Soybean rust is back in the news after being absent all year. It is on the move and is now occurring only four counties south of Cherokee county in Oklahoma. In that location, rust was detected on about 3% of the leaves. That doesn’t sound like much, but rust can infect the leaves very quickly once the infection has begun. This is particularly true when temperatures cool down and there is ample moisture on the leaves from rainfall and heavy morning dew.
I have been looking at quite a few fields here in the county and I have not seen anything that looks like rust. There are several different types of leaf spotting occurring right now but these are due to downy mildew, brown spot, frog eye leaf spot and some bacterial blight. However, it is important to point out that I haven’t been in every field and haven’t looked at every leaf so there is the possibility that soybean rust has already established itself here in the county.
Most of the beans that I have looked at in the last few days are getting pretty mature. The beans have greatly expanded in the pod and some leaves are already turning yellow in some fields. There is no reason to worry about rust in fields where leaves are beginning to turn yellow and fall off of the plant. This signals that the beans are mature and even if rust is present, it can’t hurt the yield. Hopefully, the rust will hold off for a while longer.
Two years ago, we had almost an identical situation where there were late beans and rust fast approaching from the south. It did finally get here but it was too late and the beans suffered no harm from the rust. It never pays to assume but I honestly believe that we have less than a fifty-fifty chance of seeing significant soybean rust problems in immature soybeans this year. I sound like the weather man now, I know, but based on the history of this disease, I am not as scared of the possible bad outcome as I was a few years ago.
So farmers need to keep their ears, eyes and options open on the chance that the disease becomes a problem before soybeans mature, and be ready to act if something does show up. Be alert, but don’t lose any sleep over this one.
PITTSBURG —
