Evaluation of chemical controls and entomopathogenic nematodes for control of Phyllophaga white grubs in a Fraser fir production field.

The results of 2 yr of field trials evaluating various chemical and biological controls of Phyllophaga anxia (LeConte) white grubs in a Fraser fir [Abies fraseri (Pursh) Poir] Christmas tree production field are reported here. Chemical insecticides evaluated included bifenthrin, chlorantraniliprole, thiamethoxam, and time-released imidacloprid tablets (Coretect, Bayer CropScience, Research Triangle Park, NC). Entomopathogenic nematodes evaluated included Heterorhabditis bacteriophora (Poinar) and Steinernema carpocapsae (Weiser). Overall, the chemical controls provided the best root protection and grub control. Targeted treatments of an insecticide in the root zone may provide adequate tree protection and can be a way to reduce overall insecticide input compared with banded sprays. The nematode H. bacteriophora provided limited root protection and grub control, whereas S. carpocapsae did not provide effective control. Differences in efficacy and persistence of the two entomopathogenic nematode species can be attributed to the biology and environmental preferences of these organisms.