Author
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Lynch, Robert |
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Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/1/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Fungicides are routinely used to control plant diseases, such as early and late leafspot and white mold, in the production of peanut. Several new fungicides with a different mode of activity have recently been registered for use on peanut. When applied as a foliar spray to peanut, fungicides not only affect plant pathogenic fungi, but also are consumed by insect larvae as they eat peanut leaves. Therefore, we evaluated Bravo 720, Bravo Ultrex, Folicur, and Tilt for activity against larvae of the corn earworm. fall armyworm, and velvetbean caterpillar. Bravo 720 and Bravo Ultrex had the greatest activity against these insects by reducing survival of larvae, extending the time required to complete the larval stages, and reducing the number of insects that survive to become adults. The active ingredient in Bravo 720 and Bravo Ultrex is chlorothalonil. Evaluation of several other fungicides that contain chlorothalonil for activity against the fall armyworm showed that the activity was due to chlorothalonil and not to formulation of Bravo 720 or Bravo Ultrex. Folicur and Tilt were less harmful to survival and development of insect larvae; larvae that were fed peanut leaves treated with Tilt were actually bigger at 10 days of age than larvae that were fed untreated leaves. Technical Abstract: The fungicides chlorothalonil, tebuconazole, and propiconazole commonly used for control of peanut diseases were evaluated for activity against the corn earworm (CEW) (Helicoverpa zea (Boddie)), fall armyworm (FAW)(Spodoptera frugiperda (J. E. Smith)), and velvetbean caterpillar (VBC)(Anticarsia gemmatalis Hubner). Chlorothalonil most adversely affected early establishment and survival of neonates of all 3 insect species on peanut terminals. Chlorothalonil also decreased the weight of larvae of all 3 species at 10 days and extended the time to pupation for FAW and VBC larvae. Similarly, tebuconazole adversely affected early survival and establishment, decreased 10-day weight and extended time to pupation of CEW and VBC larvae, but had little effect on FAW larvae. Propiconazole had no effect on establishment and survival of CEW and FAW larvae on peanut terminals, and actually increased the weight of 10-day-old larvae over that recorded for all 3 insects on the untreated control. Orthogonal comparisons of the activity of five chlorothalonil-based fungicides against the FAW showed that the activity was due to chlorothalonil rather than to formulation. At concentrations used in the field, Bravo Ultrex was significantly more active against larvae of the FAW than was a comparable concentration of Bravo 720. |
