Spots in the Canopy Peanut Notes No. 187 2020
In recent weeks, growers, consultants, dealers and distributors and Extension specialists and agents have seen spots on leaves associated with Provost Silver. These spots likely will pose no threat to peanut yield but they are confusing in that they look like the leaf spot diseases we are spraying fungicides to prevent. However, when plated out the lesions do not sporulate.
Over the years we have observed similar injury with Provost. Dr. David Langston looked closely at his plots in Virginia and found spots present in the canopy. The location was associated with Provost Silver applications. Images are included in the link below. I have observed similar spots in the disease management trials I have at Whiteville. Next week I will look closely at the treatments I have that contain Provost Silver (trials at both Lewiston-Woodville and Whiteville) to see if more injury is present. While the spots are not going to be yield limiting, they do cause confusion on effectiveness of fungicide sprays. There has been a degree of panic with some about how to handle this. If you are seeing spots that look like early or late leaf spot consider where they are appearing in the canopy. In most cases, leaf spot will begin infecting the lower part of the canopy first and over time spores will infect the mid and then upper part of the canopy. It is possible to have infection and lesions for these pathogens higher in the canopy and not at lower levels, but generally leaf spot lesions (those caused by pathogens) will be present at the lower level and then move up over time. If you are seeing scattered spots in the upper part of the canopy and leaves in the lower part of the canopy are healthy, it is likely the spots are caused by a chemical.
Also, very few people are spraying one thing in the tank these days, and we don’t know how all of these components affect peanut response and possible injury. This may be contributing to injury we are seeing.