Martin Shapiro, left, and Merle Shepard with some of the materials they are testing as sunscreens to protect viruses of insects which are pests in vegetable, field and flower crops.

DATE: 7/25/2006

CONTACT: Dr. Merle Shepard, 843-402-5393; mshprd@clemson.edu

Dr. Martin Shapiro, 843-402-5310; mshapir@clemson.edu

WRITER: Tom Lollis, 803-284-3343, ext. 241; tlollis@clemson.edu

Clemson scientists seek protection for biological enemies of plant pests

CHARLESTON – To protect your skin from the damaging ultraviolet rays of the sun, you apply a sunscreen. Clemson University scientists at the Coastal Research and Education Center think the same idea might help protect biological organisms used in natural warfare against insect pests of agricultural crops.

The main pest in question is the beet armyworm, also known as Spodoptera exigua by entomologists such as Merle Shepard, long-time researcher at Coastal REC, and Martin Shapiro, who became a Clemson adjunct professor after retiring in 2004 from a 30-year career with the USDA-Agricultural Research Service.

They lead a team seeking a way to prolong the life of a nuclear polyhedrosis virus (NPV) which is lethal to beet armyworm, a serious pest of vegetable, field and flower crops. When sprayed on a crop – broccoli, for instance – the virus is eaten along with bits of broccoli. Once in the gut it multiplies, liquefying the insect larvae’s cells.

Selectivity is one of the beauties of viruses as a tool for pest control, according to Shepard.

“You target specific pests and conserve their natural enemies,” he said. “One of the limitations is that sunlight breaks down viruses quickly when you spread them on a field.”

For 30 years Shapiro has been looking for organic chemicals that might absorb the harmful rays of sunlight and for chemicals that might compromise the immune systems of insect pests so that they would be more susceptible to a given virus.

“It would take less virus to kill the insect, or it would die more quickly and do less damage (to the crop),” he said.

A visiting scientist from Cairo University, Said El Salamouny, spent six months at Coastal REC in 2005 helping screen more than 70 materials for potential as viral protectors. The list of materials ranges from herbs and spices found in your local grocery store to health food supplements, also known as nutraceuticals.

“He left us an unusual problem,” said Shapiro. “We have a lot of chemicals that look good.” Black pepper, ginger, garlic, clove, sage, catnip, paprika and cumin all show promise.

Shapiro and Shepard now have to intensify the screening of those materials plus noni juice, peppermint oil, hawthorn extract, neem, cranberry and dozens of other substances to see which fall by the wayside.

Screening is done in an artificial sunlight box – a 48-quart cooler which has been modified with two fluorescent lights. One tube gives off ultraviolet A (UVA) and the other, UVB. The beet armyworm virus is placed on plates in a solution inside the box and exposed to UV light. To find the best materials, solutions will be diluted and exposure times increased.

Within the next year the best sunscreens will be field tested.

In future years the team plans to extend their efforts to protecting other natural pathogens such as Bacillus thuringiensis, fungi and nematodes.

“We have a wide array of natural insect enemies that we can test against our model insect,” said Shapiro. They also want to try spraying viruses out in oil, rather than in the usual water suspension.

The NPV which the scientists are working with is already a commercial product, under the name Spodex, but many growers are reluctant to use it because of the rapid breakdown, according to Shapiro.

He points out that viruses have been pushed by governments for insect pest control in developing countries more than in the United States.

“Merle and (retired Clemson entomologist) Jerry Carner helped establish a cottage industry in Indonesia for collection of the beet armyworm virus,” he said.

“In West Sumatra 10,000 farmers collect the virus and use it in the field,” said Shepard.

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