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


HEAD CABBAGE: Brassica oleracea L. 'C-G Cross'

Diamondback moth (DBM); Plutella xylostella (Linnaeus)

Treatments were evaluated using the leaf dip method. Head cabbage was seeded in community pots. Each pot contained approximately 10 cabbage plants. Potted head cabbage in the 5 true leaf seedling stage were dipped in each respective solution for complete coverage and allowed to air dry. Leaves from treated plants were detached and placed in a ventilated plastic petri dish. DBM larvae from a laboratory colony that originated from individuals collected from a cabbage field at Kula, Hawaii and Kamuela, Hawaii were used. Ten late second instar larvae were placed on each leaf. Fresh leaves from the original treated plant were added every two days. The number of dead larvae was counted at 24-hour intervals. Larvae were recorded as dead when there was no movement when probed.

Three days post treatment, the Xentari and Neemix+Xentari combinations were significantly more effective than the Neemix treatment alone. In comparing post treatment mortality, the two treatments provided greater and more raid kill than did the Neemix treatment or the untreated check. Larvae on the Neemix treated leaves were smaller compared to those in the untreated check. The product affected the normal development of the larvae. While the untreated check larvae completed development to the fourth instar stage, approximately 80% of the remaining larvae on the Neemix leaves remained in the second instar stage. However, these smaller larvae continued to feed causing small shot-hole injury. None of the surviving larvae on the Neemix treated leaves pupated. Neemix might provide control by disrupting the normal development of larvae under field conditions.


                                                                  ______% Mortality (DAT)______
Treatment     Concentration
    1     2     3     4  
Neemix 4.5     7.0 oz.     11.4a     21.2bc     25.0b     45.1b  
Neemix 4.5 + Xentari     7.0 oz. + 0.5 lb     27.3a     54.9a     82.3a     91.0a  
Xentari     0.5 lb     22.3a     46.3ab     81.4a     95.1a  
Untreated Check     ---     11.5a     20.8c     22.9b     23.8c  

Numbers in the same column followed by a different letter are significantly different (P<0.0001 Tukey's studentized range test SAS Institute version, 6.08). Data was subjected to arcsine transformation prior to analysis. Untransformed number are presented.


Trade Composition\Common name     Formulation         name     Source
Neemix     EC         azadiractin     W. R. Grace
Xentari     ME         B. thuringiensis     Abbott