MSU Extension

Crop stages

Blueberries are still developing rapidly at the sites we visited in Van Buren and Ottawa counties. We expect to see some coloring of fruit on early varieties at warmer sites in the next week.

Weekly insect pest report

Cherry fruitworm moth flight is over at all the farms we visit, and cherry fruitworm traps can be removed from fields. Similarly, egglaying by cherry fruitworms should be over, and in general very little damage was seen at our scouting sites. To help with management plans for future years, be sure to make note of where cherry fruitworms were trapped and where you saw cherry fruitworm damage on your farms.

Cranberry fruitworm flight should continue for at least another week in Van Buren County and longer in Ottawa County and areas further north. According to the MSU Enviro-weather model for cranberry fruitworm, on June 10 egglaying by cranberry fruitworms was predicted to be complete in Grand Junction, Mich. (first moth capture May 5), and 83 percent complete in West Olive, Mich. (first capture May 11). The cranberry fruitworm model on Enviro-weather can be used to see when cranberry fruitworm egglaying is expected to finish in your area. Cranberry fruitworm traps should be checked weekly until harvest. A detailed article about fruitworm management has been posted at the MSU Extension Fruit News website.

The number and size of blueberry aphid colonies has been reduced at sites where growers have applied insecticides for aphid control. The percentage of shoots that are infested with blueberry aphids is still high in some spots at the farms we visit (0 to 45 percent of shoots with aphids). 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.

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. See the Blueberry Facts website or this previous article from the June 8, 2010, Blueberry IPM Newsletter for more information on aphids.

Spotted wing drosophila (SWD) are still being trapped at berry farms in Allegan and Ottawa counties, and catches have increased from five females and zero males trapped in the week of June 1, to six males and 16 females trapped last week. Of last week’s captured flies, 19 were in yeast-baited traps and three females were in apple cider vinegar-baited traps. Eight of them were trapped in the woods, whereas 14 were in traps placed in the fields.

As of June 10, no SWD captures have been reported in Michigan south of Allegan County, but we expect activity to be starting there, too. Captures in 2012 are about a month earlier than the first capture in 2011, so this will allow blueberry growers to plan for controlling this pest when fruit is ripe and at risk from infestation by SWD. Traps for SWD should be out now to identify fields where this pest is present, before fruit begins to ripen. Check traps at least once per week and be sure to replace the bait in the trap each week for maximum efficacy. For more information on how to monitor and control this new pest, visit the MSU IPM Spotted Wing Drosophila website.

Blueberry maggots have emerged near Grand Junction and West Olive, Mich. Growers and scouts should be sure monitoring traps are hung, especially in areas where blueberry maggots have been an issue previously. To monitor for blueberry maggots, use yellow sticky traps folded into a V-shape with the sticky side facing the ground. Traps should be put in the outside portion of the upper canopy of bushes near the border of the field. If using unbaited traps, add an ammonium acetate "charger" when the traps are hung. If using traps baited for blueberry maggots, the charger should be added to the trap after one week in the field. Traps should be checked at least once per week, and the charger should be refilled or replaced if it becomes less than half full or if gets water-logged.

For more information on monitoring and controlling blueberry maggot, including pictures of traps and pictures of the pest, see the Blueberry Facts website or a previous article in the June 21, 2011, Blueberry IPM Newsletter.

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