Control Methods Needed in Sweet Potato Production

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In mid-November, a new root knot nematode was discovered in a sweet potato field in Sampson County. The nematode is Meloidogyne enterolobii, and commonly referred to as enterolobii. This nematode is far more prolific and aggressive than other root knot nematodes, and can threaten crops due to the extensive damage that it can cause.

Crops that have been affected in the US by this nematode include sweet potato, watermelon, cucumber, pepper, tomato, potato, tobacco, soybean, and cotton. Many of these crops have varieties that are host resistant to root knot nematodes. However, this resistance is not effective for the enterolobii species, therefore additional control methods will need to be implemented for its control.

NCSU vegetable pathology lab has conducted several trials on enterolobii control and found that soil fumigation before planting with the active ingredient 1,3-dichloropropene found in products such as Telone II is effective in controlling this nematode. Further testing is being conducted on other products and active ingredients and the information will be forthcoming when testing is completed.

The only way to determine if your fields are infected with the enterolobii nematode is to collect nematode samples from your fields and submit as a research sample for molecular diagnosis. Dr. Weimin Ye, NCDA&CS chief nematologist, recommends that if initial nematode samples indicate that there are 1000 nematodes per 500cc of soil, that a second sample should be collected and submitted as a research sample. The fee for a research sample is $10.

As is the case with other root knot nematodes, enterolobii can be spread through infested soil and infected plant material. It is critical that growers that have infected fields with enterolobii avoid moving soil via farming equipment to uninfected areas. Not planting pulled sweet potato slips or infected transplants is also essential to avoid infecting your fields. Also keep in mind that planting infected material will negate any control provided by soil fumigation. Bin boxes may also become contaminated with enterolobii nematodes. Dr. Ye recommends steaming bins or disinfecting with a 50% chlorine solution to kill nematodes or their egg masses that may be left in bin boxes.

If you observe root knot nematode damage in your crops, we strongly suggest that you collect nematode samples and send to the NCDA&CS nematode lab ($3 each), collect plant samples and submit to the NCSU Plant, Disease, and Insect Clinic ($30) and contact your local extension agent.

For more information on this nematode, visit the NCSU Extension Plant Pathology portal at https://plantpathology.ces.ncsu.edu/2017/05/emergent-nematode-in-sweetpotato-and-other-vegetable-crops/.

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