Imperial Farmers Spared from Alfalfa Aphid

Imperial Farmers Spared from Alfalfa Aphid

June 12, 2017

Fungi Stops the Spread of Alfalfa Aphid

By Melissa Moe, Associate Editor

Blue alfalfa aphids can pose a huge threat to farmers. The toxins that they inject into the alfalfa causes slow growth and low yields. Alfalfa farmers in Imperial County saw high numbers of alfalfa aphids. However, the recent rain may have spared farmers from further damage that the aphids might have caused. We spoke with Eric Natwick, a UC cooperative extension entomology advisor in Imperial County, about the blue aphids that farmers saw in the area.

“As far as the weather goes, the wet weather seemed to really take care of the blue alfalfa aphids. Sometimes with the aphids down here, we get what we call an epizootic fungus that infects those aphids, and quickly moves through the population and wipes them out. This entomopathogenic fungus seems to be very specific to the blue alfalfa aphid,” Natwick said.

The sudden disappearance of these aphids is good news for producers. Epizootic fungi are usually very specific to insects and can wipe out entire populations very quickly. These fungi do not pose a threat to other animals or plants.

“The blue alfalfa aphid left the pea aphids in the field. We did have some aphids, and of course we had some weevils, but the blue alfalfa aphid disappeared. This is also true over in Arizona. I've been working with Iman Mustafa. He's located over there at Mac in Arizona. He's getting the same results. I guess the good news is, well, we got the Sivanto [insecticide] for use in Arizona and California,” Natwick said.

Photo by Jack Kelly Clark for UC Statewide IPM Project