Antibiotics, HLB and Psyllids

Entomologist Kirsten Pelz-Stelinski recently shared findings from trials on the use of foliar-applied and trunk-injected antibiotics for controlling HLB and the Asian citrus psyllids (ACP) that spread the disease. Pelz-Stelinski is associate center director at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center (CREC) in Lake Alfred. 

In a May 17 presentation at CREC, Pelz-Stelinski emphasized that ACP infestation reduces tree health with and without HLB. “The combo is lethal,” she stated. She added that the current practice of managing ACP with broad-spectrum insecticides is unsustainable because of its high cost and ACP resistance to insecticide. 

“Only IPCs (individual protective covers) prevent young tree infection” by HLB, Pelz-Stelinski reported, referring to trials testing foliar application of the antibiotics oxytetracycline (OTC) and streptomycin as well as IPCs. Those trials also indicated that there is less HLB infection in ACP that were caged on mature trees treated with foliar antibiotics. There was also reduced acquisition of HLB by ACP from trees treated with foliar antibiotics, she noted.

A summary slide on managing psyllids and HLB stated that:

• Psyllid density is related to tree stress. More psyllids lead to higher damage, which compromises tree health and yield.
• Antibiotics reduce HLB infection in ACP.
• OTC injection appears promising for reducing fruit drop and increasing citrus yield while improving fruit-quality characteristics.
• Trunk-injected OTC treatment seems to be showing promising results. Researchers are working to obtain more data from the field.

A take-home message stated that foliar antibiotics are not effective for preventing HLB in young citrus trees or managing existing HLB infections in mature trees. The presentation also concluded that antibiotic foliar applications do reduce HLB transmission and reduce HLB acquisition by ACP nymphs.

Pelz-Stelinski will become director of the UF/IFAS Mid-Florida Research and Education Center in Apopka on Aug. 1. Read more about her appointment here.   

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