Ohio State University Extension Factsheet

Horticulture and Crop Science

2001 Fyffe Court, Columbus, OH 43210-1096

Diagnosing Kernel Set Problems in High Oil Corn

Crop Advisory - 9701

The following is a summary of observations and a preliminary assessment of pollination/kernel set problems encountered during visits to ten high oil corn fields north of Urbana in Champaign Co. Ohio on Saturday, 8-16-97.

"poor kernel set"

Poor kernel set was observed in a number of TC-BLENDS with different pollinators and from different seed companies. In the severely affected fields, most (if not nearly all) plants showed significantly reduced kernel numbers, i.e. usually less than 50% kernel set. However, many plants were producing normal sized cobs with only a few scattered kernels on the ears.

Problems with kernel set were primarily observed in fields where corn followed corn; in fields following soybeans, poor kernel set was usually not a problem. This association with crop rotation was strongly evident at one site where the same TC-BLEND had been planted (using the identical management practices) in two adjacent fields - in one field the previous crop was corn and in the other soybeans. Poor kernel set was widely observed in the field following corn but not in the field following soybeans.

In the fields following corn, there was usually extensive silk clipping of ears ( probably caused by rootworm beetles) and root lodging (or "goosenecking") which was less evident or absent in the fields following soybeans.

Silk clipping may have limited pollination and resulted in reduced kernel set. Rootworm beetles can cause significant yield losses during pollination if silks are severely clipped before 50% pollination is completed. The potential for such injury could be considerably greater with a TC BLEND compared to a normal hybrid since less than 8% of plants in a blend would be producing pollen.

"silk clipping"

Pollinator plants appeared more vulnerable to root lodging. In the past I've used plant and ear height as well as ear size as a means to differentiate pollinator 19 from normal plants but in certain fields looked at on Saturday, it was difficult to see such differences, especially the field that included strip plots of different TC BLENDS. I think this was due in part to goosenecking and root lodging of pollinator plants which lowered their height. (Since the corn was well past pollination, pollen shed could not be used to identify pollinators).

"root lodging"

Reduced pollinator plant height caused by root lodging may have limited pollen dispersal if tassel height was below that of the ear shoots of normal male sterile plants. While there may not have been adequate numbers of pollinator plants at some sites, at other sites, where sufficient numbers of pollinator plants were present, poor kernel set was still observed - this suggests that the problem was not directly related to a specific pollinator or absence of pollinator plants.

Root lodging resulting from rootworm feeding may have occurred even though a soil insecticide was used at planting in the continuous corn fields. Wet soil conditions reduced the efficacy of soil insecticides by moving soil insecticide out of the zone of root worm activity and cool conditions delayed insect development. Strong winds associated with rainstorms during pollination may have also contributed to root lodging problems.

Uneven plant development was also evident in most fields to varying degrees, with some ears still showing green silks while most plants were at the R3/R4 (late milk/early dough) stage of development. Although most of the fields visited were planted early, 4-9 through 4-20 (earlier than in the past two years), emergence was delayed by cold wet soil conditions throughout much of May. These conditions contributed to uneven plant emergence and development and probably resulted in wider range of silking dates than normal. As a result there may have been inadequate pollen available for late silking normal plants. This variation in plant development was probably responsible for some kernel set problems in a field following soybeans planted 4-9 as well as the early planted fields following corn.

This evaluation - although based on a limited number of high oil corn fields - suggests that the risk for poor kernel set in TOPCROSS grain production is increased by planting TC-BLENDS in fields previously planted to corn. The potential for silk clipping and root lodging (especially of pollinator plants) is greater following corn. Moreover these risks are magnified when planting early. Early plantings will often result in reduced and uneven crop emergence, especially when cold, wet soil conditions persist as long as they did this year.

Prepared by:
Peter R. Thomison
Extension Agronomist