The latest issue of PMN Update has four items that deserve an in-depth look by soybean producers.

The first is a Focus on Soybean webinar entitled “Fungicide Resistance in the Cercospora Leaf Blight and Purple Seed Stain Pathogen of Soybean” presented by Dr. Trey Price, LSU AgCenter Assistant Professor. In this presentation, Dr. Price discusses the development of fungicide resistance in Cercospora kikuchii, a pathogen that causes Cercospora leaf blight (CLB) and purple seed stain in soybean. Seed that are infected with purple seed stain will be docked at the elevator, and Cercospora leaf blight can cause late-season defoliation with resultant yield loss. The increasing development of fungicide resistance in this pathogen has resulted in there being no fungicide recommendation for control of CLB in Louisiana. Since there are no efficacious fungicides for this pathogen, planting a tolerant variety early is the best management strategy to avoid or reduce infection.

The second is a Focus on Soybean webinar entitled “A role for Oomycete Biology in the Development of Disease Resistant Soybean” presented by Kevin Fedkenheuer of Virginia Tech University. Oomycetes are a class of fungi that includes Phytophthora sojae, the causal agent of root and stem rot in soybean. Most soybean varieties that are currently planted in the Midsouth have some level of resistance due to Rps (Response to Phytophthora sojae) genes that enable them to avoid infection, and effective seed treatments are available for early-season but not season-long control. In this presentation, Mr. Fedkenheuer discusses the mechanisms of genetic resistance to this pathogen, as well as molecular breeding techniques that can be used to develop durable resistance genes that will offer long-term effectiveness against the numerous Phytophthora sojae pathotypes.

In a United Soybean Board Press Release article entitled “Seed Treatments Can Help Farmers Manage SCN”, the results from a field project designed to examine the effectiveness of the Clariva seed treatment against SCN are summarized. Though the very slight and inconsistent yield increases are touted in this article which presents results from one year of research, the lowered SCN population where this product was used is the most promising result. This is briefly discussed in a blog on this website.

In another United Soybean Board Press Release article entitled “Soil Residual Herbicide Options After Soybean Emergence”, a treatment guide for a list of residual herbicides that can be applied after soybean emergence is presented. This information should be useful to those producers who were not able to apply pre-emergence residual herbicides before soybean emergence. A few of the listed residual herbicides have foliar activity to control small, emerged weeds, but most must be tank-mixed with other herbicides that provide post-emergence control of emerged weeds at the time of application. See the article on this website for the mode of action classification of the herbicides listed in the above article, as well as links to their labels.

Composed by Larry G. Heatherly, June 2015, larryheatherly@bellsouth.net