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Get the whitefly swatters - fast!

They are not much larger than the head of a pin. Yet these flat, white bugs have so deeply wounded agriculture in the Southwest and Florida that the mere thought of them makes growers shudder.

The pests, currently considered a new strain of sweetpotato whitefly, were first found on Florida greenhouse poinsettias in 1986. Ever since, they've been munching their way - nearly year round - through crops in California, Texas, Florida, and Arizona. They suck the sap from more than 600 plants including fruits, vegetables, ornamentals, alfalfa, and cotton. In their wake last year, they left multimillion-dollar crop losses and other damage.

While producers worry and count up their losses, scientists try to get a handle on how to control the insects.

Around the country, researchers struggle to help. They're showing the textile industry how to wash off the sticky goo the insects deposit on cotton fiber. They're uncovering ways to alleviate plant viruses carried by whiteflies. And they're testing legions of environmentally friendly controls: insect parasites and predators, fungi, extracts of exotic plants - even dish detergent mixed with vegetable oil.

To get the job done, the Agricultural Research Service and other USDA agencies - Animal and Plant Health Inspection Service, Cooperative State Research Service, and Extension Service - have joined with a dozen universities, state agricultural experiment stations, and the cotton, vegetable, ornamental, and nursery crop industries.

The efforts are all part of a national research and action plan. "The overall goal is to find which method or combination of methods best controls the whitefly infestation in a given area," says Robert Faust, ARS National Program Leader for crop protection, who is also one of the two coordinators of ARS' anti-whitefly effort.

But scientists have been dogged by complications that make the task more difficult-starting with the pest's true identity.

The sweetpotato whitefly - Bemisia tabaci - has been in the United States since the 1890's. Scientists have been calling the newly emerged pest "biotype B" of this species. But tests suggest it may be a different Bemisia species.

Whatever you call it, its numerous biological advantages make control difficult. For starters, it reproduces about every 3 weeks, quickly becomes resistant to synthetic insecticides, and has a wide-ranging appetite.

We need a greater understanding of these and other biological and ecological factors. That should help us determine the best ways to control this whitefly by the many routes we're already exploring and by others we hope to turn up," says Faust.

A Sugary Problem Sours the

Cotton Crop

For the cotton industry, these whiteflies could be the worst thing since the boll weevil," says Thomas J. Henneberry, director of the ARS Western Cotton Research Laboratory in Phoenix.

As whiteflies in Arizona, California, and Texas devour the sap from cotton leaves, they excrete partially digested sap and leaf sugars onto cotton fibers and leaves.

This excretion, euphemistically called honeydew, is similar to the sticky coating you may discover on your car if you parked it under a tree full of leaf-sucking insects. Honeydew can reduce prices paid to cotton growers, since fiber contaminated with it gums up cotton gins and interrupts processing in the textile mill.

About a year ago, University of Arizona scientists discovered that whitefly honeydew contains a sugar called trehalulose. Until then, this sugar apparently had been found only in microorganisms.

Later, ARS scientists at the Phoenix cotton lab found that trehalulose makes up about 40 percent of the sugar in the whitefly's honeydew. And they found something else.

We discovered a sugar in the honedew of the biotype B whitefly that has never been reported to occur elsewhere in nature," says Donald L. Hendrix, ARS plant physiologist in Phoenix. He named the new sugar "bemisiose."

He says 80 percent of the honeydew sugars in the biotype B whitefly are a type known as nonreducing or poorly reducing - a reference to their reaction to classical simple sugar tests. Common reducing sugars include glucose, fructose, and galactose.

Those tests work well to measure cotton lint contamination by cotton aphid honeydew, which has a higher percentage of reducing types of sugars," he says. "But this whitefly's honeydew has a preponderance of nonreducing and poorly reducing sugars. Those same tests therefore sometimes fail to measure die contamination."

In lab experiments to clean honeydew contaminated cotton fiber, the scientists sprayed the fiber with Tempanil, a commercial product from India. "One spray lowered the sugar content to one-fifth that of untreated cotton," says Hendrix. "Such treatments may alleviate the problem at gins and textile mills."

Chemicals that may ease processing problems are also of interest to ARS scientists and engineers at the Southwestern Cotton Ginning Research Laboratory in Mesilla Park, New Mexico, and at the Cotton Quality Research Station in Clemson, South Carolina.

"I think we have available to us compounds that will improve processing," says chemist Henry H. Perkins, Jr., who works at Clemson. The scientists are examining commercially available mineral oils and surfactants to see if they will ease processing of cotton that's too sticky to pass smoothly through equipment at textile plants.

Perkins and ARS engineer Ed Hughs at Mesilla Park are experimenting with correct amounts to spray on contaminated cotton before it begins its pass through high-speed textile-processing machinery.

Spreading Bad News:

Viruses

As if honeydew and feeding damage weren't enough to contend with, the whitefly carries a disease known as cotton leaf crumple. Many varieties of upland cotton are susceptible to extensive damage from this virus-caused disease.

Fortunately, researchers have developed germplasm for resistant cotton lines.

"We bred resistant plants by crossing one of our most important commercial varieties with Cedix, a highly resistant or immune cultivar from El Salvador," says F. Douglas Wilson, plant geneticist at the Phoenix lab.

Wilson, with Judith K. Brown of the University of Arizona, identified two pairs of genes responsible for cotton leaf crumple resistance. "This information will allow cotton breeders to transfer greater virus resistance into commercial varieties," says Wilson.

Unfortunately, cotton leaf crumple is just one of many viruses the pest transmits-viruses that cause more than 40 other crop diseases worldwide and account for yield losses of 20 to 100 percent.

On the other hand, recent research indicates that biotype B whiteflies spread at least some viruses less efficiently than other biotypes do.

Raiding Nature's Cupboard for

Cures

Feeding, honeydew, and viral damage may be lessened if scientists can find ways to control or eradicate the six-legged source.

The sweetpotato whitefly can thrive on a continuous series of host plants in the warm climates of the Southwest and Florida, where crops grow year round. So interruptiug the crop cycle could become an important tool.

Researchers are also scouring the landscape and the scientific literature for the sweetpotato whitefly's own natural insect enemies. So far, they've identified some 30 predators and 25 parasites.

In Arizona, ARS has given one native predator, the big-eyed bug, a dietary boost, making it feasible to rear and release it in massive numbers.

When a big-eyed bug attacks an adult sweetpotato whitefly, its mouth parts exude a sticky substance that glues the pest's wings to the plant. The whitefly can't take off, and the bug proceeds to eat it.

Next summer, USDA's Animal and Plant Health Inspection Service (APHIS) will be ready to use an ARS-designed, hamburger-based diet to rear and release several hundred thousand big-eyed bugs. Smaller releases may be made sooner.

ARS entomologist Allen C. Cohen designed the diet to replace a far costlier rearing method - growing plants to feed to insects that big-eyed bugs, in turn, like to eat.

Cohen, who is with the Western Cotton Research Laboratory in Phoenix, developed the diet after studying Agriculture Handbook No. 8, the bible for human nutritionists.

"I knew what the big-eyed bugs ate in nature - other insects. So I gathered some of these insects and analyzed them for their nutritional content. Then I used the handbook to see what readily available foods closely matched their natural diet," says Cohen. The main ingredients are hamburger, liver, and sugar solution.

Last January, for the bug's first field test Robert T. Staten and Nick Colletto of APHIS used Cohen's recipe to rear big-eyed bugs from hatchlings to immature adults. In Phoenix, Staten directs APHIS' Methods Development Center for beneficial insects.

Once the bugs reached early adulthood, they were released along with whiteflies into cages in alfalfa fields in California's Imperial Valley. The big-eyed bugs devoured up to 40 percent of the whiteflies. Another successful test - in grapefruit trees - was run in February and March.

Named for its bulbous eyes, the big-eyed bug is a native of the United States an Mexico. Adult bugs are about half the size of Lincoln's head on a U.S. penny and are gun-metal gray.

A different predator, a tiny beetle, has an appetite that's somewhat like the whitefly's - insatiable. But while the whitefly feeds almost indiscriminately on plants, the picky Delphastus pusillus beetle savors only whiteflies - plenty of them - in all stages, from eggs to adults.

The shiny black Delphastus is a Florida native that's also found, across the central and southern United States, through Central America and the Caribbean, and as far south as Peru. ARS scientists in Orlando, Florida, are studying and testing the beetle in cooperation with the University of Florida.

"It's hard to rear the beetle because of its demanding appetite," says Kim A. Hoelmer, an ARS entomologist at the U.S. Horticultural Research Laboratory in Orlando. "One beetle can devour several hundred whitefly eggs a day."

And during the beetle's 6- to 9-week lifetime, it can consume as many as 10,000 whitefly eggs or about 700 nymphs.

"To raise whiteflies as food for the beetle means growing and maintaining host plants and infesting them with the insect," says ARS Orlando entomologist William J. Schroeder. "That's time consuming and expensive."

Instead, researchers are first trying citrus weevil and Caribbean fruit fly eggs. "We're hoping one or both types of eggs will appeal to the beetle's discriminating palate," Schroeder says.

Just in case that doesn't pan out, he and Hoelmer are working on an artificial diet for die beetle. It has already been distributed to several companies for testing in commercial Delphastus rearing.

Recruiting Wasps for Whitefly

Patrols

Strangely, the Delphastus beetle can detect a wasp-infested whitefly and avoid it, searching instead for a healthy specimen for dinner, says Hoelmer.

So, a whitefly snubbed by the beetle may have been attacked by any one of five parasitic wasps studied at Orlando.

The wasps include Eretmocerus californicus and four Encarsia species: formosa, nigricephala, transvena, and tabacivora. All are native to Florida, and none is harmful to humans, livestock, wildlife, domestic animals, or plants.

Another advantage of these wasps, Hoelmer says, is that they develop in as few as 12 to 14 days. Since the whitefly takes about 25 days to develop, the wasps have plenty of time to find, attack, and destroy their prey.

Other parasitic wasps that kill whiteflies are found abroad, and ARS researchers based in Montpellier, France, are exploring for them in several countries.

Promising anti-whitefly insects discovered on the trips are shipped to the United States and put into quarantine, usually at the agency's research quarantine facility at Stoneville, Mississippi. Before an insect is released from the facility, it must be identified according to genus and species.

"I think these new insects coming from Europe will be more difficult to identify than the wasps we have received so far," says Fannie Williams, quarantine officer at Stoneville.

A taxonomist at ARS' Systematic Entomology Laboratory in Beltsville, Maryland, is responsible for making the identifications.

Even if its identity is known, an imported biocontrol insect stays in quarantine for at least one generation before release. This gives scientists an opportunity to study it and ensure it will not pose a threat to crops or beneficial insects.

"We're searching for an extremely prolific wasp that will be a voracious parasite of the whitefly," says D.D. Hardee, director of ARS' Stoneville Insect Management Laboratory. "We're screening several species of wasps in hopes of finding one that fills the bill."

Imported Encarsia formosa wasps went through this screening process before their release to research facilities in California's Imperial Valley to aid the establishment of insect colonies in the region. The species is also indigenous to some areas in the United States.

The female E. formosa wasp stings immature whiteflies and lays its eggs on their undersides. When the eggs hatch, wasp larvae feed on the young whiteflies.

The stingless wasp Eretmocerus mundus takes a different tack, laying its eggs inside whitefly larvae and pupae. The adult wasp can also kill by directly feeding on its host.

While both of these wasps - and others - have cleared quarantine and show promise, Hardee says they aren't likely to be a quick solution. That's because finding "good" wasps isn't the same as knowing how best to use them.

"We suspect that the wasp's ability to parasitize or feed on young whiteflies may vary among different host crops," explains Hardee.

Entomologist Jo-Ann Bentz at the Beltsville Agricultural Research Center is currently working on a different piece of the wasp puzzle using the indigenous Encarsia formosa. How does it home in on its victim? "Once we know this mechanism we'll be better able to use wasps as biocontrols," she says.

Bentz has supplied a particularly aggressive strain of these wasps, which she found in Beltsville, to APHIS' mass-rearing facility in Mission, Texas. Earlier this year, APHIS reared and released 40,000 female E. formosa wasps in sunflower fields in Texas.

Fighting Back With Fungi

Besides insects, nature also produces microscopic enemies of the sweetpotato whitefly. One of them turns the ravenous pest into an inert puff ball.

Found in soil throughout the world, the fungus Beauveria bassiana was first identified in the 1870's. But a strain discovered by ARS entomologist James E. Wright killed up to 85 percent of the whiteflies in small test plots of cotton and vegetables.

The fungus kills immature whiteflies, or nymphs, by spreading through their bodies after contacting their outer covering, or exoskeleton.

"Eventually, the fungus covers the whole whitefly, so it looks just like a little white puff ball," says Wright, who works at the Subtropical Agricultural Research Laboratory, Weslaco, Texas.

Wright found the fungus on bodies of boll weevils, longtime pests of cotton. He was searching for a new way to knock down weevil populations without using pesticides.

Working with scientists at Fermone, a company in Phoenix, Wright developed a liquid formula - based on the fungus - to kill boll weevils. In tests with cotton, he says, the formula "completely controlled boll weevils - without any insecticides. Yields were as high on those plants as on other cotton sprayed with insecticides."

But boll weevils weren't the only losers. During field trials in 1990, Wright noted that the fungus kept whitefly numbers low. "The following year," he says, "we tried it again on cotton and for the first time on broccoli, bell pepper, cabbage, cantaloupe, celery, cucumber, tomato, and watermelon - with very good results."

The fungal formula is applied to plants in a fine mist, using conventional sprayers, special high-pressure sprayers, or airplanes.

Last summer, the U.S. Environmental Protection Agency granted Fermone an experimental use permit to test the fungus nationwide.

Most of the tests are against sweet-potato whiteflies: on cotton and vegetables in California, Texas, and Arizona; vegetables in Florida; and peanuts in Goergia and Texas. Other tests pit the fungus against boll weevils on cotton in Louisiana, Mississippi, and Texas.

In Orlando, Kim Hoelmer of ARS and University of Florida scientist Lance Osborne are testing a different natural fungus, Paecilomyces fumosoroseus. Isolated and patented by Osborne, the fungus destroys all stages of the whitefly. W.R. Grace Co. is licensed to develop and commercial it as a biocontrol agent.

"Because of the patent rights, we can't say much about the research at this time, but suffice it to say this fungus carries a real wallop," says Osborne. "In addition to infecting all stages of the whitefly, the fungus tolerates pesticides and is easy to produce."

Hoelmer and William Schroeder have established experimental watermelon and tomato field plots to test the effectiveness of P. fumosoroseus and B. bassiana. Osborne is cooperating in the tests, which began in June.

Meanwwle, isolates of other fungal pathogens sleep - chilled in liquid nitrogen - in an ARS lab in Ithaca, New York.

"We have more than 200 samples of whiteflies that apparently died from fungal diseases," says insect pathologist Tad Poprawski who is with ARS' U.S. Plant, Soil, and Nutrition Research Laboratory.

The sleeping pathogens are mostly from Mexico's Baja California; the states of California, Florida, and Texas; Nepal; and Pakistan. They were collected by scientists based at Ithaca and other ARS locations including the lab in France, as well as colleagues at APHIS and universities. Ithaca scientists have just begun the tedious work of isolating, identifying, reviving, multiplying, and testing the fungi. Poprawski says none of them are new species and some are the same species being tested by Wright and Osborne.

There's no guarantee any of them will pay off, but anything that kills a whitefly is worth knowing more about," Poprawski says. "Finding just one good new pathogen isolate could make a big difference to growers."

Biosoaps To Wash Those Whiteflies

Away

While natural enemies - insects and pathogens - may play a big role in controlling whiteflies, the reality is that most farmers rely on chemical insecticides as well as other conventional pesticides because they act more quickly than biological controls.

But many currently registered pesticides can harm natural enemies. To try to avoid this problem, scientists have turned to soaps, oils, and plant extracts.

Researchers at the Beltsville center's Florist and Nursery Crops Laboratory hope to deal the whitefly a double blow from the stinging power of E. formosa wasps and a biosoap made from an Australian plant.

The plant, Nicotiana gossei, is a relative of tobacco, says Beltsville entomologist John W. Neal. Nicotiana produces a detergentlike compound that kills whiteflies in their immature or nymphal stage," he explains. The extract easily mixes with water, and when sprayed as a biosoap in greenhouse tests, it gave nearly 100 percent control of whiteflies, along with aphids and mites.

The experimental biosoap kills young whitefly nymphs by dissolving the waxy coating of their cuticle, or body covering. The researchers plan some tests in which they'll release wasps to clean up surviving whiteflies after the biosoap does its job.

The active compound in Nicotiana was isolated by George Buta of Beltsville's Horticultural Crops Quality Laboratory. Retired ARS agronomist George Pittarelli was first to note the compound's effect on the whitefly.

Of 66 known species of Nicotiana, only about half have been evaluated and several have yielded "very effective" extracts, Neal says.

Last summer, two of Neal's ARS colleagues in Georgia - agronomist Mike Stephenson in Tifton and chemist Ray Severson in Athens - grew Nicotiana plants and distilled extract from them for outdoor field tests at several sites around the country.

Another natural insecticide is found in the seed of a mahogany tree from India, known as neem. Available commercially, neem extract can control the whitefly in greenhouses.

More than a decade ago, ARS scientists helped identify one of the extract's active chemicals, azadirachtin.

"The extract disrupts hormonal changes in insect larvae, causing death during molting," says James Locke, a plant pathologist in the Florist and Nursery Crops lab.

The extract works against more than 80 other pests such as beetles, grasshoppers, aphids, weevils, fruit flies, gypsy moths, and mosquitoes. It doesn't harm beneficial insects, earthworms, birds, or humans.

The extract's complex molecular structure hinders target insects from becoming resistant - as some have with synthetic insecticides such as diazinon, malathion, and carbaryl.

At least three companies are marketing neem extract insecticides. Currently, they're registered for use only on ornamentals and other nonfood plants.

Grace Sierra Horticultural Products, Milpitas, California, sells to commercial growers an azadirachtin-based product, Margosan-O. For home gardeners, Ringer Corp. of Minneapolis, Minnesota, markets a similar product, BioNeem. AgriDyne Technologies of Salt Lake City, Utah, recently registered Azatin.

Locke and scientists at W.R. Grace Co. in Columbia, Maryland, are patenting other components from neem seed. Neem seed oil apparently repels whiteflies and may also protect plants from fungi that cause plant diseases such as rusts and mildew.

While extracts from exotic plants may thwart whiteflies in the future, other remedies may be right in your kitchen.

ARS researchers in Arizona found that a mix of common liquid dishwashing detergent and cooking oil kills sweetpotato whiteflies, as well as several common home garden pests.

The detergent and oil act as pesticides, and the detergent makes the oil disperse into minuscule, easily spread droplets.

"It's simple to mix and as effective as commercial insecticides that may cost three times as much. And it's clean environmentally," says George D. Butler of the ARS Western Cotton Research Laboratory.

"We used commercial spray equipment to apply the mixture on cottonfields," adds lab director Thomas Henneberry. "Results were encouraging - we killed 50 percent of the adult whiteflies.

But the pests seek protection from sun and wmd by hiding under plant leaves, so we must be careful to spray all leaf and stem surfaces with a hght coat."

Unfortunately, Henneberry notes, most commercial cottonfields are sprayed by airplanes, with an insecticidal mist that covers only the tops of the leaves.

Entomologist David H. Akey is working to modify ground sprayers. For example, he is installing special pipes and upward-tilting nozzles that will direct the spray to the undersides of leaves. "Then we can try using oil/detergent mixtures on a commercial scale," says Hennebeny.

Modified sprayers could also apply other kinds of sprays - conventional insecticides as well as promising new ones such as fungi and plant extracts."

At three research farms in Arizona and California, scientists from the Phoenix center are testing all these types of control agents-on a variety of crops and with four types of modified sprayers.

"This of comprehensive testing is possible only because of the extensive cooperation and coordination between researchers at ARS labs and our university colleagues," says Henneberry. "That cooperation is the glue that holds together all the components of the national whitefly plan we worked out last winter." - Hank Becker, Julie Corliss, Jim De Quattro, Marcie Gerrietts, Dennis Senft, Doris Stantley, and Marcia Wood contributed to this article.

A Pest Is a Pest ... Or Is It?

Is the whitefly pest merely a new or previously unidentified strain (called biotype B) of Bemisia tabaci - a species that invaded the United States from Eurasia about 100 years ago? Or is it another species altogether?

The answer may be crucial. For example, while some beneficial wasps attack many species of Bemisia, others are extremely picky. Before scientists can recommend deploying a given wasp in a big way, they must determine whether it will aggressively pursue this particular whitefly.

Fortunately, scientists can distinguish the two insects. But the assignment of official taxonomic labels is still an unsettled matter. Traditionally, species are distinguished by differences in physical form and structure. And so far, "We haven't seen any differences that justify assigning the new pest to a different species," says ARS whitefly taxonomist Steve Nakahara.

This summer, however, scientists at the agency's Western Cotton Research Laboratory in Phoenix turned up provocative evidence to the contrary. Geneticists Nick Gawel and Alan C. Bartlett relied on a high-tech method called RAPD-PCR, short for "randomly amplified polymorphic DNA-polymerase chain reaction." In several hours' time, RAPD-PCR can multiply - more than a million times - specific sequences of the four chemical bases in the nucleic acids that make up genes. Bartlett and Gawel used PCR-amplified sequences to compare genetic material from whiteflies in biotypes A and B.

In each of 20 separate PCR comparisons, Gawel and Bartlett found striking genetic differences. "If the insects were the same species, all tests would have shown close similarities," says Bartlett.

But other genetic evidence supports the idea that the new pest,B. tabaci, is like the better-known but less destructive biotype A of sweetpotato whitefly. Certain genes - such as those that make ribosomal RNA (rRNA) - serve as a kind of evolutionary clock, explains entomologist Bruce Campbell of ARS in Albany, California. "By comparing sequences in the RNA'S nucleotide building blocks, we can estimate how closely species are related."

Recently, Campbell compared more than 1,000 nucleotides and found that the two whitefly biotypes' rRNA's were 99.8 percent similar.

He and colleagues also found highly similar rRNA'S in beneficial bacteria that whiteflies inherit from their mothers. "Both of these rRNA indicators," he says, "appear to be too similar for the insects to be different."

A classical test of whether two insects are the same species is if they can mate and, more important, produce fertile offspring of both sexes. Female whiteflies need not mate to produce males, but they must mate to produce females. In lab studies in which the two biotypes had opportunities to interbreed, they produced few female offspring. But there are several reasons why the insects of the same species might fail such tests.

It would be convenient if insects were born with labels, but Bemisia whiteflies have a history of thwarting taxonomists' efforts to pigeonhole them. One Bemisia trademark is unusually high variation in physical form and structure, host plant preference, behavior, and other factors. Not long before the new pest burst on the scene, in fact, taxonomists folded 18 previously "different" Bemisia species into the single species B. tabaci. And the debate over their correct placement will probably continue.

The consensus of the scientific community, based on all the evidence, will eventually yield an answer," says James R. Coppedge, ARS national program leader for applied entomology. "Meanwhile, we have to attack this pest as best we can with what we now know."

Toxic Spit?

Much to the surprise of growers and scientists, the new biotype B whitefly is a wimp at spreading plant viruses. Its type A cousin, which has been around for decades, does a far better job.

"Growers have already seen that their problems with type B whiteflies aren't due to viruses," says ARS plant pathologist James E. Duffus who is based in Salinas, California.

The question ... is: Why? The answer may be in the whitefly spit that spreads plant viruses.

Both types of whitefly, Duffus explains, use a strawlike stylet to puncture the veins of a plant leaf. Then the insect sucks out the sweet juices - and virus particles that may be present. As the pest moves to other plants, its virus-laden saliva can give the disease a new home.

But the saliva, Duffus points out, also contains a natural toxin that can kill the virus. And saliva of the biotype B whitefly may carry more of this toxin than biotype A. He believes this difference could explain why, for example, biotype B is about 100 times less effective in transmitting lettuce infectious yellows virus, which attacks lettuce and sugarbeets. His own tests have shown that biotype B is also a weaker vector of squash leaf curl, a viral disease of squash and melons.

Duffus is testing the toxic-spit theory in his lab at ARS' U.S. Agricultural Research Station.

"In the future," he says, "it might be possible to move the gene responsible for the anti-viral compound into plants like lettuce. That would give the plants new, natural protection against viruses."

Egypt's Whitefly Mummies

Two mummy hunters and their boatman glide across the Nile in a felucca, a small vessel bearing a single triangular sail.

The mummy hunters, entomologists with the Agricultural Research Service, reach their destination at an island not far from the Aswan High Dam.

The mummies they seek are dead sweetpotato whiteflies. But their real quarry is whatever killed these Nile whiteflies whose relatives have created a modern-day plaque thousands of miles to the west.

While the boatman finds shade for a nap, Alan A. Kirk and Lawrence A. Lacey roam through a garden of botanical rarities. The scientists search the garden for the telltale red, pink, orange, and white blossoms of lantana bushes. Soon they spot the flowers and, clinging to the small lantana leaves, hundreds of tiny, gray and black mummies encasing dead whitefly pupae.

Kirk and Lacey gather the lantana leaves, taking care not to dislodge the mummies. Many of the husks, or pupal cases, harbor living wasps that killed the whiteflies by feeding on them.

When Kirk and Lacey finish their collecting, they rouse the boatman.

By felucca, car, and jet, the wasps will travel to France, to the ARS European Biological Control Laboratory in Montpellier, 500 miles south of Paris.

If descedents of the wasps pass research tests there and in the United States, they could be reared by the thousands and set free to help solve this country's whitefly scourge.

The Montpellier laboratory serves as the staging area for Kirk, Lacey, and other ARS scientists searching for and studying potential biocontrol agents - insects, fungi, and other organisms - in Europe, Asia, North Africa, and the Middle East.

Over the past year, Lacey and Kirk traveled to seven countries to hunt for and collect the whitefly's natural enemies.

Scientists think the whitefly may be native to India and nearby countries, since many of its relatives abound there. Accordingly, Kirk and Lacey journeyed to Pakistan, Nepal, and India.

In Padappai, India, a village near Madras, the researchers discovered what Lacey calls "one of our most exciting finds," a fungus that invades and destroys adult whiteflies and immature ones, or nymphs.

"The infected whiteflies looked like woolly white patches on the leaves," says Kirk. Back in Montpellier, Lacey isolated a pure culture of the fungus, might thrive in regions of the United States that have a hot and humid climate similar to southern India's, such as Florida or the Texas gulf coast. It might also do well in a hot, dry area under irrigation.

A concept called "habitat and climate matching" guides the scientists' collection efforts. "It's important to find organisms that will do well in the various regions and climate found in the United States," says Lacey.

Scientists take detailed notes at each collecting site, such as the type of crop, nearby plants that might serve as alternative hosts for whiteflies,and the site's history of pesticide use. Geology, elevation, time of year, climate, and historical weather records are other crucial details.

Eretmocerus mundus wasps collected during a 1991 expedition have already been released to fight whiteflies in California and Texas.

"In our recent journeys, we've found E. mundus in many places from Spain to India, in many different habitats, and on many different crops," says Kirk. That increases the chances for a good habitat match with locales in the United States.
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Title Annotation:includes related articles; whitefly infestation control research
Author:Becker, Hank; Corliss, Julie; De Quattro, Jim; Gerrietts, Marcie; Senft, Dennis; Stanley, Doris; Woo
Publication:Agricultural Research
Article Type:Cover Story
Date:Nov 1, 1992
Words:5115
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