STATEWIDE DISTRUBITION OF VIRUS PROBLEMS ON PROCESSING BEANS

Authors: GERMAN, THOMAS - UNIV OF WISCONSIN; THOMPSON, ARNE - UNIV OF WISCONSIN; Willis, David

Submitted to: Wisconsin Fertilizer Aglime and Pest Management Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/5/2004
Publication Date: 1/20/2004
Citation: GERMAN, T., THOMPSON, A., WILLIS, D.K. STATEWIDE DISTRUBITION OF VIRUS PROBLEMS ON PROCESSING BEANS. WISCONSIN FERTILIZER AGLIME AND PEST MANAGEMENT CONFERENCE. 2004.

Interpretive Summary:

Technical Abstract: Wisconsin is the leading producer of succulent beans in the United States with 79,800 acres in production creating a fresh market and processing industry valued at 36 million dollars/year (Wisconsin Ag Statistics, 2003). Virus problems in the Midwest continue to seriously affect the financial viability of this industry. A virus complex involving cucumber mosaic virus (CMV) alfalfa mosaic virus (AMV) and perhaps others first appeared in 2000 in production fields in eastern and south-central Wisconsin causing significant losses. In 2001 losses were less but the presence of virus symptoms was noted in these same growing areas. Losses in 2002 were minimal and appeared to relate to reduced populations and delayed appearance of the soybean aphid. During the 2003 growing season, losses were widespread in Wisconsin and in southern Minnesota, western and southeastern Michigan, and parts of New York State. With the sudden and dramatic appearance of the soybean aphid (Aphis glycines) in soybean fields in 2000 and its known role in virus transmission (Wang et al., 1962; Hill et al., 2001) it was logical to suspect its involvement in the sudden rise in virus-like symptoms in succulent bean. While several viruses have been known to occur on succulent beans intermittently in Wisconsin (Delahaut et al., 2001) they had not previously created serious problems. Therefore, a preliminary survey was undertaken to assess the virus status of the crop in 2000 and 2001. Various experiments have demonstrated that Aphis glycines can transmit AMV and suggest that it may be involved with other virus components of the succulent bean virus syndrome (Hill et al., 2001). Taken together, these data clearly implicate these viruses and the soybean aphid as the cause of the problems associated with snap bean production. In 2002 and 2003 an extensive survey from the major production regions of Wisconsin was undertaken to determine the incidence of CMV, AMV and (in 2003) bean common mosaic virus (BCMV). Leaf samples were selected at random to obtain incidence and ELISA was used to determine infection. These data show that the incidence of CMV and AMV is extremely high in all growing regions of the state and that CMV is more common than AMV. In 2003 we included BCMV in our survey and found it to be present at a relatively low level. Notably, spread of the virus in commercial fields and small research plots was uniform throughout the plantings. Either the plantings were affected or not and this seemed to relate to whether the plantings were in the path of aphid migrations. Symptoms were relatively uniform throughout the plantings indicating a near simultaneous inoculation of susceptible materials. The incidence of virus-infected plants was clearly less in early-planted succulent beans as compared to planting after mid-July and the arrival of soybean aphids to these fields was timed as to expose the later crop to insect pressure at an earlier stage of development resulting in more serious damage to the crop. The dynamics of insecticide use on the soybean aphid has been discouraging and succulent bean germplasm adapted to the North Central region has not been thoroughly characterized for reaction to viruses found in Wisconsin. We have been working with the rest of the management team to address these concerns. In the last two years, efforts to devise acceptable control by preventing aphid transmission have been unsuccessful. As part of our testing efforts we tested leaf samples from insecticide trials conducted in Dr. Jeff Wyman's laboratory. In 2002 and 2003 fourteen different trials involving multiple locations and 56 replications using various combinations of systemic insecticides (imidacloprid and thiamethoxam), foliar insecticides (bifentrin and acephate) and oil applications at various rates and timings were conducted. In all of this work no