Efficacy of RH-2485, a new non-steroidal ecdysone agonist, against the cotton boll worm; Helicoverpa armigera (Lepidoptera: noctuidae) in the laboratory and field
2003
Zhao, Xiao-Fan | Li, Zhao-Min | Wang, Jin-Xing | Wang, Jia-Bao | Wang, Shengli | Blankespoor, Harvey D.
Efficacy of the non-steroidal ecdysone agonist, RH-2485, was determined on Helicoverpa armigera larvae under laboratory and field conditions. RH-2485 sprays (25-150 μg/ml) caused premature, incomplete molting in 28-94% of the treated 2nd instar larvae within 24 h. Topical application of RH-2485 to 6th instar larvae (30-200 ng/larva), caused premature molting in 3-83% within 24 h, and 66-96% in 15 days, post-treatment. The eD10, eD50 and eD90 for 24 h were determined as 37, 100 and 250 ng/larva, and for 15 days as 0.65, 7.50 and 100 ng/larva, respectively, according to the corrected trend line. Ingestion of 0.1-1000 ng RH-2485 by 6th instars caused premature molting in 10-65% of the larvae in 24 h and 8-64% in 15 days. Field trials indicated that RH-2485 sprays at 50-150 g (AI)/ha decreased the larval population of boll worms by 68-73%. Correspondingly, the injury by the pest to bolls and apical buds of the cotton plants was decreased by 54-65% and 57-77%, respectively.
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