Crop Update From Dan Anco Clemson Peanut Notes No. 140 2019

— Written By

Most of the crop is in good condition this far, though we have some dry spots. Chances of rain across the state are fairly low for the time being but look to pick up into the middle of next week. Peanuts planted earlier on April 23 are 85 DAP, with peanuts planted more recently in the first week of June closer to 43 DAP.

Crop oil concentrate/methylated seed oil is commonly added to grass herbicides to improve efficacy. Injury on peanut leaves caused by oil can be confused with leaf spot disease symptoms. Injury caused by oil more commonly shows up near the top of the plant, whereas leaf spot lesions are more commonly seen starting at the bottom of the canopy. A key characteristic for late leaf spot lesions is looking for bumpy brown/black spore structures on the undersides of lesions. Injury caused by oils, herbicides or Thimet do not have these structures. Surfactant can also cause spots of leaf injury, but usually it is not as much as with oil. If we see injury from oil or surfactant, this is mostly okay and by itself does not mean we have a problem.

If more than 0.5 lb/A boron is applied, boron toxicity can show up on leaves and look like burned leaf margins. This usually doesn’t impact yield much, and there is no corrective action to take once it occurs. New growth that comes out later will not be affected by previous applications.

Dan Anco

Extension Peanut Specialist and Assistant Professor

Department of Plant and Environmental Sciences

Clemson University – Edisto Research and Education Center

64 Research Road

Blackville, SC 29817

803-284-3343 x261 office

630-207-4926 cell

Clemson University