WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Gall Midge and Tip Midge

(Dasineura oxycoccana)

Insects & Invertebrates

 

Tip Midge

 

Symptoms

Hatching larvae feed in the terminals causing the foliage to curl and deform. Terminal growth feeding releases apical dominance and will often cause branching and a witches-broom appearance.

 

Identification

Adults are very small gnats, less than 1/16 of an inch long. Early larval stages are clear to ivory white in color. As larvae mature, they become pink or orange in color and are less than 1/16 of inch long at maturity. This pest is also referred to as the cranberry tipworm.

 

Tip Midge

 

Life History

The blueberry tip midge overwinters in the pupal stage at the soil line. Adults emerge from the soil in May and June to oviposit eggs in the terminal growth of new shoots. Larvae hatched from the eggs become adults in about 2 to 3 weeks. This allows for several generations per year, with generations overlapping.

 

Monitoring

Begin scouting for deformed terminal growth in April. Look for blackened tips of unfolding leaves of the terminal growth. Using a hand lens, inspect the tip for the small maggot, usually located at the stem and leaf junction. Record the percent of shoot tip infection to track population trends. Overlapping generations result in multiple stages (egg, larvae, pupae, and adult) present at one time.

In-field identification is difficult because of the small size of the larvae and adults; identification can be made more easily by collecting and rearing blueberry gall midge in-situ. Collect growing shoot tips in 1-gallon resealable bags and include a folded damp paper towel. Larvae of infested shoot tips will emerge after 1 to 2 days at room temperature. Adult flies will emerge after 2 weeks.

Tip Midge

 

Thresholds and Management

In new plantings, the threshold is when greater than 4 tips per plant show distortion symptoms.  The pest has not been determined to be an economic issue and treatment may not be necessary on established plantings.

Keep annual records of tip midge scouting reports. Watch for decreases in yield of infested fields. If branching, much like witch’s broom, occurs to a large degree, prune out damaged branches to promote normal bush growth, especially in young plantings. Contact your local extension office regularly and keep yourself up to date concerning the pest status of blueberry tip midge in highbush blueberries.

Tip Midge

 

Resources

Oregon State University Extension, Blueberry Gall Midge: A Possible New Pest in the Northwest
http://extension.oregonstate.edu/catalog/pdf/em/em8889.pdf

University of Florida Extension, Blueberry Gall Midge: A Major Insect Pest of Blueberries in the Southeastern United States
http://edis.ifas.ufl.edu/pdffiles/IN/IN45800.pdf

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • (360) 778-5800 • whatcom@wsu.edu