Dry and hot now and looks like into the week ahead for parts. Peanut has some flexibility for water during this part of the season compared to later during pod fill, but some good and needed rain will go a long way in helping them all the more. Hot and dry conditions can increase insect activity as well as some diseases including but not limited to white mold and the less frequent Diplodia collar rot. Not many options should Diplodia come around for dryland fields, as it is mostly a disease during stressful conditions that is more cosmetic than economically damaging.
Delaying fungicide application?
Can we delay our fungicide applications with it being so dry and hot? We do have some flexibility as far as leaf spot is concerned to delay a few days. If a field with a susceptible cultivar has some history of white mold/stem rot in it, hot and dry conditions are favorable for its development, in which case extended delaying would not be optimal for its management.
Paraquat burn on peanut can look unpleasant but keeping the application inside the recommended window (28 days after cracking, ballpark 35 days after planting) bodes well for its recovery without a drag on yield.
Cadre is compatible to be applied with several fungicides, including Bravo or Lucento or Provysol, or several others.
TSW
Symptoms of infection by tomato spotted wilt virus are starting to show more prominently in earlier planted fields. Visual symptoms in the canopy range from chlorotic yellowing, to ring spots, to mottling, stunting, and more. Our management options for this disease are preventative in nature, effectively being sealed and finalized once planting is finished. Taking notes now will allow their use for consideration when planning next year's production practices.
As a general precaution, avoiding mowing around peanut fields during prolonged hot and dry conditions will help to reduce movement of pests (mites) into fields if present.
LCB
Continued hot and dry weather is also favorable for lesser cornstalk borer. Larvae can be damaging to peanut by boring into plant tissues above and below ground and have been associated with increasing risk for Aspergillus flavus, aflatoxin, and white mold. LCB is more common in highly sandy soils. Pictures of the larvae, silk tubes they create on the peanut plant, and a pupa are included in the attached pictures from a dryland sandy field. Like some other insects, LCB can more preferentially land on and be first found on more isolated plants with a gap around them (skippy sections). To scout a field, at least 10 different spots should be looked at for the presence of larvae or pupae. If between 10 and 30% of plant spots have larvae or pupae, treatment is recommended with a targeted insecticide such as chlorantraniliprole (Vantacor/Prevathon/Shenzi) or novaluron (Diamond). If plants are not yet pegging, I would use the higher threshold (~25 to 30%) versus a more conservative lower threshold (~10%) if actively pegging with pod fill having begun.
Dan Anco
Extension Peanut Specialist and Associate Professor
Department of Plant and Environmental Sciences
Clemson University – Edisto Research and Education Center
64 Research Road
Blackville, SC 29817
630-207-4926 cell