EVALUATION OF EMAMECTIN BENZOATE (MK-244) AND OTHER INSECTICIDES AGAINST DBM, 1995:
 
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
 
D. Dunbar
Merck Research Laboratories
7555 N. Del Mar Ave.
Fresno, CA 93711
 
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 May to June. 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. Treatment plots in each block were separated by a 4.5 ft. row spacing. Blocks were separated by a 10 ft. wide space 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 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. The first treatment was applied using hollow cone TX-18 (Spraying Systems) nozzles at 100 psi. Due to excessive drift caused by the small droplet size, the nozzles were changed to TX-26 for the second to fifth treatment application. The pressure was reduced to 45 psi to give an output of 100 gallons per acre. For the last two treatments, the twin jet TJ-60 8006 nozzles at 25 psi were used for an output of 100 gallons per acre. The first treatment was made on 16 May, 12 days after transplanting. Subsequent applications were made on the following dates: May 23 and 30, June 6, 13, 20, and 27.

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 immatures were counted in separate age groups: early larvae, late larvae, and pupae. Early larvae instars were larvae in the first two instars. These larvae were identified by the black colored head capsules. The late larvae were those in the last two larval instars. They were differentiated using body size and the green or brown head capsules. Pupae were easily identified by their net like cocoons.

Significantly fewer late larvae were found in the MK-244 and B. t. treated plots at survey 2. However, only MK-244 controlled larval populations to harvest. Plants treated with MK-244 were relatively free of fresh feeding injury whereas the Pounce and untreated check plants were extensively damaged. Plants treated with B. t. products exhibited moderated levels of damage. At harvest, more marketable heads were harvested from the MK-244 treated plants compared to the other treatments.

 

                                                                                        Mean number of DBM/10 plants
                                                      _Survey 1 (15 May) Pre-treatment_         __Survey 2 (30 May) 7 DAT 2__
Treatment     Rate/Acre     Early
Larvae
  Late
Larvae
  Pupae         Early
Larvae
  Late
Larvae
  Pupae
MK-244 0.16 EC     6.0 oz.     1.13+0.23a   0.73+0.15a   0.0         0.75+0.18b   1.25+0.23b   0.15+0.07a
Xentari     1.0 lb.     0.70+0.15a   0.40+0.14ab   0.0         1.35+0.27b   2.43+0.27b   0.13+0.06a
Dipel 2X     1.0 lb.     0.98+0.20a   0.33+0.10ab   0.0         2.60+0.34a   2.20+0.35b   0.05+0.03a
Mattch     1.0 qt.     1.33+0.29a   0.40+0.09ab   0.0         1.05+0.20b   2.30+0.36b   0.08+0.04a
Pounce 3.2 EC     4.0 oz.     0.60+0.15a   0.33+0.14ab   0.0         3.58+0.60a   6.83+0.80a   0.08+0.04a
Untreated check     ---     0.70+0.17a   0.23+0.08b   0.0         1.03+0.29b   5.15+0.61a   0.15+0.07a

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
                                                    __Survey 3 (13 Jun) 7 DAT 4__                 __Survey 4 (29 Jun) 2 DAT 7__
Treatment   Rate/Acre   Early
Larvae
  Late
Larvae
  Pupae   Early
Larvae
  Late
Larvae
  Pupae   %Marketable
heads at harvest
MK-244 0.16 EC   6.0 oz.   0.03+0.03b   0.23+0.13b   0.40+0.12c   0.70+0.24c   0.60+0.16d   0.30+0.12c   87.5+2.63a
Xentari   1.0 lb.   0.45+0.14ab   0.53+0.13b   1.65+0.29ab   4.40+0.68b   3.88+0.60c   2.43+0.41b   17.5+1.33b
Dipel 2X   1.0 lb.   0.20+0.15ab   0.98+0.24b   1.93+0.27ab   4.95+1.01b   14.30+1.50b   3.40+0.60b   0.0+0.00c
Mattch   1.0 qt.   0.10+0.05b   0.68+0.14b   1.48+0.23b   6.15+0.80b   10.05+1.67b   3.95+0.73b   22.5+3.65b
Pounce 3.2 EC   4.0 oz.   0.40+0.14ab   2.75+0.33a   2.83+0.42ab   13.43+2.28a   37.95+3.58a   12.20+1.72a   0.0+0.00c
Untreated check   ---   0.58+0.15a   1.93+0.31a   2.88+0.41a   7.33+1.34b   31.7+2.08a   14.95+2.38a   0.0+0.00c

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) and percent marketable by arcsin ransformation prior to analysis. Untransformed means are presented.

 

 

Trade Composition\Common name     Formulation         name     Source
Dipel 2X     ME         B. thuringiensis     Abbott
Mattch     ME         B. thuringiensis     Mycogen
                       
MK-244     EC         emamectin benzoate     Merck
                       
Pounce     EC         permethrin     FMC
                       
Xentari     ME         B. thuringiensis     Abbott