Garfield County Cooperative Extension

Falling Pecans

Rick Nelson Extension Educator, Ag/4-H

Falling Pecans

Every year, usually in August, I hear another sad story – it’s raining pecans! What can start out as a bumper crop might look like it will all end up on the ground months before harvest time. A certain amount of premature nut drop is unavoidable. Here are some of the reasons why pecan trees shed their crop early.

Shortage of Nutrients. This can cause pecans to drop at any time during their development, but most of these drops occur in August and early September as the nuts are rapidly growing and filling. Drops due to a shortage of nutrients will always be greatest on heavily loaded trees. In many cases, the nutrient-deficient nuts that drop will be abnormally small on the basal or stem end. Nitrogen and zinc are the most commonly deficient nutrients in pecans. Good fertilization practices starting in early spring are needed to avoid this problem.

Soil Moisture Stress. Pecans require a very large amount of soil moisture to mature satisfactory crops of nuts. A shortage of water in the late spring or summer will result in small pecans that will shed in large numbers in July and August. This is probably the number one reason pecans fall at that time. Soil saturation from excess rain can also cause stress symptoms and related nut drops.

Regular, soaking irrigations (preferably weekly) are needed to avoid stress-related drops. Apply at least 1 to 2 inches per watering when using a sprinkler (measure with a rain gauge, tin can, etc.) or water for 8 to 10 hours per application with a drip system. Remember that the tree’s root system extends out to and well beyond the ends of the branches. This is where the active roots are – not near the base of the trunk.

Nuts of certain tightly filled varieties, like Wichita and Cherokee, will split and drop in August and September if stressed excessively between irrigations. Also, very large varieties, like Mahan and Mohawk, are notoriously difficult to fill and poor nut quality often results in dry years when irrigation has been insufficient in August and September.

Pest-related Damage. There are several insects and diseases that can cause nut drop. The pecan nut casebearer is a tiny worm that bores into the base of the nut and hollows it out. The major attack is in late May or early June, but later generations in July and August can also cause nut drop, but to a much lesser extent.

Stink bugs and their relatives suck sap from the nuts. They can be a continual problem throughout the summer. Damage prior to shelling hardening (mid-August) causes the nut to blacken internally and drop. Nuts injured after shell hardening mature with blackened, bitter tasting spots on the kernels.

Pecan scab is fungal disease that causes dark spots or lesions on leaves, twigs and the shuck of pecans. A severe infection can cause premature nut shed, particularly in August and September.

If all that weren’t enough, at the end one will still have to fight off the squirrels for the maturing crop.

Bottom Line. What I always come back to is the fact that it is not an easy task to bring a good crop of pecans to maturity. It takes a lot of water and regular spraying to keep the crop clean and healthy. So, I figure let the commercial folks grow the pecans for me and I’ll buy them in the store for a lot less time and money than I could raise them. Enjoy your pecan trees for the great shade they provide and be thankful for the years you do get a nut crop.

 

 

 

Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Oklahoma Cooperative Extension Service is implied.

 

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