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.

Brome mosaic virus (BMV) was first detected in Alabama on wheat in 2002. Since that time it has been detected in wheat plants in all counties where wheat is grown, indicating it has become established in all wheat growing regions of the state. Wheat is an important winter crop in Alabama and is grown for both seed and animal feed. A vector for BMV has been reported to be the dagger nematode, Xiphinema spp. This study was conducted to determine if this nematode was associated with wheat production and the occurrence of the virus in Alabama. Soil samples were collected from a wheat variety trial and grower wheat fields throughout the state monthly during the growing season. Nematodes were extracted using the sugar flotation method and identified. The virus was detected using a BMV-specific direct double antibody sandwich ELISA. Although plant parasitic nematodes were detected in all samples, no Xiphinema spp. were found in relation to any wheat field in which BMV-infected plants occurred. However, in some locations Xiphinema spp. were isolated from soil samples taken from adjacent fields associated with other crops which are not considered hosts for BMV. In Alabama, Xiphinema spp. were not found to be associated with the occurrence of BMV in wheat fields and, therefore, is not the primary vector of this virus.

During October 2003, soybean (Glycine max (L.) Merr.) plants showing symptoms of delayed maturity of stems, or green stem, were observed in a soybean cultivar trial on Dee River Ranch in Pickens County, Alabama. Symptoms were characteristic of those caused by Bean pod mottle virus (BPMV). BPMV infections have been identified in other southern states, including Arkansas, Louisiana, and neighboring Mississippi, but had not yet been identified in Alabama (1,2,3). In this study, a cultivar trial was established as a nonreplicated strip test to evaluate the performance of nongenetically modified soybean cultivars in high-pH soils. The trial consisted of 12 maturity group V cultivars planted side by side in 24-row plots approximately 1 km long. The cultivars consisted of Anand, Asgrow 5547, Asgrow 5944, Delta King 5995, Deltapine 4748, Deltapine 5110, Deltapine 5989, Essex, Hutcheson, Pioneer 9594, Pioneer 9597, and USG5601T. During the season, a known vector of BPMV, the bean leaf beetle (Cerotoma trifurcate Forster), was identified in the plots (4). On 10 October, the majority of plants in the trial had senesced; however, it was observed that plants of 6 of the 12 cultivars were showing symptoms of green stem typical of BPMV infection. A visual assessment was taken to determine incidence of green stem for Asgrow 5547, Delta King 5995, Deltapine 5110, Deltapine 5989, Pioneer 9594, and USG5601T. Incidence between 1 and 5% was observed for Delta King 5995, Deltapine 5989, and Pioneer 9594. Incidence of less than 1% was observed for Asgrow 5547, Deltapine 5110, and USG5601T. Twenty soybean plants showing symptoms of green stem and retaining green leaves were sampled from each of the six cultivars by collecting one trifoliate leaf near the top of the plant. All samples were tested for BPMV using double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) according to the manufacturer's instructions (Agdia, Inc., Elkart, IN). BPMV was detected in 30% of Deltapine 5989, 10% of Delta King 5995, and 45% of Pioneer 9594 plants. BPMV was not detected in Asgrow 5547, Deltapine 5110, and USG5601T. Ten of the samples shown to be infected with BPMV using DAS-ELISA were mechanically transferred to soybean seedlings in the greenhouse. These plants developed systemic mottle symptoms typical of those caused by BPMV and tested positive for the virus BPMV using DAS-ELISA. To our knowledge, this is the first report of BPMV in Alabama. References: (1) N. S. Horn et al. LA. Agric. 13:12, 1970. (2) H. N. Pitre et al. Plant Dis. Rep. 63:419, 1979. (3) J. P. Ross. Plant Dis. Rep. 47:1049, 1963. (4) H. J. Walters. (Abstr.) Phytopathology 48:346, 1958.

Herbivorous insects often feed on pathogen-infected plants in nature, and it is likely that pathogen infection alters host plant quality. We documented the effects of plant infection by a widespread plant virus on host plant quality for a generalist insect herbivore and tested the hypothesis that these effects vary among plant genotypes. We found that infection by Cucumber mosaic virus (CMV) altered the host plant quality of Mimulus guttatus (Phrymaceae) for meadow spittlebugs, Philaenus spumarius (Hemiptera: Cercopidae). The effects of CMV infection on host plant quality, however, varied among full-sib M. guttatus families, suggesting that these effects vary among plant genotypes. In most full-sib families, CMV infection either had no effect on host plant quality or increased host plant quality as measured by spittlebug size and development time. In a few M. guttatus families, however, CMV infection decreased host plant quality. There was no relationship between the effect of CMV infection on plant growth and the subsequent effect of CMV infection on spittlebug performance, suggesting that broad changes in host plant performance (e.g., growth rate) were not responsible for the effects of CMV infection on host plant quality for spittlebugs. We suggest that future studies of the effects of pathogen infection of plants on insect herbivores consider variation among plant genotypes in the mechanisms and ecological consequences associated with these effects.