Chlorpyrifos immersion to eliminate third instars of Japanese beetle (Coleoptera: Scarabaeidae) in balled and burlapped trees and subsequent treatment effects on red maple.

This study examined chlorpyrifos immersion of balled and burlapped (B&B) nursery trees for elimination of third instars of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), and for phytotoxicity on red maple, Acer rubrum L. Trees were harvested as 45- and 60-cm-diameter B&B and immersed in chlorpyrifos at U.S. Domestic Japanese Beetle Harmonization Plan rate (0.24 kg active ingredient [AI/100 liters) or lower rates of 0.015, 0.03, 0.06, and 0.12 kg (AI)/100 liters. The 0.03, 0.06, and 0.24 kg (AI) rates provided 100% control of Japanese beetle grubs in both 45- and 60-cm B&B. The 0.015 and 0.12 kg (AI) chlorpyrifos rates were 100% effective in three tests. However, in another test, 0.015 and 0.12 kg (AI) chlorpyrifos treatments had four (93% control) and one (98% control) grubs recovered, respectively. Root ball soils consisted of loam, silt loam, or clay loam texture classifications. Trunk diameter and internode growth of red maple harvested as 45-cm B&B decreased linearly with increasing chlorpyrifos dip rate during the first year, but effects were unapparent in the second year. Chlorpyrifos rates had no measurable impact on growth of red maples harvested as 60-cm B&B. No visual phytotoxicity symptoms were detected for chlorpyrifos rate or root ball size treatments. In conclusion, results support lowering the U.S. Domestic Japanese Beetle Harmonization Plan chlorpyrifos dip rate for category 2 states to at least 0.03 kg (AI) for B&B diameters < or =60 cm. Chlorpyrifos rates < 0.24 kg (AI) will lower cost, reduce worker exposure, and lessen potential environmental contamination.