Phytotoxicity of Insecticides on Dendrobium Orchids, Hi, 1994

Abstract

Abstract Phytotoxicity trials were conducted from 20 Sep through 17 Dec 1993 (trial 1) at a commercial dendrobium farm in Hilo, HI and 26 Jul through 26 Sep 1994 (trial 2) at the University of Hawaii Waiakea Experiment Station in Hilo. Tests were conducted on mature plants (approximately 3.5 ft in height) growing in 2 gal. bags under 6 mil. clear FVG 3HLFI polyethylene film covering. Treatments consisted of 36 plants of each cultivar. In trial 1, six weekly insecticide applications were made to the flowers and foliage beginning 20 Sep ending 25 Oct. In trial 2, three weekly applications were made beginning 26 Jul ending 10 Aug. Insecticides were applied using a Solo backpack sprayer (Solo Inc., Newport News, VA) equipped with an 8004 Teejet nozzle at 40 psi (377 GPA). The spreader-sticker Ad-here was added to all treatments including the control at a rate of 5 fl. oz./lOO gal. Phytotoxicity was evaluated weekly and continued for five weeks after the last insecticide application. In addition, one week after the last insecticide application 5 inflorescences were harvested randomly from each plot and evaluated for vase life. Data were taken on the number of days inflorescences remained intact (start of blossom wilt or senescence) and end of vase life (≥50% of blossoms affected). Treatment means were compared by t test and the standard deviation calculated.