EFFICACY OF GRANULAR INSECTICIDES FOR CONTROLLING THE ROOT APHID, 1994:

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

University of Hawaii

Department of Entomology

3050 Maile Way, Room 310

Honolulu, HI 96822

Phone: (808) 956-6737

FAX: (808) 956-2428

 

R. S. Shimabuku

Cooperative Extension Service

310 Kaahumanu Ave., Bldg 214

Kahului, HI 96732

HEAD CABBAGE: Brassica oleracea L. 'Scorpio'

Root aphid; Pemphigus sp.

A new root aphid was found on the Hawaiian Island of Maui. The field trial to evaluate granular insecticides was installed on a cooperating grower's farm at Kula, Maui in a field that contained broccoli heavily infested by the pest. The experimental plots were adjacent to a broccoli planting that was also heavily infested by the root aphid. The adjacent broccoli crop was removed by the grower 6 weeks after the field trial began.

The field site was plowed and rotivated on 24 Nov 1993 and planted 1 week later with transplants in the 6-8 true leaf seedling stage. The treatments tested were Diazinon 14 G (14 lbs/A), Lorsban 15G (13.4 lbs/A), Di-Syston 15G (7.7 lbs/A), and an untreated check. Insecticides were applied in-furrow prior to transplanting. Treatments were replicated three times in a randomized block plot design. Each treatment replication consisted of four rows of cabbage with 25 plants per row at 18 inches inter plant spacing. Treatment plots were separated by a 3 feet buffer.

The treatments were evaluated at 3, 7, and 12 weeks after planting to assess aphid populations on the roots. During each evaluation, the roots of 15 plants were taken from each treatment plot and individually bagged. Each root sample was washed in a calcium chloride solution (1 tablespoon calcium chloride per gallon water) to float the aphids, and the aphids were counted.

Although the aphid density was generally low in the untreated check, meaningful results were obtained. All insecticide treatments provided excellent control throughout the entire crop cycle. The field trial was conducted under the worst possible pest circumstances where aphids were present on the prior crop and in an adjacent field. In view of these circumstances, we expect any of the three granular insecticides to provide economic control in Hawaii.

Means in each column followed by a different letter are significantly different (Tukey's studentized range

test P<0.001 SAS Institute, version 6.04). Data was transformed by square root (x+0.5) prior to analysis.

Untransformed means are presented.