Late Summer Pecan Scab Nut Shed

by Jan Yingling, CEA - Agriculture

Are you experiencing an early nut shed in your home orchard?  Pecan scab could be the culprit.

Pecan scab is a fungal disease that causes dark spots or lesions on leaves, twigs and the shuck (husk around the nut) of pecans. This disease will infect susceptible varieties early in the pecan growing season in Arkansas and can be devastating depending on weather patterns.  As the disease and the growing season progress, secondary scab infections can begin in your orchard from the spore-producing lesions early on.  Scab will then spread throughout the orchard wreaking havoc on twigs and shucks, eventually causing a loss in tree vigor and yield.   A severe scab infection can cause premature nut shed, particularly in August and September in Arkansas. 

What causes pecan scab nut shed?

Several issues can cause nut shed in your orchard including disease, insect damage, irrigation stresses, and overbearing nut loads.

How is it prevented?

If a fungicide spray program to control pecan scab is not feasible for you as a homeowner and you have susceptible varieties of pecan trees in your orchard you will need to rely on cultural techniques to protect your crop.

Orchard sanitation is extremely important for the prevention of disease issues.  Any plant material left in the orchard during the fall, winter, and early spring will provide a place for the pecan scab spores to overwinter.   When spring rains arrive, those spores are then splashed into your orchard starting the process all over again.  Raking and burning plant material after harvest can help reduce plant material therefore reducing the number of spores in the spring.

Limiting as many other stressors as possible for the trees in your orchard can help too.  Provide ample irrigation and proper nutrition to limit the stress on your trees.  Trees are much like people in that, the less stressed they are, the healthier they are and can resist more disease.  Additionally, pruning and thinning your orchard to provide ample airflow through the foliage can help. 

The pecan scab fungus thrives in hot, humid conditions.  Air flowing through the canopy can help to dry moist foliage therefore making the environment less favorable to the scab fungus.

If you have a late summer nut shed in your pecan orchard, look at your foliage and check for dark green to black sunken lesions on the leaves, twigs, and shucks.  Send them to your local county agent for free help identifying the disease.  

Want more tips? Visit our Arkansas Pecan Production webpage.