A phrase, commonly used throughout farm country, reads: “Rain makes grain.” However, too much rain can stir up disease growth in crops.
AUDIO: Alison Robertson, Iowa State University Extension and Outreach
Iowa State University Extension and Outreach field crop specialists report having seen signs of Gray Leaf Spot, Bacterial Leaf Streak and Physoderma Brown Spot in Iowa corn fields. Alison Robertson says Physoderma Brown Spot is evident in fields impacted by a great deal of rain early in the growing season and/or flooded areas of farmers’ fields.
“Usually around the weaker areas of the field. Those plants that have that disease tend to look a little ‘wimpy,’ they tend to be less vigorous. Obviously yield is affected with those plants. Occasionally you can see them on more vigorous plants. We don’t really have a good understanding on the more vigorous plants on how much the yield is affected,” Robertson said.
Unfortunately, the disease cannot be treated in-season due to its early onset, between the V3 and V8 stages. Robertson says the best way to treat/prevent Physoderma Brown Spot is to seek resistant hybrids for the next growing season.
“The best thing to do next season is to plant a hybrid that has resistance to disease. The one problem is that that information is not usually readily available on the seed company catalogs. If you talk to a seed dealer and they can’t help you, they should be able to get back in contact with breeders back at headquarters and then have a pretty good idea of what the resistance of certain hybrids is,” Robertson said.