EVALUATION OF BACILLUS THURINGIENSIS INSECTICIDES AGAINST DBM, 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) 956-7063
 
K. Dart
Mycogen Corp.
1612 Horse Lake Rd.
Wenatchee, WA 98801
 
R. S. Shimabuku
Cooperative Extension Service
310 Kaahumanu Ave., Bldg. 214
Kahului, HI 96732

 

HEAD CABBAGE: Brassica oleracea L. 'Supreme Vantage'

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

 

The insecticide was evaluated at the Kula Research Station, Maui Agricultural Park, from October to December. 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 of hollow cone nozzles (TX-26, Spraying Systems) 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. Sprays were applied at 100 psi at a rate of 150 GPA. Applications were made at 3- to 4-day intervals according to DBM larval and egg densities observed during the prior bi-weekly insect survey. Applications were made on Oct 6, 10, 13, 17, 20, 27, 31; Nov 3, 7, 10, 14, 17, 24; Dec 1, and 5 for a total of 15 applications. Post treatment evaluations were conducted on a bi-weekly basis. Ten plants were randomly selected from each treatment plot and carefully examined for immatures.

Significant differences in the number of larvae were observed between the untreated check and all treatments beginning from the second post treatment survey date. This trend continued throughout the trial. DBM larval densities were rather low during the field evaluation. Nonetheless, there were visible differences in the amount of feeding injury in the different treatment plots. Mattch treated plots exhibited significantly less insect feeding damage and resulted in a higher percentage of marketable cabbage. The higher rate of Mattch provided superior protection against DBM feeding damage. MVP provided moderate levels of marketable yield. Poor marketable yields were obtained in the Agree and Xentari treated plots.

 

                                                                                      Mean number of DBM/10 plants  
                                                   

Pre-treatment
___(5 Oct)___

   

2 DAT 4
__(19 Oct)__

     

2 DAT 7
__(2 Nov)__

     

2 DAT 11
__(16 Nov)__

Treatment     Rate/Acre       Larvae   Pupae     Larvae   Pupae     Larvae   Pupae     Larvae   Pupae
Mattch     2.0 qt.       0.0   0.0     0.23b   0.0     0.48c   0.03a     0.33b   0.05b
Mattch     1.0 qt.       0.0   0.0     0.28b   0.0     0.78bc   0.30a     0.15b   0.18b
Xentari     0.5 lb.       0.0   0.0     0.28b   0.0     0.65bc   0.18a     0.20b   0.03b
MVP     2.0 qt.       0.0   0.0     0.60b   0.0     0.95bc   0.05a     0.30b   0.20b
Agree     1.0 lb.       0.0   0.0     0.28b   0.0     1.13b   0.15a     0.38b   0.25b
Untreated check     ---       0.0   0.0     1.00a   0.0     2.45a   0.25a     1.28a   0.95a

Means in each column followed by a different letter are significantly different (Tukey's studentized range test P<0.001). Data was transformed by square root (X+0.5) prior to analysis. Untransformed means are presented.

 

 

                                                            Mean number of DBM/10 plants  
                                                     

6 DAT 13
___(30 Nov)___

     

2 DAT 15
___(7 Dec)___

Treatment     Rate/Acre         Larvae   Pupae         Larvae   Pupae     % Marketable
heads at harvest
Mattch     2.0 qt.         0.10c   0.00b         0.25b   0.00c     92.0a
Mattch     1.0 qt.         0.25c   0.03b         0.15b   0.03bc     80.0a
Xentari     0.5 lb..         0.33c   0.05b         1.15b   0.25bc     50.0bc
MVP     2.0 qt.         0.73bc   0.03b         0.68b   0.28bc     70.0abc
Agree     1.0 lb.         1.43b   0.18b         1.23b   0.45ab     40.0c
Untreated check     ---         5.58a   1.13a         5.93a   0.98a     2.5d

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) (inzect counts) and arcsine (percent marketable) prior to analysis. Untransformed means are presented.

 

 

Trade Composition\Common name     Formulation         name     Source
Agree     ME         B. thuringiensis     Ciba-Geigy
                       
MVP     ME         B. thuringiensis     Mycogen
                       
Mattch     ME         B. thuringiensis     Mycogen
                       
Xentari     ME         B. thuringiensis     Abbott