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Sunflower rust caused by Puccinia helianthi (Schw.) is an autoecious and macrocyclic rust that occurs on wild perennial, wild annual, and cultivated sunflower species (Helianthus annuus L.). Severe epidemics of sunflower rust can significantly reduce yield and quality of cultivated sunflower (4). Uredinia of P. helianthi were observed in individual sunflower fields in four Illinois counties in 2008, namely; Champaign, LaSalle, McLean, and Livingston. Leaves with uredinia from each field were collected and shipped to the USDA-ARS Sunflower Pathology Laboratory in Fargo, ND. Urediniospores were harvested by rinsing leaves with Soltrol 170 isoparaffin solvent (Chevron Phillips Chemicals, Woodlands, TX). Urediniospores were increased by inoculating the spore suspension onto 21-day-old seedlings of susceptible oilseed hybrid Myc-7350 with a vacuum-pump powered atomizer. After the Soltrol 170 evaporated, plants were placed in a dew chamber for 24 h and then moved to a greenhouse at approximately 20 to 25°C with a 14-h photoperiod. When sporulating uredinia were visible, a bulk collection of urediniospores was made from samples of each location. Additionally, one single-pustule derived isolate from each location was obtained by harvesting urediniospores from a single pustule and increasing as above. To determine the virulence phenotypes, each single-pustule derived isolate and bulk collection were inoculated as above onto at least two replicated sets of the nine international differential lines (each set containing three plants per line) and evaluated after 14 days (1,2). The single-pustule isolates from LaSalle, Livingston, and McLean counties were determined to be virulence phenotype 300. The single-pustule isolate from Champaign produced no infection on any differential lines, including the susceptible, and was therefore considered not viable. The virulence phenotypes of the bulk samples were coded as 330 (Champaign), 324 (McLean), and 336 (Livingston and LaSalle). Virulence of all aforementioned virulence phenotypes was found to be common in a recent survey of 400 Midwestern P. helianthi samples collected in 2007 and 2008 (1). Although sunflower production is limited in Illinois, expansion could occur. This is particularly true in southern Illinois, where double cropping sunflower after winter wheat is a possibility. Urediniospore germination and infection is favored by free moisture and temperatures ranging from 10 to 25°C, while optimum temperature for spore development ranges from 20 to 35°C (3). These environmental conditions are often more common in Illinois than in the major sunflower-producing states in the Great Plains, where sunflower rust is a concern annually. Thus, determination of P. helianthi virulence phenotypes in Illinois may be important for future management of sunflower rust. References: (1) T. J. Gulya and S. G. Markell. National Sunflower Association. Online Publication/Gulya_RustStatus_09, 2009. (2) T. Gulya and S. Masirevic. FAO Eur. Res. Network on Sunflower. Bucarest, Romania. 31, 1995. (3) T. Gulya et al. Sunflower Diseases. Page 263 in: Sunflower Technology and Production. A. A. Schneiter, ed. American Society of Agronomy, Madison, WI, 1997. (4) S. Markell et al. Plant Dis. 93:668, 2009.

In August 2008, long and narrow lesions were observed on leaves of corn (Zea mays L.) growing in a field in Pope County, Illinois. Lesions were 10 to 35 × 50 to 250 mm and were cream to tan. Dark pycnidia inside the lesions were immersed and approximately 350 μm in diameter. Affected leaves were collected and placed into a moist chamber to encourage the development of conidia. Conidia developed in cirri and were dark, one septate, and 7 to 11 × 59 to 87 μm. Cirri were streaked onto potato dextrose agar (PDA; Becton, Dickinson, and Company, Franklin Lakes, NJ) and cultures arising from single conidia were transferred and maintained. On the basis of the corn leaf symptoms and the morphological characteristics of the pycnidia and conidia, the fungus was tentatively identified as Stenocarpella macrospora (Earle) Sutton (1). To complete Koch's postulates, ‘Garst 84H80-3000GT’ corn was inoculated in the greenhouse. Conidia were produced by placing a S. macrospora isolate from Pope County, IL onto water agar containing autoclaved corn leaves and incubating at room temperature until pycnidia and conidia were produced (approximately 3 weeks). A conidial suspension was used to inoculate the leaf whorls of corn plants (approximately at the V4 growth stage). Control plants were mock inoculated with sterile water. The experiment was repeated once over time. Twenty days after inoculation, all plants inoculated with S. macrospora conidia developed lesions similar to those observed in the field, and mock-inoculated plants remained symptomless. The fungus was reisolated on PDA from the symptomatic leaves. In August 2009, symptomatic leaves similar to those observed in Pope County, IL in 2008 were observed and collected from corn fields in Gallatin and Vermillion counties. Pycnidia and conidia from these lesions were similar to those described above, and isolates from single conidia were obtained from these samples. To confirm the identity of all isolates collected, PCR amplification of the small subunit rDNA and internal transcribed spacer (ITS) region with primers EF3RCNL and ITS4 was conducted (3). The PCR product was sequenced with these primers at the Keck Biotechnology Center at the University of Illinois, Urbana. The resulting nucleotide sequence was compared with small subunit rDNA and ITS sequences deposited in the GenBank nucleotide database, which revealed 99% homology to sequences of S. macrospora. In total, six of our S. macrospora isolates from Gallatin, Pope, and Vermillion counties were submitted to the United States Department of Agriculture–Agriculture Research Service Culture Collection in Peoria, IL, where they have received NRRL Accession Nos. 54190–54195. To our knowledge, this is the first report of S. macrospora affecting corn in Illinois. Although not observed in the Illinois corn fields described above, S. macrospora has been reported to infect stalks and ears (2). Because of the large leaf lesions caused by S. macrospora and its reported aggressiveness in causing disease on leaves, ears, and stalks, this pathogen has the potential to cause severe yield and quality losses to corn in the United States (2). References: (1) M. L. Carson. Diseases of minor importance or limited occurrence. Page 23 in: Compendium of Corn Diseases. 3rd ed. The American Phytopathological Society, St. Paul, MN, 1999. (2) F. M. Latterell and A. E. Rossi. Plant Dis. 67:725, 1983. (3) N. S. Lord et al. FEMS Microbiol. Ecol. 42:327, 2002.

Soybean rust, first reported in the continental United States in Louisiana in 2004 (2), is one of the most important foliar diseases of soybean worldwide. On 10 October 2006, 20 soybean leaflets from 20 plants at physiological maturity were arbitrarily collected in research plots near Glendale, IL at the University of Illinois Dixon Springs Agricultural Center in Pope County and sent by overnight courier. On 11 October, leaflets were examined with a dissecting microscope at the Soybean Disease Laboratory at the National Soybean Research Center, and then at the Plant Disease Clinic, University of Illinois. Tan, angular lesions that were 2 to 4 mm in diameter were observed on the lower leaf surfaces of two of the 20 leaflets. Within these lesions, there was one uredinum on one leaflet and four on the other leaflet exuding hyaline, echinulate urediniospores (20 × 25 μm). On 11 October 2006, these leaflets were sent by overnight courier to the USDA/APHIS/PPQ/NIS Laboratory, Beltsville, MD Plant Disease Clinic for identification by morphological examination and by PCR using primers specific to Phakopsora pachyrhizi (1). Both tests confirmed the presence of P. pachyrhizi. The 18 leaflets that did not have sporulating pustules on 11 October were incubated in the laboratory for 5 days at near 100% relative humidity. Following incubation, nine leaflets were observed to have uredinia exuding urediniospores with a range of 1 to 43 uredinia per leaflet. These results indicate that incubation may be necessary to maximize the potential to observe uredinia exuding urediniospores. To our knowledge, this is the first report of P. pachyrhizi infecting plants in Illinois. References: (1) R. D. Frederick et al. Phytopathology 92:217, 2002. (2) R. W. Schneider et al. Plant Dis. 89:774, 2005.

In August 2001, symptomatic mature fruit of watermelon (Citrullus lanatus) cvs. Crimson Sweet and Royal Sweet were collected from six fields (48 ha) in Iroquois, Kankakee, and Mason counties in Illinois. The fruit surface had dark green, water-soaked lesions, and the rind's epidermis was cracked. Sections of infected rind were examined with a light microscope, and bacterial streaming was observed. Rind tissue was disinfested by rubbing the fruit surface with a paper towel moistened with 70% ethanol. Pieces of rind from the margins of lesions were placed in a test tube containing sterile-distilled water. The tube was shaken, and the suspension was streaked on King's medium B agar in petri plates. The plates were incubated at 26°C for 3 days. A nonfluorescent, gramnegative, anaerobic, oxidase-positive, rod-shaped bacterium was isolated that produced creamy white colonies on nutrient agar. The bacterium was identified as Acidovorax avenae subsp. citrulli based on an enzyme-linked immunosorbent assay test specific for A. avenae subsp. citrulli (kit PSA 14,800; Agdia Inc., Elkhart, IN). The disease was diagnosed as bacterial fruit blotch (1,2). The occurrence of bacterial fruit blotch of watermelon in Illinois is important because (i) watermelon is widely grown in Illinois, (ii) the pathogen also infects melons and pumpkins, and (iii) Illinois grows approximately 1,000 ha of melons and 8,000 ha of pumpkins. References: (1) R. X. Latin. Bacterial fruit blotch. Pages 34-35 in: Compendium of Cucurbit Diseases. The American Phytopathological Society, St. Paul, MN,1996. (2) G. S. Somodi et al. Plant Dis. 75:1053, 1991.