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Guava Root-Knot Nematode: A Potential New Pest for Midsouth Soybeans?

On Thursday, Sept. 6, Carol Bullard, MSPB Administrator, sent me an email about her conversation with Mr. Michael Ledlow, Miss. Bureau of Plant Industry Director, regarding the Guava root knot nematode (RKN). Since I had not seen (or rather passed over) a recent article in Delta Farm Press by Brad Robb (July 27, 2018) about this new pest found in Louisiana, I realized I should find out just what is known about this pest and its potential to infest Mississippi soybeans.

The first article that I am aware of about this pest’s occurrence in the Midsouth is one by Dr. Charles Overstreet (LSU Professor in the Plant Pathology and Crop Physiology Dept.) titled “The Guava root-knot nematode–A new pest in Louisiana”. Dr. Overstreet emphasizes the following points about the Guava RKN pest.

•   The Guava RKN is considered one of the most damaging nematodes in the world because of its wide host range, aggressiveness, and ability to overcome current RKN resistance in crops.

•   Presently, it is thought to have very limited distribution in Louisiana, occurring at only one location.

•   Since it is likely that this nematode will spread, producers should be aware of what to look for.

•   The Guava RKN is very similar to the common Southern RKN that is pervasive in the Midsouth (and increasing in prominence as per my conversations with Miss. pathologists).

•   Distinguishing between Guava and Southern RKN’s can be difficult because both can produce rather large root galls.

•   Its presence can be recognized when plants that are resistant to Southern RKN have large galls on their roots and suffer serious damage.

•   The isolate found in Louisiana is particularly damaging to sweet potato and tomato, but soybean, cotton, and peanut are also susceptible to this pest.

•   The best defense against this potential nematode pest is to prevent its incursion into uninfested fields where susceptible crops are/will be grown.

Public agency and regional commodity group administrators are aware of this new pest and its potential to infest Midsouth soybeans. Hopefully, their support for a proactive vs. reactive approach will lead to increased knowledge about this pest and the development of potential remedies that can be used if/when it invades upper portions of the Midsouth.

The intent of this article is not to convey a doomsday scenario, but rather to make producers, consultants, and other agricultural practitioners aware of this new invasive pest so that they can be involved in its detection and use/evaluation of possible remedies should they be necessary.

Composed by Larry G. Heatherly, Sept. 2018,