Can Physical Barriers Improve Sting Nematode and Root Weevil Management?

Larry Duncan, professor of nematology with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), recently presented his research regarding the management of sting nematodes and diaprepes root weevils. The presentation was part of an ongoing series of Zoom meetings organized by Mongi Zekri, UF//IFAS citrus Extension agent.

STING NEMATODE

Sting nematode is an important pest, especially in younger citrus trees. With the amount of new trees being planted, Duncan noted this is an essential pest to monitor.

He has observed some benefit of planting cover crops to help suppress sting nematodes. Sunn hemp, velvetbean and perennial peanut have shown some suppression of the pest.

In addition, modern rootstocks seem to resist sting nematode better than earlier ones like Cleopatra. According to Duncan, UFR-5 rootstock is one that appears to be more resistant.

He also discussed research comparing different nematicides to manage sting nematode. Oxamyl was the most effective. However, the research showed that managing sting nematodes with nematicides in an HLB-endemic environment was not cost effective.

Duncan observed a grove next to his nematicide trial that also was highly infested with sting nematode. These trees had individual protective covers (IPCs) and looked much better than those in his nematicide trial.

“We noticed the difference in growth in that grove,” he said. “So, it raised the question: Is it worth applying nematicides where we have IPCs? And, after the covers come off, are those trees and root systems far enough along to grow past sting nematode problems?”

Duncan has started a new trial with various treatments comparing IPCs with non-covered trees to get answers to these questions.

DIAPREPES ROOT WEEVIL

Duncan has conducted research on the use of ground covers to lower the incidence of diaprepes root weevil in citrus. The concept is the cover acts as a barrier to the root weevil larvae entering the soil where they damage the roots and make them vulnerable to phytophthora.

“We know the fabric improves water-use efficiency, helps with weed management and reduces herbicide programs,” Duncan said. “Tree growth is better, but not as good as IPCs. The degree to which ground covers help with weevil management is still somewhat unknown.”

Duncan is conducting research to get a better handle on weevil management using ground covers. The trial is in its second year. The research already shows the cover does limit the entry of weevil larvae into the soil. But ground covers are expensive, so further research is required to determine if it is a profitable practice.

View Duncan’s full presentation here.