Recent Information About Mature Soybean Seed Damage
In the Midsouth, inclement weather [above-normal/frequent rain concurrent with cloudy weather, hurricanes] just before soybean maturity and during the normal harvest season [when harvest is delayed because of the inclement weather] will result in greater damage to seed. This may cause significant adjustments in a buyer’s discount schedule in a given year because of the expected greater volume of damaged seed they will receive. The effect of damaged seed on a producer’s bottom line at the elevator is discussed in detail here.
Significant weather-related damage to soybean seed can occur before harvest in all locales of the Midsouth if adverse weather conditions occur over an extended period that will prevent timely harvest. These conditions will exist whenever periods of rain and moderate to high temperatures occur simultaneously for extended periods of time and soybeans are near or at harvest maturity. This condition will likely be exacerbated by insect damage that will allow moisture and pathogens to enter the seed before harvest.
An article titled “ID and Management of Seed Disease on Soybeans” (Arkansas Row Crops Blog, Oct. 4, 2021) by Spurlock and Bateman of the Univ. of Arkansas provides insights about the mature soybean seed damage that is often a problem in Midsouth soybeans. Major points from their article follow.
• The most common fungal diseases that cause lowered seed quality in soybeans are Phomopsis seed decay (caused primarily by Diaporthe longicolla) and purple seed stain (caused by Cercospora flagellaris and C. kikuchii). Seed damage resulting from infestations by both diseases will result in dockage at the elevator.
• Varieties differ in their susceptibility to fungal pathogens, but all varieties will have damaged seed if the environmental conditions referenced in the above paragraph occur.
• In a study conducted in Arkansas in 2019, fungicides applied at stage R5 were more effective against purple seed stain than those applied at stage R3. Thus, an automatic fungicide application at R3 should not be considered effective against diseases that affect maturing or mature soybean seed. Where seed disease was an issue, an R5 application proved beneficial.
• Fungi that cause the primary seed diseases survive in field soil and on soybean residue left in the field following harvest.
• The likelihood of damage from seed diseases increases with delayed harvest. Thus, timely harvest after maturity is a sound management practice to minimize seed damage from diseases.
• Significant damage to developing/maturing soybean seed can result from stink bug (green and brown) feeding up to about stage R6. Insecticide applications to control this pest can generally be terminated after stage R6.5.
• See pictures in the article that show damaged seed resulting from infestations by each major pest involved in mature seed damage.
Click here and here for additional articles from the Crop Protection Network about the damage to seed that can result from infestations by fungal pathogens.
Composed by Larry G. Heatherly, Oct. 2021, larryh91746@gmail.com