Effect of Seasons and Insecticides on Orchid Thrips Injury of Anthuriums in Hawaii

Abstract

Dimethoate 4EC, fenpropathrin 2.4EC, fluvalinate 2F, oxamyl 2L, chlor-pyrifos 4EC, malathion 5EC, diazinon 4EC, and oxydemeton-methyl 2EC insecticides significantly reduced injury of anthurium ( Anthurium andraeanum Lind. & Andre cv. Ozaki) flowers by the orchid thrips, Chaetanaphothrips orchidii (Moulton). Injury was characterized by white streaks and/or scarrings occurring primarily on the abaxial surface only or on both adaxial and abaxial surfaces of the spathe. Injury on the adaxial surface occurred only at 0.15% of all thrips-injured spathes observed during the study period. Thrips injury on anthurium flowers in control plots during Aug. 1984 to Sept. 1985 decreased to 3% during Feb. and Mar. 1985, and increased to 90% during Sept. 1985. Chemical names used: O,O -dimethyl S-[2-(methylamino)-2-oxoeth-yl]phosphorodithoate (dimethoate); (Rs)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethyl cyclopropanecarboxylate (fenpropathrin); N- [2-chloro-4-(trifluoromethyl)phenyl]-DL-valine (±)-cyano(3-phenoxyphenyl)methyl ester (fluvalinate); S -{2-(ethyl suffinyl)ethyl} O,O -dimethylphosphorothioate (oxydemeton-methyl); methyl 2-dimethylamino)- N -[[(methylamino)carbonyl]oxy]-2-oxoethanimidothioate (oxamyl); O,O -diethyl 0-[6-methyl-α-(1-methylethyl)-4-pyrimidinyl] phosphorothioate (diazinon); O,O -diethyl O -(3,5,6-trichloro-2-pyridyl)-phosphorothioate (chlorpyrifos); and diethyl [(dimethoxyphos-phinothiovl)thio] butanedioate (malathion).