The seed composition in the upper 15-cm soil horizon was determined and correlated with weed seedlings growing with fieldbeans (Phaseolus vulgarisL. ‘Valley’). The total seed reservoir averaged 250 seed/kg of soil, and 19 species were represented. Seed occurring with the most frequency were redroot pigweed (Amaranthus retroflexusL. ♯ AMARE), common lambsquarters (Chenopodium albumL. ♯ CHEAL), and common purslane (Portulaca oleraceaL. ♯ POROL). Seed from these plants accounted for over 85% of the seed found. The number of barnyardgrass [Echinochloa crus-galli(L.) Beauv. ♯ECHCG], buffalobur (Solanum rostratumDunal ♯ SOLCU), common lambsquarters, common purslane, and common sunflower (Helianthus annuusL. ♯ HELAN) seed in the soil was correlated with the number of plants growing in the field with fieldbeans. A correlation occurred between redroot pigweed, yellow foxtail [Setaria lutescens(Weigel.) Hubb. ♯ SETLU], and barnyardgrass growing in corn (Zea maysL.) fields in the fall of the year and plants growing in the field with fieldbeans the following year.

Surveys conducted from 1970 through 1973 indicated that dry edible bean (Phaseolus vulgaris L.) plants in western Nebraska irrigated fields averaged 30% infection, and bean fields averaged 13% loss due to the white mold fungus, Sclerotinia sclerotiorum. Plants severely infected by S. sclerotiorum sustained a mean decrease in seed yield of 44% when compared to healthy plants. Total seed yield, and the components of yield, including number of seeds per plant, 100‐seed weight, and number of pods per plant, were significantly reduced by S. sclerotiorum. Reduced number of seeds per plant was the major component of yield loss followed by reduced weight of 100 seeds. Field conditions favoring vigorous foliage growth and high yields of Great Northern and Pinto bean types also favored white mold development. Thus, regression analysis indicated that low to moderate levels of infection by S. sclerotiorum were often associated with higher yields, but with a high percentage of infection yield reduction occurred. A second degree polynomial gave the best correlation of the data (r = 0.56). The assessment of disease losses due to S. sclerotiorum is discussed.

No abstract

No abstract

Systematic sampling of waterways and irrigation runoff from agricultural lands in the North Platte Project of Nebraska in July and August of 1972–1974 demonstrated that phytopathogenic organisms were disseminated. The organisms monitored included the bean common blight bacterium Xanthomonas phaseoli, the bean white mold fungus Whetzelinia sclerotiorum and various nematodes. Although many types of nematodes often were recovered from irrigation water, Heterodera sp. cysts which cause significant disease problems in the valley were found infrequently. Patterns of movement of the bacterial and fungal organisms were correlated with previous or current season infection of bean plants. The short‐term survival of X. phaseoli in sterile deionized water may explain the detection of this organism only in runoff or ditches receiving runoff from common blight infected bean fields. Sclerotial bodies of W. sclerotiorum remained viable for at least 10–21 days in flowing water and were found throughout the irrigation waterways. Irrigation of beans with contaminated water can result in both common blight and white mold diseases. Dissemination of phytopathogenic organisms in irrigation reuse systems as well as agricultural land runoff should be considered in irrigation planning and system design.

Number of hours of leaf wetness on sugar beet foliage and average leaf surface temperature during the period of leaf wetness were determined by a leaf wetness sensor and an infrared thermometer (LWS/IRTI, respectively,

The sugar beet nematode is a major pest for western Nebraska sugar beet (Beta vulgaris) farmers, and is costly to control. Three field studies were conducted to help establish the relationship between preplant nematode egg and larva concentration (eggs per cm 3 of soil) before plant ing, and final yield. Response functions were estimated and economic thresholds were calculated for each field study. Economic threshold levels from each field study were very different. For a selected study, the sensitivity of results to changes in important parameters (percent sugar, percent control, cost of control and sugar price) was evaluated. The threshold level was influenced by each of the parameters evaluated.

No abstract