Blueberry Insect Scouting Report for July 29-August 4, 2012

Harvest is winding down, but spotted wing Drosophila catches are ramping up.

Crop stages

Harvest of most early and mid-season varieties is complete across much of the region and harvest of Jersey and Rubel should be finishing in the next week. Harvest of late season cultivars such as Liberty, Aurora and Elliot is also well underway at the sites we scout, and harvest should be complete in 10 to 14 days across much of southwest Michigan.

Weekly insect pest report

A considerable increase in the number of spotted wing Drosophila (SWD) caught in yeast-baited traps occurred over the last week. SWD monitoring traps are catching many more males (identified by distinctive dots on their wings) compared to recent weeks. We suspect that with spray programs winding down because harvest is finishing in many fields, the number of SWD caught will increase over the next several weeks.

Fields with ripe fruit will need to be protected until the end of harvest with insecticide to prevent SWD infestation. Growers and consultants should keep in mind that unsprayed un-harvested fields next to fields that are waiting to be harvested may quickly become a source of SWD infestation, and these un-harvested fields may need to be treated before all other harvest is complete. Somewhat cooler weather this week should bring about an increase in SWD activity. We have not found SWD larvae in the fruit samples we have taken from the farms we visit and tested using the salt test method. However, we have received reports of SWD larvae in harvested fruit from commercial blueberry and raspberry farms.

We are not recommending any sprays for this pest after the last harvest as there is no evidence that this will reduce SWD pest pressure next year. We are starting a research project to determine if post-harvest sprays will be an effective way to reduce SWD populations and limit SWD infestation. Results of that study will not be available until next season.

The number of blueberry maggot flies trapped last week increased at some farms in southwest Michigan. Catches were also up at the research planting 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 increasing trend to continue; growers and scouts should see more blueberry maggot flies on traps this week after the recent rain.

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

Very few Japanese beetles were found in the fields we visited last week. As harvest and insecticide applications slow down at the end of the season, we can expect to see an increase in beetles in and around fields after harvest. 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, but 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 beetles at blueberries.msu.edu.

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

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