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Abstract
Cytokinin activity was indicated in roots of Chrysanthemum morifolium Ramat, cv. Polaris cultured using a nutrient film technique and assayed at 3 stages of plant development: young, actively growing; mature flowering; and senescing with dried flowers.
Zonate leaf spot (ZLS) caused by Cristulariella moricola, apparently a rare disease of tomato, was identified in a commercial tomato field in southeastern Arkansas in June, 1991. Although lesions of ZLS were similar to early blight (Alternaria solani) lesions, which were also present, there were several distinctions between the lesions: the concentric rings in lesions of ZLS were more symmetrical than early blight lesions, no distinct chlorosis was associated with the lesions, and ZLS lesions were not localized near the bottom of the tomato canopy. Koch's postulates were completed on several greenhouse grown tomato cultivars. Inoculum was produced on autoclaved tomato leaves incubated at 20 C and consisted of large (300-400 um long) “Christmas tree” shaped propagules. When free moisture was maintained at 20 C, large (> 1 cm), rapidly expanding, water-soaked lesions were observed on leaves of inoculated plants 1-3 days after inoculation. Lower humidities caused lesions to rapidly dry out. Epidemiological factors, such as temperature, leaf wetness, and cultivar susceptibility also have been examined.
No reduction in yield and quality of pecan nuts or leaf mineral nutrient concentration occurred when 100 lb/acre of N was applied through a drip-irrigation system compared with 200 lb/acre applied either all broadcast or half broadcast and half fertigated. Yield of `Stuart', percentage kernel of `Schley', and nut size of both cultivars were increased by irrigation or irrigation and fertigation. The 100 lb/acre N-all-fertigated treatment resulted in less soil pH reduction and less loss of K, Ca, and Mg from soil underneath the tree canopy than broadcast treatments. No evidence of excessive soil pH reduction in the wetted zone of fertigated trees was noticed. Calcium and Mg were higher within than outside the wetted zone.