Effects of aerial spray volume, coverage, and sabadilla on Scirtothrips perseae (Thysanoptera : Thripidae)

Helicopter applications using sabadilla (27-57 g [AI]/ha and 11.1-23.7 kg/h a sugar bait) in different volumes of water were made on avocado against Sc irtothrips perseae Nakahara in Ventura County, CA. On small (2.8 m tall) tr ees, volumes of 374 and 795 liter/ha resulted in 3-18% and 19-43% spray cov erage, respectively, on water-sensitive papers. On large (6.9-8.4-m tall) t rees, these volumes resulted in only 1-3% and 6-11% coverage, respectively. On small trees, sabadilla in 374 liter/ha significantly reduced numbers of larvae 3 and 6 d after treatment (DAT). In contrast, on large trees, 374 l iter/ha did not reduce larval numbers and was less effective than 561-1,964 liter/ha from 3-11 DAT. However, volumes of 1,543 and 1,964 liter/ha did n ot increase efficacy compared with 1,169 liter/ha. The results indicate tha t large trees require sabadilla in higher spray volumes for control of S. p erseae, making applications on large trees more costly. The extra costs may not result in larval control beyond 11 d, making it especially critical to properly time applications on large trees.