Influence of cotton microhabitat on temperature and survival of Trichogramma (Hymenoptera: Trichogrammatidae) within cardboard capsules
2002
Suh, C.P.C. | Orr, D.B. | Van Duyn, J.W. | Borchert, D.M.
Field studies were conducted in 1996 and 1997 to determine the most suitable release sites in cotton for inundatively released encapsulated Trichogramma exiguum Pinto & Platner. Atypical applications of a plant growth regulator, mepiquat chloride (Pix), were used to manipulate cotton plant size and canopy closure to produce a range of plant sizes that might be present in North Carolina when Trichogramma releases for suppression of third-generation (F3) heliothines were made. Pix treatments had a significant effect on canopy closure, which significantly influenced the number of hours soil surface temperatures between rows were greater than or equal to 35 degrees C. The mean daily number of hours temperatures were greater than or equal to 35 degrees C was greatest on the soil surface between rows, followed by in the canopy, then soil surface within rows. A significant correlation between the number of hours preimaginal Trichogramma were exposed to temperatures greater than or equal to 35 degrees C and Trichogramma emergence was found in 1997. Consequently, suitability of the soil surface as a release site for Trichogramma capsules depended significantly on the level of canopy closure, location of capsules relative to the center of rows, and length of time capsules remained in the field before parasitoid emergence. Our results indicate that these factors should be considered when implementing augmentative releases of Trichogramma wasps in cotton.
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