Survey of Fungal, Nematode and Virus Diseases of Soybean in Alabama

Abstract

Observations on incidence of foliar diseases, plant viruses, and plant-parasitic nematodes were collected from soybean fields in Alabama from 2008-2010. Cercospora leaf blight (Cercospora kikuchii), downy mildew (Peronospora manshurica), and target spot (Corynespora cassiicola) were the most common foliar diseases observed in the study. Cercospora leaf blight was found in 45% (2008), 77% (2009), and 70% (2010) of the fields surveyed. Downy mildew was observed in 72% (2008), 38% (2009), and 29% (2010) and target spot was detected in 45% (2008 and 2009) and 29% (2010) of the fields in the study. Soybean rust (Phakopsora pachyrhizi) was found in 43% of the fields surveyed in 2009 but was only found in one field in 2008 and was not detected in 2010. Bean pod mottle virus was detected at relatively high levels in all three years, whereas Soybean mosaic virus occurrence was less consistent and of lower incidence. Tomato spotted wilt virus was detected for the first time on soybean in Alabama. Reniform (Rotylenchulus reniformis), soybean cyst (Heterodera glycines), root-knot (Meloidogyne spp.), and lesion nematodes (Pratylenchus spp.) were the most common plant-parasitic nematodes collected with reniform nematodes found in over 30% of the fields surveyed. Soybean cyst nematode races 2, 4, 5, 6, and 14 were identified among the field population collected. The survey has increased disease awareness among growers and has aided in directing research efforts in the state. Accepted for publication 18 November 2011. Published 27 December 2011.