Management of the Guava Root Knot Nematode in Sweetpotatoes

— Written By

In recent years, some North Carolina sweetpotato growers have found Meloidogyne enterolobii, also known as the guava root knot nematode, affecting their crop. These reports have prompted previous alerts from the North Carolina Department of Agriculture and the NC State Vegetable Pathology Lab, as well as research regarding chemical control methods. Management information available to date is described in our sweetpotato root knot nematode fact sheet.

This root knot nematode was reported infecting cotton and soybean in North Carolina in 2013, and has also been officially reported in Puerto Rico (1988) and Florida (2012). Recent reports of M. enterolobii from Louisiana have resulted in the enactment of an internal quarantine from the North Carolina Department of Agriculture & Consumer Services to help prevent further spread of this nematode. Following this action, the Louisiana Department of Agriculture and Forestry also enacted an external quarantine for Florida, South Carolina, and North Carolina to restrict entry of items that can potentially spread M. enterolobii.

The North Carolina internal quarantine states that sweetpotato seed roots need to be inspected and certified to be free of M. enterolobii and soil before they leave the state. Sweetpotato slips will also be required to have no soil or roots on them before they can leave the state. Sweetpotato roots for the fresh market are not regulated under this quarantine. For specific questions regarding how the inspection and certification process will be implemented, please contact your NCDA Plant Protection Specialists. It is important that you make plans for this process with enough time since M. enterolobii cannot be identified visually, which means that sweetpotato seed root samples with general root knot nematode damage will need to be sent to the NCDA Nematode Lab for specific identification of M. enterolobii. Because multiple producers may be seeking certification of a shipment at one time and the molecular testing required to do this is time consuming, this may delay the process. Samples found to be positive for M. enterolobii will not be allowed to leave the state. Sweetpotato slips only need to be free of soil and roots and may not need the more specialized molecular testing to undergo certification.

The Louisiana external quarantine states that sweetpotatoes, soil, and equipment from Florida, South Carolina, and North Carolina that may harbor M. enterolobii cannot enter Louisiana. Equipment can enter Louisiana only if it is free of soil and has a certificate from the state of origin that indicates that the equipment is clean and has been inspected. Certified seed sweetpotato roots will be allowed entry with a special permit from the Louisiana Department of Agriculture and Forestry. Nursery crops will be allowed entry with a certificate from the state of origin that indicates that they are free of M. enterolobii.

North Carolina sweetpotato growers are recommended to implement aggressive management strategies to prevent M. enterolobii from entering fields and to reduce nematode levels in already infested fields. Management recommendations are available in our sweetpotato root knot nematode fact sheet and previous alerts. If you observe root knot nematode damage in your sweetpotatoes, we strongly suggest contacting your local extension agent and sending samples to the NC State University Plant Disease and Insect Clinic or the NCDA Nematode Lab. Sweetpotato growers are also encouraged to determine nematode levels in their fields by submitting samples to the NCDA Nematode Lab and fumigating with a high rate of 1,3-dichloropropene if the nematode threshold warrants it. The NCDA Nematode Lab can test soil to detect M. enterolobii but this service needs to be specifically requested in the submission form for soil samples.

As is the case with other root knot nematodes, M. enterolobii can be spread through infested soil and infected plant material. It is critical that growers that have infested fields with M. enterolobii avoid moving soil via farming equipment to uninfested areas. Not planting pulled sweetpotato slips or infected seed roots is also essential to avoid infesting your fields. Planting certified clean sweetpotato seed is recommended, which can be obtained from certified sweetpotato seed producers. Also, keep in mind that planting infected material will negate any control provided by soil fumigation.