Female blueberry gall midge. Photo courtesy of Oscar Liburd.

Symptoms of blueberry gall midge infestation. Photo courtesy of Oscar Liburd.

• The adult stage (during which mating and egg-laying take place) lasts only from two to four days.
• Eggs are laid (oviposited) between the scales of flower and leaf buds shortly after the buds begin to expand.
• Dormant buds are not infested.
• Eggs hatch in two to three days.
• Because larvae digest plant tissues, they are the plant-damaging stage.
• There may be from one to nine larvae in a single flower bud.
• Larvae apparently feed on the developing bud tissues.
• Larvae develop through three instars, exit buds and drop to the ground after feeding, then pupate and transform into the adult stage.
• Under laboratory conditions, infested flower buds yielded adults after 12 days.
• As plants progress to vegetative budding, oviposition also occurs on the new shoot meristems. Infested vegetative buds swell and the outer leaves curl, enfolding feeding larvae inside.
• Gall midges lay eggs on warm days in late winter, usually after a heavy rainfall. The optimum temperature range for egg laying is between 70 degrees and 80 degrees.

Damage:

• Immature larvae or maggots feed on the developing floral and leaf buds of blueberries.
• Some rabbiteye varieties are highly susceptible to both flower and vegetative bud injury.
• Blueberry gall midge occurs sporadically, but when present they can cause reductions of 20 to 80 percent flower buds/fruit.

Scouting:

• Emerging adults can be monitored by deploying white inverted bucket traps with sticky transparent tops. A minimum of two traps per acre are required (one on the border of the field and another in the center of the field).
• Larval numbers can be monitored by collecting buds and holding them at room temperature for 10-16 days until larvae emerge.

Control:

• It is strongly recommended that farmers begin a pre-bloom insecticide spray program for blueberry gall midge only after the pest has become active on the farm or in nearby fields.
• Apply legal insecticides for gall midge control when flower buds reach stages 1 and 2; i.e., when swelling buds are starting to show signs of scale separation.
• Repeat pre-bloom sprays during warm spells.
• Cease spraying when bloom begins and bees are actively foraging in the field.
• Contact your local Cooperative Extension Service office for insecticides recommended in your region.

Sources:

Gagné, RJ. 1989. The Plant-feeding Gall Midges of North America. Cornell University Press, Ithaca, NY. 356
Isaacs, Rufus. Blueberry gall midge. Retrieved 06 July 2010.
Lyrene PM, Payne JA. 1992. Blueberry gall midge; a pest on rabbiteye blueberry in Florida. Proceedings, Florida State Horticulture Society 105: 297-300.
Liburd, Oscar E., Erin M. Sarzynski, Blair J. Sampson and Gerard Krewer. Blueberry Gall Midge: A Major Insect Pest of Blueberries in the Southeastern United States. Retrieved 05 May 2010.
Lyrene PM, Payne JA. 1995. Blueberry gall midge: a new pest of rabbiteye blueberries. Journal of Small Fruit Production.