Guess the Pest! Week 20 Answer: Root Knot Nematode

David Owens, Extension Entomologist,

Congratulations to Mike Ciborowski for correctly figuring that what has happened to this field is an outbreak of nematodes. Mike will be entered in for the end of year drawing for a scouting toolkit.

This from Dr. Alyssa Koehler:

To figure out the culprit of last week’s Guess the Pest, we have to look underground where we can see extensive galling of the root system caused by Root Knot Nematodes (Figure 1). At lower populations, aboveground symptoms are difficult to observe, but in highly infected fields non-uniform stunting, wilting, and chlorotic patches can all be visible (Figure 2). Nematodes can be moved mechanically through equipment, workers, and vehicles. Sanitizing equipment between affected fields can minimize the chance of moving nematodes from one field to another. Due to a wide host range, rotation options are limited. Selecting soybean varieties with resistance to RKN is the most cost-effective management strategy.

Figure 1. Severe root galling on soybean caused by root knot nematode

Figure 2: Soybeans plants from the same field with varying levels of stunting due to infection by root knot nematodes