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    Author(s): David B. Orr; Charles P.-C Suh; Michael Philip; Kenneth W. McCravy; Gary L. DeBarr
    Date: 1999
    Source: In: Proceedings of an informal Conference The entomological Society of America, Annual Meeting, December 12-16, Atlanta, Georgia, eds. Berisford, C. Wayne; Grosman, Donald M., 34-44
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (903 KB)

    Description

    Because the Nantucket pine tip moth is a native pest, augmentation (mass-release) of native natural enemies may be the most promising method of tip moth biocontrol. The tip moth has several important egg, larval, and pupal parasitoids. Egg parasitoids are most effective as biocontrol agents because they eliminate the host before it reaches a damaging stage. Trichogramma egg parasitoids are the most important of these, and are the most commonly augmented arthropod in biocontrol programs worldwide. lnundative releases of encapsulated Trichogramma exiguum Pinto & Platner were evaluated for suppression of R. frustrana in first year loblolly pine, Pinus taeda L., plantations. Three releases of 328,238 ± 88,379 _q/ha, spaced 7 d apart, were made in three 0.4 ha plots during second generation R. frustrana egg deposition. The quality of each release was very high in comparison with published values of biological characteristics of T: exiguum. Parasitism of R. frustrana eggs was significantly increased by 29 percent when compared to check plots, egg survival (hatching) was significantly reduced by 47 percent, and larval populations were significantly reduced 60 percent. There was no significant difference in the percentage of terminals damaged between T: exiguum-treated (31 ± 16 percent) and control plots (45 ± 10 percent), however, length of terminal damage was significantly lower in treated plots. The percentage of damage to top whorl shoots was significantly lower in T: exiguum-treated plots compared with control plots, but there was no significant difference in length of damage. Microhabitat significantly affected the number of consecutive hours per day that were 35°C or above (critical temperature for preimaginal 7: exiguum survival). Soil surface with no cover had the greatest number of hours 35°C or greater, followed by soil surface with herbaceous cover, and canopies of small trees (0.4 m tall). Canopy habitats in larger trees (0.9 - 1.8 m tali) had the most moderate temperature conditions. Parasitoid emergence was significantly reduced in response to increasing number of consecutive hours 35°C or greater. Predation of 7: exiguum prior to emergence, though relatively minor, was significantly affected by microhabitat and by the length of time capsules were in the field before emergence (i.e. cohort number). The reduction of R. frustrana populations by mass-release of Trichogramma is technically feasible. In order to make these releases practical, however, we suggest several considerations for future research. Large scale Trichogramma releases could be studied to evaluate possible area-wide effects and residual effects over multiple tip moth generations. Combining several releases of Trichogramma into a single application may be accomplished by a single release of multiple cohorts timed to emerge over a 7-8 day period. The efficacy of such an approach should be studied. Consideration might be made of plantation management practices that result in adequate vegetational cover for survival of encapsulated Trichogramma broadcast on the soil surface, but do not interfere with tree growth. Though unlikely with a native parasitoid, the potential for non-target impacts should be considered in any future evaluations.

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    Citation

    Orr, David B.; Suh, Charles P.-C; Philip, Michael; McCravy, Kenneth W.; DeBarr, Gary L. 1999. The potential for trichogramma releases to suppress tip moth populations in pine plantations. In: Proceedings of an informal Conference The entomological Society of America, Annual Meeting, December 12-16, Atlanta, Georgia, eds. Berisford, C. Wayne; Grosman, Donald M., 34-44

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