Comparison of weather-based advisory programs for managing early leaf spot on runner and Spanish peanut cultivars

Wu, L. and Damicone , J.P. and Jackson, K.E. (1996) Comparison of weather-based advisory programs for managing early leaf spot on runner and Spanish peanut cultivars. Plant Disease, 80 (6). pp. 640-645.

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Weather-based advisory programmes for scheduling applications of chlorothalonil to control Cercospora arachidicola [Mycosphaerella arachidis] on groundnut were evaluated for 2 runner cultivars (Florunner and Okrun) and 1 Spanish cultivar (Spanco). Advisory programmes included the following: (1) the Parvin, Smith and Crosby programme that utilizes daily infection indices based on the favourableness of RH and temp. (T) for infection over a 2-day period (PSC); (2) the modified PSC programme for cultivars with partial resistance that reduces daily infection indices by 0.85 (0.85*PSC); (3) the Virginia programme that accumulates hours of T and RH favourable for infection with spray thresholds of 36-96 h (VA-36 to VA-96); and (4) the AU-Pnuts programme based on precipitation events and/or probability forecasts. Using the standard 14 d programme, 6.7 sprays/year were applied to Spanco and 7 sprays/year were applied to the runner cultivars. Disease control and the reduction in area under the disease progress curve was >90% for all cultivars. The PSC and 0.85*PSC programmes failed to recommend needed sprays for all cultivars in 1992 and 1993 when disease incidence for these programmes did not differ from the unsprayed control. For Spanco the VA-36 (3.3 sprays/year) and AU-Pnuts (4.5 sprays/year) were the most effective advisory programmes and provided 53-78% control. Except for the VA-48 and VA-60 programmes in 1992, disease control on Spanco for VA programmes was reduced with increasing spray thresholds of 48-96 h. The VA and AU-Pnuts programmes provided better control on the runner cultivars than on Spanco. Disease control for the VA-36 (3.3 sprays/year), VA-48 (2.3 sprays/year) and AU-Pnuts (4.5 sprays/year) programmes ranged from 62 to 95% and was 80% or greater in 1992 and 1993, when levels of leaf spot were highest. The VA-60 and VA-72 programmes reduced disease incidence and area under the disease progress curve (AUDPC) for the runner cultivars each year. In 1992 and 1993, when leaf spot reduced yields of Spanco, the VA-36, VA-48 (2.3 sprayers/year), VA-60 (2.5 sprays/year) and AU-Pnuts programmes were the only advisory programmes that had yields equal to the 14 d programme. Yields of the runner cultivars were not reduced by leaf spot in any year. The VA programme was the most efficient advisory programme tested. The opt. spray threshold for the VA program depended on the cultivar grown and the level of control desired. Spray thresholds of 36 h for Spanish and 48 h for runner cultivars were implemented commercially in Oklahoma.

Item Type: Article
Additional Information: SNNigam Collection
Author Affiliation: Department of Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
Subjects: Plant Protection
Divisions: Groundnut
Depositing User: Mr Balakrishna Garadasu
Date Deposited: 14 May 2013 10:15
Last Modified: 14 May 2013 10:15
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