FIELD EVALUATION OF FIPRONIL FOR DBM CONTROL, 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

HEAD CABBAGE: Brassica oleracea L. ‘Tastie’

Diamondback moth (DBM); Plutella xylostella (L.)

The insecticides were evaluated at the Kula Research Station, Maui Agricultural Park, from June to August. The field was set up in a randomized block design with six treatments and four replications (blocks). Each treatment plot measured 70 ft. by 7.5 ft. It consisted of four rows of cabbage on 36 in. centers and 18 in. in-row spacing. Adjacent rows were offset to allow equidistant plant spacing between rows. Treatments were applied using a tractor mounted with a PTO driven spray pump equipped with a 30 ft. boom. The boom was set with three banks nozzles that coincided with row spacing. Each group of nozzles had its own line from the main tank, therefore, spray output to specific treatment plots could be easily controlled by the sprayer operator. Treatments were applied at 45 psi with an output of 125 GPA. One TJ 60-8006 nozzle was used per row. The first treatment was made on 2 Jul, 1 day after transplanting. Subsequent applications were made on the following dates: 8, 16, 23, 30 Jul, 6, 13 Aug.

A pre-treatment census for larvae was made the day before the first field spray application. Subsequent evaluations were conducted on a bi-weekly schedule. Ten plants were randomly selected from each treatment plot and carefully examined for larvae.

DBM was the predominant lepidopteran pest throughout the season. Population levels developed quite rapidly. There were no larvae present at the pretreatment survey but DBM larvae and pupae were found in nearly all treatments two weeks later. Fipronil treatments provided excellent control. Thiodan and Pounce were ineffective. Larval numbers continued to increase in all of the treatments, however, fipronil treatments provided significantly better control than the untreated check. More of the produce harvested from the fipronil treated plots were marketable and percentage would have probably been better if it were not inundated with DBM produced in the Thiodan, Pounce, and untreated check plots. There were mixed results when we compared the fipronil formulation and application rate treatments. We detected no statistical difference when DBM larvae were used as a measure; however, the 80 WDG treatment provided significantly greater marketable yield than in the comparable SC treatment.

^{Means in each column followed by a different letter are significantly different (Tukey's studentized range test P<0.01 SAS for Windows, version 6.08). Data was transformed by square root (X+0.5) prior to analysis. Untransformed means are presented.}

^{Means in each column followed by a different letter are significantly different (Tukey's studentized range test P<0.01 SAS for Windows, version 6.08). Data was transformed by square root (X+0.5) prior to analysis. Untransformed means are presented.}

^{Means in each column followed by a different letter are significantly different (Tukey's studentized range test P<0.01 SAS for Windows, version 6.08). Percent marketable datum was transformed by arcsin prior to analysis. Untransformed means are presented.}