Introduction

The reniform nematode is not a common nematode pressure for soybean growers in North Carolina, but is limited to several southern counties of the state. This nematode is very damaging in other southern states, and can be yield limiting where it is found in North Carolina. Detection is difficult because the nematode does not produce root galls like root knot nematode or cysts like soybean cyst nematode.

Pathogen

The reniform nematode, Rotylenchulus reniformis, is a sedentary semiendoparasite, meaning that the nematode's body survives on the outside of the root and is no longer mobile after establishing a feeding site. Reniform is commonly found in subtropical and tropical regions, and is an endemic nematode in southern soybean production regions. Sedentary female nematodes can be observed on roots with a hand lens, and appear kidney-shaped.

Host Range

More than 300 species of plants are host for this nematode; among them, cotton, cowpea, soybean, pineapple, sweet potato, and various vegetables are susceptible hosts.

Symptoms

Reniform nematode damages include general stunting and chlorosis of infected plants in the field. Aboveground symptoms are usually more uniformly distributed within fields other nematode species found in North Carolina. Roots may be stunted and less developed. Foliar symptoms may appear similar to nutrient deficiency symptoms. It is difficult to visually see reniform nematodes with the unaided eye, unlike other common nematode pressures in the state (root knot nematode and soybean cyst nematode). Should reniform nematode be suspected in a field, soil samples or root samples should be submitted to a diagnostic lab for confirmation.

Disease Cycle and Conditions Favorable for Disease

Reniform nematodes overwinter as eggs in egg masses attached to roots or as juveniles and immature adults free in the soil. In the spring, immature adult females partially enter roots and establish a feeding site. As the females mature, they become kidney-shaped and sedentary. Once females become established, they begin to produce eggs in egg masses. The entire life cycle can occur in just over two weeks and is favored by warm temperatures (81-86°F / 27-30ºC).

Management

Management practices are limited for reniform nematode management. Crop rotations to non-hosts (e.g. corn, sorghum) and managing weed hosts may be beneficial to reducing nematode populations. Seed treatments for managing high populations of nematodes is ineffective, but may provide early season (2-5 weeks) of control.

Useful Resources

The North Carolina Department of Agriculture Nematode Assay Lab provides soil nematode assay information and has sampling strategy recommendations available for producers.

The NC State University Plant Disease and Insect Clinic provides diagnostics and control recommendations.

The NC State Extension Plant Pathology portal provides information on crop disease management.

The North Carolina Agricultural Chemicals Manual provides pesticide information for common diseases of North Carolina. The manual recommendations do not replace those described on the pesticide label, and the label must be followed.

Acknowledgements

This factsheet was prepared by the NC State University Field Crops and Tobacco Pathology Lab in 2020.

• Check out our Facebook and our Twitter!