Soybean Aphid Life Cycle

An identifying feature of common buckthorn (Rhamnus cathartica) is the blue-black berries produced in early fall.Read more about this invasive shrub» Photo credit: Plant Conservation Alliance

The soybean aphid has a complicated life cycle that is completed in two very different plant species. During the summer, cycles of live births can result in 15 generations a season. Under favorable conditions, populations can double in just a few days.

Winter

Soybean aphids overwinter as eggs on common buckthorn (Rhamnus cathartica, Figure 1). In the early spring, two wingless generations are produced on buckthorn, followed by a winged generation that flies in search of soybean.

Summer

In the summer, the aphid population on soybean consists of females that give birth to live young females. These female nymphs mature in 5-7 days and begin producing their own young. This cycle results in a population doubling time of just a few days under favorable conditions.

Researchers at the University of Minnesota have determined that daily temperature is a good predictor as to how quickly aphid populations increase. Population growth will be fastest at temperatures between 75-80°F. Population growth will slow, stop, and may even decrease when temperatures are hot (greater than 90°F) (Figure 1).

The female nymphs do not have wings, but can produce winged aphids when conditions become crowded. Winged aphids may stay in the same field, fly to nearby fields, or migrate longer distances up to 6 miles per day.

Figure 1. Optimum temperature for aphid population growth is around 80°F. From: McCornack et al, Journal of Economic Entomology, 2004.

Late summer and fall flight

In late summer, aphids mature into winged females and migrate back to buckthorn. They mate with winged males and lay eggs. According to David Voigtlin at the Illinois Natural History Survey, the number of aphids at fall flight may be a good predictor of next year's early population.

Research publications

Soybean Aphid Biology in North America (pdf)
David Ragsdale, David Voegtlin and Robert O'Neil

Assessing the Invasion by Soybean Aphid. Where Will It End? (pdf)
R. C. Venette and D. W. Ragsdale

The Entomological Society of America published a series of research articles on the soybean aphid. You can read the full (pdf) articles in the special feature on the soybean aphid, Entomological Society of America.

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