Author
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YEE, WEE - UNIV OF CA, RIVERSIDE |
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TOSCANO, NICK - UNIV OF CA, RIVERSIDE |
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Hendrix, Donald |
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Henneberry, Thomas |
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings Publication Acceptance Date: 6/1/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Whitefly densities and honeydew production were both affected by frequency of insecticide applications. Densities of adults per 5th mainstem leaf, adults per 10-s vacuum sample, 1st and 2nd instars, and 3rd and 4th instars per square centimeter of leaf were generally higher in control plots (1 insecticide application), plots treated at 25 adults (4 applications), and untreated plots than in plots treated at 5, 10, and 15 adults (11, 6, and applications, respectively). In general, numbers of honeydew drops per square centimeter were higher in control, 25 adult and untreated plots than in 5, 10, and 15 adult plots. Papers placed on uppermost bolls received more drops later in the season than did papers placed on the lowest bolls. Honeydew production was generally lowest throughout the season in the 5 adult treatment. However, it was not significantly different than the 10 or 15 adult treatments on 13, 20, and 27 August. Seed cotton yields differed only between 10 and 25 adult threshold plots. At Brawley, CA, insecticide treatments at 5 and 10 adults per leaf seemed equally sufficient for reducing whitefly honeydew production. However, fewer applications were needed to maintain the 10 threshold, which would reduce the immediate costs to growers and also would reduce longer term problems associated with pesticide resistance. Technical Abstract: Whitefly densities and honeydew production were both affected by frequency of insecticide applications. Densities of adults per 5th mainstem leaf, adults per 10-s vacuum sample, 1st and 2nd instars, and 3rd and 4th instars per square centimeter of leaf were generally higher in control plots (1 insecticide application), plots treated at 25 adults (4 applications), and untreated plots than in plots treated at 5, 10, and 15 adults (11, 6, and applications, respectively). In general, numbers of honeydew drops per square centimeter were higher in control, 25 adult and untreated plots than in 5, 10, and 15 adult plots. Papers placed on uppermost bolls received more drops later in the season than did papers placed on the lowest bolls. Honeydew production was generally lowest throughout the season in the 5 adult treatment. However, it was not significantly different than the 10 or 15 adult treatments on 13, 20, and 27 August. Seed cotton yields differed only between 10 and 25 adult threshold plots. At Brawley, CA, insecticide treatments at 5 and 10 adults per leaf seemed equally sufficient for reducing whitefly honeydew production. However, fewer applications were needed to maintain the 10 threshold, which would reduce the immediate costs to growers and also would reduce longer term problems associated with pesticide resistance. |