Influence of time of sowing and groundnut varieties on the incidence and severity of late leaf spot (Phaeoisariopsis personata) of groundnut

摘要

The field experiment was conducted to study the influence of sowing dates on the incidence and severity of late leaf spot on groundnut. The study on incidence, severity, corresponding defoliation, frequency and size of the leaf spot revealed that allthese aspects were significantly influenced by the sowing dates and crop varieties which directly affected the pod yield and test weight.The crop sown early on 25th June exhibited maximum late leaf spot disease incidence (range 46.45-56.25%), disease severity (range 40.12-49.58%), defoliation (range, 13.18-18.36%), frequency (range, 1.38-1.76/mm~2) and size (range, 1.44-1.52/mm~2) followed by the crop sown on 10th June and 25th July. Among the groundnut cultivars, susceptible cv. JL-24 exhibited maximumdisease incidence (range, 35.83-56.25%), disease severity (range, 31.07-49.58%), defoliation (range, 7.70-18.36%), frequency (range, 1.21-1.76/mm~2) and size (range, 1.29-1.52/mm~2), followed by TAG-24.TG-26 and LGN-1.The late leaf spot disease incidence, severity and corresponding defoliation recorded at various intervals were found to be increased with the age of the crop and both were found maximum at the physiological maturity of the crop. The results obtained in respect of the influence of sowingdates and crop varieties on pod yield and test weight indicated that the crop sown early (25th June) was affected severely with the disease and thereby gave reduced pod yield (range, 1197-1679 kg/ha) and test weight (25.19-29.40 g) followed by the crop sown on 10th July and 25th July.The epidemiological implications of the disease occurring simultaneously are important because the establishment of the disease management strategies depends on the disease interactions.