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Ontario Grain Farmer Magazine

Management of corn and soybean nematodes

Principal Investigator: Albert Tenuta

Research Institution: Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)

Timeline: March 2014 – March 2017

Objectives:

  • Survey Ontario field crop fields for nematode distribution and population levels to gain baseline information.
  • Investigate the potential impacts of combinations of corn-soybean rotation schemes and cover crop combinations on plant parasitic nematode population densities in Ontario agricultural fields.
  • Evaluation of new nematicide seed treatments for corn and soybean nematode control.
  • Increase awareness of corn nematodes in Ontario and soybean cyst nematode (SCN) in new regions of the province such as eastern Ontario.

Impacts:

  • The adoption and increased awareness of integrated management options for nematodes in corn and soybeans will allow farmers to manage SCN effectively.
  • The evaluation and registration of new nematicide seed treatments will provide more options to farmers who have to manage SCN.
  • The investigation of agronomic benefits and detriments of cover crops species in relation to root lesion nematode and other pathogens will allow farmers to effectively integrate cover crops into their cropping system.

Scientific Summary:

The most familiar example of nematodes to most Ontario farmers is the soybean cyst nematode (SCN – Heterodera glycines), which causes the greatest yield loss in soybean of any pathogen. Conversely, in those same fields, is a diversity of other less familiar plant parasitic nematodes that infect roots of corn, soybean, wheat, and other crops. In contrast to SCN, these nematodes are native to Ontario and are present in every production field to some extent. Instead of a single species, there are more than a dozen species of nematodes commonly found in fields where corn is grown. Unlike soybeans where many management options are available to the producer, such as resistant varieties and crop rotation, this is not the case in corn. Often misdiagnosed and misunderstood, corn nematodes as stated above have become a growing problem in Ontario and the US corn-belt as a result of changes in production practices. The use of cover crops integrated into traditional corn-soybean production is a sustainable agriculture practice that is also increasing in use throughout Ontario. Cover crop and crop rotation impacts on nematode population densities are largely dependent upon the nematodes that are present and the suitability of the crop plants as their host.

1. Survey Ontario field crop fields for nematode distribution and population levels (baseline nematode)

Distribution maps for SCN and root lesion nematodes were produced and updated annually.

2. Investigate the potential impacts of combinations of corn-soybean rotation schemes and cover crop combinations on plant parasitic nematode population densities in Ontario agricultural fields.

Field trials examined 26 different cover crop species to determine reproduction on these plants for SCN, root lesion and other nematodes. All 26 single species cover crops were examined for soybean cyst nematode reproduction. None of the cover crop species supported reproduction but SCN juveniles did colonize legume cover crops. Root samples were collected from each of the 26 cover crops species for root lesion and other nematodes colonization of the root tissue.  For soybean cyst nematode, SCN was inside the roots of a few of the legume species with “hairy vetch” having the highest.

Root lesion nematode was found to reproduce or colonize many of the 26 cover crop species, particularly clover, pea and bean species. Sunn Hemp, which is promoted for SCN reduction, had significantly higher root lesion numbers per gram of root compared to the other cover crop species. Sunn Hemp maybe problematic in that it may reduce SCN but increase root lesion risk to the grower.

The cover crop information from Ontario was used in a new Crop Protection Network Publication (CPN 4002) January 2017 called “Cover Crops Do’s and Don’t’s”.

3. Evaluation of new nematicide seed treatments for corn and soybean nematode control.

This three-year study was conducted in Illinois, Indiana, Iowa, Michigan, and Ontario, from 2013 through 2015 to determine the effect of soybean (Glycine max) cultivars’ source of soybean cyst nematode (SCN; Heterodera glycines) resistance on SCN population densities, sudden death syndrome (SDS; caused by Fusarium virguliforme), and yield of soybean. Five cultivars were evaluated with and without fluopyram seed treatment at each location. Cultivars with no SCN resistance had greater SDS severity, greater postharvest SCN egg counts (Pf), and lower yield than cultivars with plant introduction (PI) 548402 (Peking) and PI 88788-type of SCN resistance (P < 0.05). Cultivars with Peking-type resistance had lower Pf than those with PI 888788-type and no SCN resistance. In two locations with HG type 1.2-, cultivars with Peking-type resistance had greater foliar disease index (FDX) than cultivars with PI 88788-type. Fluopyram seed treatment reduced SDS and improved yield compared with a base seed treatment but did not affect SCN reproduction and Pf (P > 0.05). FDX and Pf were positively correlated in all three years (P < 0.01). Our results indicate that SDS severity may be influenced by SCN population density and HG type, which are important to consider when selecting cultivars for SCN management.

External Funding Partners:

This project was funded in part through Growing Forward 2, a federal-provincial-territorial initiative. The Agricultural Adaptation Council assists in the delivery of Growing Forward 2 in Ontario.

Project Related Publications:

King, C. 2017. Nematodes in Soybeans and Corn. Top Crop Manager Magazine. December: 10-13.

Tenuta, A. 2017. Effect of Soybean Cyst Nematode Resistance Source and Seed Treatment on Population Densities of Heterodera glycines, Sudden Death Syndrome, and Yield of Soybean. Plant Disease. 101(12): 2137-2143.