The following is a continuation of brief summaries of some presentations made at the 1996 National Meeting of the Entomological Society of America in Kentucky.
1. Factors affecting mortality of the European corn borer in Illinois - M. Venditti, Univ. Illinois
The parasitoid Macrocentrus grandii was the most important mortality factor for both generations of ECB. Infection by the fungi Nosema pyrausta and Beauveria bassiana were low. Only 5% of the eggs were parasitized by Trichogramma.
An intermittent spray nozzle was adapted to create this new liquid mechanical release technique for green lacewing egg application in crops. It does not affect hatching of the eggs or their adhesion on the crop. Eggs are held in suspension by gently bubbling air through the water in the tank, and the eggs can then be sprayed onto plants.
An autodissemination trap was used to disperse the fungus Metarhizium anisopliae: an attractant lures in adult beetles, which then have to walk through a spore preparation to exit the trap. Over 40% of the beetles in the treated area were carrying the fungal spores, compared with only 6% in control areas. Population counts next year will give an indication of the effectiveness of such treatments in controlling the larval stage.
Pitfall trap data suggest that total arthropod activity is higher in plots with a living cover than those that are tilled or left weedy. The dominant predator in their plots was the thin-legged wolf spider, Pardosa sp.
The fungus Paecilomyces fumosoroseus, neem, and the predatory mite Neoseiulus cucumeris were tried against western flower thrips. The best control was achieved with fungus sprays and granules on the potting mix surface. Other combinations with the fungus were good too, and neither the fungus nor neem harmed the predatory mites.
Gazing into the crystal ball: Future success in microbial control will be through integration with other natural enemies in IPM systems and fine-tuning of those microbial control agents we have in hand in addition to discovery of new isolates and organisms.
7. Are insect predators more active in diverse hedgerows? - J. Varchola, Univ. No. Iowa
Ground beetles are not more numerous in woody hedge habitats than in simple grass habitats (typical of Iowa corn fields), but there are differences in their activity in the adjacent field. Beetles appear to move from the hedges into fields more than from grasses (although the author suggests this could be an artifact of the sampling method).
Asynchrony between natural populations of the twelvespotted lady beetle and first generation Colorado potato beetle reduces the possibility of manipulating lady beetle populations to provide any practical impact on potato beetle populations.
Anaphes iole is an egg parasite of the tarnished plant bug that is now commercially available. Releases of 15,000 adult wasps/week/acre reduced plant bug populations about 50%, which is equivalent to chemical control success. However, this and other release rates and timing of releases that were tried were not economical. Research is continuing to address the factors limiting implementation.
Despite annual applications of cypermethrin (used to control leafrollers, but toxic to predatory mites) the New Zealand strain of the predatory mite T. pyri colonized trees and reached relatively high numbers. European red mite numbers dropped from 13/leaf to only 1/leaf after 3 years. Summer pruned shoots can be used to easily spread T. pyri to other trees.
The wasp parasitoid Eretmocerus is able to suppress silverleaf whitefly populations on poinsettia in greenhouses, but much higher release rates (>7 female wasps/plant) are necessary to achieve effectiveness in the Southwest than in the Northeast (only 3 females/plant).
N. oculatus is a small black lady beetle, common in Florida, that appears to be a good candidate for biological control of silverleaf whitefly.
The fungus B. bassiana alone was not sufficient to control lygus bugs on small alfalfa plots. The impact on the bugs was minimal, although the fungus was more effective on adults than large nymphs.
These are only some of the many facets of biological control that were covered at the Entomology meetings.
| Return to Contents Menu Vol. IV No. 3 |