Wow, leave the country for a couple of weeks and all hell breaks loose. Actually, it wasn’t that bad. But, the day that I arrived in Beijing, I received notice from Dr. Hillary Mehl, Extension Plant Pathologist, that soybean rust was discovered in Suffolk. This may have been the earliest that we’ve discovered the disease in Virginia. And it came in a year that many of our soybean had not yet reached the R6 (full-pod) stage. So, Dr. Mehl went into attack mode and begin letting everyone know of the discovery. Overall, I think that our communication system worked well.
Then the question of whether to spray or not began to arise. We took the conservative approach and recommended that all soybean that had not reached the R6 stage and was within 100 miles of the Tidewater AREC should be treated with a triazole fungicide. This recommendation really only affected our late-planted double-crop soybean as our full-season soybean crop and much of the double-crop soybean that were planted in late June had already reached the R6 stage.
Was this recommendation correct? Yes, I believe it was. But, only because we cannot predict future weather conditions. In actuality, the dry weather slowed down the disease’s spread. It really never got worse in Suffolk, where we first found it. Yes, it has now been confirmed in several other counties (see the map below for the latest update), but the incidence and amount of leaf coverage is very low. So, in the end, a fungicide application would probably have done little good. But, we will verify this with our research plots.
Will the disease continue to spread? If we get the rainfall early next week, I think we’ll see it start sporulating again and begin spreading a little faster. But, I’d think that most of our soybean are safe now. If the soybean hasn’t yet reached R6, then a frost may make the disease irrelevant. Plus, it’ll take a few weeks before the disease will get to yield-reducing levels. By that time, our crop will like be physiologically mature.
We’ll keep looking an tracking the disease’s spread and incidence. We should be able to learn much from this year. And this knowledge will help us to make better decisions in the future.