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Pecan Crop Needing Some Sunshine

With the exception of some scab pressure throughout July, we’ve had pretty good growing conditions all season to this point and the appearance of the crop shows it. Growers have done a fine job of protecting the nuts from scab throughout the rainy periods. Industry forecasts currently have Georgia estimated at about 130 million lbs. But, as we have learned in years past, just because we can see the finish line, doesn’t mean we’ve crossed it.

We have been in a similar position as recently as last year when we had low solar radiation season-long. But, the most serious blow to the 2021 crop came from cloudy weather during the kernel filling stage. The sunniest part of the year in our part of the world usually runs from September 11-December 10. If you recall, crop development in 2021 was somewhat late. For these purposes, solar radiation is measured in energy units known as megajoules per square meter (MJ/m2). During that time period from July-September, anything over 20 MJ/m2 represents good solar radiation on a sunny day. As we reached the final stages of kernel filling for most mid-season maturity cultivars during the 7 day period of September 16-22, 2021, solar radiation levels were, for some locations, half of what they should have been. During this period in 2021, Ft. Valley’s solar radiation averaged 10.1, Cordele averaged 12.7, Tifton averaged 12.9, and Albany averaged 12.1. Thus, it appears that we simply did not get the solar radiation at the time we needed it to fill the kernels properly.

This year, we had good solar radiation up through shell hardening of most mid-season harvest varieties. For the last week, we have seen nearly continuous cloudy weather over much of the pecan producing region of the state. From August 1-August 16, solar radiation averaged 21.65, 22.33, 20.1, 19.04 MJ/m2 for Cordele, Ft. Valley, Tifton, and Albany, respectively. Since August 16, these same locations have averaged 16.1, 14.7, 15.7, and 15.06 MJ/m2 .

Our crop appears to be relatively on time this year, if not a week or so early. Pawnees have completed kernel filling. We should see a normal kernel filling period of August 15-September 15 for our mid season harvest varieties.

Kernel filling is an extremely energy demanding process. Even under optimum conditions, pecan trees can be somewhat depleted of energy during the carbohydrate manufacturing process by which the kernels are filled. However, when one of the 2 key ingredients (soil moisture and sunlight) is missing there is often not enough energy to finish out this process. The heavier the crop load on the tree, the more demanding the process.

The good news at this point is that we still have some time. We still have a ways to go before the kernels are done filling and this means if we can get some clear, sunny days over the next few weeks and accumulate some better solar radiation levels, it will help to fill the crop out and leave the trees in better condition for next year.

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About Lenny Wells

I am a Professor of Horticulture and Extension Horticulture Specialist for pecans at the University of Georgia. My research and extension programs focus on practical cultural management strategies that help to enhance the economic and environmental sustainability of pecan production in Georgia.