Current Research on Biological Control of Insects in the Midwest

At the annual meeting of the North Central Regional Committee on Arthropod Biological Control (NCR-125) in Madison, Wisconsin in late October, state representatives reported on biological control activities in their states. Some of the many projects are summarized here. For further information contact the state representatives that are listed.

1) Illinois - Rob Weidenmann

• Nematode assays against the Asian longhorned beetle found that the entomopathogenic nematode Heterorhabditis marelatus was particularly successful and is being tested for its ability to locate the host in cut logs.
• Surveys of the Asian soybean aphid found that at least one ubiquitous entomophthoralean fungal pathogen, in the Erynia group, is present in some areas, and may have initiated epizootics that reduced aphid densities.
• Illinois scientists are collaborating with scientists in Switzerland in testing host specificity of five species of weevils and leaf beetles for control of garlic mustard.
• Parasitism of bagworms was about 40% higher on shrubs that were surrounded by flowering plants. Vertebrate predators (birds and rodents) were also found to reduce populations.

2) Indiana - Bob O'Neil

• An extension education project, in collaboration with Illinois, trained Master Gardeners in the basics of biological control, and allows participation in one or more projects such as evaluating the effectiveness of Trichogramma releases or using nematodes to control iris borer.
• Research is planned to examine augmentation with the lady beetle Coleomegilla maculata and an entomopathogenic nematode for Colorado beetle control.

3) Iowa - John Obrycki

• Biological interference with Galerucella beetles could interefere with biological control and reduce the control of purple loosestrife. Lady beetles (particularly Coleomegilla maculata), minute pirate bugs and spiders were abundant predators found on the foliage, while ground beetles, rove beetles and wolf spiders were the most abundant ground-dwelling predators. Maximum egg predation occurred in mid summer, with up to 43% mortality (average 27%). Releases of Galerucella could be made during periods of lower predator abundance to reduce this mortality.
• Biointensive management of alfalfa — leaving an uncut strip area between first and second harvest — provides refugia for both potato leafhopper and its natural enemies. This uncut strip provides a suitable microhabitat for the fungal pathogen Zoophthora radicans to develop and potentially spread into adjacent regrowth.

4) Kansas - Jim Nechols

• The imported eriophyid gall mite, Aceria malherbae, was recovered on field bindweed for the fourth consecutive year. This summer nearly all of the bindweed had uniformly distorted and stunted leaves.

5) Kentucky - David Wise

• The economic threshold (ET) and economic injury level (EIL) for alfalfa weevil was modified to include natural enemies. Including the presence of Bathyplectes parasitoids or the entomopathogenic fungus Erynia phytonomi reduced the need for pesticide treatments by about 20%, and increased profit about 10%. This model will continue to be tested in 2001.
• Research on employing the bacterium Wolbachia for mosquito control includes surveying for natural Wolbachia infections, looking at infection dymanics and testing release models in cage experiments.
• The biology of two species of tiphiid wasps (Tiphia pygidialis and T. vernalis) that parasitize the masked chafer and Japanese beetle is being studied. Increasing parasitism through the addition of adult food resources (flowering plants) will be tested in 2001.

6) Michigan - Doug Landis

• Japanese beetle populations are being intensively sampled at 10 locations (all golf courses) to survey for larval natural enemies. The parasitoids Tiphia vernalis and Istocheta sp. (a fly) that are found in other areas of the country were absent in Michigan. One of two protozoan pathogens found in other areas was detected at 4 of the 10 sites. The parasitic fly and one of the protozoans were released at half of the study sites, and two entomopathogenic nematodes were release to evaluate their long-term persistence and impact on beetle populations.
• Parasitism rates of the armyworm were compared in complex and simple landscapes (quantified using aerial photographs and digital land-use data). Two generalist species were responsible for most of the 28% parasitism, but there was greater parasitoid diversity in the complex landscape than in the simple landscape.
• Studies on seed predation by ground beetles suggest that damage to crop seeds is minimal while certain systems have large enough seed predator populations to reduce weed abundance.
• Reduced insecticide use and large border area contributes to better biological control of onion maggot in small test plots compared to large fields. Refuge strips and alternative chemicals are being studied to determine if they can improve biological control in commercial onion production.

7) Minnesota - Dave Ragsdale

• Predation on European corn borer eggs by the lady beetle Coleomegilla maculata was lower when corn pollen was present. However, aphids (normally a favorite lady beetle food) did not affect predation, but beetle foraging behavior and plant architecture explain this.
• Weekly point releases of Trichogramma brassicae were not as good as synthetic pesticides or Bt in controlling imported cabbageworm on cabbage. This was the best release method tested, but it still did not reduce damage below acceptable levels.
• The extent to which adult parasitoids actually utilize sugars in diversified crop habitats is largely unknown. Upcoming studies will use newly developed biochemical sugar analysis to examine sugar feeding by the most abundant parasitoids of the imported cabbageworm and cabbage looper.
• The alfalfa blotch leafminer (ABLM) parasitoid Dacnusa dryas was released and recovered in Minnesota, but only within 10 yards of the release site, indicating very limited dispersal. However, another wasp, Chrysocharis liriomyzae, that had been released in the Eastern U.S. in the 1970's was also found to be parasitizing 32% of the ALBM. Monitoring efforts will expand next year to determine its impact on ABLM populations.
• High sunfish densities likely limit populations of the milfoil weevil that is used for biological control of Eurasian water milfoil. Visit the Biological Control of Eurasian Water Milfoil website.

8) Missouri - Ben Puttler

• Musk thistle rosette weevil populations continue to build and spread. Reduction in musk thistle populations is becoming evident where both this weevil and the flower head weevil have been established for the past 10 years.
• Cowpea aphid natural enemies included the wasp Lysiphlebus testaceipes, a fungal disease and various species of lady beetles and syrphid flies. The natural enemies contributed to reduced aphid numbers, which was virtually non-existant in alfalfa from late spring throughout the summer.

9) Nebraska - Bob Wright

• Lady beetles in field crops were surveyed in the south central part of the state. Two native beetles, the convergent lady beetle and Coleomegilla maculata, were the most common species during all years and in all crops, comprising 77% of the individuals observed.

10) North Dakota - Denise Olson

• A five-year IPM research and demonstration project called TEAM Leafy Spurge educates landowners and managers about control techniques based on IPM strategies. A fall herbicide treatment combined with Aphthona flea beetles results in a more rapid increase in the biological control agent and control of the weed.
• The entomopathogenic fungus Beauveria bassiana is compatible with resistant potatoes for control of Colorado potato beetle. Sprays of the fungus and Bt reduced beetle numbers and feeding on a resistant potato variety in field trials.

11) Ohio - Dave Horn

• The mite Typhlodromus pyri, a predator of European red mite on apple, is active earlier in the season than the native Neoseiulus fallacis, and is also tolerant of the acaracide Pyramite while N. fallacis is not. T. pyri is established, and appears to be compatible with the native mite speices Zetzellia mali.
• Coccinella septempunctata is the dominant lady beetle in both cultivated habitats and low vegetation in natural areas, while Harmonia axyridis has become the most common lady beetle in forested areas throughout Ohio.
• At least 8% of cucumber beetles in a pumpkin field were parasitized by a tachinid fly (species not determined yet), despite the fact that insecticides were used on the field.

12) Wisconsin - Dan Mahr

• Over 60% of the summer generation of obliquebanded leafrollers on apple were parasitized, with most affected by the tachinid fly Actia interrupta. Plantings of perennial flowers did not improve parasitism in one year, but did in another.
• The wasp Chrysocharis liriomyzae was found parastisizing 92-100% of alfalfa blotch leafminers. Large numbers of predators (damsel bugs, minute pirate bugs, a ground beetle and a rove beetle) also fed on ABLM eggs, larvae, or prepupae. A combination of predation and parasitization appeared to be the cause of the huge population reductions and complete control of ABLM in Wisconsin in 2000.
• In a three year study, the major difference between declining and healthy red pine stands was higher resident predator populations (includingthe clerid beetle Thanasimus dubius and the hister beetle Platysoma) in the latter.

Go to Index