Codling moth larva
feeds on a Red Delicious apple. Click the image for more information about
Insect Virus Targets the Proverbial Worm in
the Apple By Jan
August 16, 2004
A virus that infects and kills codling moth larvae can offer
fruit growers an insecticide alternative for fighting the pest,
Agricultural Research Service studies
ARS entomologists Lawrence Lacey and Steven Arthurs conducted
tests in 2003 at four Washington State apple orchards, where they sprayed trees
with the Cydia pomonella L. granulovirus. The treatment killed moth
larvae for up to 14 days, with 94 percent becoming infected within the first
few days of application. All infected larvae died shortly thereafter. Lacey and
Arthurs, with the agency's
Vegetable Insect Research Unit at Wapato, Wash., reported their findings in
the journal Biological
Besides apples, codling moths attack walnuts, pears and other
fruit. The larvae damage the fruit by boring deep inside it, ruining
Until integrated approaches to controlling codling moths were
adopted in the Pacific Northwest--including use of sex pheromones to disrupt
the moths' mating--the standard defense was to spray orchards with insecticide.
But such spraying is costly, ecologically worrisome and dangerous to beneficial
insects. Although heavy infestations of codling moths may still necessitate
insecticide use, moderate infestations can be subdued by combining biocontrol
agents with mating disruption or other measures.
Researchers have studied the granulovirus for 30 years,
thoroughly documenting its safety, host specificity and biocontrol potential.
Even so, fruit growers have been slow to use it. Lacey attributes this to
formulation, quality and other problems tied to early granulovirus products,
including their rapid degradation by sunlight.
The recent study compares the persistence and effectiveness of
three new or improved formulations, which the manufacturers registered for use
on apples, pears, walnuts and plums. The key is timing the applications of
granulovirus so they prevent larvae from penetrating the fruit too deeply.
Infected larvae die in five to 10 days, but the granulovirus poses no threat to
humans, other mammals or non-host insects.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.