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
- 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
- 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
- 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,
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
- 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
4) Kansas - Jim
- 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
5) Kentucky - David
- 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
- 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
- Predation on European corn borer eggs
by the lady
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
- 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
- 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
- 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 -
- 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
- 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.
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