Great weather for ducks. . .and Pythium. . .and anthracnose

It’s hard to believe that a few months ago we were in a severe drought. Last week I drove a van load of plant pathology graduate students around Iowa for a field pathology class and it was not uncommon to see ducks making themselves at home (on ponds) in corn fields. Not surprisingly, we also have started to see some disease.

Pythium damping off is again causing stand loss in several fields in southeastern Iowa. We have received several samples and have isolated the usual suspects. We will be evaluating these isolates for sensitivity to seed treatment fungicides. Remember though, most fungicides are only effective for around three weeks, so it is more likely that the fungicide has worn off and these wet conditions have favored infection by Pythium, rather than resistance occurring.

It is not uncommon to find anthracnose leaf blight on the bottom leaves of corn seedlings in corn-on-corn fields. This fungus survives in surface corn residue and spring rains splash spores onto corn seedlings infecting the bottom four to five leaves. This disease is not economically important since once canopy closure occurs, rain droplets no longer disperse the spores and the disease rarely spreads up the canopy. There has been some speculation that anthracnose leaf blight could serve as a source of inoculum for anthracnose stalk rot, however, in our field trials we have been unable to show any association between the leaf blight and stalk rot phases.

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