Printer Friendly

It's "bugs-r-us." (management of the Agricultural Research Service's Beneficial Insects Introduction Research Laboratory)(includes related article) (Cover Story)

It's "Bugs-R-Us"

Across the road from the huge Chrysler assembly plant in Newark, Delaware, a different sort of factory specializes in foreign imports.

The imports--flies, wasps, beetles, and other bugs--will wage a deadly but nonchemical war against devastating agricultural pests.

The good bugs' staging site, tucked next to a pasture on the grounds of the University of Delaware, is the Beneficial Insects Introduction Research Laboratory of USDA's Agricultural Research Service.

Here, a team of three research entomologists conducts lab and field studies of natural enemies for some of the worst pests, such as gypsy moths, tarnished and alfalfa plant bugs, and Russian wheat aphids.

The lab also serves as an Ellis Island for tens of thousands of beneficial bugs. The insects are collected in foreign countries almost entirely by ARS scientists based in U.S. or overseas labs.

Good Bugs In, Good Bugs Out

The new arrivals are quarantined "to make sure the shipment has no contaminants, such as mites that would attack a beneficial insect," says Lawrence R. Ertle, the lab's quarantine officer.

He also arranges for background checks confirming each bug's scientific moniker before rearing and distributing it.

If descendants of immigrant bugs pass rigorous research trials, they're let go. Mostly, they're released by the millions in seasonal pest-control programs or freed in smaller numbers to make new, year-round homes in crop fields or forests.

Last year, 253 batches of insects arrived in Newark from a dozen countries: Argentina, Brazil, Canada, Chile, China, France, Germany, India, Indonesia, New Zealand, South Korea, and the Soviet Union.

The bug-importing business tends to be a seasonal affair, says Ertle, with fall, winter, and spring relatively slow times for incoming shipments. June is different: that's when three-fourths of 1990's shipments arrived--nearly all from the European Parasite Laboratory in France.

During that same year, 410 lots of bugs left Newark for cooperators in ARS, other agencies, universities, and private insectaries in 17 states and 3 foreign countries.

Fully 238 of the outbound lots went to ARS and a cooperating agency, Washington State's Department of Agriculture. Nearly all were Korean and Chinese Ageniaspis fuscicollis wasps, parasites of the apple ermine moth, received during the summer.

After these wasps cleared quarantine, Ertle eyeballed each of the 36,950 adults (21,962 females) under a microscope to make sure they were really A. fuscicollis. Then, from mid-July to mid-August, he shipped them in several lots to ARS entomologist Thomas Unruh, based in Yakima, Washington, and a colleague at the state's Department of Agriculture.

"The scientists were on the move, releasing wasps at many sites, so we sent wasps to various places to keep up with their itinerary," Ertle says.

Have Bug, Will Travel

Lab technician Kenneth S. Swan is the receiver for most of Newark's newly arriving imports. "Usually this means going to the Philadelphia airport, where I sign the forms to get the bugs released to me and load them into our van," he says.

To give traveling insects a safer, cozier journey, Swan and former Newark entomologist Richard Dysart (now based in Sidney, Montana) devised a reusable bug-shipping box in 1978. They got the idea from cut-to-fit Styrofoam packing used to ship fragile equipment like computers and stereos.

The container consists of two slabs of insulating foam with three molded cutouts. Two cutouts carry round specimen boxes with tight lids. The third holds a pint container of coolant to keep bugs from overheating in transit.

"Three-fourths of the insect labs we deal with use this kind of container now," says Larry Ertle.

Inside the Bug Vault

Three sets of heavy steel doors lead into the quarantine's main work area, a 20- by 12-foot clean-up room with a large sink and an autoclave--a gizmo resembling an industrial-size washing machine. It uses heat and pressure to sterilize material to be scrapped, like "plant parts that come in with a shipment, packing material, hyperparasites, dead hosts--anything that must be disposed of," says Ertle.

The clean-up room also has two stainless-steel refrigerators. "We keep some bugs in the cooler to slow their development," Ertle notes, "because the recipients aren't ready for them, or it's the wrong time of year to release them in the field, or we're waiting for results of identification work.

"The insects usually aren't much trouble if they get a nutritious diet, are kept at the proper temperature and humidity, and get exercise."

He's not joking. Once a day, even on weekends and holidays, Ertle or Swan removes bug-filled containers from the refrigerators and puts them by a window. There, the insects warm up, stretch, soak up some light, and walk around their paper or plastic prisons.

Even though insects are carefully packed for transit, "we have to act fast once they get to the quarantine," says Ertle. Newly arrived packages are taken straight to the unpacking room in a high-security area just past the clean-up room. Unpacked eggs and immature insects are taken to another high-security cubicle until they emerge as adults. Then they go to one of the quarantine's two rearing rooms, where a new generation will be raised.

One of the more unusual items to enter Newark's quarantine this year is the "parasite pill." Each capsule, made of soft gray cardboard and about the size of an oyster cracker, holds about 500 eggs of the Mediterranean flour moth. And inside each moth egg is a surprise for European corn borers in Iowa: an egg of the parasitic wasp Trichogramma maidis.

This wasp delivery system, called Trichocaps, has been successfully tested and used for about 10 years in France. But the capsules' first U.S. tryouts came this past summer.

Last spring, after wasps hatched from a sample of a small test shipment and Ertle determined that the sample was "clean," he completed paperwork required by USDA's Animal and Plant Health Inspection Service. APHIS, which issues permits for all imported bugs, soon gave the go-ahead for a French firm to ship Newark thousands of Trichocaps containing 4 million wasp eggs divided into lots of 100 Trichocaps.

After testing a sample from each lot, Ertle obtained APHIS approval to ship the Trichocaps to Iowa State University for cooperative field tests with ARS and Pioneer Seed Co.

"The test is part of a comparative economic study of biological controls--the first of its kind," according to research leader Leslie Lewis at the ARS Corn Insects Research Laboratory in Ankeny, Iowa. He says the 2-year study, on 1-hectare (2.47-acre) plots of Pioneer corn seed production fields, aims to find out how well--and how economically--the European corn borer is controlled by the wasps, by the bacterium Bacillus thuringiensis, or by the fungus Beauveria bassiana.

During this past summer, Iowa State University entomologist David Orr scattered Trichocaps in the plots.

"In France," says Orr, "they've gotten an average of 74 percent control with the capsules and 72 percent with insecticide for the same cost. We want to know if Trichocaps can be a cost-effective alternative for farmers in this country."

Newark's role as an import and distribution center goes hand-in-hand with the lab's own research. A case in point is a wonder-wasp with the tongue-twisting name of Coccygomimus disparis.

Newark has imported these wasps since the 1970's from collections in India, Japan, Korea, and China. ARS and cooperators in 16 states have freed more than 800,000 of them.

The wasp has a lot of help--from other ARS scientists and technicians in the United States and at the ARS Asian Parasite Laboratory in Seoul, South Korea, as well as the New Jersey Department of Agriculture, Pennsylvania Bureau of Forestry, Delaware State College, and other universities.

"A few years ago, first new gypsy become established in the United States in 50 years," says Newark entomologist Paul W. Schaefer.

While most parasitic wasps are gnat-size or less, C. disparis is about 10 times bigger: a sleek, coffee-colored inch of aerodynamics.

The female wasp lays its eggs inside the pupal cases of soon-to-be-adult gypsy moths, attacking about 200 pests over a 3-week period. One parasite develops per pupal case, devours the pest from the inside, and emerges as an adult.

"This wasp doesn't sting people or animals, even though it's bigger than some wasps that do," notes Schaefer.

Size helps but isn't the key reason the wasp got established so readily. "This wasp's best advantage," says research leader Roger Fuester, "is that it thrives on other pest species when there aren't many gypsy moths around." That's critical: Newark studies have shown that gypsy moth parasites often fail to take hold unless the moths are fairly abundant.

University of Minnesota entomologist Willis Schaupp and colleagues have released some 3,600 C. disparis wasps since 1989.

While the state has exterminated small invasions of gypsy moths, Schaupp wants the wasps to form part of a vanguard of natural enemies ready to attack the moths if and when they invade in large numbers.

In the meantime, he hopes that "even if the state escapes large invasions of gypsy moths, the wasps will do us a favor by ganging up on forest tent caterpillars, eastern tent caterpillars, and fall webworms."

But Schaupp wanted to release wasps that hadn't been reared for several generations in a lab "where they can become conditioned to looking for food in the bottom of a cage instead of on tree branches in a forest." So he asked Schaefer for wasps that were "as near to wild as possible."

Schaupp's first shipment--from Korea via Newark--arrived in 1989.

The second shipment, in 1990, was from China. Early that summer, pupae of apple ermine moths harboring wasp larvae were rounded up in Shanxi Province, China. The pupae were collected by ARS' Robert Pemberton of the Asian Parasite Laboratory in South Korea and Wang Ren, director of the Sino-American Biological Control Laboratory in Beijing.

Three lots of immature wasps arrived in Newark in mid-July 1990. When adults began to emerge, quarantine officer Larry Ertle sent a few specimens to scientists at ARS' Systematic Entomology Laboratory at the Smithsonian Institution in Washington, D.C. [See Agricultural Research, February 1990, pp. 8-11] When they positively identified the wasps as Coccygomimus disparis, Ertle sent 28 to Schaupp.

Schaupp used these wasps to rear a new, larger batch that was only one generation removed from the wild Chinese parents.

"To precondition these adults for the hosts they'd be finding," says Schaupp, "we brought them webworm and tent caterpillar pupae from the field to practice on."

Last fall, he and colleagues released about 2,000 wasps at sites near the Minneapolis-St. Paul metropolitan area. "That's where the gypsy moth would first be likely to show up in large numbers," he says.

Last spring, for the first time, Schaupp recovered young wasps near one of the sites, proof that some of the Chinese wasps had found mates and laid eggs.

"We're ahead of schedule and very happy for it," says Schaupp, who hadn't expected to find the wasps so soon.

While Coccygomimus disparis is a relatively recent arrival, an old beetle import is spreading new trouble among gypsy moths. Released in New England since 1906, the bright green caterpillar hunter Calosoma sycophanta wasn't seen in Delaware until 1984.

"It seems to be slowly following the gypsy moth's own spread," says Paul Schaefer. "I'd like to see this beetle tried farther west, such as Michigan, where the moth recently invaded."

Calosoma acts as if it has mighty grudge against gypsy moths. "Sometimes it will attack and chew up a gypsy moth caterpillar just a little, leave it for dead, and go find another one," says Schaefer. One beetle can eat as many as 100 to 150 gypsy moth larvae in a season.

"The strangest thing about this beetle," notes Roger Fuester, "is that if the adult doesn't find a lot of gypsy moths, it won't reproduce. It may eat a few caterpillars of some other moth species, but then go back underground and try again next year."

The Calosoma beetle is part of an elite group. Of the more than 50 imported gypsy moth biocontrols, it's one of only 15 to 20 to become settled in the United States--primarily the Northeast and mid-Atlantic regions.

"We don't have as complete a team of natural enemies in this country as in Europe or Asia," Fuester says. "And we don't have any illusions about eliminating the gypsy moth completely. But we think it's feasible to cut back the number of years in which severe damage occurs--from 4 in 10 to perhaps 1 or 2."

Far better known than Calosoma beetles are lady beetles, the most famous biological controls among farmers and home gardeners in the United States. The most common domestic species, Hippodamia convergens, will eat dozens of pesky aphids per day--if it's hungry.

Newark imports, rears, and distributes more specialized models of lady beetles that are found overseas by ARS scientists. Enthusiasm for them has surged because of the Russian wheat aphid, first spotted in the United States in 1986 and already considered one of our grain farmers' worst pests in the West.

Imported lady beetles released so far haven't begun to work against this aphid, says Schaefer.

"We think that's because it's just too soon," he says. "Natural enemies can take years to become established and start taking a toll. But also, wheat leaves under attack by the Russian wheat aphid roll up lengthwise around it, almost like a tiny green scroll." That helps shield the aphid from chemical sprays and, some scientists speculate, from many natural enemies.

Most lady beetles, the theory goes, are too big to squeeze inside the rolled leaf and get at the aphid. "But that isn't at all clear," Schaefer says. "Scientists overseas, as well as people monitoring lady beetle levels in this country, have found lots of them in aphid-infested fields. The beetles must be finding food or they wouldn't be there."

Still, scientists are covering their bets by trying more economy-size lady beetles, like Scymnus frontalis, discovered in 1988 in Turkey by scientists from the European Parasite lab. At 4 millimeters, it's about half the length of the American H. convergens. Colonies of S. frontalis at Newark feed on tiny pea aphids raised by the hundreds on potted fava bean plants.

In a rearing room, Schaefer takes a fava bean plant, turns it sideways and taps it, knocking dozens of aphids onto a tabletop. He then sweeps them up like crumbs and rations them out to lady beetles in pint containers. About a dozen containers hold lady beetles in different developmental stages, from pinhead-size larvae to mating adults.

Quarantine chief Larry Ertle and lab technician Kenneth Swan ship adult lady beetles to researchers and other cooperators, mostly to the Biological Control Laboratory of USDA's Animal and Plant Health Inspection Service in Niles, Michigan.

In 1990 and 1991, according to Niles entomologist Robert V. Flanders, APHIS reared and released hundreds of thousands of S. frontalis and other lady beetles in dozens of aphid-infested grain fields in the western United States. The releases were part of APHIS' National Biological Control Program against the Russian wheat aphid and other pests, says Flanders, who coordinates the program.

"I don't know if Scymnus will have a better shot at getting at aphids inside the leaves," he says, "but one thing that makes it stand out is its unique egg-laying behavior. While other lady beetles lay their eggs in masses of 10 to 50 on a single leaf, Scymnus lays one egg at a time, then goes somewhere else and lays another. That may mean it can survive at lower aphid densities, which may further imply it is a good control agent."

A different lady beetle import--three to four times larger than Scymnus--also has a greater capacity for gorging on aphids. It's Coccinella septempunctata, the sevenspotted lady beetle, imported through Newark since the 1950's.

"One adult beetle of this species," says Schaefer, "can eat 100 to 250 aphids per day. In the lab, a sevenspotted larva averages 200 pea aphids over the course of its 8-day development."

Newark and cooperators helped the sevenspotted take hold in the East in the 1970's. APHIS began scattering it through the West in the 1980's. The beetle became established in all the western states after APHIS let go 350,000 in the Pacific Coast states and Nevada in 1988 and 1989.

The sevenspotted lady beetle now occurs in all 48 contiguous states, Canada, and Mexico, says Flanders, and is "really going to have a major impact in agriculture. It could also become the next popular backyard lady bug you'll be able to buy in retail garden shops.

"In some areas, it has moved in like crazy on apple aphids in orchards, pea aphids in alfalfa, and cereal aphids and greenbugs in grains. We won't know the full impact for several years, and we're still getting new strains coming through Newark."

Wasps Tangle With Alfalfa Pests

The sevenspotted lady beetle may be well on its way to conquering aphids. But other insects imported and studied at Newark are just beginning to set up shop.

Newark entomologist William Day aims to widen the domain of the quarter-inch-long Peristenus digoneutis wasp. Its chief quarry, the tarnished plant bug, sucks sap from flowers, young fruits, and seeds. But the bug doesn't live long enough to get the chance if a female P. digoneutis attacks it in the nymph stage.

"A few days after she stings one and lays an egg in it," he says, "a wasp larva hatches and eats it.

ARS researchers in France began collecting, testing, and shipping this wasp to Newark in the early 1970's.

From 1979 to 1983, Day made releases in northern New Jersey. By 1990, the wasps were parasitizing 30 to 90 percent of tarnished plant bugs in alfalfa fields Day sampled. They had also spread themselves across the state border into Orange County, New York, 35 miles from the release sites.

"That may not seem far," he says, "but it's encouraged more researchers to give it a try in other parts of the country."

Scientists at the Universities of Massachusetts and New Hampshire have begun new studies to check whether P. digoneutis can protect strawberries grown without insecticides. And Day has received new inquiries from scientists in six other states and Canada.

In Mississippi, ARS entomologist Gordon Snodgrass plans to see if P. digoneutis can rein in tarnished plant bugs that attack cotton. Next spring he will release the wasps--still in cocoons--near the Mississippi Delta in an alfalfa field with a natural infestation of plant bugs. He wants the alfalfa to be a natural reservoir for the wasps.

"When the wasps emerge, I hope they'll become established on plant bugs in the alfalfa and then spread to attack others that live on wild host plants near cotton fields," says Snodgrass, who is with the Southern Insect Management Laboratory in Stoneville.

On the wild plants, the pests breed a springtime generation that later invades cotton. Releasing wasps in cotton wouldn't work, he explains, since most fields get early-season insecticide applications that kill beneficials along with pests.

An Oak View, California, firm--Rincon-Vitova Insectaries, Inc.--has received starter colonies of P. digoneutis to release against the lygus bug, a notorious enemy of strawberries, cotton, and seed alfalfa.

"The wasps could be especially useful if they help out on lygus bugs," says Day. "California doesn't have a good parasite for the pest's nymph stage. Plus, several insecticides registered for use on lygus probably won't be re-registered, so nonchemical alternatives will become more important."

Comeuppance for the Alfalfa Weevil

In the 1970's, Day and colleagues helped pioneer one of the most successful biocontrol battles of the century. The enemy: the alfalfa weevil, a voracious pest from Europe that had invaded the western states at the turn of the century.

During World War II, the weevil also entered in the East; by 1980, its reach was coast to coast.

"Until the late fifties," Day notes, "chemical control was king and there was a lot of official skepticism about biocontrol in general."

But times were changing. One sign of that was the discovery, in the mid-sixties, of anti-weevil pesticides in cow's milk. "Our lab then hired additional people to attack the weevil problem, though we'd actually begun importing and releasing parasites in the late 1950's."

Through the 1960's and 1970's, Newark scientists released millions of about a dozen species of weevil parasites.

In the late 1960's, a battery of about six species--mostly Bathyplectes and Microctonus wasps--had the pest under control in New Jersey. "In the early 1970's," says Day, "Rutgers University found that the percentage of New Jersey alfalfa growers using pesticides against the weevil had dropped from 93 percent to 7 percent."

By 1980, beneficial parasites had a stranglehold on the weevil in 10 states in the mid-Atlantic region and New England. "We were seeing powerful mortality--about 80 percent in all," Day says. Less than one-fourth of the millions of acres of alfalfa in these states needed pesticides against the alfalfa weevil.

The successes of the releases by ARS and cooperating agencies prompted APHIS to take the parasites nationwide in 1980.

In a 1989 report of a study by University of Massachusetts economists, biological control of the alfalfa weevil was estimated to be saving growers across the country $88 million annually in pesticides and application costs.

"No single parasite would have made a dent," Day says, "because one female alfalfa weevil can lay as many as 4,000 eggs. It was the total combination that did the trick."

That, plus the human team: insect researchers and collectors in overseas labs; quarantine personnel; APHIS biocontrol workers; ARS, university, and state scientists; federal, state, and commercial insectaries.

Without these sponsors, weevil-killing wasps and other biocontrol bugs would have remained in the old country, stinging or nibbling pests in obscurity.

PHOTO : Entomologist and quarantine officer Larry Ertle gently places beneficial insects in custom-designed packaging for shipment.

PHOTO : Trichogramma wasps are packaged in shipping capsules for later release in corn fields. Bags are color-coded according to insect maturity to help researchers determine optimum release dates.

PHOTO : Scymnus frontalis (left) and Coleomagilla maculata (right) beetles feed on pea aphids.

PHOTO : Coccygomimus disparis wasp inserts its eggs in a gypsy moth pupa.

PHOTO : Research entomologists Roger Fuester (left) and Paul Schaefer collect Calosoma beetles and mark them to identify their sex.

PHOTO : Calosoma beetle attacks and feeds on a gypsy moth caterpillar.

PHOTO : The tarnished plant bug is reared in the lab as a factory for parasites.

PHOTO : Entomologist Larry Ertle conducts preliminary examination for contaminants in Trichogramma capsules.
COPYRIGHT 1991 U.S. Government Printing Office
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:De Quattro, Jim
Publication:Agricultural Research
Article Type:Cover Story
Date:Oct 1, 1991
Words:3755
Previous Article:Putting the bio in biocontrol.
Next Article:Orient Express for wasps.
Topics:

Terms of use | Copyright © 2016 Farlex, Inc. | Feedback | For webmasters