Confirmation by fluorescent tracer of coverage of onion leaves for control of onion thrips using selected nozzles, surfactants and spray volumes

Track sprayer and field sprayer trials were completed to assess the effect of different nozzles, surfactants and carrier volumes on product delivery to the inner leaves of onion plants using a fluorescent tracer. Track sprayer trials revealed more tracer on the inner leaves of onions using either the TeeJet® XR8004 flat fan or D4/DC25 disc-core hollow cone nozzles. In three of four experiments, more tracer was detected on onions sprayed alone or combined with Sylgard® 309 at 200 L/ha than plants sprayed with tracer+Companion®. When the carrier volume was increased to 400 L/ha, more tracer was detected on onions sprayed alone or combined with Companion. In field trials, the XR8004 delivered more tracer than the D4/DC25 (F=32.8; P<0.00; d.f.=1,77). The best coverage was observed on plants sprayed with the flat fan combined with Agral® 90, sprayed at either 400 L/ha (29% coverage) or 600 L/ha (23% coverage).