Pecan scab

About

Scab is the most important pecan disease in humid areas. It attacks both leaves and nuts, and badly infected trees drop nuts early or fill them poorly (Clemson; NC State).

Also called pecan scab, scab (pecan), pecan_scab

How to recognize it

Symptoms

The fungus infects leaves and young nuts (NC State). Heavy infection strips leaves and makes nuts drop early or fill poorly (Clemson).

Worse when

Rainy, humid weather; Texas A&M notes that scab-prone varieties can't be grown well in rainy areas without fungicide sprays, and poor air movement around the tree makes it worse (Clemson).

How it spreads

It carries over the winter on old leaves and shucks under the tree (Clemson).

When

During the growing season in wet weather.

Where

Worst in humid areas such as the Southeast and East Texas; Texas A&M flags higher scab risk for susceptible varieties in the eastern part of the state.

What to do, gentlest first

Prevention works best; most sprays only protect healthy leaves and can't cure infected ones. Always read and follow the product label.

1. Plant scab-resistant varieties Prevent

   This is the best control for home trees (Clemson). Resistant choices include Elliott, Kanza, Lakota, Gloria Grande, Cape Fear, Stuart and Creek; avoid Pawnee, Desirable and Oconee where scab is common.

   Sumner was long rated very resistant, but some scab has shown up on it in Georgia (UGA).

2. Let air move Prevent

   Plant where air moves freely and remove limbs that touch the ground so leaves dry faster (Clemson).

3. Winter cleanup By hand

   Rake up and dispose of fallen leaves and shucks in winter to cut down next year's infections (Clemson).

4. Fungicide program (orchards) Conventional spray

   Susceptible varieties need a full-season fungicide program where scab is common (UGA), but Clemson notes that spraying large backyard trees usually isn't practical.

   Follow the label.

Plants it affects

Pecan