Novel Bio-Insecticide Demonstrations and Advances in Spray Timing
Flea beetles remain a major problem for Wisconsin cranberries, and 2020 brought together a team of cranberry growers and researchers who were working on ways to mass propagate insect-killing nematodes. There were many set-backs and some learning experiences, but also some significant successes. We generated some of the best data yet on flea beetle control—nearly 95% control in a bed that had major flea beetle issues. Other cranberry beds had modest but solid control, ranging from 50-60% control. One grower manufactured his own gravity-fed nematode spraying mechanism, allowing for low-trauma applications of the nematodes.
Studies of degree-day (DD) ‘benchmarks’ suggest that the use of such benchmarks for spray timing can significantly improve spray efficacy. Results from 2019 show that insecticide sprays timed for either the 10% or 25% egg-hatch benchmarks represent the best timings for Sparganothis fruitworm control. In effect, the 10% and 25% spray timings represent a window in time. When Sparg is targeted within this window, current evidence suggests that insecticides are most effective.
The degree-day accumulations are easily tracked using the temperature readings on any given marsh. When growers reach the 10% benchmark at their marsh, they will have entered the ideal spray window. Growers simply continue keeping a running total of DDs on their marsh, so they will know when the end of the ideal spray window (the 25% benchmark) is reached.
