Pod Rot Peanut Notes No. 175 2023

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Question:

I’m trying to diagnose the cause of this pod rot I’m seeing. This is in Lenoir County, and these peanuts are behind tobacco. The grower had a similar issue last year that wasn’t noticed until harvest time, also in fields behind tobacco. Samples submitted after harvest were inconclusive. Can you ID by these pictures? Or know who to ask? Or know where I should submit samples?
Answers:
David Langston:
Could this be the result of southern corn rootworm damage? I see holes in 2 of the pods.
Dan Anco:
Following David’s question, other questions I would be curious about include how much of the field was affected like this, and what were the soil test results in that field, for example, for K? While not necessarily the case here, in a different field I have seen a ton of potash applied to tobacco prior to planting peanut, which resulted in serious pod fill problems there due to excessive K interfering with Ca absorption. Curious what Rick says on the insects.
Rick Brandenburg:
Doesn’t really fit anything. I thought with tobacco rotation, maybe wireworms, but I don’t think so. Not rootworms and I don’t think cutworms although those can be quite variable. Burrower bugs? Not consistent with that either.
Jordan:

This may be pod rot caused by excessive potassium that prevents calcium from moving into developing pegs and pods. This occurs when previous crops were fertilized with relatively high amounts of potassium. That is not uncommon in tobacco, and given it happened last year with the same rotation, it points to that possibility. Issues with pod rot can be exacerbated in some cases when soils are dry but this can also happen when adequate water is present. Under dry conditions, there is less soil water to move calcium (native in soil or from gypsum) into the developing fruit. When K is high in the pegging zone, the amount of calcium that gets into the fruit can be even lower. Potassium can also occupy sites on soil colloids that allow calcium to move through the pegging zone with water from rain or irrigation. The calcium only has to leach a few inches down in the profile to be out of the pegging zone.

There is nothing that can be done at this point to correct the issue. Hopefully it won’t be widespread. It would be interesting to see a soil test to see just how high the K is in the soil. The consensus from the group is that the problems with the pods are not caused by disease or insects. It is possible that overtime secondary pathogens could establish themselves on the damaged pods and kernels, but the problem is more than likely caused by not having enough calcium in pods and kernels, and the reason for that is likely elevated K that is compounded by dry soils.
We recommend that farmers apply K to peanuts if the soil test recommends it. It does not hurt to use modest levels for maintenance in peanuts. In surveys, well over half of growers apply potash to peanuts. Back in the day, K was not recommended for application the year peanuts were planted. The recommendation was for application needs for peanuts to be addressed in the previous crop. Deep tillage to distribute the K throughout the soil profile to keep it from being at high levels in the pegging zone.