News and Reviews

Biological Control at National Entomology Society Meetings

The following is a continuation of brief summaries of some presentations made at the 1995 National Meeting of the Entomological Society of America in Las Vegas (see previous issue):

1. Control of coleopteran and homopteran pests of semi-irrigated alfalfa with Beauveria bassiana - I. MacRae, Colorado State University

Fungus applications (as Mycotrol WP) reduced numbers of alfalfa weevil larvae, but had no effect on pea aphids or natural enemies.

2. Evaluation of the biological impact of natural ememies on the population dynamics of the Russian wheat aphid - J. Lee, USDA, Stillwater, OK

Predation, not parasitism, was an important mortality factor. Bad weather was the cause of the most aphid mortality, however.

3. Effect of Beauveria bassiana on aphid infestations of chrysanthemums - D. Olson, Georgia Expt. Sta., Griffin, GA

This fungus in a water formulation kept aphid populations low; an oil formulation didn't work well. The water formulation also did not adversely affect a natural infestation of the aphid parasite Lysiphlebus testaceipes.

4. Effect of Beauveria bassiana GHA (Mycotrol WP) on parasitoids of Bemisia sp. infesting cantaloupe - K. Hoelmer, USDA, Brawley, CA

The parasitoid Eretmocerus sp. and silverleaf whitefly were less abundant in fungus-treated plots, but the overall percent parasitism was not significantly reduced by fungus applications. Parasites can be infected, but large numbers of parasites survive treatment.

5. Effect of feeding stress and fungal pathogens on survival of Colorado potato beetles - S. Costa, North Carolina State Univ.

Soil applications of Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces fumosoroseus did not kill Colorado potato beetles and food availability did not alter susceptibility to infection.

6. Reduction of Leptinotarsa decemlineata populations through foliar applications of Beauveria bassiana and releases of Perillus bioculatus - T. Poprawski, USDA, Weslaco, TX

Two releases of twospotted stinkbugs (P. bioculatus) resulted in 83% control of small Colorado potato beetle larvae, partly through egg predation. The oil formulation of the fungus B. bassiana (as Mycotrol GH-ES) outperformed both Furadan and Mycotrol WP (a water formulation). The fungus is slow acting. In lab trials it took 4 days to kill Colorado potato beetle larvae with the oil formulation and over 5 days with the water formulation.

7. Summary of the performance of spinosad against pests of turf and ornamentals - M. Tolley, DowElanco, Indianapolis, IN

This new natural insecticide showed both ingestion and contact activity against some key turf and ornamental pests. It provided good control of sod webworm, black cutworm, fall armyworm, and billbugs in turf, but not chinch bugs, white grubs, and some others. In ornamentals, it was good against elm and willow leaf beetles, thrips, sawflies, gall midges, leafminers, caterpillars, and some spider mites, but not Japanese beetle adults or late instar beet armyworms. This product is considered "practically non-toxic" to most natural enemies.

8. Biotic factors affecting chrysopid mortality: Field and laboratory studies - J. Ruberson, CPES, Georgia

Green lacewings are attacked by numerous parasites and predators. Larval parasites are most common, but eggs, pupae, and adults are targets, too. Do lacewing releases provide control of the target pest, or are they just food for other generalist predators?

9. Efficacy of transgenic corn against the corn earworm - R. Bowling, Kansas State Univ.

Transgenic Bt-corn is efficaceous against early-season foliar-feeding corn earworm, but not late-season, ear-feeding earworms. Developmental time is extended because of reduced feeding, and may allow more predation or cannibalism.

10. Criteria used to determine release rates for Hymenopterous pupal parasitoids on Kansas feedlots - G. Greene, Southwestern Kansas Res. Ext. Cent., Garden City, KS

Parasite release numbers are dependent on sanitation levels and other factors, including feedlot operator's tolerance for flies. The number of cattle is usually irrelevant. Increase rates when rainfall is high; decrease when dry. Use more early in the season when flies are numerous and modify rates based on fly populations. Timing and placement of parasite releases is extremely important.

11. Effects of soil sterilization and a herbicide pretreatment on the virulence of Steinernema carpocapsae - W. Buhler, Purdue Univ.

The nematodes S. carpocapsae and S. glaseri were 80-90% effective against black cutworm on bentgrass turf, but did not persist in the soil. Sterilized treatments had an effect on nematode virulence, but not mortality or persistence.

12. Biologically based insect control products: Successes, failures, and opportunities - R. Ridgway, USDA, Beltsville, MD

Overall, Bt has been the most significant biological product in terms of commercial use. In general, biological control has been successful in high value crops, where one or more insects have developed resistance to commonly-used insecticides, or where water quality or worker exposure to pesticides is a concern; for example, using spider mite predators in California strawberries. Reasons for non-implementation of biological control include slow acting products, small market, technical problems in production or application, variable performance and shelf life, and high cost.

13. Effect of leaves added as soil ammendments on Carabid beetle populations - J. Ingerson-Mahar, Rutgers Coop. Ext., Vineland, NJ

Leaves collected from urban and suburban areas were applied at various depths to corn and soybean fields. They provided a long list of ground beetles recovered from these plots. The leaves probably created a favorable habitat for more ground beetles and increased numbers of beetles might affect pest populations in some cases (they didn't in this study, though).

14. Efficacy of indigenous strains of entomopathogenic fungi against the black vine weevil - S. Booth, Washington State Univ.

Strains of the fungus Metarhizium anisopliae collected in the Pacific Northwest were more effective against black vine weevil larvae in soil at cool temperatures than commercial strains of this fungus or Beauveria bassiana. These indigenous strains should also be more effective than most nematodes at cool temperatures.

15. Assessment of commercially produced Trichogramma as parasites of obliquebanded leafroller egg masses - D. Lawson, Cornell Univ., Geneva, NY

Trichogramma platneri and T. minutum parasitized more obliquebanded leafroller eggs per egg mass in the lab than did T. pretiosum. Although there was no information on economic control, T. platneri did better in field releases than T. minutum.

16. Strain of Serratia marcescens with high virulence when fed to corn earworm larvae - R. Farrar, USDA, Beltsville, MD

This bacterium is usually weakly pathogenic to healthy insects when ingested in high doses. This new strain, however, is highly virulent at low doses, killing corn earworm larvae in 2-3 days with symptoms similar to a virus infection. This has potential as a biological control agent, but some strains are low grade human disease organisms.

17. Alfalfa weevil in Tennessee: Do county extension agents really care? - K. Copley, Univ. Tenn.

A questionnaire sent to Tennessee county extension agents revealed that although agents are concernced about the alfalfa weevil (they know which insecticides can control it), 41% were unaware that weevil parasites had been released in their county. Shows the need for education!

18. Naturalis-L: Biological product (Beauveria bassiana JW-1) for the control of crop and greenhouse insects - S. Hinz, Troy Bioscience, Phoenix, AZ

This fungus formulation had excellent activity against ornamental pests (sweetpotato whitefly, silverleaf whitefly and western flower thrips), turf pests (white grubs and chinch bugs), and cotton pests, but has no effect on natural enemies (including lacewings, bigeyed bugs, damsel bugs, and the parasites Encarsia and Eretmocerus). The EPA has granted the minimum REI of 4 hours and this formulation can be applied with conventional equipment.

19. Biocontrol and abundance of leafminers in low- and high-spray apple orchards in Connecticut - C. Maier, Conn. Agric. Exp. Sta., New Haven, CT

There is a difference in leafminer dominance in low- or high-spray orchards and therefore differences in the parasitoid complex. In low-spray orchards (with no sprays after June) mortality due to natural enemies was highest in the second generation, which often prevents leafminers from reaching damaging levels by the end of the summer.

These are only some of the many facets of biological control that were covered at the Entomology meetings. Future MBCN articles will highlight other areas of research.

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