Soybean Disease

Check Roots for Soybean Cyst Nematode: What’s Your Number?

Soybean Cyst Nematode in hand

Article is taken from https://agcrops.osu.edu/newsletter/corn-newsletter/2024-24/check-roots-soybean-cyst-nematode-what%E2%80%99s-your-number by Horacio Lopez-Nicora

Soybean cyst nematode (SCN) is quietly expanding its presence in Ohio, with increasing numbers across the state. Fields affected by SCN might not show aboveground visible symptoms, but SCN females can be detected attached to soybean roots six to eight weeks after planting. We encourage Ohio soybean growers to actively manage SCN by checking roots for the presence of SCN. If you’re unsure whether you have SCN in your fields, take a walk through your fields with a shovel, digging up plants every 30 to 50 paces. Carefully remove soil from the roots (a water bucket can help) and look for SCN females (Fig. 1). Initially white to cream, turning yellow and eventually brown, SCN females are significantly smaller than nitrogen-fixing nodules (Fig. 1). The SCN females will eventually fill with over 200 eggs, transforming into cysts that protect the eggs and allow them to survive for several years in infested fields. We encourage growers, agronomists, and crop consultants to check soybean roots for SCN throughout July, August, and September.

Figure 1. Soybean roots infested with SCN. Note the significantly smaller lemon-shape SCN female (red circle) attached to roots compared to larger nitrogen-fixing nodules (yellow circle).

Figure 1. Soybean roots infested with SCN. Note the significantly smaller lemon-shape SCN female (red circle) attached to roots compared to larger nitrogen-fixing nodules (yellow circle).

Knowing if you have SCN is the first step in managing it effectively. Watch this video to learn how to check your roots for SCN females. If SCN is detected in your field, a fall soil sample can determine your SCN numbers and help tailor appropriate management strategies. If you are already planting SCN-resistant varieties, checking roots can help evaluate the effectiveness of your resistance management or identify if the SCN population in your field is adapting to those resistant varieties (a shift in virulence).

Maintaining low SCN levels is much easier than reducing high numbers below damage thresholds. With support from the Ohio Soybean Council and The SCN Coalition, we can process up to two soil samples per grower for SCN testing, free of charge [read more here]. Share your #SCNRootCheck photos on social media by tagging @TheSCNCoalition on Twitter and Facebook, and @Ohiosoycouncil on Twitter and @ohiosoybeancouncil on Facebook.

Soybean Diseases Are Showing Up in Ohio

By: Horacio Lopez-Nicora, Stephanie Karhoff, CCA

Source: https://agcrops.osu.edu/newsletter/corn-newsletter/2022-28/soybean-diseases-are-showing-ohio
In early August, we recommended starting scouting fields for soybean diseases. At that time (two weeks ago), disease incidence across Ohio was very low to moderate. Conducive environmental conditions, however, are turning things around and more fields are developing disease symptoms.

Figure 1. Soybean field in southern Ohio are severely affected by sudden death syndrome (SDS) with premature defoliation in the R5/R6 growth stage (A); symptoms begin with interveinal yellowing (chlorosis) of a leaf (B); eventually, leaf tissue dies and becomes brown but veins remain green (C). The fungus infects the root and produces toxins that are responsible for the above-ground symptoms.

Sudden Death Syndrome (SDS)

We are finding fields in Ohio severely affected by sudden death syndrome (SDS) [Fig.1 and Fig. 2]. SDS is caused by the fungal pathogen Fusarium virguliforme. This species is the most prevalent in the region, however, other Fusarium species can cause SDS. SDS above-ground symptoms can be confused with those produced by a different fungus (Cadophora gregata) that causes brown stem rot (BSR). To distinguish SDS from BSR, symptomatic plants should be dug out and stem cut open longitudinally. SDS-infected plants have white, healthy-looking pith, while BSR-infected plants present brown discoloration of the pith. Moreover, fields with severe SDS symptoms can also have high levels of soybean cyst nematode (SCN). Visit here for more information on SDS.

Continue reading Soybean Diseases Are Showing Up in Ohio →

How to Identify Late Season Soybean Diseases in 2020

By Anne Dorrance

Sclerotinia stem rot – The nights have been cool this growing season, even when the days were very warm. The fog this morning in Wayne County reminded me that this is the time of the year to begin to scout for this stem disease.  Sclerotinia is caused by a fungus that survives from season to season and over several years from sclerotia.  The infections actually occurred during flowering when the canopy was closed, and cool nights can really enhance and favor this disease.  For this disease, disease levels can reach 20% incidence before there is a measurable yield loss.  Sclerotinia will occur as single plants or a small patch of dying plants, that wilt and turn a deeper olive green color. Look at the stem and white fluffy growth will appear on the stem, this is the sign of the fungus.

Sclerotinia Stem Rot

Sclerotinia Stem Rot

Sudden Death Syndrome – reports that this disease is also beginning to develop in some areas of the state where soybeans are reaching R6. Symptoms include irregular yellow spots, which turn brown or necrotic between the veins.  Interestingly the veins are surrounded by green.  The center of the stem or pith is bright white in this disease.  This is a fungal pathogen and infections most likely occurred shortly after planting and this fungus causes extensive root rots.  The figure has both susceptible and resistant cultivar.  There is a look-alike symptom caused by triazole fungicides when applied under hot conditions.  To separate these two, if a triazole had been sprayed, look at the roots.  The roots will be very healthy where SDS, the roots, and the center of the taproot are discolored. Continue reading How to Identify Late Season Soybean Diseases in 2020 →