The Gall of That Midge!
By Jan Suszkiw
January 7, 2008
Tiny wasps discovered by Agricultural Research Service (ARS) scientists in Poplarville, Miss., may
help Gulf Coast blueberry growers put the sting on their crop's top insect
pest: the gall midge.
As larvae, gall midges feed on the blueberry plant's buds, deforming
them and endangering the fruition of up to 10 berries per bud. In Gulf Coast
states like Florida, the midges are so prevalent some blueberry growers have
abandoned rabbiteye varieties, which the pests commonly attack.
But blueberry growers take heart: The pests themselves are fed
onfrom the inside out.
Entomologist Blair Sampson made the discovery while working at the
Southern Horticultural Laboratory in Poplarville. He and a research
assistant were examining a gall midge larva under a microscope when a pair of
tiny jaws appeared, tearing at the specimen.
As it turned out, the jaws belonged to an immature waspone of
four parasitic species that Sampson was to discover. The wasps belong to the
genera Synopeas, Inostemma and Platygaster, but Sampson has yet
to assign them a species name.
In blueberry fields, a female wasp seeks out midge larvae hiding
inside buds and stings them. She then injects her eggs into her prey's stomach
There, the eggs develop into immature wasps that fight for the chance
to feast on their midge host. It's a mandible-on-mandible slugfest that ends
when only one wasp remains.
Needless to say, the real losers are gall midges. Sampson has
determined that a natural population of the wasps in blueberry fields can kill
40 percent of all midges, controlling them for about 200 days.
Sampson will explore the possibility of rearing the wasps for release
into areas where years of insecticide use have diminished the insect's natural
more about this research in the January 2008 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief scientific research agency.