Blueberry gall midge, Dasineura oxycoccana

The blueberry gall midge, sometimes known as the tipworm is native to North America and invasive in Asia and Europe. It is a highly specialised pest of Vaccinium crops, such as blueberries and cranberries. The pest targets newly developed buds, stunting growth and reducing crop yield, with severe attacks causing complete crop failure. Hidden within the buds, larvae are difficult to control using pesticides. Generations can reach 5-6 per year. As part of an IPM programme, monitor adults using red Delta Traps with the highly sensitive Dasineura oxycoccana pheromone lures and Optiroll Super Plus (white-midge) for mass trapping.

Biology

Adult: a small mosquito-like fly, approximately 2-3 mm long. Females are a touch larger than the males and possess orange abdomens. Males possess yellow abdomens.

Larva: the larvae begin cream to pale-yellow in colour then become orange-red over their development. They are described as small legless maggots. Newly emerged larvae are approx. ½ mm in length and grow to approx. 2mm in length when mature.

Egg: eggs are approx. ¼ mm long and elliptical in shape.

Pupae: the midge overwinters as pupae in soil.

Nature of Damage

The blueberry gall midge is a particularly important pest in newly planted crops during the first 2-3 years. The females lay their eggs within the growing points of shoots, the larvae then emerge and feed on the growing shoots. The larvae live in leaf galls in the shoot tip triggering leaf distortion and darkening of buds (not to be confused with frost damage), killing the buds. The affected crops cannot produce enough foliage to support a heavy fruit crop, resulting in smaller berries with low sugar. Serious infestation of the blueberry gall midge can result in next years crops being affected due to the crops developing fewer bud-bearing shoots. 100% crop loss has been recorded in some blueberry varieties.

Begin monitoring with pheromone traps in early Spring just before the plants are growing new vegetation and new leaf buds. This will give early warning of the infestation and to help with decision-making. The pheromone lure contains the female Dasineura oxycoccana sex pheromone, which attracts the males of the species to the trap preventing them from mating with the females. The Dasineura oxycoccana lure can be used with the Red Delta Trap. For mass trapping use the Optiroll Super Plus (white-midge), which is impregnated with the Dasineura oxycoccana pheromone in the glue.

Application Guidelines

Russell IPM manufactures and supplies a pheromone lure and delta traps for the Blueberry gall midge Dasineura oxycoccana. The pheromone trap data will give early warning of the infestation and alert the user to invasion of the midges before population levels build up. For mass trapping, Optiroll super Plus (white-midge) roller traps are placed close to ground level along posts.

Pheromones

The following notes are general guidelines on implementing pheromone monitoring programmes. Local conditions and practices can vary, so please consult your local advisers for precise advice in your area.

Lures

The Dasineura oxycoccana pheromone lure lasts approx. 4-6 weeks.

Lures handling

Pheromone lures are a very sensitive tool. They can be affected by exposure to elevated heat and direct sunshine. Wear gloves to handle the lures as direct touching by hand may cause cross contamination leading to mixed catches in the trap. Some contaminants, such as nicotine, may have a repellent effect reducing trap catch.

Lure Storage

The lures can be stored for long periods (several years) in a freezer (at about -20˚C) if the pack is sealed. Lures can also be stored in a fridge at higher temperatures (4˚C) for periods of up to 1 year. Although the pheromone is not harmful to humans, lures should not be kept in a freezer or fridge where food is stored.

Trap Selection

The red Delta Trap with the Dasineura oxycoccana pheromone lure is recommended for monitoring this insect or the Optiroll Super Plus (white-midge) for mass trapping.

Trap Density

For monitoring, use two or more traps in each field. Care in choosing the location of deployment of the traps and in interpreting results will be necessary. For Optiroll Super Plus (white-midge), place a roll approximately every 10 m throughout the greenhouse, using about 10 rolls per hectare.

Trap Position

Delta traps should be placed 0.5 metres above ground level. Attach Optiroll Super Plus (white-midge) to greenhouse posts just above ground level, down the length of the greenhouse.

Data and Interpretation

Collect data weekly or more frequently if possible. midges captured may be removed on each sampling occasion which makes counting new arrivals easier, but this is not strictly necessary. Decisions on pesticide application should not be taken solely on the trap catch data. Climatic and biological considerations should be taken in account. The threshold of 30 midges per trap per week is proposed for timing sprays of insecticide, but this should be checked with your crop protection advisor as local conditions vary.