Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu
I have looked at sweet corn, soybean, and lima bean fields recently with reduced stands and low vigor plants due to poor seed quality. It is often assumed that summer plantings will not have stand issues as soil temperatures are warm and seeds should germinate and emerge quickly (if there is adequate moisture). This is not always the case, especially if seed lots are of low vigor. Signs of low vigor seed will be: abnormal appearance in the bag (shrivelled, cracked, off color, misshapen); small seedlings that emerge late or do not emerge at all; abnormal growth (twisting, snaking, or corkscrewing); small shriveled cotyledons in beans; small or distorted true leaves; swollen or split hypocotyls or coleoptiles; and bleached out seedlings. Another issue affecting seed germination and emergence would be uneven or inadequately applied seed treatments (fungicides and insecticides).
The following are some pictures of a summer lima bean planting with reduced stands due to poor seed quality.
Low vigor lima bean seedling – note the stunted and white appearance
Abnormal lima bean seedling with distorted leaves
Uneven and reduced lima bean stand due to poor seed quality