Agronomy •  6/17/2021

Corn Nematodes: Symptoms, Damage and Control

Written by Mark Jeschke


Key Points

  • Nematodes may be overlooked as a pest in corn due to their small size and non-distinctive damage symptoms, but they can cause yield loss by damaging corn roots.
  • Many different nematode species can cause yield loss in corn. Damage in a field can be caused by a single species or by several species.
  • Lumialza™ nematicide seed treatment is a biological treatment available with Pioneer® brand corn products that has activity against all major corn nematode species.

Nematodes: An Overlooked Pest of Corn

  • Over 50 species of nematodes are known to feed on corn in the U.S., several of which can cause economic damage.
  • Corn nematodes are commonly thought of as a pest specific to sandy soils, such as in Kansas and Nebraska and the coastal plains of North and South Carolina. While this is true of some species, other species can exist in a range of soil conditions.
  • Nematodes normally do not kill plants but act as parasites on the host plant.

Are Nematodes Becoming More Common?

  • Recent trends in farming practices may be increasing nematode numbers as well as their economic impact in corn.
    • Reduced tillage is known to favor some nematode species, as is corn following corn.
    • Reduced use of carbamate and organophosphate insecticides for rootworm control has likely caused an increase in nematode populations. These insecticides have activity against nematodes, whereas newer alternatives such as pyrethroid insecticides and CRW Bt corn do not.
  • Our ability to sample and diagnose nematode damage has also improved. Symptoms that may have once been attributed to some other factor are now correctly being traced to nematodes.

Crop Damage

  • Plant parasitic nematodes are typically soil-borne and feed on plant roots. Nematodes use a stylet to pierce the corn root and extract nutrients.
  • Tissue damage at the feeding site can provide easy entry into the root system for commonly associated root pathogens.
  • Nematode damage can occur throughout the growing season; however, corn is most vulnerable during early-season crop establishment.

Visual Symptoms in Corn

  • Visual symptoms usually show up as “hot spots” in the field.
  • Plants may appear to be moisture-stressed, stunted and chlorotic, or exhibit less-extreme signs of poor plant growth.
  • Symptoms are often mistaken for another problem, such as low fertility, soil compaction, weather stress, or insect damage.
  • No specific patterns are usually identifiable with nematode damage, although as the problem grows, it often moves in the direction of field tillage.
  • Root pruning is usually evident, as well as proliferation of fibrous roots, thickening or swelling of the smaller roots, and mild to severe discoloration.
  • Soil may stick to the roots due to the oozing of damaged cells.

Photo - Corn lesion nematode

A lesion nematode, one of the more ubiquitous nematode pests of corn.

Photo - Severe feeding damage from corn lance nematodes.

Severe feeding damage from lance nematodes.

Primary Corn Nematode Species

  • There are many species of nematodes with different biological characteristics that are capable of reducing corn yield. Different soil environments will favor different nematode species.
  • It is difficult to establish widely applicable economic thresholds for nematode populations given their tendency for patchy distribution and other stress factors that can influence yield.
  • Scientists at Corteva Agriscience have developed high population indicators for corn nematode species as a relative measure of low, medium or high population levels (Table 1).
  • The foundation of these indicators is university and nematol-ogist thresholds plus yield results from Corteva research trials. The purpose of the high population indicator is to simplify characterization of nematode population levels while taking into account varying thresholds across states.

Managing Corn Nematodes

  • Sampling conducted by Pioneer agronomists across hundreds of locations has shown that potentially damaging levels of corn nematode populations are prevalent throughout corn production areas in the U.S. (Gumz, 2020).
  • If damaging levels of corn nematodes are found, implementing control measures such as rotation, sanitation or use of nematicide seed treatments should be considered.
  • Nematode species vary in their host range, so rotation can be effective for reducing populations of some, but not all, corn nematode species.
  • Pioneer® brand corn products are available with a seed treatment option for nematode control:
    • Lumialza™ nematicide seed treatment is a biological product that contains the active ingredient Bacillus amyloliquefaciens – Strain PTA-4838 and has activity against all primary corn nematode species.
    • National trials have shown yield improvements of 3.7 bu/acre under low pressure and up to 9 bu/acre in high pressure fields.*
    • Research has shown that nematode protection lasts for over 80 days in the upper, middle, and lower root zones.

Reference



Table 1. Corn nematodes of economic importance in North American corn production.

Table - Corn nematodes of economic importance in North American corn production.

Table - Corn nematodes of economic importance in North American corn production.

Table - Corn nematodes of economic importance in North American corn production.

 




Logo - Lumialza nematicide seed treatment*Data is based on 10-state broad-acre head-to-head strip trial comparing Lumialza™ nematicide seed treatment vs. non-nematicide seed treatment utilizing the same insecticide and fungicide recipe in seed-applied technology replicated and strip trial data. Yields ranged from 3 to 9 bu/A depending on nematode species and population, in 184 low stress and 54 moderate to high stress locations.

The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary. Pioneer® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents.