Blueberry Insect Scouting Report for July 1-7, 2012

Pest abundance is low at many sites, but the threat from spotted wing Drosophila continues.

Crop stages

Bluecrop harvest is well underway in Van Buren County and first harvest in Jersey has begun. Early varieties have been picked multiple times in Ottawa County and the second picking of Bluecrop and first harvest of Jersey should begin this week as well.

Weekly insect pest report

The overall steady increase in the number of spotted wing Drosophila (SWD) caught in yeast-baited traps is continuing at the farms we scout, but in recently sprayed fields the number of flies has been greatly reduced. No larvae have been detected in fruit we have sampled using the salt bag test method. The number of flies per trap and the percentage of traps that are catching flies are higher in Ottawa and Allegan counties compared to Van Buren County.

We are still catching mostly female SWD in yeast-baited traps and most have been caught in crop fields, but the number of male flies trapped has increased greatly over the past week. Growers should be aware that if this pest has been caught on your farm you should protect the ripening and ripe berries because this is the period of risk from infestation by SWD. Through the ripening period and harvest, traps should be checked at least once per week. Be sure to replace the bait in the trap each week for maximum efficacy. For more information on managing spotted wing Drosophila, see the recent MSU Extension News article Managing spotted wing Drosophila update.

We did not catch any blueberry maggot flies at the farms we visited this week, but catches have increased to an average of four flies per trap at the Trevor Nichols Research Station in Fennville, Mich., and we expect to see fly emergence increase if we receive significant rainfall. Although sprays for SWD are likely to control blueberry maggots, growers and scouts should still be checking traps, especially in areas where blueberry maggots have been an issue previously. Be sure to replace ammonium acetate bait containers to keep the traps attractive to the flies. For more information on monitoring and controlling blueberry maggots, including pictures of traps and pictures of the pest, see the MSU Blueberry Facts website or a previous article in the June 21, 2011, Blueberry IPM Newsletter.

There were fairly low numbers of Japanese beetles at the fields visited last week. Feeding damage on leaves or fruit is still very low at our scouting sites, and this is probably due to insecticides applied for SWD management. Regular monitoring will aid growers and scouts in timing control measures to keep fields clean of Japanese beetles before harvest and reduce the possibility of contamination during picking. To monitor for Japanese beetle, examine 10 bushes on the field border and 10 bushes in the field interior and record the number of beetles on each bush. Keep in mind Japanese beetles are normally more common adjacent to grassy areas on sandy soils, and they prefer to be in sunny areas. Read more about Japanese beetle at blueberries.msu.edu.

Blueberry aphid colonies are still present in some fields, but they are becoming harder to find as the season progresses. This decrease is also most likely due to insecticide applications for SWD control. Parasitized aphids are increasing slightly, but numbers are still low. Growers and scouts can discontinue scouting for aphids at this time. Be sure to keep a record of where aphids were found and the amount of control achieved with insecticide applications to help plan for aphid control in future years.

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

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