Saturday, June 13, 2015

Areas of Corn not Growing Well? Could it be Corn Nematodes?

Recently, I have run into many areas of fields, especially in corn on corn fields in Northern Illinois, that appear to exhibiting symptoms caused by corn nematodes.  The cool, wet weather has unfortunately, caused symptoms to be easily seen.  We can confirm nematode injury by testing the soil for corn nematodes.  If the population is extremely high, the nematodes may also be seen under a microscope within the corn roots.
Kevin Burrus sampling for corn nematodes at Burrus Seed Farm
Burrus Dealer, Jason Zimmer and Burrus Intern, Austin Kocher, testing for corn nematodes
Suspect corn nematode "hot spots" in corn

Corn nematodes should be diagnosed before the V6 growth stage of corn.  Soil (not overly wet) and root zone should be sampled randomly throughout the field. Different labs recommend different amounts of soil cores (12 to 25) and soil depths (6 to 12 inches) from the root zone (this is because you want to get a sample of roots to test for endoparasitic nematodes such as lesion nematode. ) It is a good idea to keep track of where you have sampled, so that you can go back and monitor nematode populations. Do not try to break up the soil cores or drop the soil samples, because this could kill corn nematodes before they reach the lab, which could cause you to have inaccurate lab results. If you think that you have corn nematode “hotspots” in the field, you may want to sample from that area as well as a “healthy” area, so that you can compare results. If you are still in doubt, it may be best to call the lab before you send a sample, so that you can provide the lab with an adequate sample. For example, some labs do not recommend that you sample after the R3 corn growth stage.

Depending on the corn nematode species, rotation of crops, tillage, and controlling grassy weeds may help to keep nematode populations in check or below damaging thresholds. Rotation to crops such as alfalfa, cotton, rice, soybeans, or sorghum may be a good control of needle, sting, and some lesion nematode species that have narrow host ranges.There are limited choices of soil applied nematicides. One common example of a soil applied nematicide is Counter insecticide, which has been known to reduce nematode populations in season. However, this occurs early in the season, and there could be a nematode resurgence later in the season. Also, Counter is an organophosphate (OP) insecticide, which can interact with ALS herbicides. For more information:  http://www.ipm.iastate.edu/ipm/icm/2000/5-22-2000/interaction.html

Corn nematicide seed treatments include Avicta ® and VOTiVO™. Again, each of these will have to be used each year and only provide early season control. Nematode numbers could again resurge in mid or late season. Avicta’s active ingredient is abamectin, which is a natural fermentation product of Streptomyces avermitiles, which can inhibit the nematode’s nervous system. This nematicide seed treatment is not systemic or taken up by the roots and can be considered mobile or eventually lost within the soil profile. VOTiVO’s active ingredient is Bacillus firmis and does not kill nematodes. It acts as a repellant or physical/chemical barrier and is also not systemic or taken up by the roots. It can grow on the root surface, but only provides early season protection.
When you plant any of our brands you are covered with either Avicta or VoTiVO, which reduces your concern for corn nematodes in early season.

Again, nematode testing should be done to evaluate whether corn nematode populations are being kept in check by these management options. 

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