Augmentative Releases Research Articles

Augmentative Releases of Entomophagous Species in Annual Cropping Systems

Abstract Augmentative releases, because of their repetitive nature, are often more expensive and time consuming than importation methods of biological control, and thus have been considered a less desirable approach to biological control. From the view of semipermanent ecosystems, e.g., orchards, this perspective may be appropriate; however, for annually disturbed habitats, periodic releases may be the biological control method of choice. Matching the characteristics of annual cropping systems to appropriate natural enemies would expand the basis for using entomophagous species in augmentative releases. When this approach is used, selection of natural enemies for augmentative releases would move beyond the ability to mass rear entomophagous species. A focus on quality control, enhanced effectiveness of released individuals, and ecological and economic assessment of releases is required to increase the use of augmentative biological control in annual cropping systems. Increased knowledge of the biosystematics and basic biology of entomophagous species is necessary to use these species effectively in augmentation programs.

Suppression of Beetles in Stored Wheat by Augmentative Releases of Parasitic Wasps

Field studies were conducted to assess the effectiveness of the parasitoid wasps, Cephalonomia waterstoni (Gahan), and Choetospila elegans (Westwood), for controlling Cryptolestes ferrugineus (Stephens), rusty grain beetle and Rhyzopertha dominica (F.), lesser grain borer. On 6 July 1993 and 7 July 1994, adults of both C. ferrugineus and R. dominica were released at monthly intervals into 6 steel grain bins each containing 27.2 t of hard red winter wheat, Triticum aestivum L. Adults of both parasitoid species were released into 3 of the bins 21 d after the 1st beetle release. The amount of suppression of C.ferrugineus by C. waterstoni could not be measured in either year of this study because C. waterstoni infested the control bins. However, C. elegans was effective in suppressing R. dominica populations. In 1993 and 1994, R. dominica populations were suppressed by 98 and 91% compared with the control bins. After 198 d from initial beetle release in 1993, the treatment bins averaged 0.05 R. dominica per kilogram and the control bins averaged 2.06 R. dominica per kilogram. After 131 d from initial beetle release in 1994, the treatment bins averaged 6.94 R. dominica per kilogram and the control bins averaged 81.03 R. dominica per kilogram.

Augmentative Releases for Aphid Control on Landscape Plants

This report summarizes the findings of four augmentative releases of insect predators, lady beetles and lacewings, for controlling aphids on landscape plants. Releases of the convergent lady beetle and seven spotted lady beetle reduced populations of spirea aphid on firethorn when dispersal was limited. Neither species of lady beetle reduced populations of woolly aphids on firethorn. A field release of convergent lady beetles was followed by reduced aphid populations on Elaeagnus in a landscape. Releases of lacewings on stonecrop and hawthorn provided no evidence of reductions in aphid populations. Some impediments to the success of augmentative releases in landscapes are discussed.

Biological Control through Augmentative Releases of Natural Enemies: A Strategy Whose Time Has Come

The augmentation of natural enemies for biological control of agricultural pests has long been considered a viable strategy in the field and greenhouse. However, research on and the practical application of this method have not been developed fully compared with other strategies designed to encourage natural enemy populations (e.g., environmental manipulation). Reasons for this include: (1) high cost of natural enemies and hence the economics of such programs, (2) problems associated with the availability and quality of natural enemies, (3) lack of rigorous research projects documenting success versus release rates as wel1 as economic analyses, and (4) the widely held belief that such a strategy utilizes natural enemies as a pesticide and therefore takes the ecology out of biological control. Whereas some of these limiting factors are still a concern today, the situation is changing dramatically in favor of augmentative releases. This article discusses the changing attitudes regarding this biological control strategy with respect to the limiting factors presented above. In addition, it provides an experimental approach, methodology, and validation criteria utilizing augmentative releases of parasites for biological control of leafminers attacking greenhouse-grown chrysanthemums through the development of a predictive mathematical model.

Augmentative release ofLixophaga diatraeae [Dip.: Tachnidae] for suppression of early-season sugarcane borer populations in Louisiana

Augmentative releases of the tachinidLixophaga diatraeae (Townsend) at 3 plantations in south Louisiana at 3 rates [\(\bar X = control\) (none), 119–129 (light), and 796–924 (heavy) mated Φ/ha] resulted in an average of 25% parasitization byL. diatraeae of 1st-generation larvae of the sugarcane borer,Diatraea saccharalis (F.), in all plots. Therefore, parasite dispersal apparently negated rate effects, and results within plantations were pooled.

Augmentative Release of Two Established Parasite Species to Suppress Populations of the Gypsy Moth1

Strategically timed augmentative releases of adult Compsilura concinnata (Meigen) and Brachymeria intermedia (Nees) were made agamst larval and pupal populations, respectively, of the gypsy moth, Lymantria dispar (L.),. in 1976. These eastern Pennsylvania studies were conducted in attempts to inoculate established parasite populations within nondefoliating host infestations and thereby reduce the temporal lag in parasite abundance. Year-of-release inundative effects also were anticipated based on a proposed B. intermedia augmentation model. Evaluations of release effects in 1976 and 1977 included weekly collections of 3rd–6th stage host larvae in C. concinnata study areas and weekly collections and field-monitering of host pupae in B. intermedia study areas. A statistically Significant, but managerially impractical, increase in C. concinnata parasitism was noted in treatment areas only dunng the year of release. Release of B. intermedia had no detectable effect on the host population sampled.

Tobacco Budworm Control in Caged Cotton With a Resistant Variety, Augmentative Releases of Campoletis sonorensis, and Natural Control by Other Beneficial Species1234

A tobacco budworm, Heliothis virescens (F.), population in field cages deposited ca. 1/2 as many eggs on a nectariless-high terpenoid-hirsute line of colton (XG-31) as on a nectaried-normal terpenoid-hirsute line (M-8). Fewer small larvae developed to medium size on XG-31 than on M-8, indicating small larval mortality most likely due to the high terpenoid content. About 8 times more medium-size larvae and twice as many large larvae were present on M-8 as on XG-31 in the F1 insect generation. Releases of Campoletis sonorensis (Cameron) resulted in 81–100% parasitism of medium larvae and, thus, considerably fewer large larvae. A native parasite, Trichogramma pretiosum Riley, and a predator, Orius insidiosus (Say), also preyed heavily on the tobacco budworm population. As a result, F2 tobacco budworm larval populations did not develop in the XG-31 plots where C. sonorensis was released. The numbers of small- and medium-sized tobacco budworm larvae also were greatly reduced in the M-8 parasite release plots. The nectariless XG-31 had fewer cabbage looper, Trichoplusia ni (Hubner), eggs and larvae than the nectaried M-8, but the high terpenoid content of XG-31 did not significantly affect numbers of cabbage looper larvae.