Sclerotinia sclerotiorum is the causal agent of Sclerotinia stem rot (SSR) of canola (Brassica napus). In North Dakota, the leading canola producer in the United States, SSR is an endemic disease. In order to estimate the impact of this disease on canola yield, field experiments were conducted from 2000 to 2004 at several locations in North Dakota and Minnesota. Experimental plots were either inoculated with laboratory-produced ascospores or infected by naturally occurring inoculum in commercial fields. Applying fungicides at different concentrations and timings during the flowering period created epiphytotics of diverse intensities. Disease incidence was measured once prior to harvesting the crop on 50 to 100 plants per plot. Results of the study indicated that 0.5% of the potential yield (equivalent to 12.75 kg/ha) was lost for every unit percentage of SSR incidence (range of 0.18 to 0.96%). Considering the current cost of fungicide applications and the market value of this commodity, a 17% SSR incidence could cause losses similar to the cost of a fungicide application. Additional efforts are required to improve current levels of tolerance of canola plants to this pathogen.

Increased interest in alternative sources of oil for edible and industrial uses have stimulated interest in the producti on of new oilseed crops. Spring sown canola (Brassica napus L. and Brassica campestris L.) and crambe (Crambe abyssinica Hochst) have excellent potential to expand the diversity of agricultural crops available to North Dakota producers. The three species are cool season oilseed crops that are adapted to this area. "Canola" is a tradename for varietie of rapeseed from which the oil can be used for hu man con umption, while crambe oil is used for industrial purpose .

Sclerotinia stem rot (SSR), incited by Sclerotinia sclerotiorum, causes yield reductions to canola (Brassica napus) grown in North Dakota and Minnesota. Field trials were conducted in North Dakota and Minnesota from 2000 to 2004 to evaluate the effect of foliar fungicides on SSR and canola yield. Levels of SSR varied among years and location. In general, fungicides that consistently reduced SSR incidence compared with an untreated control were azoxystrobin, benomyl, boscalid, iprodione, prothioconazole, tebuconazole, thiophanate-methyl, trifloxystrobin, and vinclozolin. Significant reductions in SSR incidence with fungicides did not always translate into differences in canola yield, however. Inconsistent results were observed with different timings of applications based on percent bloom. This indicates that application timing should be based on factors in addition to percent bloom.

Sunflower rust caused by Puccinia helianthi (Schw.) is widespread in North America and occurs annually on cultivated sunflower (Helianthus annuus L.) and wild annual and perennial Helianthus spp., although severity on the U.S. sunflower crop has been increasing in recent years (2). P. helianthi is a autoecious, macrocyclic rust, but the aecial stage is rarely observed in the field (1,3,4). In most years, the earliest appearance of sunflower rust in North Dakota (ND) and surrounding states usually occurs in early August as the uredinial stage. Initial inoculum can result from urediniospores that overwinter in the Northern Great Plains, urediniospores blown in from areas south of North Dakota, or basidiospores completing the life cycle. However, aecia have been noted very infrequently and never widespread, indicating initial inoculum is usually urediniospores. Aecia of P. helianthi were first observed on 24 June 2008 in a commercial sunflower field (confection hybrid CHS 3126) near Mohall, ND. Aecia cups measuring 0.2 to 0.3 mm in diameter were observed in clusters that were 1 to 7 mm wide in diameter and containing as many as 150 cups. Aecia cups were bright orange but turned brown-black as they senesced. As many as 15 aecial clusters occurred on individual leaves or cotyledons. Aeciospores were ellipsoid, hyaline, and measured approximately 20 μm in diameter. On 4 July 2008, uredinia were first observed in the same Mohall, ND field. At that time, uredinia, aecia, and senesced aecia could all be found on the same leaves. In a non-fungicide-treated strip of the field, pustule coverage on the lower leaves was 10 to 20% by mid-July, pustule coverage on the upper four leaves of plants in the untreated strip was 56% by 27 August, and yield at harvest was less than 200 kg/ha. The rest of the field was sprayed twice with fungicides and yielded 1,571 kg/ha, which is similar to the statewide yield average of 1,573 kg/ha in 2008. To determine the prevalence of aecia in the primary growing regions of ND and Minnesota (MN), surveys were conducted in 75 sunflower fields in 18 counties between 22 and 24 July in ND and 34 fields in 8 counties between 17 and 31 July in MN. Incidence of aecia and uredinia were determined by visual observation of a minimum of 20 plants scouted in a ‘W’ pattern in the field. Rust was found in 31 and 53% of fields in ND and MN, respectively. In fields where rust was found, both aecia and uredinia were observed in 37% of the fields, aecia only in 29% of the fields, and uredinia only in 34% of the fields. Although it is uncertain why aecia were widespread in 2008, night temperatures in Mohall, ND, where aecia were first observed, reached the dew point temperature on 51 of 61 days in June and July, suggesting that dew or fog likely formed. Thus, favorable conditions for germination and infection early in the growing season indicate widespread occurrence of rust was likely a result of local inoculum sources. The early appearance of aecia is cause for concern for two reasons: significant yield loss can occur when rust appears early in the growing season; and the presence of aecia suggest that the pathogen completed its sexual cycle. When P. helianthi completes its life cycle it is likely that a greater diversity of races will result (4). References: (1) D. L. Bailey. Univ. Minn. Tech. Bull. 16:1, 1923. (2) D. Berglund. Natl. Sunflower Assoc. Online publication. /Berglund_2007_NSA_Survey_08. 2008. (3) H. S. Jackson. Mem. Torrey Bot. Club 18:1, 1931. (4) G. A. Kong et al. Australas. Plant Pathol. 28:320, 1999.

All malting barley (Hordeum vulgare L.) cultivars adapted for production in the upper midwestern USA are susceptible to Fusarium head blight (FHB), incited primarily by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein)]. Quality of FHB‐infected barley is reduced due to a mycotoxin called deoxynivalenol (DON) that is produced by the pathogen. Malting barley buyers severely discount or refuse to purchase barley with DON concentrations >0.5 mg kg−1. Individually, use of genetic resistance or fungicides has not successfully reduced DON concentrations to acceptable limits. The objective of this research was to determine if the integrated use of the fungicide tebuconazole (α‐[2‐(4‐chlorophenyl) ethyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol) and barley genotypes with partial FHB resistance could reduce DON to acceptable concentrations. Field research, using two rates of tebuconazole (0 and 118 mL a.i. ha−1) and 13 barley genotypes with varying levels of FHB resistance, was conducted in North Dakota from 2000 to 2002. No supplemental inoculum or irrigation was used in any of the environments. Data for FHB severity, DON concentration, foliar disease severity, and kernel color were collected and analyzed. Deoxynivalenol was detected in all environments at concentrations >0.5 mg kg−1. Overall, the response of the FHB‐resistant and moderately resistant genotypes to tebuconazole was inconsistent for FHB severity and DON accumulation. Furthermore, tebuconazole applied to FHB‐resistant or moderately resistant genotype did not consistently result in DON concentration of ≤0.5 mg kg−1 in any of the environments. Thus, the integrated use of FHB‐resistant or moderately resistant genotypes and tebuconazole will not reduce DON.

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