No. 7 Article 4/May 7, 2004

Windy Planting Conditions and Application of Granular Soil Insecticides: Is Placement Significantly Affected?

On April 28, extremely windy conditions prevailed across much of Illinois. Despite gusts that exceeded 40 miles per hour at times, the planters were rolling across a good portion of the state. We too had planting crews in the field near DeKalb and Monmouth. At the Monmouth location, we used only transgenic seed or seed treated with an insecticide. No granular products were applied. However, at the DeKalb location, we did apply some granular soil insecticides. Several questions were raised regarding the potential loss of efficacy that might result from poor placement of granules due to sustained and gusty winds.

To answer these questions, I turned to an article published in the Journal of Economic Entomology in 1991 titled "Effect of Wind Speed on the Application and Distribution of Granules Applied to the Soil for Control of Corn Rootworm (Coleoptera: Chrysomelidae)." Authors C. R. Ellis, M. K. Bergman, and L. W. Bledsoe used wind tunnel and field experiments to evaluate the influence of wind on the displacement of sand and clay insecticide granules.

A John Deere 7000 Max-Emerge planter with Noble insecticide metering units (REM-COR, Howe, Texas) was used in their research. The planting direction of their field studies was always perpendicular to wind direction. In 1985, the investigators relied on natural winds in their field studies. In 1986, the scientists were able to control wind speed by using the following approach: "Controlled winds were generated by a furnace blower driven by a 1/3-hp (250 W) electric mower, which was powered by a 3,500-W portable generator mounted on the tongue of the planter. A beam bolted to the tool bar supported the blower perpendicular to the corn rows."

Results from their 1986 field study indicated that in-furrow placement of granules was far less influenced by wind compared with the band application. They also made this conclusion: "Our results indicate that the effect of winds perpendicular to the direction of planting is most evident in the windward, outside row of the corn planter. In leeward rows, however, applications in front of the furrow closure wheels were displaced more than applications behind them because of air funneling through the opening between the depth wheels and the closure wheels. Two possibilities for reducing drift are indicated: installing a flexible wind screen on each side of the planter, or applying the granules in-furrow."

The researchers reported that at wind speeds of 24 kilometers per hour the width of the concentrated insecticide band was approximately 25 centimeters wide (approximately 10 inches) on the windward side of the planter. At a wind speed of 0 kilometers per hour, the band width was slightly less than 10 centimeters (approximately 4 inches) on the windward side. At a wind speed of 24 kilometers per hour, the insecticide band width on a leeward planter unit was just above 10 centimeters. The displacement of granules was relatively minor at wind speeds of 0 to 36 kilometers per hour for in-furrow applications. Clearly, wind can affect the placement of granular soil insecticides. Variables such as wind speed, wind direction, band versus in-furrow applications, and windward versus leeward planter units all can affect the magnitude of the displacement.

In July, we will conduct our root-injury evaluations in DeKalb and determine how the various insecticide treatments performed. We will certainly take a careful look at the performance of those products that were applied in a band.--Mike Gray

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