Blueberry Insect Scouting Report for June 11-17, 2012

Spotted wing Drosophila captures increase and Japanese beetle emergence starts.

Crop stages

Warm growing conditions continue and fruit is maturing rapidly at the sites we visited in Van Buren and Ottawa counties. Harvest of early varieties should begin at warmer sites this week.

Weekly insect pest report

Cranberry fruitworm flight is ending at most sites in Van Buren County and flight is declining sharply in Ottawa County. Traps can be removed from fields to get ready for harvest. According to the MSU Enviro-weather model for cranberry fruitworm, on June 17 egglaying was predicted to be complete in Grand Junction, Mich., and West Olive, Mich. As with all pests and diseases, be sure to make note of hotspots on your farms to help you make management plans for next year.

We found the first capture of spotted wing Drosophila (SWD) in Van Buren County this week, in Grand Junction, Mich. Spotted wing Drosophila are still being trapped at berry farms in Allegan and Ottawa counties, and the number of flies caught as well as the number of traps capturing SWD increased over the last week. This activity is earlier and higher than in the 2011 season, indicating that early cultivars should be monitored to assess the need for protection from SWD through the harvest period. Most of the flies that were captured were females in yeast-baited traps and most have been caught in crop fields. Note that the female flies do not have the spot on each wing, so their identification will take some careful observation. See the new MSU spotted wing Drosophila identification guide for more information.

Additionally, the number caught in traps in woodlots is also increasing. The early SWD captures this season 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 already 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 weekly for maximum efficacy. For more information on how to monitor and control this new pest, visit the MSU IPM Spotted Wing Drosophila website. There is a new guide to SWD identification, as well as a blueberry-specific management plan.

Blueberry maggots have emerged near Grand Junction, Gobles and West Olive, Mich., in the past week, and the recent rain is expected to bring higher activity. Growers and scouts should be checking monitoring traps, 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 yellow 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. Check traps once per week, and the charger should be refilled or replaced if it becomes less than half full or gets waterlogged.

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 beetles have also started to emerge. We saw low numbers of beetles at all the farms we visited last week. Very few were on bushes and no feeding damage was observed on leaves or fruit at the sites we visited. Recent rains are expected to bring out higher numbers in the coming weeks. 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. 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.

Blueberry aphid colonies have been reduced at most sites in response to insecticide applications. The number of parasitized aphids also increased over the last week. Continue to monitor aphids in order to assess the amount of control achieved by recent sprays and to help decide if reapplication is necessary. 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.

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

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