News and Reviews

Biological Control at National Entomology Society Meetings

Biological control of insects was the topic of numerous oral and poster presentations at the National Meeting of the Entomological Society of America in Louisville, Kentucky, December 8-12, 1996. Many of these will be the basis of future articles in MBCN. The following are very brief summaries of a few presentations. (Only the presenting author is mentioned.)

1. Incorporation of entomopathogenic nematodes for integrated pest management of diabroticite in cucurbit production - C. Ellers-Kirk, Penn. State Univ.

Cucumbers and melons grown under plastic are very susceptible to bacterial wilt transmitted by cucumber beetles. Several nematodes were tested for effectiveness in controlling cucumber beetles when applied through drip irrigation lines. Steinernema riobravis was the best of those tested, reducing cucumber beetle emergence by about half. Nematodes alone were not sufficient to prevent losses pesticides were needed to control immigrant adult beetles and larval escapes.

2. Integrated biological control of leafminers, Liriomyza trifolii, on greenhouse chrysanthemum - R. Sher, Univ. Calif - Davis

Both nematodes and wasps are necessary for effective leafminer control, and can be used together. The wasp Diglyphus begini avoids ovipositing on nematode-infected leafminers, but can host-feed on infected leafminers without harm. The nematodes do not discriminate between healthy and wasp-parasitized leafminers, but parasitized larvae are less susceptible to nematode infection.

3. Combined predation by Feltiella acarisuga and Phytoseiulus persimilis for biological control of Tetranychus urticae on greenhouse tomato - J. Rogers, Simon Fraser Univ., B.C., Canada

The predatory mite P. persimilis is not completely effective for twospotted spider mite control on tomato, probably because trichomes prevent movement to other infested plants. A recently commercially available midge, F. acarisuga, is more mobile since the adults can fly. The midge eats more mites than P. persimilis, although it requires fairly high humidity to be effective. The two predators seem compatible for use together.

4. Feeding behavior, development, and survival of Feltiella acarisuga in relation to prey availability - N. Sawyer, Simon Fraser Univ.

This midge predator of twospotted spider mite lays eggs in spider mite egg patches. They hatch in 2 days and can complete development in 5 days under ideal conditions. The only catch is that the midge larvae don't migrate well, so they will starve if they deplete their food or the mites disperse.

5. Quantity assessment of shipments of the predatory mite Phytoseiulus persimilis from six U.S. suppliers - C. Stewart, Georgia Exp. Stn.

Internal quality control of the number of predator mites sold to consumers is needed. The low quantities of live mites and high variability is alarming.

6. Plant architecture and weather conditions affect egg parasitism of Ostrinia nubilalis by Trichogramma ostriniae - B. Wang, Univ. Mass.

This parasitoid of Asian corn borer may also be effective against European corn borer. Wasps prefer to parasitize eggs on the lower and middle part of a corn plant (where most ECB eggs are laid). A decrease in parasitism at higher temperatures may limit its use to cooler geographic areas.

7. Search for Bacillus thuringiensis isolates toxic to stored grain beetle pests - J. Sedlacek, Kentucky State Univ.

Five species of stored grain beetles were assayed for susceptibility to various Bt strains. Maize weevil was not susceptible, but several isolates show promise for control of other beetles. No single Bt will be effective against a complex of beetles, but several candidates exist that warrant further investigation for individual species.

8. Development and implementation of biological control of Liriomyza leafminers in glasshouses - M. Parrella, Univ. Calif. - Davis

There are many parasitoids in several genera that attack the four economically important Liriomyza leafminer species in greenhouses. Recommendations have been developed for Diglyphus and Dacnusa, specifying release rates per unit area for preventative or curative releases. However, these wasps are expensive, and other pests are not controlled, so only a few growers are utilizing these parasitoids regularly. Combining the parasitoids with nematodes or fungi for control of other major floricultural pests is now being investigated.

9. Impact of soil insecticides on carabids - Z. Chen, Ohio State Univ.

The three insecticides tested were toxic to ground beetles, but the beetles can be conserved by field boundary preservation, by reducing insecticide use, and refinement of application techniques and timing. Dispersal from boundary areas or untreated fields is the only way beetle populations recover.

10. Are there characteristics of phytoseiids used in successful conservation biological control? - J. Nytrop, Cornell Univ., Geneva, NY

Typhlodromus pyri provided consistent, effective biological contol of European red mite (ERM) once the predator became established and initially suppressed the pest mite. T. pyri is able to maintain itself at relatively high densities by feeding on alternate food when ERM are scarce, doesn't disperse out of trees when prey are scarce, and is able to suvive winter conditions in trees. In contrast, another mite, Amblyseius fallacis, does not persist in trees because it disperses when prey are scarce and doesn't overwinter well.

11. Influence of pollen on predation and cannibalism by Coleomegilla maculata in sweet corn - T. Cottrel, Univ. KY

The twelvespotted lady beetle feeds on pollen and fungus in addition to insects and can complete its development on corn pollen alone. This helps keep the beetles in the field, but reduces rates of predation (such as on corn earworm eggs) as the beetles eat pollen instead of eggs.

12. Efficacy of nematodes and Bacillus thuringiensis against shore flies and fungus gnats - S. Roy, Univ. Mass.

Nematodes didn't control fungus gnats on potted poinsettia, but the Bt formulation (Gnatrol) did, particularly at the high rate of application. Shore fly populations were too low to tell if either treatment had any effect on them.

13. Parasitism of oblique banded leafroller egg masses by inundative release of Trichogramma platneri - A. Roda, Cornell Univ., Geneva, NY

T. platneri parasitized only 46 eggs of each obliquebanded leafroller egg mass (usually 50-300 eggs). Lower damage may be achieved by increasing the frequency of wasp releases from every 5 to every 3 days, thereby having a parasite population present to parasitize newly deposited egg masses.

14. Effects of spider manipulations on pest control in vegetable gardens - P. Tuntibunpakul, Univ. Kentucky

Adding mulch to a mixture of cucumber, potato, and eggplant increased the density of spiders on the ground, but not in the vegetation. The more numerous ground-dwelling spiders did not decrease pests numbers, and squash bugs even increased in the mulched areas.

15. Comparison of a lacewing and a parasitoid for whitefly control on poinsettia- J. Sanderson, Cornell Univ., Ithaca, NY

The high release rate of lacewings (8 eggs/plant) suppressed silverleaf whitefly better than low rates (1 egg/plant), but the wasp Eretmocerus californicus was even better. Overall, the best control was achieved with a low rate wasp release, followed by high rate lacewing release and then a low rate lacewing release. Lacewing eggs were applied using a BioSprayer, which delivers the eggs in a starch-based carrier and water. Although target release rates were achieved, egg hatch was reduced, and some design modifications need to be made before this delivery system will be practical for use in a greenhouse.

- to be continued in the next issue of MBCN!


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