Head smut—Sphacelotheca reiliana—a soil-borne fungus disease, which can not be controlled by chemical seed treatment, is one of the most destructive enemies of corn, sorghum, and sudan-grass. It has become established in central California and appears to be increasing in severity and spreading in area.

SynopsisRates of laboratory germination were increased by gibberellic acid in three varieties of grain sorghum. Field emergence rate in Midland grain sorghum was increased by dust and slurry applications to seed. Final emergence, maturity, plant height, grain yields, and components of yield were not influenced. Yields were not consistently increased by foliar sprays.

SynopsisGrain yields of main culms of 3 grain sorghum varieties were not significantly influenced by defoliating the tillers, and vice versa. Yield compensation for loss of leaf blade area was restricted to the defoliated culms.

SynopsisSignificant variety, date, and variety ✕ date interaction variances were found for grain yield and for the three components of yield. Tillers contributed differentially to total yield over planting dates and genotypes. Grain yield was significant correlated with 2 and 3 of the yield components, respectively, in 1958 and 1959. Except for one instance, yield components were mutually independent. Leaf area and yield were not significant correlated.

The sorghum midge—Contarinia sor-ghicola (Coquillet)—the most important pest of grain sorghums in the Southern states—was found in Tulare county on October 6, 1960. This apparently is the first record of this midge west of New Mexico. Surveys at the time of the initial discovery indicate that it is firmly established in Tulare County and is also present in Madera, Fresno, Kings, and Kern counties.

SynopsisA curvilinear relationship between grain yield and leaf area was found. Generally, changes in each of the 3 yield components were responsible for yield differences, although number of seeds per head and seed weight underwent greatest change. Greater yield reduction resulted from removing leaf area from upper than from lower portions of the plant. Likewise, removing alternate leaves was more deleterious than removing half of each leaf. In 1959, mean yield decreases of 23, 35, 43, and 95%, respectively, were obtained from removing approximately 33, 50, 67, and 100% of the leaf area at late boot and anthesis stages.

Competition between genotypes of Rhizobium japonicum was studied by using chlorosis-inducing strains 76 and 94 to facilitate identification of strains recovered from the nodules of soybean plants. Chlorosis-inducing strains were individually mixed in varying proportions with each of nine normal strains and the mixtures were used as inoculants on the Hawkeye and Lee varieties. The plants were cultured in the greenhouse under conditions previously described. Technique studies indicated that with rare exceptions a single nodule contained only one bacterial strain and that chlorosis of sorghum seedlings produced by a water extract of a nodule was a reliable indication that the nodule contained a chlorosis-inducing strain. Strain 76 had a pronounced competitive advantage over all normal strains regardless of the proportions of the strain in the mixtures. As little as 1.1% of strain 76 in the mixture with strain 38 caused 85% of the nodules. Strains 31 and 71 were more competitive against strain 76 than were the other normal strains. Chlorosis-inducing strain 94 was much less competitive against 8 of the 9 normal strains than was strain 76. The extent of chlorosis of the soybean plants gave a rough estimate of the competitive relationships between strains. The varieties Hawkeye and Lee were essentially identical in response to the various mixtures.