Stand in the middle of your garden, close your eyes and listen.
Mentally screen out any urban noise — planes overhead, barking dogs, traffic, children — and focus on the natural world. You might hear the hum of honeybees, chirping of birds, wind rustling through leaves or tall grass, or rhythmic drips of moving water.
Those familiar sounds bring a feeling of peace, right?
But take out a magnifying glass and you’ll find that that sense of calm masks a silent war of sorts. On a microscopic level, pests and predators are battling to the death amid the leaves and soil of our gardens.
That’s not a bad thing.
To flip it, predators of pests are actually beneficial. They help keep our gardens healthy by combating pests that might otherwise damage or destroy our crops.
Use of predator insects dates back some 1700 years, when citrus growers in China colonized yellow fear ants to protect against insect pests. The growers linked their trees with bamboo strips so the ants could more easily move from one infestation to the next.
Most of us were introduced to beneficials when we were children, via ladybugs. The cute, round bugs are real charmers. However, their ability to annihilate pests should not be underestimated. Indeed, the importation of Australian ladybird beetles to southern California in the 1880s saved the fledgling citrus industry from a deadly wipeout threatened by cottony cushion scale.
The Big Three
Today, aphids are often the gateway pest that sparks interest in beneficial insects.
Ron Whitehurst, a pest control advisor and co-owner of Rincon-Vitova Insectaries, a company in Ventura that produces and distributes insects and other organisms, supplies and tools for biological control of pests, advises first simply blasting aphids with water. Next up, a soapy solution of an ounce and a half of liquid soap to a gallon of water.
If neither works, he then suggests releasing beneficial insects.
Convergent ladybugs (Hippodamia convergens) are a good start, especially early in the year when other beneficials might not be as active. They are voracious eaters: a single black and orange-spotted alligator-shaped larva may eat 400 aphids before it pupates, while an adult may eat 5,000 aphids during its year-long life.
When temperatures warm up, green lacewings can be even more effective.
The larvae devour not only aphids, but caterpillar pests, eggs and young larvae of Colorado potato beetles, flea beetles, leaf hoppers, mealy bugs, psyllids, scales, spider mites, thrips and whiteflies. As a bonus: unlike ladybugs, green lacewing larvae can’t fly away.
Also, it’s interesting to note that once the larvae mature to gossamer-winged adults, they become vegetarians, supping only on pollen and nectar.
A third aphid-eater Whitehurst recommends is Aphidoletes aphidimyza.
“The mamma Aphidoletes comes around and finds aphids. The baby, a little orange maggot, spears the aphids and sucks them dry and throws them off the plant,” he said. “They tend to colonize. You could do one release, then let them grow and develop.”
To conquer spider mites, thrips, moths and other pests, a second tier of beneficial insects awaits.
“If people are growing lettuces and culinary herbs, spider mites would be one of the things that would be a major pest problem,” Whitehurst said. “From a cultural standpoint, use overhead watering. Spider mites like it hot and dry. So increase the humidity and decrease the temperature to make them less competitive.”
Absent that, he recommends predator mites. Neoseiulus californicus battles spider mites as well as persea mites, which are especially pernicious bugs that suck the chlorophyll from avocado leaves and eventually defoliate the trees.
Minute pirate bugs (Orius insidiosus) go after western flower thrips, onion thrips and whiteflies.
Or for a one-two punch, Whitehurst recommends Ambleyseius cucumeris, which tackles thrips on the upper part of a plant, and Hypoaspis miles, a soil-dwelling mite that feeds on thrips as they drop on the soil to pupate.
“If you grow a bunch of culinary herbs, it would make sense to inoculate early in the season with those two predator mites to bring down the population of thrips,” he said.
Trichogramma wasps are parasitic insects that lay their eggs within the eggs of over 200 pest moth species. The trichogramma larvae eat the innards of the pest eggs, pupate, then emerge as winged adults, ready to lay ever more eggs. The wasps are especially effective against cabbage caterpillars and worms.
Creating a Habitat
You can grow your own beneficial insects by the way you garden.
“We want to emphasize the whole basic organic or biological approach to gardening,” Whitehurst said. “Focus on feeding the microbes in the soil so the roots on the plants are healthy. Then fertilize with compost and use mulch where appropriate. That will again feed the soil microbes and feed the decomposer insects that feed the predator insects, like the predatory ground beetles and wolf spiders.”
Now you don’t have to be a purist. It’s fine to buy beneficials. But to entice them in the first place, or encourage them to stick around after they’ve devoured your pests, sustenance is a must.
The trick is to plant plants that provide a succession of pollen and nectar year-round. The patch can be left a little weedy or wild, and should never be sprayed.
“Dill is a real champ as far as having this umbel-shaped flower that has nectar available to big insects and little insects,” Whitehurst said. “Several others in the Apiaceae family are fennel, cilantro and anise. You can grow more moderate versions. Ornamental bronze fennel is a little more reserved than the wild fennel.”
Other herbs to sustain beneficials include angelica, anise hyssop, borage, caraway, chamomile, marjoram, oregano, parsley, sage, teucrium, thyme and yarrow.
Native plants include milkweed (Asclepias), saltbush (Atriplex), coyote brush (Baccharis), wild lilac (Ceanothus), buckwheat (Eriogonum), toyon (Heteromeles), bladder pod (Isomeris) and coffeeberry (Rhamnus).
A handful of miscellaneous plants includes golden marguerite (Anthemis tinctoria), bell beans, black-eyed peas, bachelor’s buttons (Centaurea cyanus), corn, cosmos, sweet alyssum (Lobularia maritima), yellow sweet clover (Melilotus officinalis), sunflowers and white clover (Trifolia repens).
Lending a Hand
After you’ve built up an ecosystem and colonized beneficials in one spot, it’s easy to move them to wherever trouble is brewing by spraying an attractant.
For instance, if aphids are massing on your broccoli, Whitehurst advises the following.
“Mix equal parts sugar and dried brewers yeast. Add water. Then spray large droplets, widely scattered. That simulates the situation where you have plants that are real sticky with honeydew. That will draw in the lacewings and ladybirds and syrphid flies and such… It’s pretty effective as far as drawing in the aphid predators.”
Helping Combat the Enemy
While beneficial insects dominate their prey, they are vulnerable to ants.
“Ants collect the honeydew, the sugary poop from aphids, whitefly, scale,” Whitehurst said. “If they’re working the plants, they will be collecting that honeydew and driving off the beneficial insects that are trying to eat the pests that are generating their candy.”
Controlling ants, then, is an important aspect of supporting and maintaining your beneficials. Whitehurst recommends buying or mixing up a borate-based bait. The ants will eat the bait, take it back to their colonies and perish.
Thanks to the California Department of Food & Agriculture for providing these photos.
A slightly condensed version of this article was first published in Edible Santa Barbara.
Copyright, Joan S. Bolton. All rights reserved. Reproduction of text or photos in any form is prohibited without written permission.