Resistance of avocado thrips (Thysanoptera: Thripidae) to sabadilla, a botanically derived bait

Bioassays were conducted on four avocado thrips (Scirtothrips perseae Nakahara) populations in southern California that had had limited past exposure to the botanical pesticide sabadilla, with the objective of establishing baseline susceptibility levels for the purpose of resistance monitoring. Reports of avocado thrips resistance in a grove that had received six sabadilla sprays over 2 years were confirmed when a bioassay indicated resistance ratios of 7.6 and 18.8 at the LC50 and LC90, respectively. Owing to the availability of other unrelated pesticides, sabadilla sprays were discontinued at this site, and, after 5.5 years, resistance ratios had dropped to near baseline levels. Avocado thrips baseline susceptibility to cyfluthrin was also obtained from one grove for future resistance monitoring studies. Resistance management principles are discussed in relation to the limited future options available for avocado thrips control.