BIOLOGICAL CONTROL AT NATIONAL ENTOMOLOGY, PLANT PATHOLOGY MEETINGS

Biological control of insects and plant diseases was the topic of numerous oral and poster presentations at the Joint Annual Meeting of the Entomological Society of America and American Phytopathological Society in Las Vegas, Nevada, November 8-12, 1998. The following are very brief summaries of a few presentations. (Only the presenting author is mentioned.)

1. Individual and combined effects of lycosid spiders and carabid beetles on cucurbit pests and productivity - W. Snyder, Univ. Kentucky

In the spring, both ground beetles and spiders reduced densities of striped cucumber beetles on cucumber. The beetles had little impact on cucumber fruit yield, but the spiders reduced pest numbers enough to increase fruit production 25%. In the summer gardens, squash bugs were the dominant pest. Ground beetles increased summer squash yield by 33% by preying on squash bugs, while the spiders had the opposite effect they apparently increased squash bug densities by preying upon minute pirate bugs and perhaps also nabid bugs, which eat squash bug eggs.

2. Interference between Verticillium lecanii and biological control agents of greenhouse pests - J. Brodeur, Université‚ Laval, Québec

The V. lecanii strain 198499 was effective against several common pests, including potato aphid and the fungal pathogen that causes cucumber powdery mildew, and was also able to infect many parasitoids and predators. However, the pests are more susceptible than the natural enemies, so sublethal doses could be used to minimize the impact on the natural enemies while still killing the pests.

3. Hymenopterous parasitoids of filth fly pupae in cattle feedlots of Alberta, Canada - K. Floate, Agri-Canada, Alberta

Apparently there are regional differences in the parasitoid complexes of pest flies. The abundance of Trichomalopsis sarcophagae and rarity of Spalangia spp. is in marked contrast to results of similar surveys in the United States. These differences suggest that species sold to manage pestiferous flies associated with livestock in the U.S. may be inappropriate for use in Canada.

4. Biological control of Phytophthora blight of pepper by Trichoderma atroviride - J. McBeath, Univ. Alaska

T. atroviride is an aggressive hyperparasite of a wide spectrum of fungi, and an effective biological control agent of Phytophthora capsici. Hyphae penetrate the Phytophthora hyphae, causing lysis and death of the fungal mass. Pepper plants treated with the good fungus had significantly increased survival and developed more quickly.

5. Residual Toxicity of Abamectin and Sanmite on Eight Commercially Produced Beneficial Species Used for Control of Greenhouse Pests - K. Wang, Agric-Canada, Ontario

Abamectin and Sanmite are effective acaricides for twospotted spider mite on greenhouse cucumber and tomato. In laboratory and greenhouse trials Abamectin had less residual toxicity, and is therefore more compatible with beneficals than Sanmite. Encarsia formosa, Aphidius colemani, Amblyseius cucumeris, A. degenerans, Phytoseiulus persmilis, Dacnusa sibirica and Orius insidiosus can be released just 1 week after application of the acaricide. For Sanmite, the waiting period varies from 1-3 weeks depending on the biological control agent. They could also be integrated with biological control agents as spot treatments for mite control.

6. Biological control of European corn borer with inoculative releases of Trichogramma ostriniae - M. Hoffman, Cornell Univ.

Even under low ECB density, the wasp successfully established in small fields of fresh market sweet corn grown on diversified vegetable farms in New York, survived insecticide treatments and dispersed considerable distances. Parasitism rates of 40-80% were recorded. Although total control is not anticipated, early season releases of the wasp have great potential for suppressing ECB in sweet corn throughout the season and reducing insecticide inputs.

7. Survey of predators and parasitoids of rapeseed and canola pests - B. Harmon, Univ. Idaho

Parasitoids of flea beetles (Microctonus sp.), diamondback moth (Diadegma insulare, Spilochalcis albifrons), and cabbage aphid (Diaeretiella rapae) were found during a survey in northern Idaho to establish baseline data on natural enemies in these crops. Few lygus bugs were parasitized. General predators included spiders, ground beetles, lady beetles, and lacewings. It is hoped this information will be utilized in the development of integrated pest management systems that optimize biological control.

8. Biological control of the common asparagus beetle, Crioceris asparagi, by Tetrastichus asparagi - P. Kaliannan, Mich. State Univ.

Parasitism by the parasitoid wasp T. asparagi is very low in commercial fields, but can be greatly improved by reducing insecticide applications (using thresholds and less toxic materials). Wasp effectiveness can be enhanced by providing non-crop habitat adjacent to the asparagus field to provide nectar sources that increase longevity of the female wasps.

9. Biologically based IPM of Colorado potato beetle D. Vacek, USDA, Mission, TX

Control of Colorado potato beetle with Beauveria bassiana (three sprays) was compared with conventional chemical control (two imidacloprid or three carbofuran sprays) on two halves of a center pivot field. Border treatments with carbofuran reduced very high beetle numbers as overwintering beetles migrated into the field. There was no difference in yield in the two treatments.

10. On farm evaluation of Beauveria bassiana for long-term suppression of the European corn borer in Midwestern cropping systems - D. Bruck, Iowa State Univ.

Studies in 1996 and 1997 confirms earlier tests that whorl (V7) stage applications of Beauveria bassiana can provide season-long control of ECB. The amount of damage was significantly lower in treated plots (when the borer was present) and yields were higher in some cases.

11. Entomopathogenic nematodes for the control of flies in beef cattle feedlots - D. Taylor, Univ. Nebraska

The virulence of 27 strains of Heterorhabditis and 13 of Steinernema, towards 3rd instar house fly larvae was evaluated with a filter paper assay. Although 22 of the 27 strains of Heterorhabditis infected house fly larvae, none resulted in mortality significantly greater than the control. Ten of the 13 strains of Steinernema infected house fly larvae and 7 caused significant mortality. Two strains of S. feltiae and 2 of the best Heterorhabditis strains produced significant fly mortality in a fresh bovine manure substrate, although fewer S. feltiae were necessary to kill the flies--with doses equivalent to 5.1 to 104 infective juveniles per cm2 of surface area.

12. Host plant effects on parasitism of Lygus hesperus by Anaphes iole - S. Udayagiri, Univ. California

Inundative releases of the egg parasitoid Anaphes iole resulted in 40-60% tarnished plant bug suppression in strawberries. A high proportion of the bug's eggs are laid in the strawberry fruit However, many of these eggs escape parasitism, perhaps due to reduced accessibility of eggs. Inundative releases need to be integrated with other strategies for tarnished plant bug control in strawberry.

13. Factors affecting pathogenicity of Metarhizium anisopliae - S. Screen, Univ. Maryland

Desert locusts are killed in 5 days by M. anisopliae. Infection by this fungus requires a precise sequence of events, with over 60 different proteases produced on the insect cuticle. Appressorium formation is essential for infection, and studies are looking at genetic alteration to enhance infection.

14. Control of black vine weevil, Otiorhynchus sulcatus in herbaceous perennial nurseries - S. Gill, Univ. Maryland

Thresholds for black vine weevil on herbaceous perennial plants vary by plant tolerance to root pruning by the larvae. Entomopathogenic nematodes (Heterorhabditis bacteriophora) applied at 5,000/pot compared favorably with two systemic insecticides in trials in a wholesale nursery.

15. Control of spotted knapweed, Centaurea maculosa, with the biological control agent Sclerotinia sclerotiorum - T. Anderson, Montana State Univ.

A granular canola seed formulation of auxotrophs (an isolate produced by radiation that requires yeast extract for growth and therefore has limited ability to spread) of Sclerotinia controlled mature rosettes of spotted knapweed when applied early in the spring, but did not affect seedlings of this biennial weed.

16. Efficacy of four biocontrol agents on the green peach aphid, Myzus persicae, in greenhouse peppers - D. Gerace, Colorado State Univ.

Parasitic wasps, predatory midges, lady beetle larvae, and green lacewing larvae were examined for their effectiveness in controlling the green peach aphid on greenhouse pepper plants. Lacewings performed better under hot temperature regimes, while the midge (Aphidoletes) and lady beetle did better at cooler temperatures. Aphidoletes was the best of the four at all temperatures, keeping aphid populations low and plant quality acceptable to growers. Although the other natural enemies reduced aphid numbers, plant quality was not always acceptable.

-- to be continued in the next issue of MBCN.


Return to Contents Menu Vol. VI  No. 1/2


Go to Index