Submitted to: American Phytopathological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2006
Publication Date: 10/1/2006
Citation: Donald, P.A. 2006. Host resistance and seed treatment to manage the soybean cyst nematode, 2004-2005. American Phytopathological Society. Fungicide and Nematicide Trails 61:NO22
Interpretive Summary: A systemic seed treatment applied to soybean cyst nematode resistant cultivar seed was tested to determine if the combination would protect plant roots better than plant resistance alone. In our two-year study there was no significant yield gain with use of either the seed treatment or plant resistance despite the significant decrease in egg population density with the resistant cultivar.
Technical Abstract: Soil at the field site was Memphis silt loam (fine-silty, mixed, active, thermic Typic Haplaudalf) infested with HG Type 2.5.7 (race 5) soybean cyst nematode (SCN). Plots were 4 rows, 6 m long, spaced 76-m apart with a seeding rate of 9 seed/0.3 m. The design was a randomized block design with four replications. Commercial fertilizer was applied following University of Tennessee soil fertility recommendations. Plots were planted to SCN-susceptible cultivar (Hutcheson) and a SCN-resistant cultivar (Fowler). Personnel with Syngenta Crop Protection applied STAN (100 g ai/100 kg) to seed of each cultivar, then, STAN treated and untreated seed of each cultivar were planted 7 May 04 and 6 May 05. Soil samples for determining population density were a composite by plot from each treatment and cultivar and were collected at planting and harvest. Cysts were recovered from the soil using a semiautomatic elutriator and ground. Eggs were recovered, stained and enumerated using a dissecting microscope. Six soybean roots/plot were dug at R1 soybean growth stage, cysts were recovered from plant roots by forcible spray of water over a 60-mesh standard soil sieve, and enumerated. The center two rows of each plot were harvested for grain yield 4 Nov 04 and 26 Oct 05. Rainfall patterns in 2004 were close to the 30-yr average and deviated greatly in 2005 from the 30-yr average with a wet early spring, lack of rain mid-May to July and a dry fall according to records from a NOAA station 0.6 km south of the test site. Differences in SCN egg population density at harvest were not due to significant differences in population density of plots at planting in 2004 or 2005. By the beginning of the soybean reproductive stage, STAN tended to reduce cyst formation, based on the number of cysts recovered from the roots at mid-season. STAN also tended to reduce SCN egg population density by the 2005 soybean harvest. However, the effect of STAN on cyst and egg numbers was not significant. The most effective method for reducing SCN cyst and egg numbers was planting a SCN-resistant cultivar. Combination of STAN with plant resistance did not protect the roots enough to boost yield over the untreated seed. Yields of the SCN-resistant and SCN-susceptible cultivars were equivalent.