by Louis Nottingham and Betsy Beers, June 1, 2017
A laboratory bioassay was conducted to test the toxicity of various insecticides/miticides to pear psylla nymphs (Fig. 1). Nexter (pyridaben), Vendex (fenbutanin-oxide), Nealta (cyflumetofen), FujiMite (fenpyroximate), and Bexar (tolfenpyrad), were chosen due to their similar modes of action: disrupting mitochondrial function. Bexar (tolfenpyrad) is still undergoing registration for pears. This assay is a part of a series involving Bexar which will help determine its most apt placement in future pear IPM programs, if approved. Actara (thiamethoxam) was included for comparison to a common product used in late spring and early summer.
Leaves with heavy pear psylla nymph infestations were gathered from potted plants in the greenhouse at WSU-TFREC, and sprayed in the lab with the products listed in Table 1. There were 5 replicated of each treatment. Percent mortality of 4th and 5th instars, combined, was analyzed.
Bexar was the most toxic product to pear psylla nymphs. Of the registered products, Actara 25 WG and Nexter 75 WP were the most toxic (killing ca 60% of nymphs), while FujiMite SC and Vendex 50 WP were marginally toxic (killing 25 and 10% of nymphs, respectively), and Nealta showed no toxicity (killed 0 nymphs). No phytotoxicity by any treatment was observed.