Fruitworm control options in blueberries

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Pheromone traps should already be out in Michigan blueberry fields for monitoring of adult cherry fruitworm and cranberry fruitworm. Cherry fruitworm flight is well underway in most areas of southwest Michigan. We have also trapped the first cranberry fruitworm moths in the past few days at the Trevor Nichols Research Complex in Fennville, and we expect heavy adult flight and egg laying this week with the forecasted warm temperatures.

There is an array of insecticides available for control of fruitworms, but their performance characteristics are not all the same. It is important to refrain from using compounds that are toxic to pollinators when these insects are in your fields. Two products registered for use during bloom and/or in the presence of pollinators have provided consistent control of fruitworms in trials at the Trevor Nichols Research Complex and at grower fields. These are the B.t. products (such as Dipel) and the insect growth regulator Intrepid. These products must be consumed by fruitworm larvae to be effective, so they are best applied over the top of fruitworm eggs so they are eaten as the larvae emerge. B.t. products have short residual activity, typically around five days, so are best applied when daily temperatures reach 70°F. Intrepid is more resistant to breakdown, giving between seven and 14 days activity. Other options for control of cranberry fruitworm are the growth regulators Rimon and Esteem. These insecticides are strong ovicides and disrupt the adult moth’s ability to lay viable eggs and hinder the development of larvae. As with all fruitworm control applications, excellent coverage of fruit clusters is required.

After 100 percent petal fall, the range of options for fruitworm control increases with Guthion, Imidan, Asana, Danitol, Mustang Max, Lannate and Sevin being some of the available broad-spectrum insecticides. With all these products, maintaining good coverage is still important to get residue to the parts of the berry where fruitworms are found. Recent research trials in Michigan have demonstrated that Intrepid, Rimon, Avaunt, Assail, and Delegate applied after petal fall to fields can also achieve control of fruitworms with minimal negative impact on natural enemies such as parasitic wasps, ladybeetles and lacewings. Correct timing and coverage are critically important, so regular scouting of fields, use of sufficient spray volume to get good fruit coverage and selecting appropriate spreader-stickers can increase activity of most insecticides applied for fruitworm control.

The table and figure accompanying this article are designed to summarize several key factors that can help you select an insecticide for your Integrated Pest Management program for fruitworm control in blueberries.

Details of insecticide options and timing for fruitworm control in blueberry.

Compound trade name Chemical class Life-stageactivity Optimal spray timing Pollinator/parasitoid toxicity rating *
 Guthion/Imidan  Organophosphate Eggs, Larvae, Adults 100% Petal Fall H
Lannate/Sevin Carbamate Eggs, Larvae, Adults 100% Petal Fall H
Asana/Danitol/Mustang Max  Pyrethroid Eggs, Larvae, Adults 100% Petal Fall H
Avaunt Oxidiazine Larvae 100% Petal Fall S (H for bees)
Assail Neonicotinoid Eggs, Larvae 100% Petal Fall M
SpinTor/EntrustDelegate Spinosyn Eggs, Larvae Early fruit setover eggs M
Dipel B.t. Larvae Early fruit setover eggs S
Intrepid Growth regulator Larvae Early fruit setover eggs S
Rimon Growth regulator Eggs, Larvae Early fruit setunder eggs M
Esteem Growth regulator Eggs, Larvae Early fruit setunder eggs S

* Pollinator/Parasitoid Toxicity rating; S – relatively safe, M – moderate toxicity,
H – highly toxic.

Population emergence of cranberry fruitworm adults, eggs, and larvae and the optimal timing to begin sprays of various insecticides.
Blueberry Graph

The work of Dr. Wise and Dr. Isaacs is funded in part by MSU‘s AgBioResearch.

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