Time to scout for and treat against mid-sized ABW larvae in New England
This week's samples from our WeevilTrak sites have revealed a range of larval stages at most of our sites. About 43–63% of larvae in the samples were still 1st and 2nd instar, stages that feed inside of the stem. Some larvae (~10 % ) already have reached 4th instar, the stage that can be easily detected in soil. What surprised us was that we are seeing about the same kind of larval activity for most of the locations (larval stages 2.3-2.6), even though some sites (for example, Oak Hill, Pocasset and Tedesco) have been much cooler throughout the spring and so are further behind on degree days.
Usually we use Rhododendron (catawbiense) full bloom as the plant indicator for timing a larvicide application. This plant now is in full bloom or reaching full bloom throughout the area. It is time to scout for mid-sized larvae and if necessary to apply larvicides. As field trials have shown cyantraniliprole (FerenceTM) is effective against small larvae that are still inside the stem, as well as the slightly larger third instars just as they emerge from the stem. Spinosad (MatchpointTM) and indoxacarb (ProvauntTM) do not appear to be as effective against the larvae that feed inside of the stem, but they work well against larvae which have come out of the stems and are feeding outside on the turfgrass crown.
Submitted by: Dr. Olga Kostromytska and Dr. Pat Vittum
