WHITE RUST INFECTION AND LEAF CHLOROSIS IN RELATION TO CROP STRATEGIES IN SPINACH
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abstract
The interaction of spinach (Spinacia oleracea L.) crop management strategies on white rust caused by Albugo occidentalis G. W. Wils., leaf chlorosis, aphid numbers, root growth and yield were evaluated in 1992. Irrigation levels were low (I-low), medium (I-med) and high (I-high); fungicides were none (F0), metalaxyl at planting (F1), and metalaxyl at planting plus experimental CGA 2014 foliar (F2); and genotypes were ACX 5044 and ARK 88-354. The Gompertz model best described the white rust disease progress. At all irrigation levels, ACX 5044 had a higher rate of disease increase (rG) and an earlier disease onset than ARK 88-354. Metalaxyl delayed disease onset and rG in ACX 5044 only at I-low, but not at I-med and I-high. ARK 88-354 was the less sensitive genotype to fungicides. Chlorosis, estimated by spectrophotometry, was higher at I-med and I-high, while ARK 88-354 had less chlorosis than ACX 5044. Root diameter was increased with F1 compared to F0. Lateral and tap root dry weights were higher for ARK 88-354. Yields for ARK 88-354 were significantly higher than ACX 5044. No treatments influenced the number of live green peach aphids [Myzus persicae (Sulzer)] or aphids parasitized by Pandora neoaphidis (Remaudire and Hennebert) Humber. Genotypes with partial resistance to white rust, superior leaf color and growth are recommended to use with minimum irrigation for winter plantings. 1994.
