We’re looking at a lot of early-planted soybeans and trying to decide on continuing insect and disease sprays. We know Asian Soybean Rust is in Alabama and on the Florida boarder. It has not been located in Georgia yet. Most of the fields have already been sprayed for disease and questions about spraying is coming up. I was talking with Colquitt Ag Agent Jeremy Kichler this morning and here are some of the considerations about follow up disease sprays:
- How long ago and what did you last spray? Some fungicides last two weeks and others last three weeks.
- Growth stage – Many of our early-planted soybeans are in full pod (R4) or beginning seed (R5) growth stage. Once the plant reaches R6 – seeds are touching inside the pod – soybean diseases are not an issue.
- Environmental conditions – Right now we are very hot and moving to a hot weekend with high temperatures and almost no chance of rain until Sunday. On through next week, we have smaller chances of rain until the end of the week. If lots of rain show in 10-day forecast, conditions are more conducive for disease.
- Importance of 1st Spray – Most of our fields have been sprayed soon after bloom. UGA Extension Pathologist Dr. Bob Kemerait says, “From field studies, it is clear that the FIRST fungicide application is more important than the second. In 2006, a well-timed application of our best fungicides was at time as effective as two fungicide applications, and sometimes better than two application of a lesser effective fungicide.”
We’ve also been checking insects this week. I’ve not seen a lot of kudzu bugs at all. The most insect pressure is coming from foliage feeders – mainly loopers. UGA Extension Soybean Entomologist Dr. Phillip Roberts says it is usually going to take 8 or more per row foot to cause 25% leaf damage. Right now, insects are below thresholds. Growers can terminate insecticide applications when their soybeans have reached the R7 growth stage and are mostly insect pest free. This is when at least one pod can be found on the plant that is mature (turning brown or tan).