Sting Nematodes in the HLB Era

The University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center hosted an OJ Break seminar in mid-May. Topics included management of nematodes, results of trunk-injection therapies and the use of cover crops in citrus.

Larry Duncan, a UF/IFAS professor of nematology, presented research findings on the impact of sting nematodes in citrus. He provided a history of the nematode, which became a pronounced problem after the 1980s freezes and subsequent replanting of many Florida groves.

The sting nematode loves grasses. So, when mowing replaced disking in groves, the pest had a more reliable food source to get established. However, the sting nematode problem receded somewhat as trees grew older after the surge of new planting that occurred after the freezes.

“When we replanted those groves back in the 1980s, you’d have these spots where there was not good growth of the trees,” Duncan said. “That was sting nematodes. We did a lot of research on the sting nematode back then and showed it to be responsible for the lack of tree growth and affected root systems. But those groves remained profitable even with the nematode. That’s not the case today.”

The reason for the change is the presence of HLB in groves, which has greatly reduced production and profitability. Duncan did offer some good news, however. He said recently developed rootstocks are more tolerant to sting nematode than previous generations of rootstocks that were commonly used in the 1980s.

Duncan also noted that cover crops can help reduce sting nematode populations in groves. Sunn hemp and perennial peanut are good crops to help remove the pest from the soil.

The nematologist presented results of research that studied the effectiveness of six nematicides. The research found that oxamyl was the most effective against sting nematode among the treatments. However, given the persistence of HLB and its impact on tree health and productivity, the study showed that by the time the trees were 4 years old, the treatments were not profitable enough to justify the applications.

Learn more on nematicides and cover crops here.

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