Soybean Cyst Nematode: a Continually Growing Problem in Soybeans? X Greg Tylka Iowa State University Department of Plant Pathology and Microbiology January 31 & February 1, 2017
cyst (dead female) full of eggs female+eggs Tylka Tylka eggs Tylka ~24 days per generation 3-6 generations per year >200 eggs per female eggs can survive >10 years dormant in soil adult female and male mating occurs on root Baum juveniles adult male swollen juvenile adult female Tylka Tylka Tylka
Challenges for the Future SCN continues to spread
Known SCN-Infested Counties Feb. 2014
Known SCN-Infested Counties Feb. 2017 33 North new Dakota: since 2014: Alabama Bensen = 1 Georgia Cavalier = 3 Indiana Foster = 1 Iowa McIntosh = 1 Kansas Rolette = 2 Kentucky Stutsman = 3 Minnesota Walsh = 2 South Missouri Dakota: = 1 N. Campbell Carolina = 4 N. Dakota = 7 Minnesota: Ohio = 3 S. Ladena Dakota = 1 Virginia Lake of the = 2 Woods Wisconsin = 1 Quebec = 1
How Does SCN Spread? anything that moves soil wind-blown soil water-eroded soil wildlife field equipment tare soil
Challenges for the Future SCN continues to spread lack of symptoms
SCN Eggs / 100 cc Soil 0 1-1000 1001-5000 5001-10000 10001-15000 15001-20000 Yellow plants Soybean Yield (bu/acre) 13.5-20.4 20.5-29.4 29.5-36.4 36.5-44.4 44.5-56.4
Dig roots and look for females
Dig roots and look for females SCN females
Collect soil samples to test for SCN
Challenges for the Future SCN continues to spread lack of symptoms selection of resistant varieties
field infested with SCN Photo: University of Minnesota susceptible soybean variety resistant soybean variety
field infested with SCN - 2006 Richland Co., ND susceptible soybean variety resistant soybean variety Photos: B. Nelson, North Dakota State University
Yield and SCN Control SCN-resistant vs Susceptible Soybean Varieties East Central Iowa (1,310 eggs/100 cm 3 at planting) 52.7 bushels per acre 45.9
Yield and SCN Control SCN-resistant vs Susceptible Soybean Varieties East Central Iowa (1,310 eggs/100 cm 3 at planting) bushels per acre 52.7 $0.00 45.9 2,169 8,875 10,000 8,000 6,000 4,000 2,000 eggs per 100 cm 3 soil at harvest 0 SCN
Number of SCN-resistant Soybean Varieties Available for Iowa (MG 0-3) 1991-2016 Number of varieties 1000 900 800 700 600 500 400 300 200 100 0
Companies with SCN-resistant Soybean Varieties for Minnesota & North Dakota a few per company several per company Source: S. Markell, North Dakota State University
Challenges for the Future SCN continues to spread lack of symptoms selection of resistant varieties lack of resistance diversity in soybeans
Registered Germplasm Lines that are Sources of SCN Resistance for Breeding PI 548402 (Peking) PI 88788 PI 90763 PI 437654 PI 209332 PI 89772 PI 548318 (Cloud) Many other breeding lines with different sources of resistance to SCN identified and released by breeders as well. The ability of SCN populations to reproduce on resistant sources determined with the HG type test.
Number of SCN-resistant Soybean Varieties Available for Iowa (MG 0-3) 1991-2016 Number of varieties 1000 900 800 700 600 500 400 300 200 100 0 PI 88788 Other Can you guess which source of resistance is not very effective in Iowa any more?? PI 88788 Why will seed companies not develop more varieties with other sources of resistance?? $0.00
Challenges for the Future SCN continues to spread lack of symptoms selection of resistant varieties lack of resistance diversity in soybeans some dry beans are good hosts for SCN
Female index 130 120 110 100 90 80 70 60 50 40 30 20 10 0 SCN Reproduction on Dry Bean in the Greenhouse Buster GTS-900 Maverick PINTO NAVY Othello Rally Remington Topaz Winchester Cirrus Ensign Mayflower Navigator Norstar Premiere Seahawk Vista Cal Early KIDNEY Percent of SCN females on a plant relative to the number on a susceptible a soybean. Source: S.H. Poromarto and B.D. Nelson, North Dakota State University Susceptible soybean BLACK Chinook Montcalm Red Hawk T-39 Condor Jaguar Eclipse Lee 74
Prospects for the Future SCN will continue to spread and thrive in MN, ND, and SD obvious symptoms will not occur for years after initial infestation detecting SCN infestations before symptoms become obvious is a unique management opportunity it s easier to keep low SCN numbers low than it is to drive high numbers back down
Prospects for the Future growing SCN-resistant soybean varieties with PI 88788 will likely produce profitable yields in ND, MN, and SD for some time growing nonhost crops will be the primary means of reducing SCN population densities (5 to 50% annually) but reduces only for 2 or 3 years
Effects of Continuous Corn on SCN Population Densities in Iowa End-of-season SCN numbers (eggs/100 cc soil) 20000 15000 10000 5000 0 soybeans 1st year 2nd year 3rd year corn corn corn
Effects of Continuous Wheat on SCN Population Densities in North Dakota * = susceptible Source: B.D. Nelson, North Dakota State University
Prospects for the Future growing SCN-resistant soybean varieties with PI 88788 will likely produce profitable yields in ND, MN, and SD for some time growing nonhost crops will be the primary means of reducing SCN population densities (5 to 50% annually) but reduces only for 2 or 3 years nematode-protectant seed treatments are a muchneeded addition to the toolbox, but are not a replacement for resistant soybean varieties
Prospects for the Future growing SCN-resistant soybean varieties with PI 88788 will likely produce profitable yields in ND, MN, and SD for some time growing nonhost crops will be the primary means of reducing SCN population densities (5 to 50% annually) but reduces only for 2 or 3 years nematode-protectant seed treatments are a muchneeded addition to the toolbox, but are not a replacement for resistant soybean varieties effects of cover crops on SCN population densities is not yet well documented
Questions? Comments?