Influence of row pattern and plant population on the epidemiology of southern stem rot (sclerotium rolfsii) on peanut, arachis hypogaea l.
Sconyers, Layla Eileen
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Several field studies were conducted to determine the effects of row pattern, plant population, and cultivar growth habit on the development of southern stem rot (Sclerotium rolfsii .) and tomato spotted wilt disease of peanut (Arachis hypogaea L.). A microplot and grid study were set up in order to determine the development of stem rot in seed spacings ranging from 5.1 cm to 30.5 cm. Two conventional field studies were also designed in order to assess disease development in either single (91.4 cm) or twin (20.3 cm) rows and at three seeding rates (single rows: 12.5, 17.4 or 22.6 seed/m; twin rows: 6.2, 8.9 or 11.5 seed/m). In one of these field studies, fungicide (azoxystrobin, 1.35 L/ha at 60 and 90 DAP) efficacy was also assessed. From these studies, it is apparent that stem rot severity and incidence is greater when plants are spaced closely together (5.1 - 10.2 cm). Further, severity, incidence and spread were also reduced when planted in a twin row pattern versus single row pattern, especially in single rows planted at a high seeding rate (22.6 seed/m). Incidence of tomato spotted wilt symptoms and actual virus incidence were also assessed, and symptoms were significantly greater in single rows planted at low seeding rates (12.5 seed/m) than twin rows at any seeding rate. However, actual virus incidence was approximately the same, regardless of seeding rate or row pattern. These results do not change the tomato spotted wilt index, however they do indicate that sometimes disease symptoms are not always a good predictor of actual virus infection. Hopefully with this information, producers will be better able to plan their inputs properly and assess their disease risk.