Are you seeing some unusual ears in your corn fields? Diagnose what went wrong by comparing your cobs to the ones below, and then develop a strategy to fix the issues.
Beer Bottle Ears
Symptoms: Kernel row numbers may decrease by half from bottom to top of ear (for example, from 16 to eight kernel rows per ear). The ear length is usually about normal.
Causes: Severe stress during the seven- to 10-leaf collar stages and late application of sulfonylurea herbicide.
Blunt Ear Syndrome
Beer Can Ears, Ear Stunting
Symptoms: Markedly reduced ear size and kernel numbers per row. Husk length and kernel row number may be normal.
Causes: Unknown but is most often associated with low temperature stress during early ear formation.
Multiple Ear Syndrome
Symptoms: Multiple ears on the same ear shank—sometimes five or six ears form a “bouquet.” Side ears may or may not be fully developed.
Causes: Unknown but similar to blunt ear syndrome.
Drought- Damaged Ears
Symptoms: Small, misshaped ears with poor kernel set at ear tip.
Causes: Severe drought and other stresses, such as nitrogen deficiency and high plant population.
Symptoms: Combination of tassel and ear in the same structure.
Causes: Injury to growing point, early-season compaction and saturated soil along field edges.
Diplodia Ear Rot
Symptoms: Partial or entire ear rotted by a white mold growing between the kernels; later the white mold changes to a grayish-brown growth over the husks and kernels. The entire ear may be shrunken.
Causes: Stenocarpella maydis fungus.
Poor, Incomplete Kernel Set
Symptoms: Poor reduced kernel set.
Causes: Similar to poor pollination at ear tip. (see next).
Poor Pollination At Ear Tip
Symptoms: Cob tissue without kernels on last 1" or more of ear tip.
Causes: May result from drought, heat, insect damage, herbicides and phosphorus shortage.
Symptoms: Poor tip fill or unfilled ear tips and kernel abortion at tip end of ear at blister and milk stages.
Causes: Stress during early kernel development, including severe drought, heat, nitrogen deficiency, foliar diseases and cloudy weather.
Symptoms: Missing kernel rows on outside or underside.
Causes: Unknown, but linked with stress after pollination.
Symptoms: Lightweight, poorly-filled ears with shrunken kernels and spaces between kernels.
Causes: Severe photosynthetic stress from the dough through
early dent stages.
Western Bean Cutworm Ear Injury
Symptoms: Scattered patches of partial or complete kernel destruction; often associated with mold growth on affected kernels.
Causes: Kernel feeding by Western bean cutworm.
Symptoms: Lightweight, weathered ears with damaged, discolored and moldy kernels; often associated with kernel sprouting.
Causes: Poor husk coverage at maturity, and upright ear orientation allows birds to feed on tip kernels.
Kernel Red Streak
Symptoms: Red streaks on sides of kernels, extending over the crown. Usually limited to kernels at tip of ear.
Causes: Toxin secreted during feeding by the wheat curl mite.
SOURCE: Peter Thomison and Allen Geyer, Ohio State University. This is a condensed version of a poster designed by agronomists at Ohio State University. To order a full-size 26”x 33” version, with more detailed text, for $10 plus shipping, call (614) 292-1607 or send an email to firstname.lastname@example.org. Ask for Poster ACE-1.