(Fields 5D and 5E)
Greg Cronholm
Objective: The objective was to evaluate the effectiveness of low impact and limited host insecticides on the second generation of Southwestern corn borer in corn.
Methodology: The effect of Intrepid, a low impact insecticide, and Tracer, a limited host insecticide were evaluated against the standard Warrior–T and XDE-225 insecticides. Warrior-T and XDE-225 are pyrethroid insecticides, which kill a wide range of pests and beneficials. Also, pyrethroids have been associated with spider mite outbreaks in corn due to disruption of predator populations by this class of insecticide. Four replicates per treatment were randomized over five acres of Pioneer 3223 planted at a rate of 28,000 seeds/acre in 30-inch rows. The crop was irrigated at 80% of the calculated evapotranspiration rate of corn (19.6” total). Total rainfall from 10 June to 21 August was 2.5 inches. Normal cultural practices were followed. Insecticide treatments were applied on 27 July and are as follows: Intrepid + Latron CS-70.25% (2oz/acre), Intrepid + Latron CS-70.25% (4 oz/acre), Intrepid + Latron CS-70.25% (8 oz/acre), Tracer (3 oz/acre), XDE-225 (3.8oz/acre), Warrior-T (3.8 oz/acre) and an untreated control. Larval counts and plant damage were recorded from September 4 through 12, 2002.
Results: The untreated plots showed significantly higher larval counts in plants, plant girdling and plant lodging (Table 1) than the insecticide treatments. No significant differences were seen between treatments.
Table 1. Second generation Southwestern corn borer, Diatrea grandiosella (Dyar) larval counts and corn damage seen after treatment with Intrepid, Tracer, XDE-225 and Warrior-T insecticides.
| Number per 10 plants | Percentage(%) | ||||||||||||||
| Treatment | Tunnel Length |
Tunnels | Live Larvae |
Plants w/Damage |
Plants w/Larvae |
Girdled | Lodged | ||||||||
| Untreated | 222.0 | a1/ | 16.75 | a | 7.00 | a | 75.00 | a | 62.50 | a | 15.00 | a | 5.00 | a | |
| Intrepid + Latron CS-70.25% (2oz/acre) | 100.50 | b | 3.50 | b | 2.25 | b | 225.00 | b | 20.00 | b | 2.50 | b | 0.00 | b | |
| Intrepid + Latron CS-70.25% (4oz/acre) | 47.75 | b | 4.50 | b | 0.50 | b | 25.00 | b | 5.00 | b | 0.00 | b | 0.00 | b | |
| Intrepid + Latron CS-70.25% (8oz/acre) | 11.50 | b | 2.75 | b | 0.25 | b | 20.00 | b | 2.50 | b | 0.00 | b | 0.00 | b | |
| Tracer (3 oz/acre) | 45.00 | b | 4.00 | b | 1.50 | b | 22.50 | b | 15.00 | b | 5.00 | b | 2.50 | b | |
| XDE-225 (3.8 oz/acre) | 66.00 | b | 6.00 | b | 2.00 | b | 22.50 | b | 17.20 | b | 5.00 | b | 0.00 | b | |
| Warrior-T (3.8 oz/acre) | 19.25 | b | 1.75 | b | 0.50 | b | 15.00 | b | 5.00 | b | 0.00 | b | 0.00 | b | |
1/Column means followed by the same letter are not significantly different at the P<0.05 level (LSD and Anova).
