Blueberry Insect Scouting Report for July 22-28, 2012

Remain vigilant with scouting and keep up with controls for spotted wing Drosophila, blueberry maggot flies and Japanese beetles.

Crop stages

Bluecrop has been hand-picked three times at many sites and a final cleanup harvest with the machine harvester should occur in the next week. The second harvest of Jersey is finishing up at the sites we visit in Van Buren and Ottawa counties, and a third harvest is possible. Elliot harvest is also well underway at the sites where we scout, and the first picking should be complete over much of southwest Michigan.

Weekly insect pest report

We saw a slight increase in the number of spotted wing Drosophila (SWD) caught in yeast-baited traps over the last week as harvest is finishing in many fields. Growers need to remain vigilant and keep protecting fields with ripe fruit to prevent SWD infestation before the end of harvest. An increase in SWD activity is expected over the next few weeks as temperatures should remain in the 80s.

Monitoring traps continue to catch female SWD, with more flies trapped in yeast-baited traps than those baited with apple cider vinegar. The number of male flies, with the distinctive dots on their wings, continues to slowly increase. On a positive note, SWD larvae have not been detected in our blueberry samples taken from four commercial blueberry farms in testing using the salt test method.

Regarding post-harvest applications for SWD, we are not recommending any sprays for this pest after the last harvest, as there is no evidence that this will reduce pest pressure next year. We are initiating some research on this question to get some information on the utility (or futility) of this tactic.

We trapped low numbers of blueberry maggot flies at the farms we visited in Van Buren and Ottawa counties this week. Catches were also up at Trevor Nichols Research Center in Fennville, Mich., and there are reports of this pest occurring at several sites across areas of blueberry production in Michigan. We expect this trend to continue and growers and scouts should see more blueberry maggot flies on traps this week after the recent rain.

Insecticides used for SWD control are likely to also control blueberry maggots, but growers and scouts should still be checking traps. 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.

Japanese beetle numbers were generally low in most fields at the farms we visited last week, but beetle numbers are up in fields that are waiting to be picked and have not been recently treated with insecticide. Beetles will be most numerous in areas that have just been picked and irrigated and are awaiting an insecticide application between harvests. Japanese beetles are normally more common adjacent to grassy areas on sandy soils and they prefer to congregate in sunny areas. Feeding damage on leaves or fruit still remains very low at our scouting sites.

This season, we are seeing much more feeding damage by birds than by Japanese beetles. There are still reports of Japanese beetles in lugs during harvest and sorting. Regular monitoring of Japanese beetles will aid growers and scouts in timing control measures to keep fields clean before harvest and also reduce the possibility of contamination during machine harvest. 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. Read more about Japanese beetle at blueberries.msu.edu.

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

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