Adult tuber moth. Chemicals emitted by the fungus Muscador albus may help protect fresh spuds from the moth's destructive larvae.Original image courtesy Central Science Laboratory, Harpenden Archives, British Crown, and www.insectimages.org/.

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Scientists Pit Fungus Against Potato Pest

By Jan Suszkiw
May 15, 2007

A fungus that packs a powerful biochemical "punch" may help knock out potato tuber moths. That's the implication of an ongoing Agricultural Research Service (ARS) study in which a blend of alcohols, esters and other gaseous compounds emitted by the fungus Muscador albus killed adult tuber moths and their larvae.

In the Pacific Northwest, where the moth (Phthorimaea operculella) is a major problem, potato growers normally treat their crop with broad-spectrum insecticides. However, some of the most effective insecticides cannot be used within two weeks of harvest. In that interim, surviving moths can lay their eggs on tubers destined for storage, notes Lawrence Lacey, an entomologist with the ARS Yakima Agricultural Research Laboratory, Wapato, Wash.

Together with Lisa Neven, an ARS entomologist there, Lacey is investigating M. albus' potential as a biobased fumigant that could be used during that preharvest period, as well as on warehoused potatoes.

Their investigation of the fungus is part of a larger program at Wapato to diminish reliance on synthetic chemical controls by using biological ones—including bacteria, viruses and roundworms—in integrated pest management programs.

In lab experiments, the researchers placed adult moths and two-day-old larvae inside special fumigation chambers and exposed the insects to one of two concentrations of M. albus—15 grams and 30 grams—for 72 hours. Exposure to volatile organic compounds emitted by the fungus at these concentrations killed 85 and 91 percent of adult moths, respectively. Of the larvae that escaped the fungal fumes, 62 and 73 percent of them died or failed to become pupae, the final stage before they emerge as adult moths.

Lacey and Neven didn't discover M. albus, first found growing on the bark of a cinnamon tree in Honduras, but they were the first to report the insecticidal properties of its emissions. Research by other groups has focused on M. albus' potential to kill other fungi and bacteria harmful to crops or humans, as well as on its ability to degrade human and animal wastes.

ARS is the U.S. Department of Agriculture's chief scientific research agency.