THRIPS CONTROL ON PEPPER, 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

 

J. J. McHugh Jr.

Waikele Farms, Inc.

P. O. Box 27

Kunia, HI 96759

PEPPER (BELL): Capsicum annuum L. ‘Jupiter’

Melon thrips (MT); Thrips palmi Karny

Western flower thrips (WFT); Frankliniella occidentalis (Pergande)

The study was conducted on Waikele Farms, Inc. located at Kunia, HI. The field was set up in a randomized complete block design with seven treatments and four replications (blocks). Each treatment plot consisted of two rows of plants 30 ft. long. Each plot was separated by a 5.5 ft. spacing. Blocks were separated by 10 ft. spacing. Plants were planted at 18 in. spacing. Total field size was 0.17 acres. Treatments were applied at 40 psi with an output of 60 GPA using a compressed CO₂ sprayer. One TJ60 8006 spray nozzle was used per row. Treatments were applied at 7-day intervals on 13, 20, 27 Sept, and 10 Oct.

Surveys were made on a bi-weekly basis for a total of two post treatment surveys. At each survey, two stages of the plant were sampled: flowers and young fruit approximately 1-2" in diameter. Ten randomly selected flowers and fruits were sampled from each treatment plot and separately placed in plastic zip lock bags. Each sample was washed separately with a detergent solution and the thrips were collected on a 150 mesh sieve. Thrips were recorded by developmental stages; first instar larvae (LI), second instar larvae (LII), and adults' (A). At harvest, mature fruits were examined and ranked on a scale of 0-5. A rating of "0" indicated no damage on the fruit. The maximum rank of "5"was assigned to a fruit showing 50% or more of its’ surface scarred with thrips damage. Each rated fruit was also rated as ‘marketable’ or ‘unmarketable’ based on established grading criteria.

Alert at 0.3 lb. ai/A was most effective in reducing the number of larvae in the flowers. The high numbers of WFT adults in the flowers was expected since there was a high infestation of these pollen feeders in the surrounding fields. There was also a high infestation of MT in the surrounding fields therefore, the high number of WFT and MT adults in the flower samples was probably due to migration into the field than non-effective treatments.

In fruit samples, Alert at 0.3 lb. ai/A was very effective in controlling thrips. Alert at 0.2 lb. ai/A and AgriMek at 16.0 oz./A were also somewhat effective in reducing thrips numbers. However, the economic impact of the treatments is shown by the fruit marketability results. Significantly more fruits harvested from the Alert at 0.3 lb. ai/A treated plots were marketable. Fruit damage rating value of the Alert at 0.3 lb. ai/A treated plots was significantly lower than the other treatments. Thrips damage is an important cause of reduced fruit marketability. The remaining Alert and AgriMek treatments gave moderate levels of marketable fruit. The grower standard, Vydate L, was no longer effective in controlling MT.

Phytotoxic injury did occur on plants in the Alert treated plots. Immature leaves became spotted after treatment. Tiny brown spots were distributed throughout the leaf and were more readily seen on the lower leaf surface. Treated mature leaves did not develop symptoms. The phytotoxic reaction occurred uniformly at all Alert treatment rates—0.1, 0.2, and 0.3 lb. ai/A. Treatment with Alert did not affect fruit appearance or yield.

Means in the same column followed by a different letter are significantly different (P<0.0001, 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<0.0001, 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<0.0001, SAS for Windows version 6.11). Data was transformed by square root (Y+0.5) prior to analysis. Untransformed means are presented.