FIELD EVALUATION OF A NEEM AND BT PRODUCT FOR DBM CONTROL, 1994:

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) 956-6737

FAX: (808) 956-2428

 

W. S. Ruggero

AgriDyne Technologies, Inc.

2401 So. Foothill Drive

Salt Lake City, UT 84109

 

R. S. Shimabuku

Cooperative Extension Service

310 Kaahumanu Ave.

Kahului, HI 96732

HEAD CABBAGE: Brassica oleracea L. 'Tastie'

Diamondback moth (DBM); Plutella xylostella (Linnaeus)

DBM parasite (DBMP); Cotesia plutella (Kurdijumov)

Aphid parasite (APA); Lysiphlebus testaceipes (Cresson)

Aphid predator (APR); Allograpta obliqua (Say)

Green lacewing (GLW); Chrysopa sp.

Insecticides were evaluated at the substation of the Kula Research Station, Maui Agricultural Park from June through 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 4.5 ft. It consisted of four rows of cabbage in 2 beds on 36 inch centers and 18 inch in-row spacing. Adjacent rows were offset to allow equidistant plant spacing between rows. Treatment plots in each block were separated by a 4.5 ft. border. Blocks were separated by a 10 ft. border that allowed sprayer access. Total field size was 150 ft. by 109 ft.

Treatments were delivered using a tractor mounted with a PTO driven spray pump equipped with a 30 ft. boom. The boom was set with three banks of hollow cone (TX-26, Spraying Systems) nozzles that coincided with row spacing. Each group of nozzles had its own line from the main tank, therefore, spray output to specific treatment plot could be easily controlled. Sprays were applied at 100 psi at a rate of 150 gallons per acre on a weekly basis from one day after transplanting into the field to one week before harvest.

Post treatment surveys were conducted on a bi-weekly basis six days after the last treatment. Ten plants were randomly selected from the two center rows and removed for examination of insects. DBM immatures were counted in separate age groups: early larvae, late larvae, and pupae. Early larvae were those in the first two larval instars. They were identified by their small size and the occurrence of black colored head capsules. Late larvae were those in the last two larval instars. They were identified by their larger size and the occurrence of green or brown head capsules. Pupae were easily identified by their net like cocoon.

MVP and Align + MVP treatments significantly reduced the number of late larvae compared to the untreated check. Although less insect feeding damage was observed with these treatments, none of the cabbage was marketable at maturity in these or the other treatments. The DBM population pressure remained high throughout the trial. The 7-day spray interval in this situation was determine to long an interval to effectively control DBM. Spray intervals of 3-4 days might have provided better control. Beneficial insects (DBMP, APA, APR, GLW) were observed throughout the field. There were no apparent differences in the distribution of the beneficial insects when untreated and treated plots were compared.

Means in each column followed by a different letter are significantly different (Tukey's studentized range test P<0.001 SAS Institute,

version 6.04). 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<0.001 SAS Institute,

version 6.04). Data was transformed by square root (X+0.5) prior to analysis. Untransformed means are presented.