Resource Information

Control of Orchid Weevils on Dendrobium, Hawaii, 1990  

By: T. Y. Hata and A. H. Hara

Beaumont Agri. Res. Center, University of Hawaii-Manoa, 461 W. Lanikaula St., Hilo, Hawaii 96720, Phone (808) 935-2885

HOST: Dendrobium Orchid: Dendrobium Jaquelyn Thomas
TARGETED PEST: Orchid weevil: Orchidophilus aterrimus

Bioassay tests were conducted on 28 Jun 1990 on dendrobium orchids growing in 1/2" crushed basalt rock. Each treatment consisted of four replicates with five plants per replicate. Sprays were applied until runoff occurred using a compressed CO2 sprayer with a No. 8004 Teejet nozzle at 40 psi. One day after treatment, 20 leaves per treatment, five leaves per rep, were excised and placed into a 12.0 x 10.5 cm unwaxed paper container. Twenty five orchid weevils collected on bamboo orchids arundina graminifolia Don was added to each container and covered with organdy. Mortality was assessed 1 and 2 days after treatment.

All treatments were effective against orchid weevils one day after exposure. Six hours after exposure, orchid weevils in Tame 2.4EC containers were observed crawling on the top of the container. This behavior was not observed in any of the other treatments. In addition, Tame 2.4EC treated leaves had less feeding injury as compared to other treatments. Apparently, Tame 2.4EC had a repelling action on the orchid weevil.

% mortality of orchid weevils

Treatment lb (AI)/100 gal 1 DAT 2 DAT Injury1
Tame 2.4EC 0.2 85.0a 97.1a 15.0
Orthene 75SP 0.5 83.7a 99.2a 75.0
Tame + Orthene 0.2/0.5 93.3a 99.7a 25.0
Control - 0.0b 0.0b 100.0

Percentages transformed to arcsine prior to ANOVA. Means followed by the same letter in a column are not significantly different by Waller-Duncan Bayesian K-ratio, K=100.
1Percent feeding injury of 20 leaves.

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