Loren Giesler, Nebraska Extension Plant Pathologist John Wilson, Nebraska Extension Educator Burt Co. Sclerotinia stem rot (White Mold) 1
Sclerotinia stem rot (White Mold) Challenges with White Mold Control Wide host range (fungus survival) Flowering period Lasts for several weeks in soybeans Timing Canopy penetration Post infection conditions 2
Frogeye Leaf Spot Cercospora sojina Sexual and asexual reproduction 7 clusters and 7 subclusters 56% similarity No geographic separation Virulence to host resistance emerging Resistance to fungicides emerging Cercospora zea-maydis Asexual reproduction 2 types 95% similar Geographically separated Host resistance still largely effective Application of fungicides still effective 3
https://www.plantmanagementnetwork.org/hub/soyfungicideresistance/ Sudden Death Syndrome (SDS) 4
Sudden Death Syndrome Sudden Death Syndrome Note discoloration at base that can extend up the plant several feet under the epidermal layer. 5
leaf symptoms Brown Stem Rot stem symptoms SDS Sudden Death Syndrome (SDS) Management Variety selection Variety selection Avoid early planting Crop Rotation Seed treatments 6
ILeVO phytotoxicity on soybean Source: Albert Tenuta OMAFRA 7
John Wilson, Extension Educator Blues a feeling of melancholy, sadness or depression! In other words: dejection, despair, despondency, gloom, misery, sorrow, unhappiness, a slump, the doldrums, the dumps, or the dreaded blue funk! 8
Common Soybean Blues What happened to my soybeans? They look so good all year. But when I get to harvest, The yields just disappear! RANDY S Soybean Blues My neighbor and I are good farmers. We plant, spray, and harvest together. Yet his bean yields beat mine, Almost every time. And he s NOT an 8-bushel-better farmer! 9
RANDY Important Points SCN is not a sign of poor management! SCN can be in one field and not be in another field right across the road! SCN reduces yields with no visible signs! Resistant varieties do work! SCN What is it? Soybean Cyst Nematode A microscopic roundworm that attacks the roots of soybeans The #1 pest for soybean farmers The silent yield robber 10
Signs of SCN Infestation Signs of SCN Infestation Up to 30% loss in healthy fields Yield maps unexplained low yields Soybean yields hit plateau or drop, corn yields continue to increase Increase in SDS or BSR 11
SCN in Nebraska As of January 1, 2016 SCN identified in 58 Nebraska counties producing 93% of Nebraska s soybeans! SCN Life Cycle 12
Managing SCN It s all about the numbers! Test to detect SCN infestation when numbers are low and keep them low! Rotate with non-host crops Plant SCN-resistant varieties Seed treatments??? Early Detection It is much easier to keep low levels low than to bring high levels down. Take a 6-8 soil sample as you would for your fertilizer recommendations. Nebraska Soybean Board program! 13
Visual Observation Nematode cysts Rhizobium nodule Program Soil sample bags are available at your local Nebraska Extension office Get a return on your checkoff dollars ON YOUR FARM! (value: $20/sample) The price is right! $0.00 14
Sampling Program (2005-2015) 7,651 samples processed 2,326 positive (30.4%) Many farmers had no idea they had SCN in their fields when sampled Program ongoing in 2016! Where to Soil Sample Anything that moves soil, moves SCN Field entry ways/high traffic areas Along creeks, flooded, or low areas Unexplained poor yielding areas Areas with SDS or BSR 15
How to Soil Sample 15-25 cores per sample 6-8 inches deep, through roots Randomly sample whole field, or Sample problem areas separately Mix thoroughly and submit in bag When to Soil Sample 24/7/365 When co-op, scout samples your field In fall, after harvest After soybeans easier to detect After corn info for next year Every 6* years, infested or not! 16
Rotate with Non-Host Crops Anything we normally grow is not a host for SCN, including alfalfa and most legumes in cover crop mixes Biggest reduction occurs in first year Some weeds allow SCN reproduction, henbit and field pennycress Plant SCN-Resistant Varieties Most seed companies offer choices Don t forget other agronomic traits Know the source of resistance Rotate the source of resistance The price is right! $0.00 17
Sources of Resistance PI88788 (most common ~98%) Peking (PI548402) Hartwig (PI437654) Cyst-X (selection from Hartwig) Others SCN Research Sites (2006-2013) 18
Research Results - YIELD Sites Res. Sus. Change 29 infested 58.0 52.1 +5.9 bu 11 uninfested 57.9 60.1-2.2 bu Research Results EGG COUNTS Sites Spring Fall Change All 29 - R 1,783 1,467-18% - S 1,516 5,906 +290% 19
SCN Population Example With Initial Population of 1,000 eggs/100ccs soil Resistant Varieties Crop Change Eggs Corn -25% 750 Soyb -18% 615 Corn -25% 461 Soyb -18% 378 Corn -25% 284 Soyb -18% 233 Susceptible Varieties Crop Change Eggs Corn -25% 750 Soyb +290% 2,925 Corn -25% 2,194 Soyb +290% 8,555 Corn -25% 6,417 Soyb +290% 25,025 SCN Population Example With Initial Population of 1,000 eggs/100ccs soil Resistant Varieties Crop Change Eggs Corn -25% 750 Soyb -18% 615 Corn -25% 461 Soyb -18% 378 Corn -25% 284 Soyb +290% 1,108 The potential effect of using a susceptible soybean variety in the sixth year of a cornsoybean rotation. You could lose everything you had gained in the previous five years! 20
Managing SCN It s all about the numbers! Test to detect SCN infestation when numbers are low and keep them low! Rotate with non-host crops Plant SCN-resistant varieties Seed treatments??? So don t be singin the Soybean Blues! Thank you! Questions? 21
Soybean Disease Videos on Crop Watch! cropwatch.unl.edu/soycal 22