This finding is the first confirmed PBLS case in Arizona pecan. The disease was confirmed in New Mexico in mid-August, according to NMSU Plant Pathologist Natalie Goldberg.

Unknown is whether the disease is found in pecan in California.

PBLS is found in some southeastern U.S. pecan orchards in different pecan varieties.

In Arizona, PBLS has been confirmed in the Western and Pawnee varieties.

Disease cause

The disease is caused by a strain of the bacterium Xylella fastidiosa, which is carried from plant to plant by xylem-feeding insect vectors. Olsen says the vector in Arizona has not been identified.

In other pecan-growing states, PBLS vectors include members of the Cicadellidae (leafhopper) and Cercopidae (spittlebug) families. Studies by Louisiana State University suggest the vectors include the glassy-winged sharpshooter, leafhopper, and adult spittlebug.

Leaf scorch diseases caused by different strains of Xylella fastidiosa are found in other crops, including California-grown almonds, grapes, and olives causing reduced yield and often plant death.

This disease has had a devastating impact on residential oleander plants in the greater Phoenix area.

Olsen and UA Cooperative Extension Horticulture Agent Joshua Sherman are conducting an Arizona grower survey on the disease to determine its distribution in pecan throughout the state.