Managing Summer Populations of OBLR

Where Oblique banded leafroller (OBLR) damage has been a problem in apple orchards, pheromone traps have been set out to monitor the flight of the moths for the summer generation. The first sustained moth catch for OBLR is the biofix and marks the start for calculating degree-days for OBLR development through this generation. OBLR have a lower developmental threshold of 6.1° C and an upper threshold of 29.4 ° C. In general moths emerge from mid June to mid July. Egg masses are laid on leaves after mating. The incubation period of the eggs is 10 to 12 days. A female is capable of laying up to 900 eggs in her 7 to 8 days oviposition period.

With weather data and the degree-day model, calculations can be made to determine when is the best time to apply insecticide treatments. For populations of OBLR that are resistant to organophosphate insecticides and other chemistries, Success and B.t products will provide control. While these products are effective, they work as stomach poisons and so, it is important to apply these products when the larvae are feeding. Over the course of the last few years, we have found that is important not to go in too soon with Bt products or Success. The best control is to wait until at least 220 to 260 degree-days and a second application 7 to 10 days may be needed if larval populations are high. For resistance management reasons, always use one chemistry to treat each generation. That is if your first spray for the summer generation is Success, then the second one 7 to 10 days later should be Success as well.

Finally, if using B.t. products the spray solution should be at pH of 7 or less. If using Success the spray solution should be at a pH of 6 or more.