Blueberry Insect Scouting Report for April 29-May 5, 2012

Cranberry fruitworm flight begins, cherry fruitworm egglaying expected this week.

May 8, 2012 - Author: Keith Mason and Rufus Isaacs, Michigan State University Extension, Department of Entomology

Crop stages

As of May 4, in Van Buren County, Bluecrop and Rubel in Paw Paw, Grand Junction, Gobles and Covert, Mich., were nearing 50 percent petal fall, Jersey were at full bloom and Elliot were nearing 50 to 75 percent bloom. In West Olive, Mich., in Ottawa County, Bluecrop, Rubel and Blueray were at full bloom, Jersey were at 50 to 75 percent bloom and Elliot were at 25 to 50 percent bloom.

Weekly insect pest report

Cherry fruitworm moths are at the peak of flight at all the farms we visit in Van Buren County, and we should see the peak of flight this week in Ottawa County. With the warmer weather over the last week, we have reached the growing degree day accumulation for the start of cherry fruitworm egglaying in Van Buren County and we should reach that mark by early this week in Ottawa County. Cherry fruitworm egglaying begins approximately 100 GDD (base 50°F) after cherry fruitworm moths are caught consistently. At this point, fields with a history of infestation by cherry fruitworm, which have also now reached the predicted point of egglaying by this pest, should be protected with a bee-safe insecticide such as B.t., Intrepid or Confirm.

Cranberry fruitworm were not trapped last week, but the firstcranberry fruitworm moths have been trapped early this week in the Grand Junction and Fennville, Mich., areas, and also in Ottawa Coounty, and we expect flight of this pest to increase during the coming week as fields get further into petal fall. Degree day accumulations can be used to predict the start of egglaying by this pest at 85 degree days past biofix, but the unusual weather this spring has made setting biofix a little more challenging than usual. The warmest night of the weekend was on Saturday (May 5), so we have set biofix for May 5 at these sites. The model is predicting the start of egglaying for the middle of next week (around May 16) in Grand Junction, Mich.,, and later as you go north. Growers and scouts can check growing degree accumulations, either on site if weather monitors are in place, or online from the nearest Enviro-weather station. (See this example of current and predicted growing degree days from Enviro-weather stations in southwest Michigan.)

A detailed article about fruitworm management has been posted at the MSU Extension News website.

At the farms we scouted, we still have not seen leafroller larvae or feeding damage, but growers and scouts should be on the lookout for these early season pests, and there have been some reports of leafroller and spanworm feeding in some fields. It has been our experience that sprays targeting cherry and cranberry fruitworm are also well-timed to effectively control other early-season moth pests, so we do not expect many growers to have to put on specific controls for these other moth pests. To scout for leafrollers, examine five flower clusters and five leaf clusters on 10 bushes on the field border and five flower clusters and five leaf clusters on 10 bushes in the interior of the field. Look for leaf or flower clusters that have feeding holes or webbing in the cluster. These pests are generally not economically important in Michigan, but if 3 to 5 percent of buds have feeding damage, growers may want to consider a specific control targeting these insects. View more information and pictures of leafrollers from our scouting pages posted at

Gall wasp emergence at infested sites in Ottawa County has increased greatly with the warm weather last week, and we should see increased emergence over the next week. Growers should not use bee toxic chemicals for gall wasp control at this time in fields where bees are foraging.

Tags: agriculture, blueberries, fruit & nuts, msu extension

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