Trichogramma wasps are small but mighty
These microscopic parasitic wasps protect an astounding collection of edible plants. It might be easier to list those they do not protect, but your almond, apple, avocado, beet, blackberry, blueberry, celery, cherry, corn, cotton, grape, orange and other citrus, legume, papaya, peach, peanut, pear, plum, pumpkin, quince, squash, strawberry, tomato, walnut, and zucchini plants and trees are better off when Trichogramma wasps are in the neighborhood. These tiny wasps protect your plants from damage by parasitizing the eggs of these garden pests:
Parasitic wasps lay their eggs in many common garden pests. This group of beneficial wasps includes braconids, chalcids, Goniozus wasps, ichneumon wasps, and Trichogramma wasps.
Female Trichogramma wasps seek out the eggs of pesky moths and butterflies and sawflies to use as nurseries for her own eggs. When she finds one, the first thing she does is drum on it with her antennae and ovipositor to see if it has already been used. Drumming also helps her determine how big and useful the host egg is. This dictates how many eggs she will insert.
After being inserted into a host egg, the wasp egg develops, pupates, and then hatches, after which it feeds on the contents of the host egg. This turns the host black. If you use a hand lens and see a healthy white host egg with a chewed hole, it means the egg was not parasitized and a healthy (destructive) caterpillar emerged instead.
Trichogramma wasp species
Unless you are a scientist with a very powerful microscope, you will never see a Trichogramma wasp. At 1/25“ to 1/50” long, you could fit 20 to 40 of them nose-to-tail across a dime. If you could see them, you might be struck by the simple beauty of a minuscule yellow wasp with red eyes. Or, you might not. There are over 200 species of Trichogramma around the world.
Before you order a shipment of Trichogramma wasps as a biocontrol, keep in mind that different species of Trichogramma parasitize different hosts. It is important that you order from a reputable seller to avoid releasing a threat to other beneficial insects into your garden. When reading product descriptions, take the time to do a little research before you buy.
Trichogramma wasp eggs are shipped as larvae in host eggs that have been glued to cards. If you buy Trichogramma wasps for release, these tips will give them the best chance at being successful:
Keep in mind that Trichogramma wasps will not kill all the pests they come across. What they do is provide one piece of an integrated pest management program that uses natural processes to reduce the overall impact of pests, rather than spraying chemical poisons on your food.
Watch out for the yellow jackets and hornets, leave mud daubers and paper wasps to go about their business, and add some insectary plants to attract and provide for beneficial wasps, such as the Trichogramma.
Goniozus wasps can sting, but you’ll never have to worry about that.
Like many other parasitic wasps, adult Goniozus wasps mostly feed on nectar, sap, and other sweets. The benefit they provide is that they also parasitize pests of almond, apple, citrus, fig, pistachio, walnut, and coconut trees, as well as blueberries, blackberries, grapes, and strawberries.
Navel orangeworm, obliquebanded leafroller, and light brown apple moth caterpillars are favorite egg-laying hosts, giving Goniozus the common name of navel orangeworm wasp. Personally, I prefer Goniozus - in my mind, it’s the Gonzo wasp. These garden helpers also use banana scab moths and several insect pests associated with galls as hosts.
Goniozus wasp description
There are 20 different Goniozus wasp species, and they all look like tiny flying ants. Walking through the garden, you may simply see a very small, shiny brown or black wasp-waisted insect. Most insects who fit that description are beneficial, so resist the urge to swat them away. Instead, take a moment and see if you can tell what they are up to.
Similar to cuckoo bird species, which lay their eggs in the nests of other birds, Goniozus wasps are also known as cuckoo wasps because they lay their eggs in the bodies of other insects.
Adult females use their stinging ovipositor (egg-laying tube) to paralyze their victims, injecting hosts repeatedly with venom. The venom of some Goniozus wasps is permanent, but not all. In those cases, the venom only lasts half an hour or so, so she has that much time to transport her victim, mostly by dragging the much larger host, to a good hiding spot. If necessary, she will continue to inject venom over several hours, if that’s how long it takes to get where she needs to go.
Once tucked safely into a crevice somewhere, some females will feed on the juices of said caterpillar over the next few days, aiding in the development of her eggs. This does not always kill the host. In some cases, the host simply walks away, a little worse for the wear, until the eggs hatch and begin feeding from the inside out.
Goniozus larvae go through several developmental stages over the next 2 or 3 days, attached to their host, ultimately spinning tiny cocoons around themselves before reaching adulthood. Apparently, Goniozus wasps have been observed paralyzing far more hosts than they can possibly use for egg-laying. No one knows why.
How to attract Goniozus wasps
Beneficial parasitic wasps can be attracted to your garden with insectary plants. Insectary plants provide the food and shelter needed by these garden helpers. Most insectary plants feature umbrella-shaped flowers commonly seen in carrot, dill, cumin, mint, and cilantro, or globe-shaped flowers, such as chives. Allowing these plants to go to seed not only attracts beneficial insects, but seeds then create perpetual, edible crops. Other insectary plants include cosmos, sweet alyssum, yarrow, dandelions, and borage.
Adding these useful plants to your yard looks nice, too!
Unlike beneficial parasitic wasps, hornets attack honey bees, steal honey, invade bat houses, girdle branches, and ruin summer picnics.
So why would we want to tolerate hornets in the garden? What good can they do? Let’s find out!
Worldwide, there are 22 hornet (Vespa) species, including:
There are also 3 species of nocturnal Asian Provespa, which are not actually hornets.
Despite their name, bald-faced hornets (Dolichovespula maculata), commonly seen in California, are not true hornets, either.
There is only one true hornet found in North America: the European hornet (Vespa crabro). Introduced in the 1800s, this hornet is now found throughout the U.S.
Hornets are highly social insects. They live in large colonies, housed in papery hives, that are commonly built in dark crevices, such as dead tree trunks, under house eaves, and in your garage. Hives are made up of interconnected brood cells. Both the queen and workers can lay eggs. Fertilized eggs laid by the queen develop into sterile females, called ‘gynes’ while eggs produced by workers develop into males, called drones. Drones mate with the queen during ‘nuptial flights’. As a result, a hornet’s nest is largely populated by two nearly distinct gender-dictated populations. Workers care for the eggs as they move through larval and pupal stages, ultimately emerging as adult hornets.
Hornets and yellow jackets are both types of wasps, though yellow jackets tend to be smaller, with more yellow and black, while hornets tend toward more black and white or yellow and brown coloration.
Most hornets average 3/4” to 1”, while queens can be 1-1/2” long. If you look closely, you might be able to see that a male hornet abdomen has six segments, while females have seven segments and a stinging ovipositor.
Hornet stings and allergies
Like many other stinging insects, hornets become aggressive when they feel accosted (swung at, stepped on, sat on, that sort of thing), or when they believe their food supply or the colony are threatened.
Hornet stings are more dangerous to humans that other insect stings because they contain higher concentrations of acetylcholine. Hornet stingers are not barbed and can be reused many times. Also, when one hornet stings you, it releases chemicals that tell other hornets to sting you, as well. These same chemicals are also released when you kill a hornet or spray a hornet’s nest with poison, so be forewarned.
If you are allergic to stinging insects, you should always carry antihistamines or an EpiPen with you. Signs of an allergic reaction include shortness of breath, swelling of the face, lips, or throat, severe itching, weak or racing pulse, nausea, wheezing or gasping. If any of these symptoms occur, get medical help immediately. Call 911, grab a family member, or a neighbor right away. These symptoms can quickly escalate into a life-threatening situation. Otherwise, follow these steps to ease your temporary pain:
You can also take aspirin or acetaminophen to ease the pain, just be cautious about mixing medications, as that can cause yet another medical problem. Generally speaking, you are going to feel really miserable for 30 to 45 minutes, moderately uncomfortable for the rest of the afternoon, and you may experience discomfort for a week or so. You may also want to apply hydrocortisone or calamine lotion to the area. Pastes made of baking soda or colloidal oatmeal can also sooth the area. If you haven’t had a tetanus shot in the past 10 years, that can be a good idea, as well.
So, why would we want hornets in the garden?
Adult hornets feed on sweets, such as fallen fruit, sap, and your lemonade. They also collect insects for their larvae. This is part of the reason why they cause us so much grief during picnic season. From a hornet’s point of view, it is simply defending a food source when it refuses to back down from your burger and fruit punch. In addition to your picnic, European hornets commonly chew up beetles, dragonflies, grasshoppers and crickets, katydids, locusts, mantises, moths, and other wasps. This pulp is then taken back to the colony, where it is fed to larvae in the nest.
If you start having a hornet problem while dining outside, you can reduce the chance of stings by placing a plate of meat and fruit somewhat away from the picnic table.
If hornets become a problem around your home, try excluding them before poisoning them. Those chemicals tend to create more problems than they resolve.
There is far more to wasps and hornets than you might expect.
This group of insects is massive and it contains many beneficial insects. You may not be familiar with chalcidoid wasps, but odds are pretty high they’ve been working hard in your garden all along.
The chalcidoid superfamily of wasps contains 22,500 known species, with an estimated 500,000 species yet to be named. One of those families in particular, the Chalcididae, gives us chalcid wasps. And figs.
Chalcid wasp description
Ranging from only 1.5 to 0.75 mm (1/50 - 1/100”), you could fit 12 to 24 chalcid wasps nose-to-tail across a dime, so you probably will never see one. If you could see them, you would understand how they got their name. The word ‘chalcid’ comes to us from the Greek word for ‘copper’ because most chalcid wasps are a metallic bronze or copper color, though some species are metallic blue or green, and some are the more classic black and yellow variety.
Beneficial chalcid wasps
Most chalcids are parasitic wasps. They lay their eggs in several common garden pests. When the eggs hatch, larvae feed on the host insect before pupating into adult wasps. [I know, it’s sounds awful.] Those hosts include the eggs and larvae of flies, beetles, moths and butterflies, some spiders and nematodes, and true bugs. Since true bugs (Hemiptera) include aphids, leafhoppers, spittlebugs, thrips, whiteflies, and scale insects, I am all for more chalcid wasps! [Plus, I love figs!]
Figs and tiny wasps
While most chalcidoid wasps parasitize all those pests, a handful of them are phytophagous, which means the larvae hide and feed in stems, galls, seeds, and flowers. Fig flowers, in particular, are hidden clusters found inside a hollow structure called a syconium. Fig pollination is usually completed by tiny specialized wasps, such as chalcid wasps.
But, not all chalcids are good.
Chalcids as pests
Other phytophagous chalcids are not so helpful. These tiny wasps are pests because they lay their eggs in seeds. When those eggs hatch, larvae eat the seeds of pistachios and alfalfa, among others, creating burrows and allowing fungal and bacterial diseases a point of entry.
In many cases, sticky barriers can be used to reduce the damage caused by these pests. Most chalcids, however, are beneficial.
You can attract chalcid wasps to your garden by installing insectary plants, such as yarrow.
Wasps may have a bad reputation, but there are beneficial wasps, and ichneumon wasps [pronounced ick-NOO-mon] are one of those Good Guys. Well, mostly.
Ichneumon wasps are parasitic wasps and they have been around for over 15 million years.
There are somewhere between 60,000 and 100,000 different ichneumon wasp species in the world, with 5,000 species in North America. Clearly, with those numbers, there is significant variety in appearance.
Ichneumon wasp description
Like other wasps, the ichneumons have a narrow body and an even narrower waist. Some females have an especially long ovipositor, which is often mistaken for a stinger. Ranging in length from 1/10” to over 5” long, they can be black, brown, yellow, or some pattern combination of those colors. These wasps have 16 or more segments in their longer than average antennae. Ichneumons are solitary wasps.
Common ichneumon prey
Adult ichneumon wasps eat little or nothing. Their larvae, on the other hand, are voracious feeders of beetle, butterfly and moth, wasp, ant, fly, and sawfly larvae and pupae or chrysalises. This is what makes ichneumon wasps so helpful in the garden. They also parasitize beet armyworms, some spiders, and wood-boring grubs.
Some ichneumon wasps do this by using their long antennae to detect prey, then inserting the ovipositor into the wood, plant, or soil, to strike their prey, piercing its skin and inserting an egg. Other ichneumon wasps crawl down the stems of aquatic plants to inject eggs into water-dwelling insects. Yet another ichneumon is the parasite of a parasite, making it a hyperparasitoid. This ichneumon lays its eggs in moth-eating ant larvae. She emits chemicals that confuse the ants as she does her deed.
Ichneumon wasp lifecycle
Most parasitic wasps lay their eggs on, in, or near their prey, but ichneumon wasps kill their prey outright and then lay eggs. When the eggs hatch, larvae feed on the host’s body. After hatching and eating their host, ichneumon larvae spin cocoons and pupate in or near the exoskeletons of their first meal. When they emerge from their cocoon, they are adult wasps who go in search of a mate.
These garden helpers do not sting and they are worth their weight in gold, so check before swatting at something just because it might be a wasp. [Swatting at wasps is usually a bad idea, anyway…}
One of the best ways to attract and provide for beneficial ichneumon wasps in California is to plant coyote brush (Baccharis pilularis) and to maintain hedgerows.
Sweet, juicy persimmons are easier to grow than you might expect.
There are many good reasons for growing your own persimmon tree, the first of which is they are not particularly fussy about soil and they are nearly pest-free. You don’t need to worry about chilling hours as much as with other fruit trees, and they bloom late enough in the season to avoid frost damage.
Persimmon is a tropical tree that grows best in Hardiness Zones 7 to 10, and they are large. Mature persimmon trees can grow from 15 to 60 feet tall and 20 feet across, with a lovely rounded canopy. Leaves are both glossy and leathery on top, with a brown, fuzzy undersurface. These leaves will fall off in autumn, being deciduous, but that makes it easier to prune and manage the tree during dormancy.
Your first decision, when growing persimmon, is to decide which type you want.
Types of persimmon
Persimmons are actually the fruit of several trees in the Diospyros (‘Zeus’s wheat’) genus. This group of trees is divided between valuable, dense ebony lumber (Diospyros ebenum, et al) and fruit-producing varieties. Within the fruit-producing varieties, there are some you can eat right away, and some you’d be better off waiting a while.
The North American native persimmon (Diospyros virginiana) tends to be smaller and seedier than its more popular Asian cousin (D. kaki). The Oriental, or Japanese persimmon is further divided into two groups: astringent and non-astringent. That astringency [read ‘pucker factor’] is caused by tannins. Those tannins can make your mouth feel as though you just washed your mouth out with witch hazel, which I do not recommend. Generally speaking, the astringent varieties need to be fully ripe and soft before becoming sweet and delicious.
With over 2,000 cultivars of fruit-producing persimmon trees, you have several to choose from, including:
Native and Oriental persimmon trees will not cross-pollinate.
Persimmon fruits and flowers
Native persimmon trees are dioecious, meaning they have male or female flowers, but not both. If you have one of these, you will need two trees. Oriental persimmon trees have both male and female flowers. In either case, those flowers are relatively small, creamy white, with a large green calyx. The calyx is the cup-like structure seen at the base of a flower’s petals and is the hard, dried leaves on top of a harvested persimmon. Botanically, a persimmon fruit is a berry because it is formed from a single fertilized plant ovary.
Fruits mature in autumn, staying on the tree into winter. Don’t be fooled, however. Squirrels and rats have an uncanny ability to gnaw the insides out of your persimmons from the side facing away from your windows. I have a friend who discovered, to her dismay, that every single piece of fruit, and there were many pieces of fruit, had all been hollowed out while she wasn’t looking.
If you only have room for one persimmon tree, just make sure it is a self-pollinating variety. Both ‘Hachiya’ and ‘Fuyu’ will produce fruit without a second tree.
How to grow a persimmon tree
If you want to grow a persimmon tree from seed, you will need to put it in the refrigerator for a couple of months. This is called stratification and it mimics the effects of winter weather. Unlike other fruit trees, which are pretty much companionable to a wide variety of root stock grafts, persimmon trees are not as amenable. You are probably best off buying bare root stock from a reputable seller. Just be gentle with your young tree. The immature taproot breaks easily.
Persimmon trees perform best in soil with a pH of 6.0 to 6.5, which may be more acidic than is present in your soil. Keep in mind that altering pH is an uphill battle that requires constant attention and effort. If you are determined, you can acidify your soil to make things more hospitable for your persimmon tree. Your persimmon tree will benefit from good air flow, but the wood tends to be brittle, so provide protection from strong winds.
When planting a young persimmon tree, it is critical that the tree is planted at the proper depth. Then, cut the aboveground portion down to 3 feet in height and mud it in well. You will also want to provide sunburn and herbivore feeding protection. Deer, rats, squirrels, birds, and gophers will gnaw roots, stems, bark, or fruit, depending on the species. Even coyotes enjoy the occasional persimmon.
Select a location with plenty of sunlight, though partial shade will work, too. California Rare Fruit Growers, Inc. suggests keeping persimmon trees away from eucalyptus trees. I’m sure there is a good reason, I just don’t know what it is.
Regular irrigation will improve fruit size and quality, though the trees are somewhat drought tolerant. Mature trees will need 36 to 48 inches of water each year.
Persimmon trees do not need a lot in the way of feeding. In fact, if you give them too much nitrogen, they will drop their fruit! Over-feeding, over-watering, and too much boron in the soil can cause blossom drop and young fruit drop. Top dressing with aged compost and some mulch is probably a better way to go, unless a lab-based soil test tells you some important plant nutrient is missing.
Persimmon fruit forms along the sides and at the tips of long, current year stems. If those stems are too long, the branches are likely to break. During the dormant season, train your persimmon tree into a modified central leader or open vase system, removing any dead, diseased, or rubbing branches. Each year, you will want to perform light to medium pruning for size, structure, and air flow. Persimmon can also be pruned into a lovely espalier. Heavy fruit loads can cause branch loss, so fruit thinning is a good idea.
Persimmon pests and diseases
While relatively pest-free, persimmons may occasionally be attacked by root nematodes, mealybugs and scale insects. If you see ant trails, look more closely for signs of scale infestation. You can use sticky barriers to eliminate the protection provide by ants. Other minor pests include whiteflies, thrips, and mites.
The diseases most likely to impact a persimmon tree include armillaria root rot, grey mold, leaf blight, leaf spot, and Phytophthora root and crown rot. Fusarium dieback may also occur.
More commonly, nutrient deficiencies can cause a number of symptoms. Low iron cause cause leaf bleaching, while insufficient calcium leads to leaf curling, and magnesium deficiencies cause brown spots on leaves. Sunburn damage is common, so whitewash exposed areas and keep trees well irrigated during the peak of summer.
We should all have such problems…
You buy a seedling.
You dig a hole. You place your fingers around the stem and gently flip the pot upside down, dislodging plant and soil.
You carefully tip the leaves skyward and lower the cube of roots and soil into the hole, pulling surrounding soil into the empty space. Then you tamp down the soil with your hands, right?
We’ve been doing it forever but it’s the wrong thing to do and there are several reasons why.
It all starts with the conditions under which seedlings are grown.
The state of a seedling
Commercially available seedlings start out life in as perfect an environment as possible. Protected by greenhouse walls or hoop shelters, temperatures, soil, moisture levels, nutrient availability, everything is working in its favor. Add sunlight and water and those seeds germinate and start growing like crazy. Then they get loaded into flats, which get loaded onto trucks. Those trucks are dark and bouncy. Roots and leaves get rattled around a bit, before being moved a few more times to end up in new lighting, new temperatures, and environments where people pick them up and put them down, repeatedly. Finally, they get in a car, go home, and [hopefully] spend some time in quarantine before being designated some garden real estate.
Even seedlings started at home end up in a pot that they are about to outgrow, if they haven't become root bound already.
As delicate root hairs reach the walls of their containerized world, they twist and turn, looking for more room. Eventually, all those twists and turns can get crowded and a little abrasive. Root hairs break off very easily.
At 1/10 the diameter of a human hair, root hairs start forming right after a seed germinates. These tiny growths profoundly increase the surface area of the root system, making the roots better at absorbing water and nutrients, anchoring the plant, and facilitating microbe interactions. When these delicate hairs break off, they can’t do their job. It is the damage done to root hairs during transplanting that causes most of the wilting associated with transplant shock.
Water and gravity
Instead of tamping down the soil and breaking off millions of valuable root hairs, let water and gravity do the job the way nature intended: disrupted soil gets rained on, rain drops collect and make soil heavier, drawing particles down into some air pockets while leaving important macropores and micropores, that allow air, water, and roots to move through the soil, intact. Your watering can or gentle garden hose spray do the same thing. No tamping down required.
As you add seedlings to your garden, resist the urge to crush those delicate root hairs and mud them in, instead. Then, tuck them in with a nice blanket of mulch, for good measure.
Cantaloupes are a unique type of muskmelon. And American cantaloupes aren’t actually cantaloupes at all.
Did you know that melons are actually berries?
It’s true! Because the fruit, or pericarp, of a cantaloupe is produced by a single ovary, cantaloupes are considered berries. Specifically melons are modified berries called pepos. Pepos are formed from an inferior (meaning internal, not less than) ovary and they feature many seeds. Pumpkins and cucumbers are also pepos.
Also known as rockmelons, cantaloupes are members of the squash family. Like other cucurbits (Cucurbitaceae), cantaloupes feature a hard outer rind that protects the lush fruit inside.
Types of cantaloupe
Here, in the U.S., our cantaloupes have a strongly textured, or ribbed, rind and bright orange flesh. This North American variety (Cucumis melo var. reticulatus) is not technically a true cantaloupe.
How cantaloupes grow
Cantaloupes are vining annuals that love heat. Temperatures between 85°F and 95°F are ideal, and these plants can tolerate temperatures as high as 104°F. Cantaloupe’s bisexual flowers are mostly pollinated by bees, so a healthy bee population is important for a good melon crop. Whereas a single bee visit is enough to pollinate other crops, cantaloupes are fickle and may need 10 to 15 bee visits before pollination is completed.
Cantaloupes can be grown successfully in all types of soil and they even seem to thrive in our heavy clay, as long as there is good drainage. Cantaloupes are sensitive to root rot diseases, so proper soil aeration goes a long way toward keeping cantaloupe plants healthy.
To grow your own cantaloupes, wait until temperatures are well above 60°F and plant single seeds 3” to 6” deep in loose mounds. Mounds should be 3 feet apart and in full sun. Keep the mound moist, but not soggy, until germination occurs.
Cantaloupes are moderate feeders, which means a top dressing of aged compost after germination is probably all that is needed. [Of course, you should still conduct a soil test to make sure your plants have access to all the nutrients they need.]
Cantaloupe pests and diseases
Aphids, green peach aphids, in particular, cucumber beetles, cutworms, leafhoppers, leaf miners, root knot nematodes, seed-corn maggots, silverleaf whiteflies, spider mites, squash bugs, and wireworms may all pester your melons, but many of these pests can be thwarted by row covers and regular monitoring. The real threat to your melon crop is disease.
Cantaloupes are prone to several fungal diseases, including belly rot, downy mildews, Fusarium wilt, Monosporascus root rot, powdery mildew, sudden wilt, and Verticillium wilt. Aphid-borne viral diseases, such as cucumber mosaic virus, cucurbit yellows stunt disorder, watermelon mosaic virus, and zucchini yellows mosaic virus may also occur, as can bacterial angular leafspot.
Proper plant spacing and the use of a trellis can interrupt many of these diseases cycles by improving air flow. Fruits grown up a trellis will need to be supported with hammocks. Melons growing on the ground should be protected with a layer of straw or sawdust, a board, or some other material that gets them up off the soil.
Choosing resistant varieties, removing weeds, maintaining good air flow, and avoiding overhead watering will all help keep your melon vines healthy.
That being said, weeds can be a serious problem in cantaloupe beds as hideouts for pests and diseases. Stay on top of those water and nutrient thieves from the start to ensure a healthy crop of melons later in the summer. And watch your watering. Heavy rain (or over-watering) can cause fruit split.
Cantaloupes are ready for harvest when a thin crack can be seen encircling the stem end and the fruit comes away from the vine easily. This is called the “full slip” stage. Cantaloupes should be eaten as soon as possible after being harvested, as they tend to lose moisture more quickly than many other members of this family. If you end up with a bumper crop of melons, your best method of preservation is to try your hand at canning some preserves. Cantaloupe pairs nicely with peaches and nectarines. And be sure to save seeds for next year's crop!
The majority of the world’s cantaloupe crop is grown in China and shipped around the world. Believe me when I tell you that harvesting a fresh melon from your yard is a very satisfying and delicious experience.
And halved cantaloupes make lovely ice cream bowls...
Cumin’s pungent aroma has made it a popular spice since ancient times.
Kept on Egyptian tables the way we use salt and pepper, cumin is said to provide many different health benefits, though there is zero scientific proof for any of those claims, There are still plenty of other good reasons for growing your own cumin.
Cumin’s umbrella-shaped flowers make it easy to identify as a member of the parsley family. Other common garden Umbellifers, or Apiaceae, include carrots, celery, dill, parsnips, and fennel. Like other umbellifers, cumin flowers attract many beneficial insects, such as hoverflies and pollinators.
Native to the Middle East, cumin (Cuminum cyminum) grows best in hot, dry regions and is very drought tolerant. It takes 3 to 4 months of hot weather to reach maturity. If temperatures drop, leaves will turn purple. If it gets really cold, cumin is very susceptible to frost damage.
The cumin plant
Cumin seeds look a lot like caraway seeds, being oblong with ridges. Those ridges are oil glands. Cumin plants grow 12 to 20 inches tall, with attractive, feathery leaves. Cumin seeds are contained in dried fruits called achenes.
How to grow cumin
If you have the heat, you can grow cumin. Seeds should be planted 1/4 deep and spaced 8” apart. These plants are very delicate when they first germinate and do not perform well in heavy clay soil. They prefer loose, sandy soil with good drainage, which makes them an excellent choice for raised beds. The ideal pH is 6.8 to 8.3.
Cumin pests and diseases
Aphids, mites, thrips, tobacco caterpillars, cutworms, cigarette beetles, drug store beetles, and root knot nematodes may cause problems for cumin. Diseases that may strike your cumin plants include Fusarium wilt, blight, powdery mildew, and damping off disease.
Cumin seeds are frequently included in birdseed mixes, so this plant has spread globally. Once established, this annual plant readily self-seeds an area.
In 2015, dreaded chili thrips arrived in California from Texas and Florida. Originally from Southeast Asia or India, this pest first hit North America in 1991 and is expected to be a permanent part of our gardening experience from here on out.
Let’s see what we’re up against.
Before we do that, however, let’s get one thing clear. Whether you are talking about many thrips, or just one (and there is never just one), they are both referred to as “thrips”, with the “s” on the end. I know, it’s strange, but there it is. It comes from an 18th century word meaning “woodworm”, which is even more strange since these pests are disease-carrying sap-suckers.
So, what does a thrips look like?
Chili thrips description
Like other thrips, chili thrips (Scirtothrips dorsalis Hood) are really tiny - often less than 1/20” long. That works out to 8 or 9 thrips, standing nose-to-tail, across the head of a dime. Their pale bodies are thin and they have dark wings, but you may never get that close. What you may see is light-colored flecks of movement as you walk past a plant. That’s your first clue there is a problem.
Plants vulnerable to chili thrips
Your habaneros and Scotch bonnets are not the only plants susceptible to these pests. In fact, over 100 species [no, make that 200 species], from 40 different plant families [rather, 70 families], have been identified. Host plants include fruit trees, such as apples, bananas, cashews, citrus, figs, lychee, mango, pears, and even the beloved cocoa bean. Other garden favorites include asparagus, basil, beans, blueberries, buckwheat, corn, eggplant, grapes, peanuts, sweet peppers, soybeans, strawberries, and tomatoes, as well as many popular ornamentals, including chrysanthemums, coleus, camellia, Gerber daisies, poinsettias, pyracantha, roses, snapdragons, and zinnia.
Damage caused by chili thrips
Symptoms of chili thrips infestation are first seen as damage to the upper surfaces of leaves, creating yellowish-green or brown angular spots on the upper surface and a grey sheen on the under surface. Leaves may become thickened or start curling. As nutrients and water are pulled from the plant, stunting, bronzing, distorted or elongated leaves, and flower bud scarring are also seen. Severe infestation can lead to the complete defoliation of a plant and these pests can carry tomato spotted wilt virus, peanut necrosis virus, peanut chlorotic fan virus, and tobacco streak virus.
Compounding the problem, chili thrips damage looks a lot like chemical overspray, aphid feeding, and micronutrient deficiencies.
Chili thrips lifecycle
Female chili thrips insert eggs into leaves, petioles, fruits, leaf axils, in curled leaves, and in leaf litter. In other words, they can be anywhere. Those eggs hatch in about one week and go through two larval stages in the second week. A single adult female can lay 60 to 200 eggs in her lifetime. That works out to a lot of sap sucking, disease-carrying insects.
Controlling chili thrips
Fast moving, highly prolific, and devastating to many of our garden plants, chili thrips have already developed resistance to insecticides containing asbifenthrin, cyfluthrin, and permethrin, so don’t bother. As of 2016, chili thrips had not yet developed resistance to insecticides containing acephate, imidacloprid, and orspinosad, but that window of opportunity may already have passed, and who wants those chemicals on their food anyway? Spinosad is actually more effective and less damaging to the environment. Sticky barriers may be used to monitor for chili thrips, but they won’t control the problem.
Your best defense against chili thrips is to encourage beneficial insects, such as green lacewings and minute pirate bugs. Certain predatory mites and thrips and parasitic wasps will also help in the battle against chili thrips. These garden helpers are all attracted to gardens with a wide variety of plants and flowers, a clean water supply, and the absence of broad spectrum pesticides. Sadly, releasing purchased predators into the garden rarely works out. If conditions are good, they will come to you. If conditions are not good, it doesn’t matter how many times you buy and release beneficial insects. They will simply leave or die.
Dusty conditions should also be avoided. Give susceptible plants an occasional quick shower with the garden hose in the morning to make life more difficult for thrips of all sorts. Also, stressed plants are more susceptible to infestation than healthy plants. This is yet another reason for selecting resistant cultivars that are suited to your microclimate, putting them into quarantine until proven healthy, feeding and watering them when they need it, and then giving them a helping hand with row covers as they become hardened off to your garden. Since shearing cuts off the ends of all twigs, it should be avoided if thrips are suspected. It is simply too stressful for the plant. Reflective mulch may disrupt thrips flight, if you want to try that.
Infested foliage should be removed, bagged, and taken to your local County Extension Office for identification. If you don’t have time for that trip, please throw the bag in the trash. Do not compost plant material infested with even one chili thrips.
You can grow a surprising amount of food in your own yard. Ask me how!