bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Sclerotia and Apothecia of Sclerotinia sclerotiorum from Infected Soybean Seed and Its Control by Fungicide Seed Treatment
Authors: Mueller D. S. , Hartman G. L. , Pedersen W. L.
Published: May 2007

Field and laboratory studies were done to evaluate the development of sclerotia and apothecia of Sclerotinia sclerotiorum from soybeans and its control with fungicide seed treatment. Soybean seed infected with S. sclerotiorum produced mycelia on both seed coats and cotyledons after 48 h on potato dextrose agar (PDA). Obviously infected soybean seed also were placed in aluminum pans containing field soil and placed in soybean fields near Urbana, Illinois and Clinton, Wisconsin. In 1997, a total of 553 sclerotia, 20 stipes, and 10 apothecia were produced from 500 infected seeds. In 1998, 201 sclerotia and 22 stipes were produced, but no apothecia were observed from the 500 infected seeds. Fludioxonil was the most effective fungicide for reducing radial growth of S. sclerotiorum on PDA plates and suppressed 99% of the radial growth at 0.1 μg a.i./ml. S. sclerotiorum was recovered from 2% of soybean seed lots containing infected seed. When this seed lot was treated with several fungicides, captan + pentachloronitrobenzene + thiabendazole and fludioxonil completely inhibited mycelial growth from infected seed; thiram and thiabendazole each reduced recovery of S. sclerotiorum by 90%. In the field, 754 sclerotia and 10 apothecia were produced from 1,000 infected seeds over a two-year period. When evaluating fungicide control in the field, thiram, fludioxonil, and captan + pentachloronitrobenzene + thiabendazole reduced sclerotia formation from infected seed by more than 98%.
Integrated Management of Sudden Wilt in Melons, Caused by Monosporascus cannonballus, Using Grafting and Reduced Rates of Methyl Bromide
Authors: Edelstein M. , Cohen R. , Burger Y. , Shriber S. , Pivonia S. , Shtienberg D.
Published: May 2007

Sudden wilt of melons induced by Monosporascus cannonballus is a worldwide problem, mainly in arid and semi-arid regions. Soil disinfestation by fumigation with methyl bromide is a common and very effective treatment for disease control. However, methyl bromide is expected to be banned from use within the next 5 to 10 years; therefore, alternative measures for disease management are urgently needed. In this study, the efficacy of methyl bromide at a reduced rate (15 g/m2 instead of 50 g/m2) and grafted plants, alone or in combination, was examined. Experiments were conducted in the 'Arava region in southern Israel in naturally infested fields. First, various rootstock accessions were tested in three experiments. Of the eight rootstocks evaluated, cv. Brava (Cucurbita maxima) was selected to serve as a rootstock in the subsequent experiments due to its effects on wilt reduction (63 to 100% reduction in two experiments and 35% reduction in one experiment) and its horticultural performance. Next, integration of grafting and a reduced rate of methyl bromide was tested in two experiments. The reduced methyl bromide rate suppressed disease, but results were variable (32 and 91% reduction in the two experiments). Grafting, when used alone, significantly reduced wilt incidence by 84 to 87% compared to untreated plots. Integration of the two control measures provided adequate and reliable results and wilt incidence was always significantly lower (75 to 100% reduction) than incidence in untreated plots. Because control by each measure alone varies, integrated application is preferable.
Integrated Control of Phytophthora Root Rot of Red Raspberry
Authors: Wilcox W. F. , Pritts M. P. , Kelly M. J.
Published: May 2007

Various components of an integrated program for controlling Phytophthora root rot of red raspberries were examined in a factorial experiment conducted for three growing seasons in a silty clay loam naturally infested with Phytophthora fragariae var. rubi. The factors were: (i) cultivar (highly susceptible Titan versus moderately resistant Newburgh); (ii) bed height (flat versus raised); (iii) straw mulch application (yes versus no); (iv) preplant treatment with the biological control fungus Trichoderma (=Gliocladium) virens (yes versus no); and (v) seasonal applications of the fungicide metalaxyl (yes versus no). Disease incidence was assessed visually, and severity was measured with respect to cane density, cane vigor, and yield. Cultivar was the most important factor, having a highly significant (P < 0.0001) main effect on nearly every measure of disease incidence and severity; it also interacted significantly with most other factors for at least some of these measures. In general, such interactions resulted from the positive response of Newburgh to treatments that had little effect on the consistently poor growth and yield of Titan, or from the variable response of Titan to treatments that had little effect on the consistently low visual disease ratings for Newburgh. Raised bed cultivation consistently reduced disease incidence and improved plant performance (particularly for Newburgh) and was the only factor other than cultivar that significantly improved yield, i.e., 5.6 versus 2.0 kg per Newburgh plot on raised versus flat beds, respectively. Although metalaxyl initially provided a substantial decrease in disease incidence on Titan, most of these plants eventually died. In contrast, metalaxyl provided modest yield benefits for Newburgh, and highest yields were obtained when metalaxyl was used in conjunction with raised beds, i.e., means of 2.2 versus 1.8 kg for the treated versus untreated plots on flat beds and 6.3 versus 5.1 kg, respectively, on raised beds. Straw mulch increased soil moisture levels and exacerbated disease incidence and severity. The biocontrol treatment had relatively little effect on disease, although there was some indication of marginally improved plant growth in treated plots.
Geographic Distribution and Genetic Diversity of Three Ophiosphaerella Species that Cause Spring Dead Spot of Bermudagrass
Authors: Wetzel Henry C. , Skinner Daniel Z. , Tisserat Ned A.
Published: May 2007

The distribution of three Ophiosphaerella spp. that cause spring dead spot (SDS) of bermudagrass was studied by systematically sampling two golf courses in Oklahoma and one in Kansas. O. herpotricha was isolated from all three locations and was the most abundant species. It was the only SDS pathogen found at Jenks, Oklahoma. O. korrae was isolated from Afton, Oklahoma, and Independence, Kansas, whereas O. narmari was only detected in samples from Afton. This is the first report of all three Ophiosphaerella species on bermudagrass at the same location. Amplified fragment length polymorphism (AFLP) marker analysis was used to investigate inter- and intraspecific genetic diversity of Ophiosphaerella isolates from North America and Australia. A majority of the O. herpotricha and O. narmari isolates from Afton were distinct haplotypes, suggesting that sexual recombination was occurring within the population. Conversely, the presence of multiple isolates of O. herpotricha and O. narmari with the same haplotype also indicated that asexual propagation was occurring. The genetic diversity among O. herpotricha isolates from Afton was not distinctly different from that of isolates collected throughout the southern United States. In contrast, O. narmari isolates from Afton were distinct from those collected in Australia. The genetic diversity in O. korrae was markedly different than that in the other Ophiosphaerella spp. The population at Afton was dominated by just a few haplotypes, and these were nearly identical to isolates collected from bermudagrass and Kentucky bluegrass throughout western, central, and northern North America. However, O. korrae isolates collected in the southeastern United States were only distantly similar to other North American isolates.
Spread and Increase of Ratoon Stunting Disease of Sugarcane and Comparison of Disease Detection Methods
Authors: Hoy J. W. , Grisham M. P. , Damann K. E.
Published: May 2007

The spread and increase of ratoon stunting disease (RSD) resulting from two mechanical harvests were compared in eight sugarcane cultivars at two locations. RSD spread and increase were detected in the ratoon crops grown after each harvest and varied among cultivars and locations. Disease spread and increase were greater in plants grown from stalks collected at the first harvest than in the first ratoon growth from the harvested field. RSD infection was determined using five disease detection methods: alkaline-induced metaxylem autofluorescence; microscopic examination of xylem sap; and dot blot, evaporative-binding, and tissue blot enzyme immunoassays. The tissue blot enzyme immunoassay was the most accurate RSD detection method. The dot blot and evaporative-binding enzyme immunoassays were the least sensitive for detection of RSD-infected stalks, and alkaline-induced metaxylem autofluorescence was least accurate for correct identification of noninfected stalks. The results indicate that disease spread and increase are variable even among cultivars susceptible to yield loss due to RSD, and the greatest threat of disease spread and increase occurs at planting.
First Occurrence of Alternaria alternata on Gypsophila paniculata in Bulgaria
Authors: Margina A. F. , Bobev S. G. , de Gruyter J.
Published: May 2007

During late summer 1996 to 1997, 27 to 30% of Gypsophila paniculata (baby's-breath) plants were noted as diseased in an experimental field (Kazanlak, Bulgaria). Symptoms on lower and middle leaves consisted of small circular spots, with light brown centers and reddish purple margins. Development of numerous spots (which grew larger) and, especially, damage to the midrib led to withering of leaflets. Conidiophores of the isolated fungus were dark, formed singly or in clusters, were unbranched with three to eight septa, and were 40 to 120 µm long. Conidia, produced in branched chains (four to six conidia or longer), were brown, globose, and ovate to pyriform with short beaks, contained four to five transverse and zero to two longitudinal septa, and were 36.6 to 46.6 × 10.0 to 13.3 µm. The fungus was identified as Alternaria alternata. Pathogenicity was confirmed by artificial inoculation of potted G. paniculata and Dianthus caryophyllus plants. Conidia (2 weeks old) produced on potato dextrose agar were sprayed on plants in a 5 × 103 suspension, and plants were incubated at 20 to 24°C in a moist chamber for 2 days. Lesion development in both plant species was observed and recorded at 4 to 5 and 6 to 7 days after inoculation, respectively. Lesions were most numerous on G. paniculata. This is the first report of A. alternata on baby's-breath in Bulgaria.

References: (1) M. B. Ellis. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, U.K. (2) E. G. Simmons. Alternaria themes and variations. Mycotaxon 37:79, 1990.
First Report of Thyronectria austroamericana Canker on Thornless Honey Locust in North Carolina
Authors: Grand L. F. , Vernia C. S. , Hodges C. S.
Published: May 2007

Specimens from a thornless honey locust (Gleditsia triacanthos var. inermis ‘Shade Master’) with cankers were submitted in May 1999 to the North Carolina State University Plant Disease and Insect Clinic by staff from the North Carolina Zoological Park (Asheboro). Abundant stromata of Gyrostroma austroamericana, the anamorph of Thyronectria austroamericana, were associated with the cankers. A visit to the Zoological Park during August 1999 revealed seven additional honey locust trees with multiple branch and stem cankers and dieback. All infected trees had perithecia of T. austroamericana and/or its anamorph. The fungus is distinguished by the large clusters of yellow-brown perithecia with dark brown tips produced on stromata emerging from lenticels, elliptical muriform ascospores, and sparse ascoconidia (1,2). Ascoconidia form as the result of ascospores budding within the ascus. Other trees of the cultivar are an integral part of the landscaping theme of the African Pavilion of the park, and park staff were concerned about disease spread. Infected trees were 8 years old, and several had evidence of sunscald cankers, a common infection court of T. austroamericana (2). Thornless cultivars of honey locust are popular landscape plants in the central and eastern United States and may be seriously affected by T. austroamericana (2). Apparently ‘Shade Master’ is very susceptible to the fungus and should not be used as a landscape tree, especially where the disease has been reported. This is the first report of T. austroamericana in North Carolina on any host. Voucher specimens have been deposited in the National Fungus Collection, Beltsville, MD (BPI 74693), and in the Mycological Herbarium, Department of Plant Pathology, North Carolina State University, Raleigh.

References: (1) E. V. Seeler, Jr. J. Arnold Arbor. Harv. Univ. 21:429, 1940. (2) W. A. Sinclair et al. 1993. Diseases of Trees and Shrubs. Cornell University Press, Ithaca, NY.
Control of Citrus Green Mold by Carbonate and Bicarbonate Salts and the Influence of Commercial Postharvest Practices on Their Efficacy
Authors: Smilanick Joseph L. , Margosan Dennis A. , Mlikota Franka , Usall Josep , Michael Ibrahim F.
Published: May 2007

The toxicity to Penicillium digitatum and practical use of carbonate and bicarbonate salts to control green mold were determined. The effective dose (ED50) concentrations to inhibit the germination of P. digitatum spores of sodium carbonate (SC), potassium carbonate, sodium bicarbonate (SBC), ammonium bicarbonate, and potassium bicarbonate were 5.0, 6.2, 14.1, 16.4, and 33.4 mM, respectively. All were fungistatic because spores removed from the solutions germinated in potato dextrose broth. SC and SBC were equal and superior to the other salts for control of green mold on lemons and oranges inoculated 24 h before treatment. When sodium content and high pH must be minimized, SBC could replace SC. Furthermore, because a higher proportion of NaOCl would be present in the active hypochlorous acid at the lower pH of SBC compared to SC, sanitation of the SBC solution should be easier to maintain. NaOCl (200 μg/ml) added to SBC at pH 7.5 improved green mold control. Rinse water as high as 50 ml per fruit applied after SC did not reduce its effectiveness; however, high-pressure water cleaning after SC did. Conversely, high-pressure water cleaning of fruit before SC improved control of green mold. The risk of injury to fruit posed by SC treatment was determined by immersing oranges for 1 min in 3% (wt/vol) SC at 28, 33, 44, 50, 56, or 61°C (±1°C) and followed by storage for 3 weeks at 10°C. Rind injuries occurred only after treatment at 56 and 61°C. The risk of injury is low because these temperatures exceed that needed for control of green mold. SC was compatible with subsequent imazalil and biological control treatments.
Assessment of Genetic Variation Among Leptosphaeria maculans Isolates Using Pathogenicity Data and AFLP Analysis
Authors: Pongam Patchara , Osborn Thomas C. , Williams Paul H.
Published: May 2007

Increased production of rapeseed in the north central and southeastern regions of the United States has been accompanied by an increase in the incidence of blackleg disease caused by Leptosphaeria maculans. In order to assess the genetic variability and relatedness of isolates from these regions to others from around the world, we analyzed 49 aggressive isolates representing three pathogenicity groups (PG2, 3, and 4) of L. maculans from North Dakota, Georgia, Ontario, Western Canada, the United Kingdom (UK), France, Germany, and Australia using pathogenicity data and amplified fragment length polymorphism (AFLP). Approximately 10% of the 400 amplified fragments were polymorphic, scored as discrete characters and analyzed by cluster analysis. The isolates from North Dakota, Western Canada, Georgia, and PHW1252 from the UK formed one tightly clustered group and were mostly of the same pathogenicity group; whereas isolates from Ontario, Australia, France, Germany, and the remaining isolates from the UK formed a second group, which exhibited greater variation and consisted of three pathogenicity groups. The similarity between North Dakota isolates collected in 1995-96 and Western Canadian isolates collected in the 1980s suggests that L. maculans was introduced into North Dakota from Western Canada, and that the populations have remained relatively unchanged over the past 10 years.
Survival of Mucor piriformis in Soil of Apple Orchards in California
Authors: Guo Li-Yun , Michailides Themis J. , Morgan David P.
Published: May 2007

Four apple orchards were sampled periodically in 1995 and 1996 to determine the population levels of Mucor piriformis, the causal agent of Mucor rot. The highest population, 119 propagules of M. piriformis per g of dry soil, occurred during winter. Populations declined during summer and fall and increased again in winter and early spring of the following year. Isolates from soil and apple fruit of these orchards contained +, −, and neuter mating types, with the + being the predominant mating type. Depending on the orchard, up to 27.7% of apples infected by M. piriformis had zygospores developed on them. The time of increase in M. piriformis populations corresponded with postharvest drop and decay of apples on the orchard floor. Experiments were carried out to compare changes in M. piriformis populations in soil with intact fruit left on the orchard floor, sliced fruit, or after removal of fruit from the orchard. The greatest numbers of M. piriformis occurred in soil with apple pieces, followed by soil with intact apples, and the lowest in soil without apples. Results suggest that the best time to sample soils to determine the occurrence of M. piriformis in California apple orchards is from January to March, and practices of flail-mowing the orchard floor after harvest may increase population levels of M. piriformis in soil.
Gliocladium catenulatum in Association with Sclerotium cepivorum on Onion Leaves in Ghana
Authors: Tsigbey F. K. , Nutsugah S. K. , Ritchie Barbara J.
Published: May 2007

During a regular survey of diseases in farmers' fields of onion (Allium cepa L.) in the Upper East Region of Ghana in March 1997, bulbs infected with white rot disease were collected for identification. A portion of the white mycelium present on the onion scale was cultured on potato dextrose agar (PDA). After 2 days of incubation, white fluffy mycelium was observed that later developed black sclerotia on the colony surface to confirm the identity of Sclerotium cepivorum. Ten days later, an unknown fungus was observed growing from the original inoculation point of the S. cepivorum mycelium. Pure cultures of the unknown fungus grown on PDA were sent to CAB International, UK, and identified as Gliocladium catenulatum Gilman and Abbott (1). G. catenulatum grew along the mycelia of S. cepivorum and completely suppressed its growth. In culture, G. catenulatum colonized sclerotia of S. cepivorum and rendered them mushy and easy to crush, whereas the uncolonized sclerotia remained firm and difficult to crush. The uncolonized sclerotia when transferred onto PDA produced the white fluffy mycelial growth typical of S. cepivorum; the colonized did not grow at all. G. catenulatum also reduced colony growth, sclerotia formation, and maturation of S. cepivorum. Cultures of S. cepivorum inoculated with G. catenulatum measured 3 cm in diameter after 3 days of incubation and exhibited sparse mycelial growth, while cultures of S. cepivorum measured 5 cm in diameter after 3 days of incubation and produced a fairly even sheet of abundant, fluffy mycelial growth. Sclerotia were produced profusely in pure cultures of S. cepivorum whereas those of G. catenulatum and S. cepivorum in combination produced only two sclerotia after 6 days and these were later colonized by G. catenulatum. A striking characteristic of G. catenulatum was the production of a yellow pigmentation around the colony margins. Species within the genus Gliocladium are known to be antagonistic to, and parasitic on, other fungi. The antagonistic and/or parasitic nature of G. catenulatum on S. cepivorum suggests a possible role in biological control. This is the first report of G. catenulatum in association with S. cepivorum on onion in Ghana.

Reference: (1) J. C. Gilman and E. V. Abbott. Iowa State College J. Sci. 1:225, 1927.
Occurrence of Leaf Blotch and Stem-End Rot of Strawberry in the Central Coast of California
Authors: Gubler W. D. , Feliciano A. J.
Published: May 2007

Leaf blotch and stem-end rot caused by Gnomonia comari P. Karst. (anamorph, Zythia fragariae Laibach) were observed in a strawberry fruit production field at Watsonville, CA, in 1996. Z. fragariae has been known for years to attack leaves and cause leaf blotch but this is the first time that the perfect stage, G. comari, was identified and documented to infect fruits and cause stem-end rot in California. Symptoms on leaves included pin-point lesions, brownish to purplish blotches, and characteristic large V-shaped lesions. On the fruit, infection showed more frequently on the calyx. Symptoms on the calyx ranged from small lesions on the sepals to a completely infected calyx that turned necrotic and brittle. Calyx infection was observed on seemingly healthy green and ripe fruits. Infected fruits ripened prematurely and turned pale red to brownish in color. They remained firm but were often invaded by secondary organisms including Botrytis cinerea. When infected leaves and fruits were surface sterilized and incubated under humid condition, perithecia and pycnidia readily developed on the lesions. Ascospores oozed from the tip of the perithecial neck while numerous spores oozed out of the pycnidium. The pathogen was identified as G. comari based on size and morphology of the perithecia, asci, and ascospores (1), and the spores were identified as Z. fragariae based on morphology of the conidia and conidiophores (2). Both the spores and ascospores produced pycnidia and perithecia on potato dextroxe agar at room temperature. Inoculation of healthy leaves and fruits with each fungus resulted in development of symptoms of leaf blotch and stem-end rot similar to those observed in the field. G. comari and Z. fragariae were reisolated from newly developing lesions on symptomatic leaves and fruits. Since 1996, stem-end rot has been observed more frequently in fruit production areas in the central coast of California, particularly during wet years.

Reference: (1) A. Bolay. Ber. Schweiz. Bot. Ges. 81:398, 1971. (2) J. Fall. Can. J. Bot. 32:172, 1954.
First Report of Rhizoctonia zeae in Turkey
Authors: Demirci E. , Eken C.
Published: May 2007

In 1997, during a study to determine the pathogenic fungi on Johnsongrass (Sorgum halepense) in the Yusufeli District of Artvin Province, 10 isolates of a Rhizoctonia sp. were obtained from necrotic roots. In anastomosis tests, Johnsongrass isolates fused at low frequency with the Rhizoctonia sp. (teleomorph: Waitea circinata var. circinata) and R. oryzae (teleomorph: W. circinata var. oryzae), and at high frequency with R. zeae (teleomorph: W. circinata var. zeae). Test isolates of the Rhizoctonia sp. (W. circinata var. circinata), R. oryzae, and R. zeae (isolate nos. W616, 231, and 590, respectively) were provided by R. H. Leiner (University of Alaska Fairbanks). In addition, Johnsongrass isolates were identified as R. zeae based on colony morphology of the vegetative state. Pathogenicity of two isolates (JR-3 and JR-8) was determined on Johnsongrass seedlings at 25°C. Six seeds were sown in a 10-cm-diameter pot containing a sterile soil mixture of coarse sandy loam and sand (1:1, vol/vol). Each pot was a replicate and each treatment was replicated four times. Four-week-old Johnsongrass seedlings were inoculated by gently removing the soil mixture from one side of the stem, placing a colonized potato dextrose agar (PDA) 4-mm-diameter plug in direct contact with the base of the stem, and covering the inoculum with the soil mixture. A sterile, uncolonized PDA plug was used as a control. Disease symptoms were observed 2 weeks after inoculation. Brownish, sunken lesions were observed on the base of stems and roots of seedlings inoculated with R. zeae. Stems and roots of uninoculated seedlings were lesion free. Isolates JR-3 and JR-8 were reisolated from plants grown in their respective treatments. This is the first report of R. zeae from Turkey.
Phytophthora Species Associated with Cranberry Root Rot and Surface Irrigation Water in New Jersey
Authors: Oudemans Peter V.
Published: May 2007

A lupine baiting technique was used to detect the presence of Phytophthora spp. in several streams, irrigation reservoirs, and drainage canals used in cranberry cultivation. P. cinnamomi was found to be widely distributed throughout the study area in the southern New Jersey Pinelands, and was present both upstream and downstream of agricultural activities. A second species, identified as P. megasperma, was more restricted in its distribution and was never isolated from a water system that did not also contain P. cinnamomi. In a survey of commercial cranberry production, 80% of the acreage represented (approximately 37% of total New Jersey production area) was exposed to one or both Phytophthora spp. through application of infested water from irrigation reservoirs. Based on the widespread distribution of P. cinnamomi, it is likely that this pathogen was introduced many years prior to its discovery on cranberry in the 1980s, which corresponded to the adoption of overhead irrigation in the crop. There were slight differences between the two species in seasonal occurrence. The highest levels of P. cinnamomi were found during the summer months (July to August) whereas P. megasperma was highest during the spring (April to May) and fall (September to October) months.
First Report of Sweetpotato Scurf Caused by Monilochaetes infuscans in Italy
Authors: Di Lenna P. , Mascarello N. , Xodo E.
Published: May 2007

In the last few years, in the Treviso area, the incidence and severity of a sweetpotato (Ipomoea batata) disease has increased to become a serious economic threat to this crop. The symptoms are small, dark brown to black spots on the surface of fleshy storage roots that under high relative humidity coalesce to completely cover the root surface. Affected roots may also develop small cracks and shrink in storage. In the past, the same symptoms were observed, but the low incidence of the disease did not cause significant economic losses, and therefore it was not considered worthy of investigation. In August 1998, an investigation was initiated to determine the causal agent of the disease and to provide growers with effective control strategies. Since the symptoms were similar to those incited by Monilochaetes infuscans, agent of sweetpotato scurf (1), samples of roots were collected and examined for the presence of the pathogen. Even though it is difficult to isolate, M. infuscans was consistently present in infected tissues. In pure culture on potato dextrose agar the pathogen formed typical, raised, domelike, dark gray to black colonies. Conidiophores were brown to black, unbranched, and support straight or curled chains of hyaline conidia. Traditional cultivation methods that ignore sanitary conditions probably caused the gradual increase in the incidence and severity of the disease. Sweetpotato scurf is common in the U.S., Japan, and some Pacific islands, but it has not been previously recorded in Italy.

Reference(1): C. A. Clark and J. W. Moyer. 1988. Compendium of Sweet Potato Diseases. American Phytopathological Society, St. Paul, MN.
Occurrence of Colletotrichum acutatum, Causal Organism of Strawberry Anthracnose in Southwestern Spain
Authors: de los Santos G de Paredes B. , Romero Muñoz F.
Published: May 2007

A wilting disease of strawberry (Fragaria × ananassa Duchesne ‘Oso Grande’) was observed in production fields in Huelva, southwestern Andalucía, Spain. Crowns of wilted plants developed a reddish brown, firm rot. Longitudinal sections of roots of diseased plants showed a black coloration of the cortex. Symptons also included blighting of flowers due to floral infection and rotting of green and ripening fruits. On the fruit, the round, firm sunken lesions were covered with masses of salmon-colored spores. Lesions on the leaves were round, ranged in diameter from 5 to 10 mm, and were light brown with purple edges. Infected tissues were surface disinfected in 20% sodium hypoclorite, blotted dry, and plated on water agar. Dishes were incubated at 25°C; hyphal tips made of fungi growing from lesions were transferred to potato dextrose agar (PDA) and incubated under cool-white fluorescent light at 25°C. One fungus was isolated consistently from lesions on different tissues. It was identified as Colletotrichum acutatum by morphological characteristics (2) and enzyme-linked immunosorbent assay (1). On PDA, the mycelium of the fungus was white to gray and covered with salmon spore masses. Colony diameters on PDA averaged 45 mm after 7 days at 25°C. Hyaline, aseptate conidia were cylindrical, fusiform, and intermediate in shape and averaged 12.8 × 4.2 μm in size. The fungus produced setae on infected fruit. Inoculations of strawberry cvs. Oso Grande and Chandler with conidial suspensions (106 conidia per ml) of C. acutatum produced lesions on the fruit, petioles, and crowns, and caused wilt. The pathogen was reisolated from lesions on the inoculated plants. This is the first report of C. acutatum causing strawberry anthracnose in Huelva.

References: (1) T. A. Cooke et al. EPPO Bulletin 25:57, 1995. (2) B. C. Sutton. The Coelomycetes. CMI, Kew, England, 1980.
First Report of Powdery Mildew of Pepper in North-Central Mexico
Authors: Velásquez-Valle R. , Valle-Garcia P.
Published: May 2007

Pepper plants showing general yellowing and white spots on the lower surface as well as brown spots on the upper surface of the lowest leaves were observed during the 1998 crop season in the states of Chihuahua, Zacatecas, and Aguascalientes (north central area of México). Light defoliation was observed. Samples were collected in Chihuahua and Zacatecas to identify the pathogen, which showed navicular conidia. A conidial suspension was sprayed on pepper varieties, but only Hungarian Yellow Wax showed powdery mildew lesions. The average size of the conidia from Zacatecas was 61.2 × 18.2 μm while those from Chihuahua measured 58.2 × 17.6 μm, which is coincident with the description given for an Oidiopsis sp. The perfect stage is Leveillula taurica (1). Cleistothecia were not observed. In Zacatecas the disease was not detected in tomato fields or in sowthistle (Sonchus oleraceae) plants contiguous to, or within, infected pepper fields. Powdery mildew incidence ranged from 35 to 80% in Ancho type and from 0 to 55% in Mirasol type pepper fields in Zacatecas. The number of powdery mildew lesions per leaf in most cases varied from 1 to 3. Incidence was higher in fields where the canopy was closed and warmer and wetter conditions may have allowed the disease to progress.

Reference: (1) J. B. Jones et al. 1991. Compendium of Tomato Diseases. American Phytopathological Society, St. Paul, MN.
First Report of Pea Enation Mosaic Virus Affecting Lentil (Lens culinaris) in Syria
Authors: Makkouk Khaled M. , Kumari Safaa G. , Bayaa Bassam
Published: May 2007

Symptoms suggestive of virus infection in lentil (Lens culinaris Medik.) fields in Dara'a in southern Syria have been observed, in epidemic proportions, almost annually since 1994. A similar epidemic was observed on many lentil genotypes at the ICARDA farm, near Aleppo, as well as in other locations in northern Syria during 1998. Symptoms included growth reduction and rolling of leaves, accompanied by mottling with tip wilting or necrosis. Field symptoms were reproduced on lentil cv. Syrian Local upon mechanical inoculation of plants with inoculum from symptomatic field plants. Transmission tests showed that the disease agent can be transmitted from lentil to lentil, pea (Pisum sativum L.), and faba bean (Vicia faba L.) plants by the pea aphid (Acyrthosiphon pisum Harris) in a persistent manner. More than 500 symptomatic lentil plants were collected and tested for the presence of 14 different viruses by the tissue-blot immunoassay (TBIA) (2). Around 80% of the samples reacted only with antiserum to pea enation mosaic virus (PEMV), a Dutch isolate (E1540) provided by L. Bos, Wageningen, The Netherlands (1). Surveys conducted during the 1997/1998 growing season showed that PEMV was widely distributed in the major lentil-growing areas of Syria: some lentil fields had more than 50% virus incidence. This is the first record of PEMV naturally infecting lentil in Syria.

References: (1) K. Mahmood and D. Peters. Neth. J. Plant Pathol. 79:138, 1973. (2) K. M. Makkouk and A. Comeau. Eur. J. Plant Pathol. 100:71, 1994.
First Report of Benomyl Resistance in Didymella bryoniae in Delaware and Maryland
Authors: Everts K. L.
Published: May 2007

Gummy stem blight, caused by Didymella bryoniae (Auersw.) Rehm, is the most severe foliar disease of watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai, in eastern Maryland and southern Delaware. The fungicide benomyl is used in combination with chlorothalonil to manage gummy stem blight. Under conducive environmental conditions, yield losses are high even when fields are sprayed weekly. Resistance of D. bryoniae to benomyl has been reported in New York State and South Carolina (1). Gummy stem blight-infected leaves and stems were collected from nine and three fields in Wicomico County, MD, and Sussex County, DE, respectively, in 1996. Infected tissue was also collected from two Wicomico County fields in 1997. One single-spore subculture was obtained to represent each field. Agar plugs were taken from actively growing subcultures and inverted on a 25% (quarter strength) potato dextrose agar medium amended with 0 and 33.1 mg of benomyl per liter, the concentration of benomyl that reduced relative colony diameter of four resistant isolates in New York and South Carolina by 50% (1). Two replicate plates were used per experiment and each experiment was repeated once. After 6 days of growth at 21°C in the dark, the colony diameter was measured. Isolates were classified as sensitive if they were unable to grow, moderately sensitive if colony diameter was reduced 40 to 60%, and resistant if colony diameter was reduced less than 10% on the benomyl-amended media, compared with unamended media. Isolates that had previously been tested were used as sensitive (W03) and moderately sensitive (NY1) standards (1). In 1996, two isolates were sensitive, four isolates were moderately sensitive, and six isolates were resistant to benomyl. One isolate from 1997 was resistant and the other was moderately sensitive. This is the first report of resistance to benomyl within the D. bryoniae population in eastern Maryland and southern Delaware.

Reference: (1) A. P. Keinath and T. A. Zitter. Plant Dis. 82:479, 1998.
Color Classifier for Symptomatic Soybean Seeds Using Image Processing
Authors: Ahmad Irfan S. , Reid John F. , Paulsen Marvin R. , Sinclair James B.
Published: May 2007

Symptoms associated with fungal damage, viral diseases, and immature soybean (Glycine max) seeds were characterized using image processing techniques. A Red, Green, Blue (RGB) color feature-based multivariate decision model discriminated between asymptomatic and symptomatic seeds for inspection and grading. The color analysis showed distinct color differences between the asymptomatic and symptomatic seeds. A model comprising six color features including averages, minimums, and variances for RGB pixel values was developed for describing the seed symptoms. The color analysis showed that color alone did not adequately describe some of the differences among symptoms. Overall classification accuracy of 88% was achieved using a linear discriminant function with unequal priors for asymptomatic and symptomatic seeds with highest probability of occurrence. Individual classification accuracies were asymptomatic 97%, Alternaria spp. 30%, Cercospora spp. 83%, Fusarium spp. 62%, green immature seeds 91%, Phomopsis spp. 45%, soybean mosaic potyvirus (black) 81%, and soybean mosaic potyvirus (brown) 87%. The classifier performance was independent of the year the seed was sampled. The study was successful in developing a color classifier and a knowledge domain based on color for future development of intelligent automated grain grading systems.
New Aggressive Colletotrichum gloeosporioides Strains on Stylosanthes scabra Detected by Virulence and DNA Analysis
Authors: Chakraborty S. , Perrott R. , Ellis N. , Thomas M. R.
Published: May 2007

Widespread use of Stylosanthes scabra cv. Seca to improve native pastures in northern Australia makes it necessary to monitor changes in the anthracnose pathogen, Colletotrichum gloeosporioides, because new damaging races have arisen to devastate many agronomically promising cultivars in the past. A total of 103 isolates collected during the past 20 years were analyzed by using virulence and molecular markers to determine whether aggressive strains have evolved in the field. Data on severity for eight host differentials were obtained from a greenhouse assay and analyzed by linear discriminant functions developed from existing data on 182 isolates of known races. A molecular analysis of a subset of 21 isolates by random amplified polymorphic DNA (RAPD) and electrophoretic karyotyping gave comparable results for both markers, although electrophoretic karyotyping detected a higher level of polymorphism. The majority of the 103 isolates were placed into three groups on the basis of RAPD analysis. Virulence analysis detected isolates that were highly aggressive toward Seca. During the past 20 years, the frequency of aggressive isolates has increased. Many of the aggressive isolates were collected during the 1990s, and one had a distinct RAPD genotype. The lack of a strong association between RAPD genotypes and pathogen races suggests that races have arisen independently within each genetic group. This work highlights the need for regular monitoring of the pathogen population.
Differential Suppression of Damping-off Caused by Pythium aphanidermatum, P. irregulare, and P. myriotylum in Composts at Different Temperatures
Authors: Ben-Yephet Yephet , Nelson Eric B.
Published: May 2007

The suppressiveness of compost amendments to pre-emergence damping-off of cucumber incited by isolates of Pythium aphanidermatum, P. myriotylum, and P. irregulare was studied. Growth chamber experiments were designed to examine the effects of temperature (20, 24, 28, and 32°C), compost type (municipal biosolids [MC] and leaves [LC]), and compost dose (40, 80, 160, and 320 mg/cm3) on suppression of damping-off (i.e., increase in seedling stands) caused by different Pythium isolates obtained from different hosts. In dose-response experiments, LC was suppressive at dosage rates ≥80 mg compost/cm3 of sand, whereas MC was suppressive at rates ≥40 mg/cm3. Damping-off severity induced by each of the three Pythium spp. was temperature-dependent. For example, P. aphanidermatum and P. myriotylum caused damping-off at each of the four temperatures tested, whereas P. irregulare caused disease only at 20 and 24°C. MC was suppressive to P. aphanidermatum at 20 and 24°C, whereas LC was suppressive at 28 and 32°C. Both composts significantly suppressed damping-off caused by P. irregulare at 20°C (85% suppression in MC and 60% suppression in LC) and at 24°C (approximately 60% suppression in both composts), and by P. myriotylum at all temperatures tested. In experiments with a variable temperature cycle (32°C for 14 h, day and 22°C for 10 h, night), only P. aphanidermatum and P. myriotylum caused damping-off of cucumber seedlings. Under these conditions, LC significantly suppressed damping-off caused by P. aphanidermatum (20% suppression) or P. myriotylum (37% suppression) but MC was not suppressive. In experiments where the two composts were mixed, a significant negative interaction between the two composts was observed for the suppression of P. myriotylum and P. irregulare at 20°C and of P. irregulare at 24°C, but not for P. aphanidermatum at any of the tested temperatures. There was no difference in aggressiveness among isolates within each of the three Pythium spp., regardless of their host origin. However, a significant variation in suppressiveness of LC was observed among isolates of P. aphanidermatum (11 isolates) derived from the same host, but not for P. irregulare (9 isolates) or P. myriotylum (7 isolates).
Effect of Compost Amendment or Straw Mulch on Potato Early Dying Disease
Authors: LaMondia J. A. , Gent M. P. N. , Ferrandino F. J. , Elmer W. H. , Stoner K. A.
Published: May 2007

Single potato plants (Solanum tuberosum) cv. Superior were grown in field microplots to evaluate the effects of spent mushroom compost or straw mulch on early dying of potato caused by Verticillium dahliae and/or Pratylenchus penetrans. Prior to planting, soil was fumigated, placed in field microplots, and then infested with pathogens. Area under the senescence progress curve (AUSPC) was greater for plots infested with V. dahliae and/or P. penetrans than for noninfested plots. Plants grown in soil infested with both pathogens developed symptoms earlier than plants grown in soil infested with a single pathogen. Both V. dahliae and P. penetrans reduced yields; the combination of pathogens reduced marketable tuber yields by 22 to 44% (A- and B-sized tubers). Although the total number of tubers of all sizes was not affected by cultural or pathogen treatments, the addition of compost increased marketable tuber weight and decreased AUSPC. Soil amendment with spent mushroom compost may be a means of reducing the effects of potato early dying and increasing tuber yield when one or both pathogens are present.
Influence of Inoculum Concentration on Production of Spermogonia and Aecia on Pine Seedlings Infected by Basidiospores ofCronartium quercuumf. sp.fusiforme
Authors: Schmidt R. A. , Miller T.
Published: May 2007

Seedlings of slash pine and loblolly pine inoculated with four concentrations of basidiospores of Cronartium quercuum f. sp. fusiforme and exhibiting large galls (≥25 mm long) were observed for spermogonial and aecial sporulation. Basidiospores from a genetically heterogeneous source at 50, 100, 1,000 and 5,000 spores/5-μl droplet were applied to the severed, succulent terminal of 6-week-old seedlings. Incidence of sporulation showing (i) spermatia (pycniospores) only, (ii) aeciospores only, (iii) spermatia and aeciospores, and (iv) absence of sporulation was recorded for 3 years. On slash pine, the percentage of seedlings showing only spermatia varied significantly and inversely with inoculum concentration. In contrast, the percentage of seedlings showing only aeciospores or aeciospores and spermatia varied directly with inoculum concentration. Results on loblolly pine were similar. It is suggested that, at low inoculum concentrations, hyphal anastomoses are limited by fewer haploid mycelia in infected tissues or fewer mating types resulting from incompatible host-parasite interactions.
Phytotoxicity of Discula destructiva Culture Filtrates to Cornus spp. and the Relationship to Disease Symptomology
Authors: Wedge D. E. , Riley M. B. , Tainter F. H.
Published: May 2007

Discula destructiva culture filtrates and partially purified culture filtrates (PPCF) inhibited radish (Raphanus sativus) and dogwood (Cornus) species in a seedling root bioassay. Noninoculated potato-dextrose broth (PDB) extracted and separated in a similar manner also inhibited seedling growth. Reverse phase high performance liquid chromatography separated this inhibitory activity into two fractions, with one associated with the inhibitory action observed with PDB controls. The active fraction without interference with PDB, determined by bioassays, was extracted from cultures grown on Murishige-Skoog (MS) medium, which had no inhibitory activity associated with noninoculated controls. The active fraction was tested in a leaf overlay technique using 10 Cornus spp. All dogwood species were sensitive to the fraction and exhibited necrotic lesions bounded by a red margin, typical of dogwood anthracnose. The active fraction was translocated in Cornus alba to the leaf margin. C. canadensis showed minimal primary lesion formation but developed leaf curling and necrosis on leaf margins of newly emerging leaves, indicating apical translocation of the fraction from the application site. Comparison of three D. destructiva (Type 1) isolates and a Discula sp. (Type 2) isolate for production of the active fraction showed that the Type 2 isolate did not produce detectable amounts of the active component.
Characterization of Phytophthora infestans Populations in Western Washington
Authors: Dorrance A. E. , Inglis D. A. , Derie M. L. , Brown C. R. , Goodwin S. B. , Fry W. E. , Deahl K. L.
Published: May 2007

The first detection in the United States of isolates of Phytophthora infestans having metalaxyl insensitivity and complex pathotypes occurred in western Washington during the early 1990s. To determine the genetic structure of the current population in western Washington, a total of 115 isolates of P. infestans were obtained during 1996 from infected tubers or foliage of potato, tomato, nightshade, and bittersweet throughout the region. An additional 45 isolates were collected from a single field. Based on mating type, metalaxyl-insensitivity, and molecular markers (allozymes of glucose-6-phosphate isomerase, peptidase, and RG57 DNA fingerprint), all of the isolates were A1 mating type and had the US-11 multilocus genotype. Analyses of an additional 120 isolates collected during 1997 from potato, tomato, and nightshade were performed. As in 1996, US-11 was the predominant genotype detected on all three hosts. However, three additional A2 mating type genotypes were also detected: US-7, US-8, and US-14. These three genotypes represent the first A2 mating type isolates detected in western Washington. Most of a subset of 60 isolates infected 4 to 7 of the 10 potato differentials tested. This included 90% of the isolates collected in 1996 (all US-11), plus 72% of the US-11 and 100% of the US-8 and US-14 isolates collected during 1997. Virulence phenotypes in this region are complex even without the selection pressure of R-genes in the local commercial cultivars. The apparent increase in genetic variation observed in populations of P. infestans in western Washington from 1996 to 1997 most likely occurred by migration rather than by sexual recombination.
Comparison of Application Methods on Deposition and Redistribution of Chlorothalonil in a Potato Canopy and Potential for Control of Late Blight
Authors: Hamm Philip B. , Clough George H.
Published: May 2007

The effect of application method by aircraft (fixed wing), ground, and chemigation on deposition of chlorothalonil in a potato canopy was compared over 2 years. Initial chlorothalonil deposition was greatest with ground application, less by aircraft, and least with chemigation. After application by aircraft or ground, the upper canopy had more chlorothalonil than the middle, and the lower canopy had the least. With chemigation, the upper canopy also had more chlorothalonil, but amounts in the lower and middle canopy were similar. Redistribution occurred with time as material from the upper canopy moved downward. With a 9-day application frequency using ground or aircraft methods, residue levels throughout the treated potato canopy were maintained, even if distribution of the fungicide within the canopy was poor from the initial application. With chemigation, low initial chlorothalonil levels were further decreased due to redistribution, increasing the likelihood that levels could fall below that which may be needed to adequately control late blight, particularly beyond 7 days after application.