Guiping Yan, NDSU Department of Plant Pathology
Plant parasitic nematodes are one of the major groups of parasitic organisms that can lower the yield of corn production in the United States. Very limited information exists on the occurrence of nematodes on corn in North Dakota and therefore this study surveyed 200 corn fields across 16 counties with major corn production counties being surveyed the most. Soil samples have been obtained using standard soil probe from 20 to 30 different spots in each field. The samples were then stored in a cold room prior to nematode assay so that the soil did not dry up and nematode populations were not affected. As of December 30th, 2015, 160 samples were subjected to nematode extraction via sugar flotation method. Nematodes were extracted, identified and quantified from each field.
Nematode identification and quantification results indicated presence of 9 groups (genera) of plant-parasitic nematodes in the corn fields of North Dakota including root-lesion, pin, spiral, stunt, foliar, stubby root, dagger, lance, and cyst nematodes. Among these nematodes, root-lesion, stubby-root, dagger and lance nematodes are considered aggressive on corn and can cause yield suppression in corn. The densities of root-lesion, stubby-root, dagger and lance nematodes we detected were as high as 1,200, 200, 875, and 380 nematodes per kg of soil, respectively. Very high population densities of spiral nematode were found in some fields (up to 16,910/kg soil).
As proposed, molecular (DNA-based) and morphological methods were used to identify nematodes to species. One root-lesion nematode species (Pratylenchus scribneri), one spiral nematode species (Helicotylenchus pseudorobustus), and one pin nematode species (Paratylenchus nanus) were identified from five corn fields. A new root-lesion nematode species was discovered in two fields. The species identity of this new root-lesion nematode is being confirmed. We will continue to identify nematode species for other fields and other groups we detected.
We processed and sent 100 field samples to Agvise laboratories for determining soil properties (pH, organic matter, soil texture) of each sample. We also sent 40 soil samples to western laboratories for nematode identification and enumeration for comparison. Data analysis indicated that the nematode extraction method used in our lab has a higher extraction efficacy than that used in western laboratories. Meteorological data will be acquired from weather stations. The relationships between nematode populations and soil and climatic factors will be disclosed. The results will be summarized and delivered to growers at field days and winter meetings and in extension publication (Plant-parasitic Nematodes on Corn in North Dakota).