Severe rainfall over the last week to ten days has caused a lot of concerns for many farmers.

In some areas more than 15 inches of rainfall has caused many low lying areas to go under water. As we all know, rain makes grain but what about too much rain? Well, that is a good question. Most of our research dealing with excessive rainfall has been conducted in the spring where we often are trying to estimate if we need to replant. However, it isn’t very common to be in the situation that we currently are in. For that reason, no data has been published on this kind of scenario. Last time, to my knowledge, that we dealt with this kind of conditions was in 1993.

First of all, if your crop is completely under water it will die within 24 hrs because of the high temperatures that we currently are dealing with. On the other hand, what about if the crop is standing in 6-12 inches of water? That is more of a challenge. The crop will rotten if it is sitting in this water for too long of a time. I would guess that it can sit there for 48-72 hrs as the maximum with the current temperatures. Stems will rotten, the crop will lodge, and seed will then also rotten.

Another issue is insect feeding. Often 2nd generation bean leaf beetles will feed on the pod so moisture can penetrate the pod wall and the seed will then rotten. Finally, we also have a lot of foliar diseases that we often don’t have to worry about in Iowa. This is especially frog eye and downy mildew. I was rating plots last night in central Iowa and they are for sure showing up quickly. However, there is a huge difference among varieties.

There isn’t a lot that we can do. Hopefully we don’t get a lot more rain now. The worst areas are the low lying areas where we often don’t get too much yield. However, the areas in north central Iowa and south central Iowa is another issues and if the water doesn’t disappear quickly they could see significant yield loss. We just have to wait and see and hopefully CBOT will respond to this.

SOURCE: ISU’s Palle Pedersen