The soybean aphid, which was practically nonexistent in soybean fields this growing season, may be back with a vengeance next year.
Ron Hammond, an Ohio State University research entomologist, says that if population patterns hold true growers should look to an Integrated Pest Management (IPM) program to control the pest and cut down on yield losses.
"The aphid seems to be following a pattern of high populations one year, low populations the next," Hammond says. "How this is working is that the multicolored Asian ladybeetle seems to be tied to the aphid. In years when aphid populations are high, the aphids provide a good food source for the ladybeetles. This cuts down aphid populations for the next year. But since populations are low this year, ladybeetles are not as predatory, and this gives aphid populations a chance to increase for the next year."
The soybean aphid, which can greatly reduce yields in soybean fields with its voracious appetite, has been in Ohio for four years. High populations were recorded in 2001, low populations in 2002, high populations again in 2003, and practically zero population this year. Hammond said that field research in Illinois is already indicating aphid populations may be high in 2005.
"The growers did a good job this year paying attention to what we were reporting and not rushing out into their fields and spraying unnecessarily," Hammond says. "They saved on spraying, which means they kept money in their pockets. But the potential is there for aphids next year, so growers need to be ready."
Hammond says that if aphid population patterns continue, researchers would take the next step into looking at ways of keeping the insect under control during high population years. For example, planting early may increase the soybean plant's tolerance of the insect, or practicing skip row production would make it easier for growers to access their fields to spray during the growing season.
"The thing we fear the most is that the aphid is going to biologically change and find new hosts to overwinter on," Hammond says.
The soybean aphid is parthenogenic, meaning that it can reproduce without the fertilization process. Because of this ability, the soybean aphid might have the capability of developing new biotypes – individuals that are like the parent, but can adapt to suit their survival needs.
"We are watching this very closely because if the insect does change, we could find ourselves four, six or 10 years down the road with a different insect that is more widespread than it is today," Hammond said.