Rotation and Variety Selection Key to Combating Fungal Diseases

Two fungal diseases made an appearance in the Carolina’s in 2013; frog-eye leaf spot in soybeans, and target leaf spot in cotton. Deneen Sebastian, Marketing Director for Cheminova located in RTP says these will probably continue to show up in years to come:

“Diseases have an uncanny way of surviving. They will bury themselves in the soil. They have the mechanism to survive. So once we see them, they will be with us as we go forward.”

To limit frog-eye leaf spot in soybean fields, Sebastian has a couple of suggestions:

“It’s a very common soybean disease. If you are growing soybeans back to back you have a higher likelihood of having the diseases show up again the following year. A lot of the recommendations lean toward crop rotation being the best thing to do as a grower to interrupt the disease cycle. There are a number of varieties out there that are resistant to these diseases.”

There is chemical treatment for frog-eye leaf spot says Sebastian:

“There are a few for frog-eye leaf and for target spot. For the frog-eye, most of the fungicides are going to be registered for that and we know in NC, in the high production areas, there was Strobi resistant frog-eye leaf spot reported early in 2013. So some of the best defense is either applying a product that has two modes of action or at least alternate chemistries.”

There is also another product group of fungicides to consider:

“We have the strobilurin chemistry used for frog-eye leaf spot and the DMIs that are also used. Both are good product groups to consider.”

Regarding the strobilurin class, some resistance has been documented, says Sebastian :

“We have seen the resistance on the coast and all the way up the Mississippi River delta, it’s a lot more prevalent than people recognize in their fields.”

As with herbicide resistance, mixing modes of action on fungal diseases is important to preserve the chemistry.


A native of the Texas Panhandle, Rhonda was born and raised on a cotton farm where she saw cotton farming evolve from ditch irrigation to center pivot irrigation and harvest trailers to modules. After graduating from Texas Tech University, she got her start in radio with KGNC News Talk 710 in Amarillo, Texas.

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