Field Evaluation of Bio-Rational Insecticides and Combinations for Controlling DBM, 1993

Abstract

Listen

Translate article

Abstract Insecticides were evaluated at the substation of the Kula Research Station, Maui Agricultural Park. The field was set up in a randomized block design with five treatments and four replications (blocks). Each treatment plot measured 70 ft. by 7.5 ft. It consisted of six rows of cabbage in 3 beds on 36 inch centers and 18 inch in-row spacing. Adjacent rows were offset to allow equidistant plant spacing between rows. Treatment plots in each block were separated by a 3 ft. border. Blocks were separated by a 10 ft. border that allowed sprayer access. Total field size was 150 ft. by 109 ft. From 1 to 7 treatments were applied on 12, 17, 24 Nov and 1, 8, 15, 22 Dec using a tractor mounted with a PTO driven spray pump equipped with a 30 ft. boom. The boom was set with three banks of twin jet (TJ 8006, Spraying Systems) nozzles that coincided with row spacing. Each group of nozzles had its own line from the main tank, therefore, spray output to specific treatment plot could be easily controlled. Sprays were applied at 150 gpa (40 psi) for the first three applications and increased to 200 gpa (60 psi) for the last three. A pretreatment count was made on 11 Nov and post treatment surveys were conducted on a weekly basis six days after treatment. Ten plants were randomly selected from the two center rows and removed for examination of insects. DBM immatures were counted in separate age groups: early larvae, late larvae, and pupae. Early larvae were those in the first two larval instars. They were identified by their small size and the occurrence of black colored head capsules. Late larvae were those in the last two larval instars. They were identified by their larger size and the occurrence of green or brown head capsules. Pupae were easily identified by their net like cocoons.