Plots of corn artificially infested with second‐brood corn borer egg masses were compared with plots treated with an insecticide to prevent infestation. Our studies were conducted to determine if the resistance of inbreds would be expressed in hybrids and if the present level of resistance was sufficient to prevent serious yield losses.Resistant ✕ resistant crosses were reduced in yield by second‐brood corn borer damage on the average slightly less than 4%, but the susceptible ✕ susceptible crosses were reduced in yield by 12%. Corn borer infestation decreased yield and the moisture content of the grain, but increased stalk lodging and ear droppage. The number of cavities per plant, which we used as a direct measure of resistance, increased with the susceptibility of the inbreds in the single crosses.

No abstract

The spotted alfalfa aphid, Therioaphis maculata (Buckton), has become the most serious pest of alfalfa in many parts of southwestern United States since its discovery in New Mexico early in 1954.Chiefly a pest of alfalfa, this insect also infests bur clover and sour clover. It does not live on red clover, Ladino clover, or sweetclover. This insect damages alfalfa by ruining hay crops, by slowing regrowth, by thinning stands, and by killing seedling fields. Spotted alfalfa aphid populations and resultant damage have beenhighest on the desert in the late fall, spring, and early summer. In cooler sections this aphid has done damage only in the summer and early fall.The use of insecticides to control the spotted alfalfa aphid has not prevented ladybird beetles from doing a good job on this aphid when conditions were right, usually when the wedther was warm.

Chromosomal interchanges were used to determine which chromosome arms of resistant corn inbreds, C.I.31A and B49, carry genes for resistance to European corn borer leaf feeding. All corn plants were infested manually with corn borer egg masses in field studies conducted in 1961 through 1964.Resistant inbred C.I.31A was found to possess a gene or genes contributing to resistance on the short arm of chromosomes 1, 2, and 4, and on the long arm of chromosomes 4 and 6. Resistant inbred B49 appears to have genes for resistance on these same chromosome arms (possibly allelic to those of C.I.31A) plus an additional gene for resistance on the long arm of chromosome 8.