Postharvest Control of Thrips with Pyrethroids on Dendrobium, 1993

Abstract

Abstract Postharvest insecticidal treatments were evaluated from Jun through Jul 1993 at the University of Hawaii, Waiakea Experiment Station in Hilo, HI. Flowers used in this study were randomly harvested from a commercial dendrobium farm in Kailua-Kona, HI. Dendrobium plants were well established growing in 0.5 inch crushed basalt rock under 30% polypropylene shade using standard cultural practices. Treatments consisted of 4 replicates with 5 inflorescences per replicate. In study 1. inflorescences were dipped floral end first into 5 gal buckets containing the insecticide solutions (25.7°C). Inflorescences were submerged for 3 minutes, and gently agitated 10 times at immersion, at 1.5 minutes, and again before removal for a total of 30 times. Control flowers were dipped in water following the same procedure as described. After dipping, inflorescences were held in buckets and allowed to air dry. In study 2, the double dip o1 Mavrik consisted of immersing inflorescences (27.3°C) as described above, followed by a 2 h waiting period and a second 3 min insecticide immersion. A 2.5 m? chamber was used to fumigate inflorescence with floragas (2 h exposure at 31.5°C). Control flowers for the floragas were held in an identical untreated chamber. Twenty-four hours after treatment, blossoms were removed from the inflorescence, counted, and placed in Berlese funnels heated with a 60 watt incandescent light bulb. Thrips were collected in a 8:2:1:1 solution of ethanol, distilled H20, acetic acid and glycerin and the number of nymphs and adults counted. Thrips counts were adjusted to the number of thrips per blossom. Data were subjected to ANOVA.