Source: P. Thomison, OSU
Symptoms:
Very small, misshapen ears with poor kernel set. Reduced kernel numbers are usually associated with reduced kernel row numbers and kernels per row and poor kernel set and kernel abortion. Nubbin ears may exhibit extreme zipper ear and tip dieback symptoms. Nubbin ears are often associated with plants that are stunted due to drought or other stresses and exhibiting symptoms associated with various nutrient deficiencies. Nubbin ears are often too small for effective combine harvest.
Cause:
Multiple factors, including severe drought from mid vegetative growth through early to mid-grain fill, nitrogen and phosphorous deficiency, excessive seeding rates, uneven emergence, defoliation caused by hail and diseases, and virus diseases can result in nubbin ears.
Management:
Follow recommended guidelines for minimizing crop stress, including maintaining appropriate soil fertility, selecting adapted hybrids and seeding rates consistent for soil yield potential and date of planting, and adjusting planting depth with varying soil conditions. Avoid planting too early in wet soils and minimize weed competition with effective herbicide application and/or timely cultivation.
References:
Thomison, P.R. 2012 Corn ear abnormalities: “Tip dieback” and “zippering” Crop Observation and Recommendation Newsletter. Available at http://agcrops.osu.edu/newsletters/2012/29#4 [URL verified 3/28/2019].