CONTROL OF CORN EAR WORM ON CORN, 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

CORN: Zea mays L. ‘Super Sweet 10A’

Corn ear worm (CEW);

Helicoverpa zea (Boddie)

Without effective treatments, CEW causes severe loss of seed kernel on corn. Currently, a pyrethroid insecticide is used as the industry standard treatment, but there are adverse impacts on mite and aphid bio-control. Several bio-insecticides were tested in collaboration with Garst Seed Company. Fields were located at Kunia, Oahu, Hawaii. The corn seeds were planted on 29 May. A RCB plot design with 8 treatments and 4 replicates was used. Each treatment plot consisted of 6 rows on 3 ft. centers at 40 ft. length. Treatment plots were separated by a 10 ft. buffer. Total field size was approximately 0.5 acres. Sprays were applied at 60 GPA using a John Deer 6000 sprayer. The boom consisted of drop nozzles equipped with four 11000VS nozzles positioned so sprays were applied from both sides of each row and from angles above and below the ears. The adjuvant, Latron CS-7 @ 1.5 pt./100 gallons, was also added to each mixture. Treatments began at first ear emergence when the silk had emerged and continued until one week before harvest. Seven applications of each RH-2485 treatment were applied at 2- to 3-day intervals. Five applications of Asana XL, Crymax, and Lepinox treatments were applied at 3- to 4- day intervals, using the industry’s standard schedule. For the rotation, treatments of RH 2485 and Asana were made at 2- to 3- day intervals. A total of four RH 2485 and three Asana applications were made. Treatments were evaluated by assessing CEW damage on twenty-five mature ears from each treatment plot.

None of the treatments prevented CEW damage. However, when compared to the untreated check, Crymax treatments limited the extent of kernel damage. A significantly lower percentage of the assessed ears exhibited tip damage > 1 in. Lepinox and RH 2485 SC did not reduce tip damage. The remaining treatments marginally reduced 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.