Cryptodiaporthe canker, caused by Cryptodiaporthe corni (Wehm.) Petrak (anamorph Myxosporium nitidum Berk. & Curt.), is known to occur only on pagoda dogwood (Cornus alternifolia L. fil.) throughout its native range in eastern Canada and most of the eastern United States (1). Cankered branches with yellow-to-orange pigmented bark were recently observed on four ≈25-year-old C. alternifolia plants in an ornamental planting on the campus of North Dakota State University in Fargo. Although the fungal anamorph was usually present on all symptomatic materials, the teleomorph was also present on branches with larger diameters (>15 mm). Collections of infected branches made on 25 April 2001 contained perithecia but did not contain mature ascospores. Shoot growth began during the first week of May. Subsequent collections made on 11 May and 8 June 2001 contained perithecia with mature ascospores. A previous collection made on 12 October 2000 contained fully developed perithecia devoid of ascospores. A range of symptoms was present among the individual trees: one tree was severely cankered (up to 4 cm diameter) with many dead branches; one tree showed only minor damage with tip dieback on a few small twigs; and two trees had intermediate symptoms (1 cm diameter with cankers) with several dead branches. Pagoda dogwood is generally seed propagated, and differences in disease severity observed in these plants may be the result of genetic variation in resistance. Selection for resistant genotypes may be a possibility. Specimens (BPI 840955A and B) consisting of cankered branches containing both fungal morphs were deposited at the U.S. National Fungus Collections at Beltsville, MD. Although Cryptodiaporthe canker was previously collected from a native woodland tree in Minnesota (1), the current North Dakota specimens were collected from cultivated plants in a landscape setting. To our knowledge, this is the first report of Cryptodiaporthe canker in North Dakota. Management of this disease may need to be considered when recommending C. alternifolia for horticultural plantings. Reference: (1) S. C. Redlin and A. Y. Rossman. Mycologia 83:200, 1991.

The effect of wounding, temperature, and inoculum on the development of pink rot caused by Phytophthora erythroseptica, was studied for its potential impact on postharvest infection. Tissue plugs cut from pink rot infected tubers and plugs of similar size from laboratory cultures of the pathogen were highly effective inoculum sources on wounded tubers. Severe wounding, temperatures of 15 to 25°C, and high inoculum density affected the infection risk. Regardless of source or amount of inoculum, any degree of wounding greatly increased incidence of infection of tubers by P. erythroseptica. Infections in unwounded tubers started at 15°C, whereas in wounded tubers infection started at 10°C. Incidence of pink rot was high when two or three of the factors (severe wounding, high temperature, high inoculum level) were favorable. Incidence of pink rot was intermediate when only one factor was favorable. Incidence of pink rot was low or absent without a favorable factor (no wounding, low temperature, and low inoculum), Since infected tuber tissue may serve as potential inoculum source for postharvest infection of tubers by P. erythroseptica, the removal of pink rot infected tubers at harvest is desirable. Avoidance of wounding and rapid cooling of storage bins to 10°C may also help control pink rot.

PP-785 (Revised); This circular provides information on "common root rot" of spring wheat and barley

A strain ofPenicillium bilaji Chalabuda (PB) has recently been commercially released as a seed inoculant to increase phosphorus (P) uptake by wheat (Triticum aestivum L.). The purpose of this study was to compare the effects of drill applied P (15 kg P ha−1) with PB seed inoculation on early growth, development, P uptake, and grain yield of ‘Stoa’ spring wheat at four sites in North Dakota.

The effect of triadimefon, propiconazole and thiabendazole fungicides on the growth of Fusarium graminearum and the production of deoxynivalenol in wheat was investigated in a field trial. The heads of wheat plants were infected with F. graminearum spores (1 × 105 conidia mL−1, approximately 62.5 mL m−2) 2 d following anthesis. Triadimefon (Bayleton 1.8 E.C), propiconazole (Tilt 3.6 E.C) and thiabendazole (Mertect 340-F) were sprayed at the dosages of 60, 120, and 360 g a.i. ha−1, respectively. Treatments of wheat plants with the fungicides were conducted at three time schedules: (1) one application at 2 d before inoculation, (2) one application at 2 d after inoculation, and (3) two applications at 2 d before and 2 d after the inoculation of wheat plants with F. graminearum. Treatments with triadimefon and propiconazole fungicides resulted in 39–61% and 34–79% decreases in F. graminearum infection and deoxynivalenol levels, respectively. Although treatment with thiabendazole resulted in the maximum reduction (83%) in deoxynivalenol level, it had no significant effect on F. graminearum infection.Key words: Fusarium graminearum, deoxynivalenol, vomitoxin, fungicides, triadimefon, thiabendazole, propiconazole

Common root rot of hard red spring wheat, durum and barley concurs throughout the Spring regions of the Great Plains in the USA and Canada. Cochliobiolus Sativas is fungus that primarily produces root rot. Crop losses were determined to be 10% in barley and 5% in spring wheat with losses up to 30% in some fields in some years. Crop rotation and plantings of resistant cultivars up to this point were the major disease management tools. Farmers found growing non-cereal crops to be unprofitable. Also, due to many agronomic and quality factors, many farmers continued to plant susceptible crops.Protectant fungicide formulations have ben long applied to cereal seed to prevent seed decay, damping-off and seedling blight and some seed-bore diseases such as 'smuts'. Cochliobolus Salivas may cause a seed-borne infection known as 'black point'. Older treatments hadn't been successful in reducing the soil-borne phase of common root rot in adult crops. When controlled, crop yields did not increase. This article discusses a systematic treatment of fungicides on root rot control' of spring wheat and barley in North Dakota. The Triadimenol and Difenconazole treatments produced the most promising returns on reducing CRR and increasing crop yields.

Cochliobolus sativus cultures were collected from symptomatic wheat plants from a plot planted continuously to wheat for over 90 yr and from symptomatic wheat plants in commercial grain fields cropped rotationally in the surrounding area. Pathogenicity of these isolates was tested in replicated greenhouse trials using wheat plants scored for disease 6 wk after inoculation. Isolates from the continuous-cropped wheat plot were more aggressive on average than were isolates from commercial fields. Long-term continuous cropping to wheat appears to shift the population of C. sativus toward more aggressive types, although many less aggressive types also remain.Key words: Aggressiveness, Drechslera sorkiniana, Helminthosporium sativum, wheat root rot

Two experiments were conducted at six locations in North Dakota in 1986 using Morex barley (Hordeum vulgare L.) as the test crop. The first consisted of a factorial combination of 3 KCl fertilizer rates (0, 50, and 200 kg ha−1 of KCl) by two rates of imazalil impregnated on the seed (0 and 0.1 g a.i. kg−1 seed). Potassium chloride application reduced plant nitrate concentrations at all sites, while imazalil had little effect. Imazalil reduced common root rot (CRR, incited primarily by Cochliobolus sativus) at four sites and KCl fertilization reduced CRR at two sites. At these latter two sites differing KCl × imazalil interactions were observed. At one site, KCl reduced CRR in the absence of imazalil but not in the presence of imazalil. Imazalil was quite effective in controlling CRR at this site, however. At the second site, both KCl and imazalil reduced CRR and their effects were complementary. Imazalil seed treatment substantially increased yield at one site where there was infection with take-all (Gaeumannomyces graminis) as well as CRR. Imazalil application significantly reduced yields at another site. Potassium chloride fertilization significantly increased yield at one site, but this yield increase could not be attributed to control of CRR. The second experiment compared seed impregnation with imazalil to impregnation of monoammonium phosphate fertilizer drilled with the seed. Fertilizer impregnation with imazalil eliminated all seedling toxicity associated with the fungicide, but imazalil-impregnated fertilizer was totally ineffective in controlling CRR.Key words: Chloride fertilization, fertilizer-fungicide interaction, fertilizer-pesticide mixtures, take-all, Cochliobolus sativus, Gaeumannomyces graminis, Hordeum vulgare

Potato stems and stolons infected with Rhizoctonia solani Kuhn were collected from ten fields in the Red River Valley of North Dakota, USA, in 1987. Six potato cultivars were sampled from dryland production areas with different crop rotation schemes. Approximately 1350 isolations from 203 plants were made for the recovery of R. solani. Pure cultures of R. solani were obtained and 119 cultures were successfully purified using a hyphal tip technique. These cultures were paired on anastomosis plates with tester isolates representing anastomosis groups AG-1 through AG-9, and tested for pathogenicity on potato. Anastomosis groups 4 and 5 were the predominant groups recovered from potato plants sampled in fields not previously cropped to potato, while anastomosis groups 3 and 5 were most frequently recovered from fields with a previous cropping history of potato. The potato plants grown in these fields also had the highest incidence of symptoms and greatest severity. There was no relationship between potato cultivar and the colonization of a particular anastomosis group of R. solani. Based on these preliminary studies, infection of potato by various anastomosis groups of R. solani appears to be influenced mainly by crop rotation in our production area.

This article discusses presents findings of a recent report on the rates of infection of 6 row planted spring barley verses 2 rowed plantings in North Dakota.