellow sticky sheets. These are inexpensive and very effective, just keep them away from your hair. Also, studies have shown that mulching under (but not touching) trees can result in 50% fewer thrips making it to adulthood. This is because 78% of larvae drop from the tree to pupate on or in the soil. Apparently, a mulch of arborist chips or composted organic yard waste contains enough different predatory nematodes, fungi, bacteria, and other killers of thrips to put a serious dent in their population. Three cheers for biodiversity!
To reduce the chances of the problem in the first place, only buy certified pest- and disease-free rootstock. Of course, while they do it badly, thrips can fly, sort of, so a brisk breeze may be all they need to reach your avocado tree. Be on the lookout. Remember, they like to hide on the underside of avocado leaves.
You can grow a surprising amount of food in your own yard. Ask me how!
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