A few disease issues have popped up within the past week on peanuts and soybeans. Some are pretty routine and some are not…

Peanuts

As you may expect, the wet, humid weather has been favorable for peanut diseases like leaf spot, southern stem rot (white mold) and Sclerotinia blight, but especially leaf spot. Sclerotinia is moving slowly due to the warmer weather over past two weeks, but with highs in the 70s today and possibly going forward I expect it to move faster. I have observed Sclerotinia blight in my trial plots. This late in the game I prefer Omega 500 for Sclerotinia blight over Miravis + Elatus. Miravis may not perform against leaf spot if there’s any out there already and Elatus is not a good stand-alone product for Sclerotinia. Remember, if you use Omega 500 you must use a leaf spot material with it. With leaf spot, just don’t extend your spray interval beyond 14 days. The leaf spot advisory has shown leaf spot risk to be steadily high and the last effective spray date jumps 2 days every day. If leaf spot is already showing up you may want to use a micronized sulfur product to temporarily arrest leaf spot along with a fungicide that gives residual control. The hot weather we experienced up until now has led to southern stem rot (white mold) showing up in some fields. If this is the case the best products for that are Excalia (3.0 fl oz), Elatus (7.0 – 9.0 oz) or Convoy at 32 fl oz.

Soybeans

Warm humid weather have led to outbreaks of FLS (frogeye leaf spot) and target spot in some fields. Frogeye will show up first in soybeans that have poor resistance to FLS, and some soybean varieties are more susceptible to target spot like AG49XF3. Both diseases can be very similar in appearance but FLS shows up more in the upper canopy and target spot starts in the lower canopy. I have seen pictures of soybeans defoliated from the bottom up by target spot recently. If you sprayed ahead of disease symptoms you shouldn’t have many problems, but you may see target spot start showing up. If you see disease is already there, use products that have an effective Group 3 fungicide that have curative disease activity. Examples would be Delaro Complete, Lucento, Revylok and Topguard or Topguard EQ.

If you have questions or concerns contact me via e-mail at dblangston@vt.edu or use my cell phone at (757) 870-8498.