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Peanut Injury from Valor & Thimet

I have received calls this week about how some of our peanut crop is looking. There are several things going on that I wanted to address:

  1. There is some Valor damage showing up after the rain we’ve been getting; most especially in fields that didn’t receive any rain until they had already started cracking.
  2. I have also seen some damage from Thimet applied in-furrow.

Growing conditions are not ideal right now, but with a little sun they will grow out of this and be fine. Here are some peanuts I looked at this week that had a little bit of both Valor and Thimet injury.


3.  There is also some yellowing going on that we are not used to seeing that I wanted to point out. Here are some comments from Extension Peanut Agronomist, Dr. Scott Monfort and Dr. Cristiane Pilon:

I have received several phone calls regarding yellow peanut from across the state.  A majority of the peanuts in question were planted between May 8 and May 12 and have experience very similar weather conditions.  Dr. Cristiane Pilon visited the peanuts in Colquitt county with me and has provided a more detailed explanation than I could have put together other than weather.  The plants should recover once we begin to get some sunlight and begin to dry out. Please see Dr. Pilon’s comments below:








Three major environmental conditions may be playing a role in the peanut plant development (leaf yellowing) these past days: sunshine, humidity, and to a lesser extent, temperature.


Leaves have small pores (known as stomata) that allow water vapor to be released (transpiration) and carbon dioxide to enter (photosynthesis). Environmental signals will trigger stomata to open or close. Low light intensity, high humidity, and low temperature usually signal the plants to close their stomata.

Water and nutrients move from roots to shoot through transpiration. For this process to take place, a difference in water potential between the soil and atmosphere surrounding the plant is needed, creating a gradient and driving water and nutrients upward (against gravity). The drier the air around the plant, the higher the transpiration, if water is available. The opposite is also true. High relative humidity surrounding the plants does not allow for this difference in gradient, stomata remain close and transpiration is reduced. This is probably what is happening with the high humidity promoted by the rain we got these past days.

Without enough light and stomata close, photosynthesis also decrease. This condition can create yellowing in the leaves and slow down growth.


I have checked the integrity of the leaf photosynthetic structures and they are normal. The issue is on the efficiency to capture and move energy to complete the photosynthesis process. Since the physiological structures are not impaired, the plants should be able to recover when weather changes and we get more sunshine to decrease humidity and increase temperature.