Northwest berry Foundation

Management Detail

Blueberry Gall Midge

in Blueberries

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Latin name: Dasineura oxycoccana

Description:

Reason for Concern:
1) This is a recently identified potential pest in the Northwest.
2) Its range and the extent of its damage are not well known although it is a serious pest of rabbiteye blueberries in the southeast. Some varieties have suffered a 100% crop loss due to depredations of this midge.
3) In the southeast, midge larvae feed inside and destroy flower buds resulting in low yields. This has not been observed in this region.
4) Larvae feed in the growing tips of the plant and causing branching of new growth. This is a potential problem where branching is excessive (Witch’s broom) and could affect number and quality of fruit buds.
5) Increased branching and loss of terminal buds is particularly a concern in young plantings as bushes may be slower to reach adequate height for machine harvesting.
6) Midge damage and resulting branching is less concern in older plantings. The increased branching could actually be beneficial, resulting in more lateral growth and more fruit buds.
7) Infested plants cannot produce enough foliage to support a heavy fruit crop, resulting in smaller berries with low sugar.

Identification:
The adult blueberry gall midge is a very small fly, about 1 to 3 mm long, and reddish. Larvae are white to yellow-orange and reach only 1 mm when mature. Both adult and larva are difficult to see. Infested vegetative buds swell and the outer leaves curl enfolding feeding larvae inside. Tissue necrosis is visible on any plant tissue fed on by larvae.

Lifecycle:
Overwinters as a pupa in the soil, and in mid-April the adult fly emerges. The adult stage (during which mating and egg-laying take place) lasts from 1 to 3 days. The female midge lays eggs in either floral or vegetative buds just after bud swell, when bud scales are beginning to separate. Each female lays 35 to 40 eggs. Eggs hatch within a few days and the larvae begin feeding within the blueberry bud. Since larvae digest plant tissues, this is the plant-damaging stage. There may be from 1 to 9 larvae in a single flower bud. Within a week’s time, the bud is dead, having a dry, shriveled appearance, often crumbling when touched. Larvae probably drop to the ground after feeding, then pupate and transform to the adult stage. The life cycle from egg to adult takes 22 to 25 days: there are several generations a year that may overlap and all stages may be present together on 1 plant. Flower buds are subject to continuous egg laying from January to March. As plants progress to vegetative budding, egg laying also occurs on the new shoot tips in April and May.

Links:

Scouting:

  • Begin scouting in April while looking for other pests.
  • Watch for vegetative shoot tips that have become distorted and have a black tip caused by midge larvae compromising vein tissues that carry nutrients to the new growth.
  • Inside some of the damaged tips should be midge larvae. They are very small and white to reddish color. It is sometimes necessary to use a small hand lens to see the small larvae.
  • Dead terminal buds may lead to a branching out or a witch’s broom effect.
  • Young plantings are most susceptible to stunting from the midge.

 
Cultural Controls:

None listed at present.

 

For information about chemical controls, check with our Pesticide Guide.

images


Puppa around 7 days - photo by W. Yang


Emerging fly - photo by W. Yang


Emerging fly - photo by W. Yang


Male fly - photo by W. Yang

 


Female fly - photo by W. Wang


BGM Lifecycle - W. Wang

 


Damage done by Blueberry Gall Midge - photo by T. Peerbolt


Damage done by Blueberry Gall Midge - photo by T. Peerbolt


Larvae seen through microscope - Photo by J. Pond


Damage caused by BGM

 

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