The efficacy of copper bactericides for control of Xanthomonas campestris pv. vesicatoria in eastern Oklahoma tomato fields was evaluated. Copper bactericides did not provide adequate control, and copperresistant (Cur) strains of the pathogen were isolated. The Cur genes in these strains were located on a large indigenous plasmid designated pXV1OA. The host range of pXV1OA was investigated; this plasmid was efficiently transferred into 8 of 11 X. campestris pathovars. However, the transfer of pXVlOA to other phytopathogenic genera was not detected. DNA hybridization experiments were performed to characterize the Cur genes on pXVlOA. A probe containing subcloned Cur genes from X. campestris pv. vesicatoria E3C5 hybridized to pXV1OA; however, a subclone containing Cur genes from P. syringae pv. tomato PT23 failed to hybridize to pXV1OA. Further DNA hybridization experiments were performed to compare pXV1OA with pXvCu plasmids, a heterogenous group of Cur plasmids present in strains of X. campestris pv. vesicatoria from Florida. These studies indicated that the Cur genes on pXVIOA and pXvCu plasmids share nucleotide sequence homology and may have a common origin. Further experiments showed that these plasmids are distinctly different because pXV1OA did not contain sequences homologous to IS476, an insertion sequence present on pXvCu plasmids.

Annual reductions in corn (Zea mays L.) yield caused by diseases were estimated by university Extension-affiliated plant pathologists in 26 corn-producing states in the United States and in Ontario, Canada, from 2016 through 2019. Estimated loss from each disease varied greatly by state or province and year. Gray leaf spot (caused by Cercospora zeae-maydis Tehon & E.Y. Daniels) caused the greatest estimated yield loss in parts of the northern United States and Ontario in all years except 2019, and Fusarium stalk rot (caused by Fusarium spp.) also greatly reduced yield. Tar spot (caused by Phyllachora maydis Maubl.), a relatively new disease in the United States, was estimated to cause substantial yield loss in 2018 and 2019 in several northern states. Gray leaf spot and southern rust (caused by Puccinia polysora Underw.) caused the most estimated yield losses in the southern United States. Unfavorable wet and delayed harvest conditions in 2018 resulted in an estimated 2.5 billion bushels (63.5 million metric tons) of grain contaminated with mycotoxins. The estimated mean economic loss due to reduced yield caused by corn diseases in the United States and Ontario from 2016 to 2019 was US$55.90 per acre (US$138.13 per hectare). Results from this survey provide scientists, corn breeders, government agencies, and educators with data to help inform and prioritize research, policy, and educational efforts in corn pathology and disease management.

Soybean [Glycine max (L.) Merrill] yield losses as a result of plant diseases were estimated by university and government plant pathologists in 29 soybean-producing states in the United States and in Ontario, Canada, from 2015 through 2019. In general, the estimated losses that resulted from each of 28 plant diseases or pathogens varied by state or province as well as year. Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) caused more than twice as much loss than any other disease during the survey period. Seedling diseases (caused by various pathogens), Sclerotinia stem rot (white mold) (caused by Sclerotinia sclerotiorum [Lib.] de Bary), and sudden death syndrome (caused by Fusarium virguliforme O'Donnell & T. Aoki) caused the next greatest yield losses, in descending order. Following SCN, the most damaging diseases in the northern U.S. and Ontario differed from those in the southern U.S. The estimated mean economic loss from all soybean diseases, averaged across the U.S. and Ontario, Canada was $45 U.S. dollars per acre ($111 per hectare). The outcome from the current survey will provide pertinent information regarding the important soybean diseases and their overall severity in the soybean crop and help guide future research and Extension efforts on managing soybean diseases.

Kolander, T. M., Bienapfl, J. C, Kude, I E., and Ma!vic!{, D. K. 2012. Symptomatic and asymptomatic host range of Fusarium virguliforme, the causa! agent of soybean sudden death syndrome. Plant Dis. 96:1148-1153.Sudden death syndrome, caused by Fusarium virguliforme, is an important disease of soybean in the United States. Fifteen species of crops, weeds, or prairie plants were evaluated for tbeir potential as bosts of F, virguliforme. Root and foüar symptoms and ptant biomass were assessed foüowing greenhouse inocu!ation studies. Root co!onization of F, virguliforme was determined with isolations and with polymerase chain reaction assays. Soybean, a!fa!fa, pinto and navy bean, white and red c!over, pea, and Canadian mi!!( vetch deve!oped root necrosis. Soybean, alfalfa, and red clover also deve!oped foüar symptoms foUowing inoculation. Sugar beet and canola did not de-Corresponding aut!ior: D. K. Malvick,