(Zea Mays). Separate 0.5 Acre Plots of Sweet Corn Were Established at the Del Monte Research Farm at Satus, WA

Section II. Foliage & Seed-Feeding Insects

INSECTICIDES FOR CONTROL OF CORN INSECT PESTS

D. F. Mayer, L. Lim and K. Volker W.S.U. and DelMonte and Zeneca Prosser, WA 99350 and Toppenish, WA 98948 and Yakima, WA 98908

This study was designed to evaluate Karate IE (Zenca), Mustang 1.5 EW (FMC), and Pounce 3.2 EC (FMC) for control of corn earworm (CEW) (Heliothis zea) and bird cherry oat aphid (BCOA) (Rhopalosiphum padi.) when applied to corn (Zea mays). Separate 0.5 acre plots of sweet corn were established at the Del Monte Research farm at Satus, WA. The sweet corn was planted 30 May in 30 inch rows. Standard planting, fertility and weed control practices were followed. Plot size was 0.5 acre (1 swath with the helicopter). Insecticides were applied 4 times during the growing season. The first insecticide applications were on 24 July at 6 am when the corn was just prior to silk. Temperature was 60 F. wind less than 2 mph. The second applications were on 29 July at 7 am. Temperature was 58 F. and wind 4-8 mph. The third applications were on 3 August at 7 am. Temperature was 68 F. and wind 3-5 mon. The fourth applications were on 9 August at 7:30 am. Temperature was 62 F. and wind less than 2 mph. Insecticides were applied by helicopter using 5 gallons of water per acre.

Evaluations were made for corn earworm control on 25 August by recording the number of corn earworm larvae and the number of ears infested with corn earworm on 200 ears of corn in the center rows of each plot. Evaluations were made for bird cherry oat aphid control on 25 August by recording the number of aphids on 25 ears of corn in the center rows of each plot.

Results

No phytotoxicity was observed. Corn earworm were abundant in 1993.

There were lots of twospotted spider mites on the corn in all the plots and lots of aphid parasites in all the plots.

Karate (2.56 oz/acre). There were significantly fewer corn earworm larvae in the plots treated with Karate (2.56 oz/acre) as compared to the untreated check (Table 1). There were fewer bird cherry oat aphids in the plot treated with Karate (2.56 oz/acre) as compared to the untreated check (Table 2).

Karate (3.84 oz/acre). There were significantly fewer corn earworm larvae in the plots treated with Karate (3.84 oz/acre) as compared to the untreated check (Table 1). There were fewer bird cherry oat aphids in the plot treated with Karate (3.84 oz/acre) as compared to the untreated check (Table 2).

Mustang (3.2 oz/acre). There were significantly fewer corn earworm larvae in the plots treated with Mustang (3.2 oz/acre) as compared to the untreated check (Table 1). There were fewer bird cherry oat aphids in the plot treated with Mustang (3.2 oz/acre) as compared to the untreated check (Table 2).

Mustang (4.3 oz/acre). There were significantly fewer corn earworm larvae in the 36

plots treated with Mustang (4.3 oz/acre) as compared to the untreated check (Table 1). There were fewer bird cherry oat aphids in the plot treated with Mustang (4.3 oz/acre) as compared to the untreated check (Table 2). Pounce. There were significantly fewer corn earworm larvae in the plots treated with Pounce as compared to the untreated check (Table 1). There were fewer bird cherry oat aphids in the plot treated with Pounce as compared to the untreated check (Table 2).

Conclusion.

Karate gave good control of corn earworm and there were no differences between the rates. Mustang gave good control of corn earworm and there were no differences in control between the 2 rates. Pounce gave good control of corn earworm.

Mustang gave fair control of bird cherry oat aphid. Pounce gave fair control of bird cherry oat aphid. Karate gave good control of bird cherry oat aphid and there was no differences in control between rates. Table 1. Effect of insecticides applied to 0.5 acre plots of sweet corn on corn earworm (CEW). Satus, WA. 1993

Total CEW %CEW % larvae in infested control 200 ears ears of CEW Treatment oz/a

Karate IE 2.56 2a 1.0a 99 Karate IE 3.84 5a 2.5a 97 Mustang 1.5EW 3.2 8a 4.0a 95 Mustang 1.5EW 4.3 8a 3.5a 95 Pounce 3.2 E 8.0 4a 2.0a 98

Untreated check 169b 70.0b --

Means within a column followed by the same letter are not significantly different at the P + 0.05 level, Newman-Keuls studentized range test.

Table 2. Effect of insecticides applied to 0.5 acre plots of sweet corn on bird cherry oat aphid (BC0A). Satus, WA. 1993

Mean % number B0LA control Der ear of BC0A Treatment oz/a

Karate IE 2.56 12 84 Karate IE 3.84 9 88 Mustang 1.5EW 3.2 32 58 Mustang 1.5EW 4.3 60 22 Pounce 3.2 E 8.0 31 60

Untreated check -- 77 --