News and Reviews

Biological Control at National Entomology and Plant Pathology Meetings

The following is a continuation of brief summaries of some presentations made at the joint Meeting of the Entomological Society of America and American Phytopathological Society in Las Vegas (see previous issue).

1. Biological control of plant frost injury and fire blight disease with a competitive bacterium: ecological principles and practice - S. Lindow, Univ. California

The practical use of BlightBan--which outcompetes the bacterium that causes fire blight to prevent infection--involves making sprays at just the right time. Too early and the flowers that need protection won't be open; too late and the fire blight-causing bacteria are already there and can't be stopped. Recommendations are application at 20% bloom, again at full bloom and once more at 2 weeks past full bloom.

2. Preliminary evaluation of Beauveria bassiana for adult suppression of western corn rootworm - B. Mullock, USDA, Brookings, SD

Twenty-one isolates of the fungus B. bassiana, originally isolated from field-collected Diabroticina and European corn borer, were screened in laboratory and greenhouse studies. The most aggressive isolate killed 30, 50 and 87% of adult western corn rootworm when applied on corn plants in greenhouses at rate equivalents of 5 x 1012, 5 x 1013 and 5 x 1013 conidia/ha, respectively. Mortality was reduced when rootworms were placed on plants 1 or 2 days after fungal application.

3. Integrated application of two biocontrol agents for the control of Rhizoctonia stem rot of poinsettia - J. Hwang, North Carolina State Univ.

One strain of Burkholderia cepacia was effective in suppressing Rhizoctonia stem rot during the rooting cube phase, while other isolates were more effective in suppressing disease after transplanting.

4. Interactions between pecan aphids and their shared green lacewing predators - M. Petersen, Univ. Arizona

Two species of pecan aphids often co-occur in S. Arizona pecan orchards. Conservation biocontrol is unlikey to be implemented if both species cannot be controlled by predators. The lacewing Chyrsoperla nigricornis did not show a preference for one aphid species over the other, so may be a suitable natural enemy for pecan aphids.

5. How acarodomatia benefit a beneficial mite: Defense from predation and enhanced microclimate - A. Norton, Cornell Univ.

The mite Orthotydeus lambi is an important consumer of grape powdery mildew. This mite is much more abundant on plants that posses acarodomatia (small tufts of hair on the under-side of leaves; commercial grape varieties do not have acrodomatia). It appears that acrodomatia (on Vitis riparia) provide a refuge from predation rather that improved microclimate.

6. Suppression of soybean cyst nematode, Heterodera glycines, by chitin degrading bacteria with chitin substrate - H. Tian, Univ. Arkansas

Adding chitin to soil stimulates populations of bacteria, actinomycetes and a limited number of fungi with chitinolytic properties. These specific groups can attack nematode eggs and egg sacs, but are not equally effective. The amount of chitin added to the soil influences the effects of the bacteria.

7. Developing strategies and organisms for biocontrol of head scab of wheat - N. Khan, Ohio State Univ.

Several antagonists have consistently reduced severity of scab of wheat, also known as Fusarium head blight and pink mold, and/or increased yield over controls. The best performers will continue to be tested to determine their commercial development potential.

8. Compatibility of Biological Control Agents of Soilborne Plant Pathogens and Entomopathogenic Fungi - R. Pereira, Univ. Tennessee

Bacterial biocontrol agents (BBAs) of plant pathogenic fungi may also have a negative impact on entomopathogenic fungi (EF). Results with Metarhizium anisopliae and Beauveria bassiana demonstrate the possiblity of selecting isolates minimally affected by BBAs. Compatible isolates of BBAs and EF could be used in integrated microbial control of diseases and insects on crops.

9. Suppression of pea root diseases by Pseudomonas corrugata - W. Chun, Univ. Idaho

This bacterium can be formulated as a dry powder with talc as a carrier. It increased yield of peas and decreased root and crown disease incidence whether used alone or in combination with fungicides.

10. Pathogenicity of the fungus Furia crustosa to the forest tent caterpillar, Malacosoma disstria - M. Filatas, Cornell Univ.

Infection and dispersal of the fungus Furia crustosa is greatest at cooler temperatures typical when its host, forest tent caterpillar, is active in the spring. Soil moisture was not important, but temperature significantly affected caterpillar mortality. At higher temperatures fewer infective conidia were produced and resting spore formation increased.

11. Comparative efficacy of Beauveria bassiana, Bacillus thuringiensis, and the [insecticide], temik, for control of Colorado potato beetle - L. Lacey, USDA, Wapato, WA

The fungus B. bassiana requires high humidity for germination and infection. In irrigated desert potatoes conditions were not adequate, even with regular overhead irrigation, until row closure. This resulted in poor control of beetles until row closure, at which time fair to good control was achieved. Yield was 33 tons/ha. Low and high rates of Bt produced fair to excellent beetle control and yielded 33 and 40 tons/ha and good survival of non-targets. Temik provided the greatest beetle control and potato yields (45 tons/ha) but lowest biodiversity. Plots treated with bacteria and fungi had low numbers of overwintering adult beetles.

12. The effects of horticultural oils, imidacloprid, and acephate on distribution, survival and parasitism of Unaspis euonymi in Pachysandra terminalis plantings - D. Sclar, Purdue Univ.

Petroleum oils are widely recommended to reduce scale problems while minimizing the impact on their natural enemies in the landscape. However, fewer parasitized euonymus scales were found after treatment with oils or chemicals on Japanese pachysandra. Most of the overwintering and parasitized scales were found in the middle or lower portions of the ground cover where oils do not penetrate as well, so these materials do disrupt the natural enemies by killing their hosts.

13. Control of Sclerotinia sclerotiorum in dry beans using Coniothyrium minitans - E. Bremer, Agri-Canada, Leth-bridge, Alberta

The fungus C. minitans applied to bean flowers prevented or decreased infection, except when disease pressure was very high, although control was not as good as with fungicides. Addition of a nutrient malt extract did not appear to enchance efficacy. Selected strains or different formulations might provide better control.

- to be continued in the next issue of MBCN -


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