Blueberry Insect Scouting Report for July 15-21, 2012

Cooler weather may increase spotted wing Drosophila activity.

Crop stages

Harvest is still going strong as Bluecrop harvest is finishing, and the harvesters are moving through Rubel and Jersey at the sites we visit in Van Buren and Ottawa counties. Elliot harvest is also underway at the sites we scout.

Weekly insect pest report

The number of spotted wing Drosophila (SWD) caught in yeast-baited traps remained steady and low over the last week as fields with ripe fruit are being treated to prevent SWD infestation. The high heat we have been experiencing over the past two weeks has also likely been keeping SWD numbers down. Growers and scouts should be aware of a potential increase in SWD activity with the 80 degree weather we are expecting during the next few weeks.

Monitoring traps continue to catch female SWD, with more flies trapped in yeast-baited traps than those baited with apple cider vinegar. We are also seeing an increasing proportion of the SWD being male flies with the distinctive dots on their wings. The good news is that no SWD larvae have been detected in our blueberry samples taken from four commercial blueberry farms, in testing using the salt test method.

We did catch blueberry maggot flies at the farms we visited in Van Buren County this week, and catches were also up at the Trevor Nichols Research Center planting in Fennville, Mich. There are reports of this pest occurring at several sites across areas of blueberry production in Michigan. We expect growers and scouts will 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, 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.

Japanese beetle numbers were generally low in most fields at the farms we visited last week. Beetles can still be found in areas that have recently been picked and irrigated and are awaiting an insecticide application between harvests. Feeding damage on leaves or fruit is still very low at our scouting sites, and this is probably due to insecticide applications. Even with all the SWD management activity, there are still reports of Japanese beetles found in lugs during harvest and sorting. 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 machine harvest.

To monitor for Japanese beetles, 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 beetles at blueberries.msu.edu.

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

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