A Survey of Plant Parasitic Nematodes of Soybeans in Delaware and Maryland 2019 to 2021

Abstract

Soybean cyst nematode (SCN; Heterodera glycines) is the most yield-limiting pathogen of soybean across Delaware and eastern shore Maryland. To update nematode distribution and population data, a 3-year survey of nematode soil samples was conducted from 2019 to 2021. Soybean fields across Delaware and nine Maryland counties were sampled from August through October in each year. In total, 311 soil samples were collected, including 222 predictive samples and 89 diagnostic samples. Across all samples, nine nematode taxa were identified. SCN (53%), root-knot nematode (RKN; Meloidogyne incognita, 18%), and lesion nematode ( Pratylenchus spp., 57%) were the most notable populations of economic concern. Among positive samples, populations were above the economic threshold for 66% of samples with SCN; 39% of samples with RKN; and 14% of samples with lesion nematode. Results from this survey highlight the continued challenge of SCN in the region and that other nematode taxa like RKN and lesion should be monitored. Many fields have multiple nematode genera present, and interactions are poorly understood.