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 5-7 true leaf seedling stage was 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 second instar larvae were placed on each leaf. Each treatment was replicated 10 times. Xentari was used as the treated check. The number of dead larvae was counted at 24-hour intervals. Larvae were recorded as dead when there was no movement when probed. Leaves were changed every other day with fresh leaves from the previously treated pots.

1 DAT, the Xentari treatment killed more of the larvae compared to RH-5992 and RH-2485. Larvae on the RH-5992 treated leaves appeared relatively normal while larvae on the RH-2485 treated leaves appeared to be lethargic and desiccated. Moreover, feeding damage to the RH-2485 treated leaves was clearly less than in the RH-5992 and untreated check treatments. RH-2485 probably produced early cessation of feeding in DBM larvae shortly after ingestion of the chemical. By 3 DAT, RH-2485 performed as well as Xentari with similar percentage rates of mortality. RH-5992 did not perform as well and surviving larvae continuing to feed on the treated leaves.


                                                            Mean % mortality (DAT)  
Treatment     Concentration
(lb/100 gal)
      1       2       3
RH-5992 70 WP     0.4 lb. (AI)       10.2b       34.4b       50.0b
RH-2485 80 WP     0.4 lb. (AI)       10.9b       72.0a       96.4
Xentari     1.0 lb.       34.7a       71.2a       94.3a
Untreated check     ---       9.0b       9.1c       11.1c


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
RH-2485     WP         RH-2485     Rohm and Haas
RH-5992     WP         tebufenozide     Rohm and Haas
Xentari     ME         B. thuringiensis     Abbott