Citrus Disease: What to Watch for in Georgia

Tacy CalliesDiseases

disease
Greasy spot on citrus leaves

The citrus greening disease (huanglongbing or HLB) that has devastated Florida’s citrus industry over the past decade has not affected Georgia commercial production. However, growers should still be aware of the potential danger it can bring.

According to Jonathan Oliver, fruit pathologist and Extension specialist in the Department of Plant Pathology at the University of Georgia (UGA), all confirmed HLB-positive trees in Georgia have been residential citrus trees. “We have not found HLB in commercial plantings,” says Oliver. “It doesn’t mean it’s not there. But in our surveys, we have not identified it.”

Currently, HLB is confirmed in Bryan, Chatham, Camden, Lowndes and Pierce counties. Even though only residential trees seem to be infected so far, the presence of HLB represents a threat to nearby commercial production. (Read “HLB Update for North Florida, South Georgia” for more details.)

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Oliver recommends that commercial growers vigilantly monitor new plantings for HLB and the Asian citrus psyllid that carries the disease.

“These (residential trees) are typically not managed in many cases, so populations of the vector could potentially build up on infected trees and move about from there to infect our commercial plantings,” he says.

According to Oliver, some of the best ways to prevent establishment of HLB are to not move plants from infested areas and to avoid receiving materials from infested states unless from a U.S. Department of Agriculture-certified vendor.

In addition to citrus greening, there are other citrus diseases present in Georgia. These include citrus scab, anthracnose, phytophthora root rot and greasy spot. Brown rot of fruit and melanose are diseases that have been identified in Florida and could become a threat to Georgia.

Oliver offers some advice on spray timing. During the pre-bloom time frame, growers should be most concerned with citrus scab, especially if it has been an issue in the past. Toward petal fall and post-bloom (about three to four weeks after petal fall), growers should be spraying for citrus scab and melanose. Early summer is the perfect time to begin greasy spot sprays, which will also help control melanose. Toward the late summer and early fall is when brown rot becomes an issue, so growers should target their sprays then. As far as phytophthora root rot goes, any time the plant is growing, the soil should be treated.

For citrus disease diagnostic questions, commercial citrus producers in Georgia are encouraged to contact their local UGA Extension agent.

Ashley Robinson, AgNet Media communications intern, wrote this article.

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