​Are you seeing spots? Black or brown spots on apples and apple leaves? It may be apple blotch.

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 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.

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.

​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.


Moth lifecycle

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.


Good moths

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.

Moth management

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.

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.

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.

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.

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.

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 sounds

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.

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.

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.

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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.

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?

Runoff

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.

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. ​

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.

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.

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.

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.

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[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.