Blueberry Insect Scouting Report for June 18-24, 2012

Sharp increase in spotted wing Drosophila captures at several farms means growers should monitor and protect ripe fruit.

Crop stages

Harvest of early varieties began at some southern sites in the past week, and picking should begin this week in early maturing varieties in Ottawa County.

Weekly insect pest report

Cranberry fruitworm flight is essentially over for most of the blueberry growing areas in west Michigan, and the MSU Enviro-weather cranberry fruitworm model predicts that the egglaying period is over in Grand Junction and West Olive, Mich. Traps should be removed from fields to get ready for harvest. Remember to make note of where cranberry fruitworms were trapped and where you saw cranberry fruitworm damage on your farms to help you make management plans for future years.

The number of spotted wing Drosophila (SWD) caught in monitoring traps, as well as the number of traps that have captured SWD, increased over the last week. This pattern was most noticeable at the farms we visit in Ottawa County. The trend we have seen in the past couple of weeks is continuing, in that most of the flies that were captured were females in yeast-baited traps and most have been caught in crop fields. Growers should be monitoring for this pest across their farms to have a good chance of detecting its presence.

If SWD is detected in your fields or in a nearby field, you should protect the fruit as it becomes ripe because this is the period of highest risk of infestation by SWD. Through the ripening period and harvest, traps should be checked at least once per week and appropriate management responses should be implemented. Be sure to replace the bait in the trap each week for maximum efficacy.

For more information about options for controlling SWD, please see the recommendations for blueberry growers at the MSU IPM Spotted wing Drosophila website. Be aware that most insecticides with efficacy against blueberry maggots (see below) are also active against SWD. However, members of the neonicotinoid class and the carbamate Sevin are not recommended for SWD control.

Blueberry maggots have emerged near Grand Junction, Gobles and West Olive, Mich. 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 and the sticky side (and the point of the V) 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 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, and the number of beetles observed during scouting has increased at all the farms we visited last week. Very little feeding damage was observed on leaves or fruit at the sites we visited. 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 are still present in some fields, but most have been reduced in response to insecticide applications. Parasitized aphids are still being observed, but numbers were lower than in the previous week. Growers and scouts should continue to monitor aphids in order to assess the amount of control achieved by recent insecticide applications 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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