Anco Comments SC Peanuts Peanut Notes No. 70 2020

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While we were spared a direct visit from Cristobal, more rain continues in the forecast.
Depending on planting dates, peanuts are closing in around from 40 days old (end of April) to less than 10 days old.
Many of these are still within the window for paraquat. Paraquat (gramoxone) timing is up to 28 days after cracking. Depending on how long peanuts took to crack (can be 5 to 7 days or longer under slower growing conditions), this timing can be 33 to 35 days after planting. If active thrips feeding damage is noticeable, first coming through with acephate (orthene) and then coming back with the paraquat can help the peanuts recover quicker. Residual herbicide can also be added to the acephate (or the subsequent paraquat) to bridge the control windows.
Earlier planted peanut (35+ DAP) are blooming or nearing bloom. With this, land plaster is going out to support later pod fill. Thankfully, from what I’ve been hearing SC does not appear to have the same land plaster shortage GA appears to be seeing in cases. Starting rates for Virginia peanuts is 1500 lb/A. This can be bumped up in sandier fields, especially dry land, up to 2000 lb/A. Large seeded runners also benefit from land plaster, though the rate can be lessened some (1000 to 1500 lb/A).
Leaf spot
The attached pictures show some late leaf spot lesions found on volunteers from fields where peanut was planted last year and had leaf spot infections. It was easier to find volunteers without lesions, and even the ones that were there were pretty small. A key identifying feature is the bumpy dark black spores on the underside of the lesions.
Herbicide/surfactant burn can make a questionable shade of brown, though those do not have bumpy spores on the bottom and can also have lighter colored centers on the top of the leaf.
In starting fungicide programs for leaf spot, this should occur between 30 and 45 days. Starting protection earlier buffers against surprises. We continue to have a wet spring. this may get the gears of spore production up and running sooner compared to 2019.
Consider starting earlier closer to 30 days for fields with:
Shorter rotations (less than 2 years out of peanut; 2 yrs out pending other factors) or those near to fields that had leaf spot control challenges last year;
That are adjacent to fields with peanut volunteers this year;
Later planting dates (end of May into June);
More susceptible varieties (Virginia types, TUFRunner 511);
No in-furrow leaf spot activity.
Flexibility for starting programs closer to 45 days for fields with:
Less susceptible varieties (Georgia 06G, FloRun 331, TUFRunner 297);
Longer rotations since peanut (3+ years out of peanut);
No field history of leaf spot control challenges;
In-furrow products with leaf spot activity (e.g., Velum Total and Thimet); If starting later (45 days), consider adding fungicides with systemic activity.
We can buffer ourselves further by incorporating fungicides with systemic activity (e.g., Alto/Aproach Prima + chlorothalonil, Priaxor, Lucento…). This helps to mitigate spores that have begun invading the peanut leaf within the previous 2 days. Chlorothalonil (Bravo) is a great multi-site protectant that acts as a barrier for new spores when applied before infection, though it does not have the “reach back” activity of systemic products.
Bravo has been effectively applied with paraquat or with Cadre if those herbicides are going out at the same time when fungicide treatment is needed.
Fungicides with more white mold (and leaf spot) activity generally are positioned starting closer to 60 DAP.
Dan Anco

Extension Peanut Specialist and Assistant ProfessorDepartment of

Plant and Environmental SciencesClemson University – Edisto

Research and Education Center

64 Research Road

Blackville, SC 29817

803-284-3343 x261 office

630-207-4926 cell

danco@clemson.edu

Clemson Extension Peanuts