European corn borer [Ostrinia nubilalis (Hubner)] is the most serious insect pest on sweet corn (Zea mays L.) grown for processing in the Midwest. This research was designed to evaluate diallel hybrid combinations of previously identified low‐ and high‐damage inbreds by second‐generation European corn borer following artificial infestation. During 3 years 10 low‐damage and 10 high‐damage inbreds were used in each of two separate diallels consisting of 45 F1 hybrids, without parents and reciprocal crosses. While the year ✕ genotype interactions were highly significant, it was possible to identify two inbreds from the previously identified low‐damage group which consistently contributed to low damage in their progeny and two inbreds from the high‐damage group which consistently contributed to high damage in their progeny. Hybrids of high‐damage parents averaged earlier in maturity and tended to have fewer tillers than those in the low‐damage diallel although there were seasonal differences. If the sample of fines used in this study is representative, selection procedures for additive gene action should be effective. However, the range in specific combining ability effects and the significant year ✕ genotype interactions emphasize the importance of testing a wide range of hybrid combinations in different seasons.

Date of planting and plant density are two cultural practices influencing grain yield of maize (Zea mays L.) . Our study was designed to evaluate the usefulness of a mass selection scheme to improve cold and density tolerance of the BS2 and BS3 maize populations . Populations were planted at an early planting date and a high plant density, and three cycles of mass selection for well-filled ears on erect plants were conducted at each of three Corn Belt locations (i .e ., Waseca, MN ; Ames, IA ; Portageville, MO).Results showed that selection improved cold tolerance traits of BS3, but not of BS2 . Mass selection did not increase density tolerance of either population at any location . Selection did not improve response to planting dates, although the early planting date did improve agronomic performance and grain yield of all entries . We concluded that mass selection at high plant densities and early planting dates at diverse geographical locations did not produce cycles adapted to specific environmental conditions .

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