In this issue:
ECB and CEW Moth Flight Update
Soybean Aphid Update
Cowpea Aphids Arrive, in Alfalfa
| Vol 5 No. 6 | August 8, 2003 |
Soybean Aphid—Snap Bean Update for Minnesota and Wisconsin
Bill Hutchison and Eric Burkness, Dept. of Entomology, Univ. of Minnesota, St. Paul, Minn.
Soybean aphid populations have been “crashing” the past 5 days in all of our snap bean plots at the Rosemount location (Dakota Co.). Although SA infestations will crash in response to excessive alate (wing) formation and dispersal, or due to natural enemies, many of the adult winged aphids in our plots have died. Previous work at the University of Wisconsin (Dr. David Hogg) has shown that snap bean is not a suitable host for survival of nymphs. Hopefully, we will see only minimal virus infection this year. As most beans move into the early pod formation, pyrethroid sprays (Warrior, Capture) should also provide SA suppression.
Soybean Aphid-Snap Bean Update from Wisconsin, August 6, 2003
Dr. Walt Stevenson, Dept. of Plant Pathology, University of Wisconsin, Madison
During the past week we've noticed intense aphid pressure on snap bean plantings in southern WI and the pressure is building on plantings in central WI. While the soybean aphid doesn't normally colonize snap beans the way they colonize soybeans, the effect of high aphid pressure on young snap beans can be profound. At our W. Madison field trial where we have 50 cultivars and breeding lines in trial to evaluate virus susceptibility, plants which should be in their second trifoliate are exhibiting severe plant stunting and leaf rolling. I've never seen this type of injury before and after treatment with insecticide to reduce aphid pressure, we are hoping that the plants can recover to the point where we can then evaluate the plants for virus susceptibility. A second planting just emerging is also exhibiting severe leaf curl. The winged aphids likely already transmitted the stylet-borne viruses we are interested in to our snap bean plantings, but it would be nice to produce at least some healthy-appearing foliage on these plants before the development of virus symptoms. It will be extremely interesting to see the impact of both aphid and virus pressure on yield. Some processors suffered severe losses to viruses in the 2000 and 2001 cropping seasons. In past years, insecticide treatment for control of virus transmission to snap beans has produced questionable results. Hopefully growers treating soybeans for aphid control will see reductions in the level of virus symptoms on nearby snap bean fields. In the end, plant resistance to aphids and virus-incited diseases is the most sensible approach. We are seeing differences in plant response to aphid pressure this year and during the past two years, we've seen significant differences in virus susceptibility among cultivars and breeding lines. The two W. Madison and one Manitowoc trials should give us some valuable answers this summer.
*For more information on SA in Minnesota, go to the August 1, 2003 article at: http://www.vegedge.umn.edu/mnvegnew/vol5/801soy.htm
*For more information on the Soybean Aphid Distribution in Minnesota, go to the Soybean Aphid Map provided by Mark Abrahamson, Minn. Dept. of Agric., at: http://www.mda.state.mn.us/pestsurvey/pestreports/2003aug01.pdf
You will need Acrobat Reader to view this file; click
here to download Acrobat Reader software.
Co-Editors: Bill Hutchison, Department of Entomology,
University of Minnesota, hutch002@tc.umn.edu
Jeanne Ciborowski, IPM Program, Minnesota Department of Agriculture,
jeanne.ciborowski@state.mn.us
Production Editor:Suzanne Wold, Research Fellow, Department of
Entomology, University of Minnesota, woldx018@tc.umn.edu
Last Revised August 7, 2003.
The University, including the Minnesota Extension Service, is an equal
opportunity educator and employer. ©1999-2003 Minnesota Extension Service,
University of Minnesota. All rights reserved. Contact
copyright@extension.umn.edu
for information on reproduction or use of this material.