ONION THRIPS MANAGEMENT ON DRY ONION, 1996:

R. F. L. Mau and L. R. Gusukuma-Minuto

University of Hawaii

Dept. of Entomology

3050 Maile Way, Rm. 310

Honolulu, HI 96822

Phone: (808) 956-7063

 

R. S. Shimabuku

Cooperative Extension Service

310 Kaahumanu Ave., Bldg 214

Kahului, HI 96732

ONION: Allium cepa L. ‘Granex 33’

Onion thrips (OT); Thrips tabaci Lindeman

The insecticides were evaluated at the Kula Research Station, Maui Agricultural Park. The field was set up in a randomized complete block design with nine treatments and four replications (blocks). Each treatment plot consisted of four rows of plants planted at 8 in. between plant spacing. Each row consisted of 45 plants. Seedlings were transplanted into the field on 26 Sept. Treatments were applied using a compressed carbon dioxide sprayer at 60 psi and 100 GPA. Silwet L-77 surfactant was used at a rate of 0.0625% v/v. One twin jet nozzle (TJ-6502) was used per row. Treatments were applied at 7-day intervals. The first treatment was made 5 weeks after transplanting. A total of five applications were made (2, 12, 19, 26 Nov, and 3 Dec).

A pre-treatment survey was made on 28 Oct. Subsequent surveys were made on a bi-weekly schedule using the following procedures. Ten plants were randomly selected. The roots and most of the leaves were removed. The remaining portions of the plant (stem, leaf axils, and 2 in. of leaves) were each bagged separately. In the laboratory, each sample was washed in a detergent solution. Thrips were collected in a 150-mesh sieve, transferred into plastic 20 ml vials, preserved with 70% ethyl alcohol, and counted at a later date. Thrips were recorded by developmental stages first instar larvae (LI), second instar larvae (LII), and adults’ (A).

Warrior II 1 EC and both rates of Fipronil 80 WDG provided excellent control throughout the test. Malathion and Alert provided moderate levels of control and could be valuable in an integrated resistance management program for onion thrips. Diazinon and Lannate were ineffective, as overall counts were not significantly different from the untreated check.

Means in the same column followed by a different letter are significantly different (P<0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.

Means in the same column followed by a different letter are significantly different (P<0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.

Means in the same column followed by a different letter are significantly different (P<0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.
^aLannate and Diazinon, 13 DAT 3. Maximum amount active ingredient allowed on crop reached at third application.

Means in the same column followed by a different letter are significantly different (P<0.001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.
^aLannate and Diazinon, 27 DAT 3. Maximum amount active ingredient allowed on crop reached at third application.

PART II (Continued) R. F. L. Mau

(808) 956-7063