Planet Moth

September 7, 2009

WITH 200,000 known species, Earth is almost Planet Moth. Only beetle species are more numerous. Moths have been denizens of Earth since prehistoric times, long before the ascent of man. Mostly nocturnal, secretive and nondescript, moths play a quiet ecological role, doing some vital pollination of plants and nourishing the food chain by feeding birds, bats, lizards, fish, frogs and many other critters.

Silkworm moths, domesticated as a crop on mulberry trees in China about 5,000 years ago, are famous in the textile industry. Clothes moths are infamous for feeding on garments, and have spurred herbal pest control innovations since ancient times. Humankind has sprayed billions of tons of synthetic pesticides against cotton bollworm moths, Indian meal moths, diamondback moths, cabbage loopers, leafrollers, leafminers, stemborers, codling moths, corn earworms, inchworms, armyworms, spruce budworms, gypsy moths and bagworms, to name but a few. However, alternatives like pheromones are becoming more widely used to monitor, trap, and confuse moths and prevent mating and egg laying (eggs hatch into caterpillars that eat, pupate and beget new moths).

Biocontrol by natural enemies, including birds, bats, toads, spiders and other insects, is part of the ancient planetary rhythm for controlling moths and maintaining global ecological balance. From Texas, Arizona, California and Mexico to China, Russia, Central America and Australia, microscopic Trichogramma wasps are among the most popular insectary-reared natural enemies released to stop moth egg hatching. Cotton growers escaping the pesticide treadmill have traditionally been big users of Trichogramma wasps. Tomatoes, corn, grapes, tree fruits, ornamental nurseries and many other crops also use Trichogramma, green lacewings and a wide array of other natural enemies purchased from Rincon-Vitova and other insectaries to lessen moth attacks and minimize pesticide use.

Of course, the moth wars are not all one-sided. Spray pesticides too often and moths become resistant. And moths can elude and make life challenging for their natural enemies. For example, many moth species respond to bat ultrasound echo-location signals with evasive aerial maneuvers and jamming signals. Moth immune systems may even encapsulate and prevent parasites from providing biocontrol. Each female of one fat Australian moth species can lay 18,000 eggs, the ultimate defense, essentially ensuring survival by sheer numbers.

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Beneficials Sweet on Alyssum

July 22, 2009

INTERPLANTING SWEET alyssum (Lobularia maritima) is an excellent way to promote natural biocontrol of a wide array of landscape, orchard, field and garden pests like aphids, stinkbugs, leaf and fruit worm caterpillars, etc. Companion planting has ancient roots, figuring in the writings of the Greek Theophrastus in 300 B.C. and the Roman Pliny (Plinius Secundus) in 1 A.D. Though popular in organic gardening and farming, floral interplants escaped serious scientific scrutiny until recent years.

Australia’s wine grape growers are among those who take their sweet alyssum companion plantings very seriously. At Australia’s EH Graham Centre for Agricultural Innovation ecological engineers and entomologists like Geoff Gurr of Charles Sturt University are fine-tuning companion planting. Firstly, you need to choose companion interplants that supply nectar, shelter and other resources to beneficial predators and parasites but not to pest species.

The Aussies focused their scientific studies on a Trichogramma species parasitizing and destroying the eggs of the lightbrown apple moth (Epiphyas postvittana), a key pest of Australian vineyards. In “clean” vineyards where weeds and ground covers are destroyed by herbicides or cultivation, biocontrol species like Trichogramma may survive as few as two days, versus three days with water only and up to 20 days with sweet alyssum (the best ground cover tested). Alyssum flowers doubled the number of moth eggs parasitized over a 10 day period. In contrast, when the alyssum plants were deflowered the Trichogramma perished and there was little biocontrol.

But there is more to the story. “Not only is plant species important, but the cultivar within the species is critical,” Gurr told an Entomological Society of America annual meeting. For example, Trichogramma survive far longer on white-flowered alyssum cultivars compared to purple and other colors. Alyssum also boosted predators without aiding the apple moths, which was not the case for every ground cover interplant tested.

Most landscape and cropping systems have not been subjected to the same level of ecological and laboratory investigation as Australian wine grapes. Thus, Rincon-Vitova and other insectaries selling beneficial insects generally recommend blends of flowering plants supplying floral nectar throughout the season.