Diseases

Pecan Scab

Carya illinoinensis (Wangenh.) C. Koch

The most economically significant fungal disease of pecans, caused by the pathogen Venturia effusa. It affects leaves, shoots, and fruit, causing the appearance of dark, velvety spots and premature crop drop.

In the reference 3 varieties crop Pecan, where this is mentioned in the description.

The disease is caused by the fungus Venturia effusa, which was previously classified under a number of synonyms, including Fusicladium effusum. The pathogen population is genetically diverse and represented by numerous pathotypes that adapt to specific cultivars, leading to the gradual breakdown of varietal resistance in production regions.

Symptoms of the infection appear on all actively growing parts of the tree as small olive-green spots, which eventually darken and become velvety. The coalescence of lesions on the shucks leads to cracking and deformation, while on leaves, the affected areas may fall out, causing a shothole effect.

Specific resistance genes in pecans have not been identified, so breeding is conducted through quantitative trait loci (QTL) mapping. Cultivar resistance is assessed empirically on a scale of 1 to 5 based on field observations that account for the plants' response to local pathogen pressure.

General information about the subject — on the page Scab.

Sources8

Varieties of Pecan mentioned in the description

Selection based on the description text, not on official evaluation: these data are absent from registers. For specific variety details, please refer to its profile.