Blueberry Insect Scouting Report for May 21-27, 2012

Fruitworm and aphid populations are increasing, and it is time to start thinking about harvest time pests.

Crop stages

As of May 25 in Van Buren County, all varieties are in green fruit. June drop berries can be seen developing across the region and in spots with inadequate pollination, the number of dropped berries is highest. In West Olive, Mich., in Ottawa County, Bluecrop, Rubel, Blueray and Jersey had green fruit. Elliot was finishing petal fall and a few sites still had bees in the field.

Weekly insect pest report

Cherry fruitworm moth flight is essentially over at all the farms we visit in Van Buren County and flight is declining in Ottawa County. Egglaying by cherry fruitworm is expected to decrease at the sites we are scouting.

Cranberry fruitworm flight has increased in Van Buren and Ottawa counties, and flight should continue to increase over the next week. According to the MSU Enviro-weather model for cranberry fruitworm, on May 27 egglaying by cranberry fruitworm was predicted to be 76 percent complete in Grand Junction, Mich. (first moth capture May 5), and 54 percent complete in West Olive, Mich. (first capture May 11). Growers and scouts in northern areas of blueberry production should be checking fruitworm traps twice weekly until the first moth is caught. The cranberry fruitworm model on Enviro-weather can be used to see when cranberry fruitworm egglaying is expected in your area of the state. A detailed article about fruitworm management has been posted at the MSU Extension Fruit News website.

The number and size of blueberry aphid colonies is increasing at all the farms we visited and colonies with more than 10 individuals are becoming easier to find. The percentage of shoots that are infested with blueberry aphid is also increasing (0 to 35 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. Insecticides that are toxic to bees should not be used for aphid control where bees are still present. See the Blueberry Facts website or this previous article from the BlueberryIPM Newsletter for more information on aphids.

Gall wasp emergence is all but finished at the sites we monitor in Ottawa County and we expect emergence to end over the next week.

Thinking ahead

As the season is progressing rapidly, insect pests are appearing early, and this trend should continue. Growers and scouts should put out blueberry maggot traps in the next week to 10 days. This pest was very active last year so we expect a large flight of blueberry maggot this summer. We usually see blueberry maggot flies after a heavy rain or after irrigation in the middle of June. With the warmer than usual year, we expect blueberry maggot emergence to be earlier, and theMSU degree day model predicts first fly captures around 900 degree days (base 50). For more information on monitoring and controlling blueberry maggot, see the Blueberry Facts website or a previous article in the June 21, 2011 BlueberryIPM Newsletter.

Additionally, scouts and growers should be thinking ahead to monitoring for spotted wing Drosophila. Identifying fields where this pest is present before fruit begins to ripen is essential for making plans for managing spotted wing Drosophila when fruit is at risk as it becomes ready for harvest. For more information on this new invasive pest, please visit the MSU IPM spotted wing Drosophila website.

Dr. Isaacs’ work is funded in part by MSU’s AgBioResearch.

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