Blueberry Insect Scouting Report for May 7-13, 2012

Cranberry fruitworm egglaying expected to start this week, and aphids are starting to develop.

Crop stages

As of May 11, in Van Buren County, Bluecrop and Rubel in Paw Paw, Grand Junction, Gobles and Covert, Mich., were nearing the end of petal fall, Jersey were at full bloom/early petal fall, and Elliot were at full bloom. In West Olive, Mich., in Ottawa County, Bluecrop, Rubel and Blueray were at early petal fall, Jersey were at full bloom, and Elliot were at 50 to 75 percent bloom.

Weekly insect pest report

Cherry fruitworm moth flight is still going strong at all the farms we visit in Van Buren County and Ottawa County, and egglaying by cherry fruitworm is predicted to continue at the sites we are scouting. Cranberry fruitworm flight is increasing Van Buren County and we saw the first cranberry fruitworm moths in Ottawa County this past week. At our scouting sites we expect to reach the growing degree day accumulation for the start of cranberry fruitworm egglaying in Van Buren County by the middle of this week and we should reach that mark by as early as this weekend at warmer sites in Ottawa County.

Cranberry fruitworm egglaying begins approximately 85 GDD (base 50°F) after cranberry fruitworm moths are caught consistently. Growers and scouts should be checking fruitworm traps twice weekly until the first moths are caught to get an accurate biofix. The cranberry fruitworm model on Enviro-weather can be used to see when growing degree accumulations have reached the point when cranberry fruitworm egglaying is expected in your area of the state. We expect to see the number of cranberry fruitworm moths in traps in Van Buren and Ottawa counties to increase considerably this week. A detailed article about fruitworm management has been posted at the MSU Extension Fruit News website.

We have seen the start of blueberry aphid colonies at all the farms we visited. It appears the recent rain and warm weather has brought on a flush of new suckers at the base of bushes, and with that, aphids are increasing. The colonies we saw were small (one to five individuals) and the percentage of shoots that are infested remains low (0 to 15 percent) at the farms we visit. To scout for aphids, examine two young shoots near the crown on each of 10 bushes and record the number of shoots where aphids are found. Also record the number of shoots with parasitized aphids. Be sure to sample weekly from as wide an area in the field as possible to have a better chance of detecting whether aphids are present. Although natural enemies (parasitic wasps, lady beetles, lacewings, hover fly larvae) can keep this pest in check, aphids can transmit blueberry shoestring virus, so growers may want to consider using an insecticide to control aphids if there are blueberry varieties that are susceptible to shoestring on the farm. See the Blueberry Facts website or this previous article from the Blueberry IPM Newsletter for more information on aphids.

We observed very low numbers of leafroller larvae in Van Buren County. It has been our experience that sprays targeting cherry and cranberry fruitworm are also well timed to effectively control other moth pests such as leafrollers, spanworms and tussock moth, 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 blueberries.msu.edu.

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.

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