FIELD EVALUATION OF BIO-RATIONAL INSECTICIDES AND COMBINATIONS FOR CONTROLLING DBM, 1993:

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

 

CHINESE CABBAGE: Brassica campestris L. 'Takii WR55'

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 October to December. The field was set up in a randomized block design with five treatments and four replications (blocks). Each treatment plot measured 70 ft. by 7.5 ft. It consisted of six rows of cabbage in 3 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 3 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 applied using a tractor mounted with a PTO driven spray pump equipped with a 30 ft. boom. The boom was set with three banks of twin jet (TJ 8006, 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 150 GPA (40 psi) for the first three applications and increased to 200 GPA (60 psi) for the last three.

Post treatment surveys were conducted on a weekly basis six days after 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 cocoons.

Treatment differences were detected after the fifth spray. The best treatment tested was the Align-MVP combination. Treated plots exhibited less feeding damage, the lowest number of caterpillars, and the highest percentage of marketable produce. Parasitoids and predators of the cabbage insect pests were not observed in the field until after the fourth spray application. However, for the remaining period of the trial, beneficial insects (DBMP, APA, APR, GLW) occurred throughout the field. The treatments did not appear to affect their distribution.

 

                                                Mean number of DBM immatures after 0, 1, 2, 3 or 4 spray applications (date of survey)
                                                  0 & 1 (11 & 16 Nov)     ___2 (23 Nov)___     ___3 (30 Nov)___       ____4 (7 Dec)___
Treatment   Rate/Acre   Early
Larvae
Late
Larvae
Pupae   Early
Larvae
Late
Larvae
Pupae   Early
Larvae
Late
Larvae
Pupae   Early
Larvae
Late
Larvae
Pupae
Align   21 oz   0.00 0.00 0.00   0.18a 0.00 0.00a   0.33a 0.05a 0.05a   0.67ab 0.45b 0.00a
MVP   3 qt   0.00 0.00 0.00   0.13a 0.00 0.03a   0.33a 0.05a 0.08a   0.28b 0.25b 0.00a
Align + MVP   21 oz + 3 qt   0.00 0.00 0.00   0.03a 0.00 0.00a   0.10a 0.03a 0.00a   0.18b 0.08b 0.00a
Align + Pyrenone   21 oz + 2 oz   0.00 0.00 0.00   0.03a 0.00 0.00a   0.08a 0.10a 0.00a   0.28b 0.10b 0.00a
Untreated check   ---   0.00 0.00 0.00   0.10a 0.00 0.00a   0.13a 0.10a 0.00a   1.33a 1.70a 0.03a

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.

 

                                                Mean number of DBM immatures after 5, 6, or 7spray applications (date of survey)
                                                        ___5 (14 Dec)___           ___6 (21 Dec)___         ___7 (27 Dec)___
Treatment     Rate/Acre     Early
Larvae
Late
Larvae
Pupae     Early
Larvae
Late
Larvae
Pupae     Early
Larvae
Late
Larvae
Pupae     % Marketable
at Harvest
Align     21 oz     1.03a 1.98a 0.00a     0.65a 3.05b 0.13b     2.10a 2.13b 0.28b     12.5b
MVP     3 qt     0.58ab 0.55bc 0.03a     0.20a 0.75cd 0.05b     0.90bc 1.40b 0.15b     35.0ab
Align + MVP     21 oz + 3 qt     0.15b 0.05c 0.03a     0.15a 0.45d 0.00b     0.28c 0.38c 0.08b     62.5a
Align + Pyrenone     21 oz + 2 oz     1.15a 1.08b 0.00a     0.53a 1.43c 0.03b     1.18b 2.33b 0.28b     17.5ab
Untreated check     ---     1.20a 2.10a 0.13a     0.60a 5.48a 0.48a     0.95b 5.68a 1.03a     0.0b

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) (insect counts) and arcsine (percent marketability) before analysis. Untransformed means are presented.

 

Trade Composition\Common name     Formulation         name     Source
Align     EC         azadiractin     AgriDyne
MVP     ME         B. thuringiensis     Mycogen
Pyrenone     EC         pyrethrins     Fairfield