Phytotoxicity of GF-120 (R) NF Naturalyte (R) fruit fly bait carrier on sweet cherry (Prunus avium L.) foliage

BACKGROUND: Six sweet cherry (Prunus avium L.) cultivars were tested with GF-120 (R) with spinosad (0.2 g L-1 spinosad bait)or without it (blank bait) to understand leaf phytotoxicity observed in the field. RESULTS: Spinosad bait and blank bait did not differ significantly with respect to damage observed. Leaf damage was found almost exclusively at the abaxial (lower) surfaces with the doses (0, 17, 20, 25 or 40%) and cultivars tested. The effects of the blank bait on abaxial surfaces increased from 24 to 168 h, and with dose, in terms of the proportion of droplets (0.00, 0.42, 0.52, 0.75 or 0.94) and area (0.0, 18.7, 23.5, 40.5 or 91.6 mm) burned. In addition, chlorophyll was reduced with increasing dose on abaxial surfaces (SPAD = 44.6, 36.1, 34.1, 31.0, 21.5), but not on adaxial (upper) surfaces (SPAD = 44.6, 44.2, 44.0, 44.8, 44.4). The chlorophyll level in undamaged leaves (adaxial surfaces) differed by cultivar. Cherry leaves were less damaged by a 20% bait application in June (0.26) than in July (0.46) and August (0.50). Incidental insect leaf feeding at bait locations occurred at a low rate and was highest on abaxial bait surfaces. CONCLUSIONS: Applying GF-120 to the adaxial leaf surface, or at doses of <= 20%, will minimize leaf phytotoxicity. (C) 2008 Crown in the Right of Canada and Society of Chemical Industry. Published by John Wiley & Sons, Ltd