Wheat Streak Mosaic Virus in Field Corn

June 30, 2000
I had a discussion this week with Shawn Kaeppler, an agronomist from the University of Wisconsin. Kaeppler and others recently published some work looking at the interaction of wheat streak mosaic virus (WSMV) and another virus they deal with a little farther west called high plains virus (HPV). In the study, Kaeppler and others looked at the virus symptom development and how well the virus replicated in the plant for each virus singly and in combination. Their results are of interest to us this year as we come out of a heavy epidemic of WSMV on the wheat crop, especially given that corn may serve as a host for the WSMV. In an earlier article on viruses in corn (the Bulletin of June 16, 2000), I said that corn can serve as a host for WSMV, although it is not affected by the infection. The Wisconsin study clarifies this issue. Most of our currently grown hybrids do not have susceptibility to the virus, but there are some inbreds that do. In testing 30 inbreds, Kaeppler et al.'s work showed that although none of the inbreds had WSMV bad enough to cause plant death or tissue necrosis, several did have high WSMV titers after inoculation. In other words, the virus replicated well in the tissue despite the absence of lethal symptoms. Those inbreds were W64A, Wf9, N215, and B79. For the breeders out there, the entire article can be found in the journal Plant Disease, volume 81, pages 195 to 198, in the article by Marcon, Kaeppler, and Jensen.

So what is so bad about that news? Well, two things could happen. First, the corn can serve as a green bridge to keep the virus around until the winter wheat is planted. Second, although the WSMV may not do a lot of damage to the corn itself, if either maize chlorotic mottle virus (MCMV) or high plains virus (HPV) should by some unfortunate circumstance move their way into the state, some very "lethal" damage can develop on the corn if the corn plants are acting as a nonsymptomatic host for WSMV. The bottom line is this: keep an eye on any unusual stunting in the corn; it may be necessary to have it tested for viruses.--Suzanne Bissonnette

Author: Suzanne Bissonnette

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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