Corn Nematode Populations in the Corn Belt

• Corn nematodes can cause significant yield loss by damaging corn roots, which impairs water and nutrient uptake and creates entry points for pathogens.
• In 2019, 2020, 2021, and 2022, Pioneer agronomists, territory managers, and sales professionals sampled corn fields across the U.S. Corn Belt to assess nematode population levels and the range of species present.
• Over 3,100 samples were collected from fields in 19 states: Texas, Oklahoma, Colorado, Kansas, Nebraska, North Dakota, South Dakota, Minnesota, Iowa, Missouri, Wisconsin, Illinois, Indiana, Michigan, Ohio, Pennsylvania, New York, Maryland, and Delaware.
  
  
  

  

  Stunted growth of the corn plant on the left due to corn nematode pressure. Above ground symptoms of nematodes are often nondescript and resemble low fertility, weather stress, or insect and disease pressure.

• A total of 3,164 corn fields were sampled for nematode populations from 2019 to 2022.
• Soil samples were taken at approximately the V6 growth stage.
• Soil samples were taken from both within and between the row and contained corn root tissue.
• Samples were submitted to a nematode testing service and analyzed using a sugar-floatation method and a 500 mesh sieve.

Nematode Pressure Levels

• Scientists at Corteva Agriscience have developed high population indicators for major corn nematode species as a relative measure of population levels (Table 1).
• The Corteva Agriscience nematode rating is based on a combination of thresholds from seven labs throughout the Corn Belt. It rates the potential for yield damage due to nematodes based on the population and species of nematodes present.
• Nematode pressure in a field was classified based on the high population indicator level for each species:
  • High: Above indicator level for one or more species.
  • Medium: Above 50% indicator level for one or more species.
  • Low: Less than 50% indicator level for all species.
    
    

    Table 1. Corteva Agriscience population level indicators for major corn nematode species.

    Species	High	Moderate	Low
    	-- nematodes / 100cc soil --
    Sting	1	NA	NA
    Needle	1	NA	NA
    Lance	50	25-49	1-24
    Stubby-Root	50	25-49	1-24
    Root Knot	50	25-49	1-24
    Dagger	100	50-99	1-49
    Lesion	150	75-149	1-74
    Ring	200	100-199	1-99
    Stunt	300	150-299	1-149
    Spiral	500	250-499	1-249

• Nearly all fields sampled had corn nematode species present at some level (Figure 1).
• 35% of corn fields sampled had medium to high levels of nematode pressure (Figure 2).
• Medium and high population levels were found across all regions in the study.
• High nematode population levels were most prevalent in the western Corn Belt states – Nebraska, Kansas, Colorado, and Texas.

• Results of this study showed that potentially damaging levels of corn nematode populations are prevalent throughout corn production areas in the U.S.
• 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 come with Lumialza™ nematicide seed treatment 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.