|Skjoldager, Lars - ROYAL DANISH AG/VET UNIV.|
Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 1997
Publication Date: N/A
Interpretive Summary: Air assisted ground sprayers use a curtain of air to force the spray down into the canopy. These sprayers are used mostly for weed control in cereal and grain crops. They are not commonly used in cotton for insect control. However, because of their potential for reducing drift and increasing canopy penetration, they may be well suited for use in cotton. Research was conducted to determine the effectiveness of an air-assisted ground sprayer in controlling two troublesome pests of cotton, the boll weevil and beet armyworm. The results showed that air assistance more effectively placed the insecticide on the flower bud and on the underside of the leaf, the respective feeding sites of the boll weevil and beet armyworm. Air assisted ground sprayers have the potential for enhancing control of boll weevils and beet armyworms in cotton.
Technical Abstract: The effects of air assisted ground application on the control of boll weevils and beet armyworms in cotton were determined using field and laboratory bioassays, as well as insecticide residue analysis by gas chromatography. A Hardi Twin air-assisted ground sprayer was used to apply malathion (1.0 lb/A) and Spod-XLC (100 ml/A). Laboratory bioassays of individual leaves and squares using boll weevils were used to compare applications with and without air assistance. A field bioassay also was conducted by caging boll weevils on individual plants. Bioassays of cotton treated with Spod-XLC were conducted by caging beet armyworm larvae on the undersides of leaves at mid-canopy. In these tests, the effectiveness of angling the air curtain was compared to application with the air oriented straight down. Air assistance did not significantly increase boll weevil mortality in the bioassays of individual leaves. Nor were there differences in malathion residues on leaves at top and mid-canopy. Bioassays of squares, caged plant bioassays, and residue analysis of squares showed enhanced efficacy when air assistance was used. Application with air assistance enhanced beet armyworm mortality. Angling the air curtain forward 30 degrees increased beet armyworm mortality above that of the other treatments in one test and produced numerically higher, though not significant, mortality in another test. Air assistance shows potential for enhancing the control of troublesome cotton pests such as the boll weevil and beet armyworm.