We were able to conduct a bioassay on a population of diamondback moth last week. Keep in mind we work in fields with severe problems and high populations. Also, responses to insecticides can vary greatly from location to location – mostly based on to which insecticides the population has been exposed.
The bioassay is a high rate exposure (leaf dip with maximum rate mixed as if spraying 100 gpa). Leaves were sandwiched in a petri dish with 10 small larvae on the underside of the leaves and sealed with parafilm. Mortality was rated at 72 hours after placing the larvae on the leaves.
Best results were obtained with Dibrom, Proclaim and Radiant. Additionally, while Avaunt and Torac did not yield many dead insects, the insects did not look well and feeding suppression was similar to the Proclaim and Radiant treatments. Dibrom did provide good mortality, but damage was not obviously suppressed.