Little-Known Virus May Cause Problems for Soybean Growers

July 24, 2001

WOOSTER, Ohio - Ohio soybean growers are getting a double whammy this season. First it was the soybean aphid, a relatively new insect that has been feeding on the plants. Now farmers must monitor their crop for a virus that may cause additional headaches.

The bean pod mottle virus, seen throughout the Midwest last year, is a little-known virus spread by a familiar insect - the bean leaf beetle. "Last year there were a lot of reports across the Midwest and Ohio that suggested the presence of this soybean virus," said Ron Hammond, an Ohio State University entomologist. "We figured we are seeing the virus more because we are seeing more of its primary vector, the bean leaf beetle. The insect has become more common over the years, partly due to the increase in early planting of soybeans." Hammond said the presence of the virus is causing concern for growers because it causes reduction in seed quality and yield, and researchers know very little about the virus and how the insect acquires the virus and spreads it from field to field.

One of the main symptoms of the virus is green-stem syndrome, where the plant stem remains green right up to harvest. Bean pod mottle virus also produces similar symptoms as soybean mosaic virus, a common virus that can be spread by the soybean aphid, a new insect found in Ohio just last year.

"Not only are we concerned about the soybean aphid transmitting the soybean mosaic virus, but now we have to contend with bean pod mottle virus," said Hammond. "We may be getting into a situation where we are may see two different insects capable of transmitting two different viruses that produce the same symptoms in the plant." OSU researchers, in collaboration with scientists from the U.S. Department of Agriculture, will monitor 20 fields in nine locations throughout Ohio to determine what generation of the bean leaf beetle is carrying the virus, how the insect is spreading the virus, and what impact the virus has on soybean yields.

Hammond said the bean leaf beetle goes through three generations: an over-winter generation that emerges from May to late June and lays eggs in soybean fields; the first generation that emerges mid to late July; and the second generation that emerges in mid to late August and over-winters into the following year. "We are just starting the see the first-generation insects emerging in soybean fields right now," said Hammond.

Growers can do little to protect their plants from the virus at this stage in the growing season. "If the virus is present, it would have gotten into the fields in early spring," said Hammond. "Right now, we are not even making any recommendations for spraying the over-winter generation because we don't know if that is effective or not." Both growers and researchers have a growing interest in controlling the insect prior to or at plant emergence in the spring to halt the spread of the virus. "The idea is to control the over-winter generation before it begins feeding in the spring," said Hammond. "I know that some growers sprayed their fields against the over-winter generation, so we are going to monitor those fields to see how well that worked out." An alternative control method that researchers suggest may be effective is to plant late in the season. "When the over-winter generation emerges, they head for the plants that are already out of the ground. Those are the early plantings of late April or early May," said Hammond. "But if a grower plants late, like mid to late May, then his fields might escape the insect and perhaps the virus altogether. It's not 100-percent effective, but is probably the first line of defense against the insect and reduces the amount of the virus coming into the field."

Author(s): 
Candace Pollock
Source(s): 
Ron Hammond