CONTROL OF DBM ON ORIENTAL MUSTARD CABBAGE, 1998:

R. F. L. Mau and L. R. Gusukuma-Minuto

University of Hawaii CTAHR

Dept. of Entomology

3050 Maile Way, Rm. 310

Honolulu, HI 96822

Phone: (808) 956-7063

FAX: (808) 956-5888

e-mail: maur@avax.ctahr.hawaii.edu

 

S. K. Fukuda

Oahu County Cooperative

Extension Service

910 California Ave.

Wahiawa, HI 96786

MUSTARD CABBAGE:

Brassica juncea L.

Diamondback moth (DBM);

Plutella xylostella (L.)

Several types of oriental mustard cabbage are extensively grown on the Hawaiian island of Oahu. DBM is the major insect pest infesting these crops. Because of sequential planting in adjacent fields, pest populations build to very high densities. Insecticides were evaluated at Aloun Farms, Inc. located at Ewa, HI. A randomized block design with ten treatments and four replications (blocks) was used. Each plot consisted of four rows planted at 12 in. in row plant spacing. Each row was 20 ft. long and planted on 16 in. centers. Total field size was 0.25 acres. Treatments were applied using a compressed carbon dioxide sprayer at 60 psi and 100 GPA. One hollow cone nozzle (TX-26) was used per row. The adjuvant, Silwett L-77 @ 3.0 oz./100 gallons, was used to facilitate spray coverage. The field was direct seeded on 11 Feb. For stand-alone treatments, the first application was made on 4 Mar. Two subsequent applications were made at 7-day intervals on 11 and 18 Mar. Rotation treatments used a 0.5 larvae per plant threshold. Plots were monitored weekly. Treatments were applied on 4 and 18 Mar. Three post treatment evaluations for larvae were made during the field trial. At each evaluation, ten plants were randomly selected and removed from each treatment plot and carefully examined for immatures (larvae and pupae).

Success @ 3.0 oz./A and Proclaim 5 SG @ 2.4 oz./A provided exceptional control of DBM larvae as stand-alone treatments. Equally effective control was obtained with the rotation of Crymax @ 1.5 lb./A and Success @ 3.0 oz./A. The stand-alone treatment of Crymax @ 1.5 lb./A gave satisfactory control with >80% marketable yield. Other treatments reduced the number of DBM, but some of the harvested produce was not marketable due to the larval feeding damage.

Means in the same column followed by a different letter are significantly different (Tukey’s studentized range test; P<0.01); SAS for Windows version 6.12.

¹Rotation 1 = Crymax @ 1.5 lb./A, Success @ 1.5 oz./A at a 0.5 DBM larvae/plant threshold

²Rotation 2 = Crymax @ 1.5 lb./A, Proclaim 5 SG @ 2.4 oz./A at a 0.5 DBM larvae/plant threshold