bluuebunny/crossref_metadata_2025 huggingface dataset:
First Record of Botrytis Flower Blight Caused by Botrytis cinerea on Geraldton Waxflower in South Africa
Authors: Swart L. , Coertze S.
Published: May 2007

Geraldton waxflower (Chamelaucium uncinatum Schauer, family Myrtaceae), indigenous to western Australia, is cultivated commercially in South Africa as a cut-flower crop and exported to markets in the Northern Hemisphere. In September 2000, disease symptoms were observed on 4-year-old plants in a commercial orchard of C. uncinatum cv. Ofir in Philippe, in the Western Cape Province. The base of the petals and the calyxes of the waxflowers showed brown necrotic lesions. Eventually the calyx and all the petals turned brown, and the flowers shriveled and abscised. B. cinerea Pers.:Fr was consistently isolated from affected petal and calyx tissues. When placed in a moist chamber, conidia and mycelia formed on the surface of dead and infected tissue. Koch's postulates were confirmed by spraying flower stems of C. uncinatum cv. Ofir with a spore suspension (1 × 106 conidia per ml). Inoculated flower stems were placed in a bottle filled with water and enclosed in transparent plastic bags for 24 h at 21°C. Typical symptoms developed on the petals and calyx within 3 days after inoculation. B. cinerea was reisolated from affected tissues. Botrytis flower blight or gray mold, causing a flower petal disease, has been recorded on C. uncinatum in Australia (1), but this is the first record of Botrytis flower blight of C. uncinatum in South Africa. Because Geraldton waxflower is a major cut-flower crop grown for export, this disease can cause significant losses to the industry, especially under cool, wet growing conditions.

Reference: (1) A. Tomas et al. Aust. Plant Pathol. 24:26, 1995.
First Report of Glomerella cingulata on Common Guava in Argentina
Authors: Carranza M. , Larran S. , Ronco B.
Published: May 2007

In Argentina, common guava (Psidium guajava L.) is frequently planted in gardens, but commercial production is limited. In February 2001, anthracnose symptoms were detected on fruits of common guava in La Plata, Buenos Aires Province. Symptoms of grayish, circular, sunken spots approximately 5 cm long were observed only on the surface of green unripe fruits. In humid conditions, acervuli containing salmon-pink masses of spores and dark setae were found within lesions. Symptomatic tissue was surface-disinfested, placed on potato dextrose agar, and incubated at 20°C. Cultures were obtained with abundant, gray, aerial mycelium and one-celled, hyaline, oblong, or cylindrical conidia with rounded ends (9.7 to 14.5 × 3.2 to 5.2 μm). Scarce dark brown perithecia developed in 2-month-old cultures but were not observed on fruit tissues. Asci were not conspicuous and contained straight or slightly curved ascospores (11.5 to 25.3 × 4 to 7 μm). The pathogen was identified as Glomerella cingulata (Stoneman) Spauld. & Schrenk (anamorph Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz), based on morphological characteristics (1,2). Ten healthy, immature, attached fruits of common guava were inoculated with 3 × 106 conidia per ml of each of six isolates of G. cingulata, and ten were left untreated. Individual fruits were enclosed in plastic bags and kept at 15 to 20°C. After 72 h, bags were removed, and after 20 days, anthracnose symptoms were observed only on inoculated fruits. G. cingulata was reisolated from fruit lesions, and Koch's postulates were fulfilled. To our knowledge, this is the first report of G. cingulata on common guava in Argentina.

References: (1) B. C. Sutton. The Coelomycetes. CMI, Kew, England, 1980. (2) J. A. von Arx. Phytopathol. Z. 29:413, 1957.
First Report of Phoradendron breedlovei in Honduras
Authors: Melgar J. , Mathiasen R. , Howell B.
Published: May 2007

The mistletoe Phoradendron breedlovei Kuijt (family Viscaceae) has only been reported from two locations in Chiapas, Mexico (1). We observed this mistletoe parasitizing Quercus salicifolia Nee approximately 4 km east of La Esperanza, Department Intibuca, Honduras, at an elevation of 1,160 m. Several trees were severely infected, and some mortality appeared to be associated with severe infection. J. Kuijt, University of Victoria, British Columbia, Canada, confirmed our identification of the mistletoe. Specimens of P. breedlovei from Honduras have been deposited at the Herbario, Escuela Nacional de Ciencias Forestales, Siguatepeque, Honduras, and at the University of Victoria. To our knowledge, this is the first report of P. breedlovei from Honduras and extends the range of this mistletoe approximately 500 km to the east-southeast of Chiapas. To our knowledge, it is also the first report of this mistletoe on Q. salicifolia.

Reference: (1) J. Kuijt. Proc. K. Ned. Akad. Wet. 93:113, 1990.
Sudden Oak Death Caused by Phytophthora ramorum in Oregon
Authors: Goheen E. M. , Hansen E. M. , Kanaskie A. , McWilliams M. G. , Osterbauer N. , Sutton W.
Published: May 2007

Sudden oak death, caused by Phytophthora ramorum (1,2), has been found for the first time in Oregon, killing tanoak, Lithocarpus densiflorus, trees. To our knowledge, this is the first report of the disease outside of the San Francisco to Monterey area in California, (300 km to the south). Nine areas of infestation, all within a 24-km2 area, were discovered on forest lands near Brookings, in southwest Oregon. Mortality centers ranged in size from 0.2 to 4.5 ha and included 5 to approximately 40 diseased trees. P. ramorum was isolated from stem cankers using Phytophthora-selective medium. Isolates had distinctive morphological features characteristic of P. ramorum, including abundant production of chlamydospores and caducous, semipapillate sporangia on solid media. Internal transcribed spacer (ITS) sequences of isolates of P. ramorum from Oregon were identical to ITS sequences of isolates from California (1). The pathogen also was isolated from necrotic lesions on leaves and stems of native Rhododendron macrophyllum and Vaccinium ovatum growing beneath diseased tanoaks. In July 2001, the disease was located by an aerial survey conducted cooperatively by the USDA Forest Service and Oregon Department of Forestry. All lands within 1.6 km (1 mile) of the mortality centers are subject to Oregon quarantine, which bars the transport of any host plant materials. An eradication effort is currently underway. Symptomatic plants and all known host plants within 15 to 30 m of symptomatic plants are being cut and burned in the first phase of this operation. The total treated area is approximately 16 ha.

References: (1) D. M. Rizzo et al. Plant Dis. In press. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.
Spatial Distribution of Aphanomyces cochlioides and Root Rot in Sugar Beet Fields
Authors: Beale Julie W. , Windels Carol E. , Kinkel Linda L.
Published: May 2007

Spatial distribution of Aphanomyces cochlioides inoculum and disease was assessed in sugar beet fields located near Moorhead, MN and Wahpeton, ND. Soil samples were collected in June and July 1994 from two main plots (60 by 60 m) in each field. Samples were evaluated for A. cochlioides using a sugar beet seedling assay in the greenhouse to determine a root rot index value (0-to-100 scale), which served as an indirect estimate of relative activity and density of inoculum. Field evaluations of Aphanomyces root rot on sugar beet (0-to-7 scale) were made at harvest in September at each soil collection site. Greenhouse root rot index values correlated positively with field disease ratings for all plots. Variance-to-mean ratios of greenhouse root rot index values and of field disease ratings among samples within each plot were calculated to compare the spatial distribution of midseason inoculum with root rot at harvest. Ratios of greenhouse root rot indices indicated that inoculum of A. cochlioides was aggregated in the field at midseason, but root rot was uniform within plots by harvest. Wet weather in July through August was conducive to infection and development of symptoms. A uniform distribution of disease at harvest likely reflects a combination of factors, including root growth into inoculum foci, redistribution of inoculum, and inoculum densities that are spatially variable but all above some minimum threshold for infection.
First Report of Phytophthora capsici on Cucumber and Melon in Southeastern Spain
Authors: Herrero M. L. , Blanco R. , Santos M. , Tello J. C.
Published: May 2007

In autumn 1999, crown and root rot along with wilting of cucumber (Cucumis sativus L.) were observed in greenhouses in southeastern Spain (Granada). Symptoms appeared again during the 2000 to 2001 growing season. In spring 2001, root and crown symptoms were observed also on melon (Cucumis melo L.) in greenhouses in another area of southeastern Spain (Almeria). Isolates from diseased plants from both locations were identified as Phytophthora capsici (Leonian). Isolates produced papillate sporangia of variable shape, some of them with two or three papilla. Sporangia were caducous with pedicels of variable lengths that could be longer than the sporangia. Three isolates were crossed with P. capsici strains of known mating type. All isolates produced amphigynous antheridia and were mating type A1. Isolates grew well at 35°C and did not produce chlamydospores. Pathogenicity was examined for one isolate from cucumber and one from melon. Cucumber and melon plants at the four-leaf stage and pumpkin (Cucurbita maxima × C. moschata) plants at the five-leaf stage were inoculated with a mycelium suspension. Both isolates caused wilting and death of plants on the three host species tested. The pathogen was reisolated from roots and stems of diseased plants. To our knowledge, this is the first time P. capsici has been found on cucumber in Spain. It is also the first time P. capsici has been found on melon in the greenhouses of southeastern Spain, and the first time it has been reported to cause root and crown rot of melon. Previously, P. capsici has been reported to cause disease of field-grown melon (2) and greenhouse-grown pepper (Capsicum annum) (1) in eastern and southeastern Spain, respectively.

References: (1) J. C Tello. Comun. INIA 22, 1984. (2) J. J. Tuset Barrachina. An. INIA 7:11, 1977.
First Report of Puccinia canaliculata on Sunflower
Authors: Gulya T. J. , Stegmeier W. D.
Published: May 2007

Puccinia canaliculata (Schwein.) Lagerh. is a macrocyclic, heteroecious rust found on Cyperus spp. (sedges) in North and South America, with the aecial stage reported on Asteraceae (1). In July 1997, aecial pustules of unknown etiology were observed on lower leaves of more than 90% of cultivated sunflower (Helianthus annuus L.) plants at the 6- to 10-leaf stage in a field near Catherine, KS. Individual leaves had one to several large, convex pustules, each measuring 5 to 10 mm in diameter, covering <0.5% of the leaf area. In contrast, the aecial pustules of P. helianthi measure 1 to 2 mm in diameter. Yellow-orange aecial cups occurred on the abaxial leaf surface, with globoid aeciospores averaging 15 × 18.5 μm. Wild common sunflowers (H. annuus) and cocklebur (Xanthium strumarium L.) in the same and two nearby fields had similar pustules. There was a severe infestation of yellow nutsedge (C. esculentus L.) in the sunflower field, but uredia were not found because the nutsedge plants had been killed with glyphosate. Based on the size of aecia, aeciospores, and peridial cells from sunflower and cockelbur (3), the fungus was identified as P. canaliculata. Although sunflower is an alternate host (2), to our knowledge this is the first report of natural infection and is significant because it occurred in a major sunflower production area. Since P. canaliculata is being considered as a bioherbicide for nutsedge control (4), nontarget hosts such as sunflower need to be considered. The possibility of confusing P. xanthii and P. caniculata exists since both rusts occur on cocklebur and sunflower and produce pustules of a similar size. However, since P. xanthii is a microcyclic autoecious rust while P. canaliculata is a full-cycle heteroecious rust, the obvious color difference between the dark telia of P. xanthii and the yellow-orange aecia of P. caniculata should serve to easily differentiate the two species.

References: (1) J. C. Arthur. Manual of the Rusts in the United States and Canada. Purdue Research Foundation, Lafayette, IN, 1934. (2) M. B. Callaway et al. Plant Dis. 69:924, 1985. (3) F. D. Kern. Mycologia 11:134, 1919. (4) S. C. Phatak et al. Science. 219:1446, 1983.
First Record of Leaf Spots on Prunus laurocerasus in Belgium Caused by Phytophthora cactorum and Peronospora sparsa
Authors: Crepel C. , Inghelbrecht S.
Published: May 2007

In fall 2000 and 2001, large leaf spots were observed on Prunus laurocerasus. Two different plant pathogens proved to be the cause. Based on morphological characteristics they were identified as Peronospora sparsa (downy mildew) and Phytophthora cactorum. The P. cactorum isolate (CBS 110121) was identified at the Centraalbureau voor Schimmelcultures (Utrecht, the Netherlands). Sporangia were papillate, ovoid, and deciduous, with a short pedicel. The isolate was homothallic. Chlamydospores were present and approximately 40 μm in diameter. Oogonia were 25 to 31 μm in diameter, and the antheridia were paragynous. Peronospora sparsa had been reported to infect Prunus laurocerasus in the United Kingdom (1). In Belgium, cv. Etna was very susceptible, but cvs. Rotundifolia and Marbled White were also infected. Rotundifolia was susceptible to P. cactorum. At first inspection, the two pathogens caused similar leaf symptoms: large, irregular, brown, necrotic spots on the tips, margins, and center of leaves. However, the undersides of leaves infected with Peronospora sparsa were covered with typical gray mycelium, which was absent on leaves infected with P. cactorum. P. cactorum caused concentric circles in the brown spots. Leaf spots caused by P. cactorum developed quickly in a moist chamber. Spots caused by Peronospora sparsa did not enlarge significantly on detached leaves, but in the field it caused serious losses within a few days. To prove the pathogenicity of P. cactorum, Koch's postulates were satisified on five Prunus laurocerasus Etna plants. The fungus was grown on corn meal agar for 1 week until sporangia formed. An agar plug was placed on five wounded leaves per plant and sealed with Parafilm. Inoculated plants were kept under a plastic cover for 1 day at 22°C, then the cover was removed, and the plants were kept at 20°C. Symptom development was visible after 3 days, and P. cactorum was successfully reisolated. This is the first record of P. cactorum and Peronospora sparsa leaf infection on Prunus laurocerasus in Belgium.

Reference: (1) G. Hall et al. Plant Pathol. 41:224, 1992.
The Role of Weed Hosts and Tobacco Thrips, Frankliniella fusca, in the Epidemiology of Tomato spotted wilt virus
Authors: Groves R. L. , Walgenbach J. F. , Moyer J. W. , Kennedy G. G.
Published: May 2007

Wild plant species were systematically sampled to characterize reproduction of thrips, the vector of Tomato spotted wilt virus (TSWV), and natural sources TSWV infection. Thrips populations were monitored on 28 common perennial, biennial, and annual plant species over two noncrop seasons at six field locations across North Carolina. Sonchus asper, Stellaria media, and Taraxacum officianale consistently supported the largest populations of immature TSWV vector species. The tobacco thrips, Frankliniella fusca, was the most abundant TSWV vector species collected, comprising over 95% of vector species in each survey season. Perennial plant species (i.e., Plantago rugelii and Taraxacum officianale) were often only locally abundant, and many annual species (Cerastium vulgatum, Sonchus asper, and Stellaria media) were more widely distributed. Perennial species, including P. rugelii and Rumex crispus, remained TSWV infected for 2 years in a small-plot field test. Where these perennial species are locally abundant, they may serve as important and long-lasting TSWV inoculum sources. In random surveys across 12 locations in North Carolina, TSWV infection was documented by double antibody sandwich enzyme-linked immunosorbent assay in 35 of 72 (49%) common perennial (N = 10), biennial (N = 4), and annual (N = 21) plant species across 18 plant families. Estimated rates of TSWV infection were highest in Cerastium vulgatum (4.2%), Lactuca scariola (1.3%), Molluga verticillata (4.3%), Plantago rugelii (3.4%), Ranunculus sardous (3.6%), Sonchus asper (5.1%), Stellaria media (1.4%), and Taraxacum officianale (5.8%). Nine plant species were determined to be new host recordings for TSWV infection, including Cardamine hirsuta, Eupatorium capillifolium, Geranium carolinianum, Gnaphalium purpureum, Linaria canadense, Molluga verticillata, Pyrrhopappus carolinianus, Raphanus raphanistrum, and Triodanis perfoliata. Our findings document the relative potential of a number of common annual, biennial, and perennial plant species to act as important reproductive sites for F. fusca and as acquisition sources of TSWV for spread to susceptible crops.
Incidence and Spatial Distribution of Viruses in Hop Gardens of Washington State
Authors: Pethybridge Sarah J. , Nelson Mark E. , Eastwell Kenneth C. , Klein Robert E. , Kenny Stephen T. , Wilson Calum R.
Published: May 2007

The incidences of Hop latent virus (HpLV), Hop mosaic virus (HpMV), and American hop latent virus (AHLV), members of the genus Carlavirus, and Prunus necrotic ringspot virus and Apple mosaic virus, members of the genus Ilarvirus, were assessed for two hop cultivars, Horizon and Nugget, in Washington State. The spatial distribution of plants infected by the carlaviruses was assessed in two Horizon gardens in 2000 and one Nugget garden in 1993, 1994, and 1995. In the first Horizon garden (garden 1) and the Nugget garden, plants were separated by 2.1 m within and between rows. In these gardens, cultivation and the wide plant spacing discouraged contact between plants in either direction. In the second Horizon garden (garden 2), plants were separated by 4.3 m between rows and 1.0 m within rows. In all gardens, mechanical operations operated predominantly along rows; however, the closer plant spacing within rows in garden 2 permitted contact between adjacent plants within rows. In both Horizon gardens, the distribution of plants infected with HpMV was aggregated within rows. However, the distribution of plants infected with HpLV and AHLV was strongly influenced by contact between plants. In the Nugget garden, the distribution of plants infected by all three carlaviruses was autocorrelated within rows by 1995.
First Report of Phytophthora syringae Causing Rot on Apples in Cold Storage in the United States
Authors: Spotts R. A. , Grove G. G.
Published: May 2007

A decay of ‘Granny Smith’ apples (Malus domestica Borkh.) was observed in 1988, 1990, and 1991 on fruit grown in the lower Hood River Valley of Oregon and stored at 0°C. Harvested fruit were drenched with thiabendazole and stored in October in all years. In mid-November, fruit were sized, drenched with sodium hypochlorite, and returned to cold storage. Decay was observed in January when fruit were removed from cold storage, sorted, and packed. Decayed areas were light brown and firm with a slightly indefinite margin. Losses were less than 1% of fruit packed. Diseased fruit were surface-disinfested with 95% ethanol, and tissue pieces were transferred aseptically to potato dextrose agar acidified with lactic acid and incubated at approximately 22°C. The fungus consistently isolated was identified as Phytophthora syringae (Kleb.) Kleb. based on morphological characters (3). Sporangia were persistent and averaged 60 μm long (range 59 to 69) × 40 μm wide (range 37 to 43). Antheridia were paragynous, and oospores averaged 37 μm (range 31 to 46). ‘Golden Delicious’, ‘Granny Smith’, and ‘Gala’ apples were inoculated with mycelial plugs from a 7-day-old culture of P. syringae and incubated 12 days at 5°C and 7 to 12 days at 22°C. Twenty fruit of each cultivar were used—ten were inoculated, and ten uninoculated fruit served as controls. Lesions developed on all inoculated fruit but not on uninoculated controls. Lesions were spherical, chocolate brown, and firm with no evidence of external mycelia. Lesion morphology was similar on all cultivars. P. syringae was reisolated from lesion margins of all infected fruit. This postharvest decay of apples has not been observed in the Hood River Valley since 1991. Fruit rot of apples caused by P. syringae is known in Canada (1) and is common in the United Kingdom (2), but has not been reported previously in the United States. To our knowledge, this is the first report of postharvest decay of apples by P. syringae in the United States.

References: (1) R. G. Ross and C. O. Gourley. Can. Plant Dis. Surv. 49:33, 1969. (2) A. L. Snowdon. A Color Atlas of Postharvest Diseases. CRC Press, Inc., Boca Raton, FL, 1990. (3) G. M. Waterhouse. The Genus Phytophthora. Misc. Publ. 12. The Commonwealth Mycological Institute, Kew, Surrey, England, 1956.
Selection of Antagonist Microorganisms Against Helminthosporium solani, Causal Agent of Potato Silver Scurf
Authors: Michaud M. , Martinez C. , Simao-Beaunoir A.-M. , Bélanger R. R. , Tweddell R. J.
Published: May 2007

Silver scurf, caused by the fungus Helminthosporium solani, is an important disease affecting potato tubers. Control of the disease has been hampered by the development of H. solani strains resistant to thiabendazole, the only fungicide used in postharvest treatment. As a result, alternative control strategies are needed. In this study, 100 selected soil samples from the province of Québec were tested for their effect on silver scurf development on potato tubers. The results showed that 10 soils were able to decrease silver scurf development on tubers incubated at 10, 15, or 24°C. Many microorganisms were isolated from these soils and tested for their individual ability to reduce H. solani development using a whole-tuber assay. Several of them, including Alcaligenes piechaudii, Aquaspirillum autotrophicum, Arcanobacterium haemolyticum, Arthrobacter oxydans, Bacillus mycoides, Kocuria rosea, Streptomyces griseus, and a fungus of the class Zygomycetes displayed an ability to reduce the development of silver scurf on potato tubers at 10, 15, or 24°C. These results can find useful applications toward a biocontrol program of potato silver scurf as postharvest or seed tuber treatment.
The Effects of Temperature and Wetness Period on the Development of Spinach White Rust
Authors: Sullivan M. J. , Damicone J. P. , Payton M. E.
Published: May 2007

Experiments were conducted in controlled environments to determine the influence of temperature and duration of wetness on development of white rust of spinach. Plants of the susceptible cv. Kent were exposed to temperatures of 6 to 28°C and interrupted wetness periods that totaled 3 to 84 h following inoculation. Disease severity was assessed following further incubation in a greenhouse at 20 to 30°C. Disease was observed at all temperatures and increased with wetness duration. The optimum temperature for disease development ranged from 12 to 18°C. Only 3 h of wetness were required for disease development at 12 to 22°C. A minimum wetness period of 6 to 12 h was required for disease development at suboptimal temperatures. A multiple regression model describing the response surface of arcsine square root transformed disease severity was developed that had significant quadratic wetness effects, cubic temperature effects, and interaction between temperature and wetness. The resulting polynomial model provided a good fit to the observed data, accounting for 89% of the variation in transformed disease severity.
Quantification of Yield Losses Caused by Barley yellow dwarf virus in Wheat and Oats
Authors: McKirdy S. J. , Jones R. A. C. , Nutter F. W.
Published: May 2007

Grain yield data obtained from five field experiments in Western Australia from 1992 to 1994, in which insecticide applications suppressed the spread of Barley yellow dwarf virus (BYDV) in wheat and oats, were used to quantify the relationships between incidence of BYDV and yield gaps, 500-seed weight, and percent shriveled grain. Yield gaps ranged from 0 to 2,700 kg/ha, and the relationship between yield gap and incidence of BYDV was always linear. Single point yield loss models revealed that BYDV infection explained most of the variation in yield gaps. There was a significant linear relationship between incidence of BYDV and 500-seed weight for wheat, but not for oats. The percent shriveled grain always increased with an increase in incidence of BYDV in wheat but not in oats. Cost-benefit relationships were determined for the return on investment when deploying imidacloprid-treated seed and/or one or two foliar applications of pyrethroid insecticides to reduce incidence of BYDV and to decrease the yield gaps in wheat and oats due to BYDV.
The Effect of Synthetic Surfactants on Disease Severity of White Rust on Spinach
Authors: Irish B. M. , Correll J. C. , Morelock T. E.
Published: May 2007

White rust, caused by Albugo occidentalis, is an economically important disease of spinach (Spinacia oleracea). Although cultural practices and partial host resistance are used for disease management, control strategies often rely on fungicides. An alternative approach, the use of ionic (cationic or anionic) and nonionic surfactants, was evaluated for its effect on white rust in greenhouse and field experiments. Surfactant treatments were compared with a water control and two commercial fungicides, azoxystrobin (Quadris) and 1,2,3-benzothiadiazole-7-carbothioic acid S-methyl ester (Actigard). Greenhouse plants were treated with a single surfactant application followed by inoculation with sporangia. Disease severity was rated on leaves 8 to 12 days after inoculation. Field tests were conducted in Arkansas and Texas and received three to five surfactant applications during the season. Disease severity was determined at the end of the growing season. In greenhouse and field tests, all surfactant treatments showed significant reductions in white rust severity compared with water controls. The surfactants Naiad and sodium dodecyl sulfate (SDS) were highly effective and comparable to fungicides in reducing white rust severity. In a laboratory assay, microscopic examination revealed that most of the surfactants at low concentrations caused rapid (<2 min) zoospore lysis.
First Report of Arceuthobium hawksworthii in Honduras
Authors: Mathiasen R. , Howell B. , Melgar J.
Published: May 2007

The dwarf mistletoe Arceuthobium hawksworthii D. Wiens & C. G. Shaw (Viscaceae) has only been reported from the Mountain Pine Ridge area of Belize (1). We observed this dwarf mistletoe parasitizing its principal host, Caribbean pine (Pinus caribaea Morelet var. hondurensis (Senecl.) Barrett & Golf.) (1), 10 km east of Gualaco, Department Olancho, Honduras (elevation 800 m). Several trees were severely infected, and some dwarf mistletoe-associated mortality was observed at this location. The identification of A. hawksworthii was confirmed by comparing specimens collected from Honduras with specimens from Belize, which are deposited at the Deaver Herbarium, Northern Arizona University, Flagstaff. The mistletoes Psittacanthus angustifolius Kuijt and P. pinicola Kuijt (Loranthaceae) were also observed at this location parasitizing Caribbean pine. However, infection by both of these mistletoes was not severe, and no mistletoe-associated mortality was observed. Specimens of these mistletoes from Caribbean pine have been deposited at the Herbario, Escuela Nacional de Ciencias Forestales, Siguatepeque, Honduras. To our knowledge, this is the first report of A. hawksworthii from Honduras and extends its range approximately 350 km to the east-southeast of the Mountain Pine Ridge in Belize. This is also the first report P. angustifolius on Caribbean pine, but P. pinicola commonly infects this host in northern Honduras and Belize (2).

References: (1) F. G. Hawksworth and D. Wiens. Dwarf mistletoes: biology, pathology, and systematics. Agric. Handb. 709, 1996. (2) J. Kuijt. Ann. Mo. Bot. Gard. 74:511, 1987.
AQ10 Biofungicide Combined with Chemical Fungicides or AddQ Spray Adjuvant for Control of Cucurbit Powdery Mildew in Detached Leaf Culture
Authors: Shishkoff N. , McGrath M. T.
Published: May 2007

The biofungicide AQ10, a pelleted formulation of conidia of Ampelomyces quisqualis, did not significantly reduce the size of colonies of the cucurbit powdery mildew (Podosphaera xanthii) in detached squash leaf culture but did reduce the amount of inoculum produced by each colony. No significant reduction in colonization of powdery mildew colonies by AQ10 was observed when it was sprayed in conjunction with the fungicides myclobutanil at 10 μg/ml or triadimefon at 100 μg/ml, suggesting that it is not sensitive to the fungicides at these concentrations. The spray adjuvant AddQ did not increase percent colonization by A. quisqualis but reduced the size of mildew colonies when used alone or with AQ10.
First Report of Herbacious Hosts for Citrus yellow mosaic badna virus from India
Authors: Aparna G. S. , Gopal K. , Subbaiah K. Venkata , Reddy M. N. , Sreenivasulu M.
Published: May 2007

Citrus mosaic disease, a potential threat to citrus production throughout India, is currently an important disease in the southern and northeastern states (2). The reported incidence of the disease ranges from 10 to 77% (K. Gopal, G. S. Aparna, M. Sreenivasuluk, K. V. Subbaiah, and A. R. K. Rao, unpublished data). This yellow mosaic disease of citrus is caused by Citrus yellow mosaic badna virus (CMBV), formerly citrus yellow mosaic disease, (CYMD) (1). Host range studies were done to find herbaceous noncitrus host plant species for virus maintenance. The following are the noncitrus plants tested in this study: Arachis hypogaea, Chenopodium amaranticolor, Chenopodium quinoa, Vigna mungo, Macrotyloma uniflorum, Cicer arietinum, Helianthus annuus, Cajanus cajan, V. sinensis, Cyamopsis tetragonoloba, V. radiata, Pisum sativum, Phaseolus vulgaris, Trichosanthes anguina, Nicotiana tabacum (Harrison special), Dolichos lablab, Petunia × hybrida, Gomphrena globosa, Cucumis melo, Cucumis pepo, Glycine max, Sorghum bicolor, Zea mays, and Canna indica. Young leaves with mosaic symptoms were collected from Citrus sinensis Osbeck, Citrus aurantiifolia Osbeck, and Citrus × limonia Osbeck plants, which are being maintained in an insect-proof glasshouse. The leaves were cut into small pieces, transferred to a chilled mortar, and macerated using 0.01 M phosphate buffer, pH 7.0, containing 0.2% (v/v) of 2-mercapto-ethanol at a tissue/buffer ratio of 1 g/9 ml (wt/vol). The extract was filtered and used for inoculation. The above-mentioned noncitrus plants were uniformly dusted with 600-mesh Carborundum and inoculated with sap extract from the citrus species. The plants were kept in an insect-proof glasshouse and observed for 6 weeks for symptom development. Only three hosts, Canna indica, sorghum, and maize produced visible symptoms. Symptoms were observed 14 days postinoculation on C. indica as chlorotic spots, which later developed into a mosaic pattern. Developing young leaves showed severe mosaic with vein banding symptoms. In sorghum and maize, chlorotic streaks were observed on young leaves after 10 days, which developed into dark green streaks in the leaf lamina. All the inoculated hosts were checked using virus double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and dot blot ELISA using CMBV polyclonal antiserum (Department of Virology, S.V. University, Tirupati, India). In both tests, only the C. indica, sorghum, and maize samples reacted positively. In dot blot ELISA, as little as 100 ng of virus could be detected in C. indica, sorghum, and maize. Virus from all three citrus sources produced the same symptoms on C. indica, sorghum, and maize. To our knowledge, this is the first report of herbaceous hosts of CMBV, which should prove useful as propagation and index hosts for CMBV.

References: (1) Y. S. Ahlawat et al. Plant Dis. 80:590, 1996. (2) G. S. Reddy et al. Page 130 in: 3rd Int. Symp. Subtrop. Hortic. Bangalore, 1972.
First Report of Pink Seed of Common Bean Caused by Erwinia rhapontici
Authors: Huang H. C. , Erickson R. S. , Yanke L. J. , Mündel H.-H. , Hsieh T. F.
Published: May 2007

In 2001, a new disease of common bean (Phaseolus vulgaris L.) caused by Erwinia rhapontici (Millard) Burkh. was detected in seed samples from southern Alberta, Canada. Infected seeds had pink or pinkish-brown lesions on the seed coat. The disease was found in great northern (cv. US1140), pink (cv. Viva), and pinto (cv. Othello) beans at low (<0.1%) frequencies. Isolation from surface-sterilized pink seeds resulted in bacterial cultures, which produced a water-soluble pink pigment on potato dextrose agar (PDA). Seven isolates were tested for physiological characteristics using conventional tests (1) and API 50CHE test strips (bioMérieux Canada, St. Laurent, Quebec), and tested for cellular fatty acids using the MIDI system (Newark, DE). All isolates were gram-negative, motile, facultative anaerobic rods with mucoid colonies and produced a pink pigment on PDA. They were positive for citrate utilization, catalase, methyl red, and Voges-Proskauer, and negative for arginine dihydrolase, lysine and ornithine decarboxylases, urease, gelatin liquification, indole production, oxidase, and gas production. Fatty acid profiles matched with E. rhapontici (approximately 30% each 16:0 and 16:1 ω7c/15:0 iso 2OH; 12% 18:1 ω7c: 8% each 17:0 cyclo and 14:0 3OH/16:1 iso; 4 to 5% each 12:0 and 14:0). Isolates were positive for acid production from: N-acetyl glucosamine, l-arabinose, amygdalin, arbutin, cellobiose, esculin (hydrolysis), d-fructose, d-fucose, d-galactose, β-gentiobiose, d-glucose, glycerol, i-myo-inositol, lactose, maltose, d-mannitol, d-mannose, melibiose, d-raffinose, l-rhamnose, ribose, salicin, d-sorbitol, sucrose, trehalose, and d-xylose. These results match published results for E. rhapontici (4). For pathogenicity tests, each isolate was inoculated in 30 pods from six bean plants (cv. US1140) as described for pink seed of peas (2). Each pod was inoculated with 0.1 ml of bacterial suspension, approximately 109 CFU/ml, by injection through the mid-rib at the basal end. The same number of uninoculated and water-inoculated pods served as controls. Plants were kept in the greenhouse (20 ± 5°C) for 4 weeks, after which isolations were done as described above. In duplicate experiments, all isolates caused lesions on pods extending up to 5 cm from the inoculation point with corresponding discoloration of seeds. The frequency of infected seeds varied among isolates, ranging from 20 to 50%. E. rhapontici was reisolated from seeds with lesions, but not asymptomatic seeds. The study concludes that pink seed of common bean is due to E. rhapontici, a pathogen previously reported on peas in Alberta, Canada (2), and Montana (3).

References: (1) D. J. Brenner. Bergey's Manual of Systematic Bacteriology, vol.1, Williams and Wilkens, Baltimore, MD, 1984. (2) H. C. Huang et al. Can. J. Plant Pathol. 12:445, 1990. (3) B. K. Schroeder et al. Plant Dis. 86:188, 2002. (4) L. Verdonck et al. Int. J. Syst. Bacteriol. 37:4, 1987.
Effect of Organic and Inorganic Salts on the Development of Helminthosporium solani, the Causal Agent of Potato Silver Scurf
Authors: Hervieux V. , Yaganza E. S. , Arul J. , Tweddell R. J.
Published: May 2007

Potato silver scurf, caused by Helminthosporium solani, is an important postharvest disease of economic significance. Control of H. solani has been accomplished primarily by postharvest applications of thiabendazole. However, many strains of H. solani have become resistant to thiabendazole, resulting in failure of disease control. Consequently, alternative control strategies are needed. This study showed that several salts significantly reduced silver scurf development on potato tuber at a concentration of 0.2 M and that the timing of application also influenced salt efficacy. Among the 23 tested salts, aluminum chloride was the only one reducing silver scurf severity when applied either 2, 4, or 7 days after H. solani inoculation. Aluminum lactate, potassium sorbate, sodium carbonate, sodium metabisulfite, and trisodium phosphate also markedly reduced silver scurf severity but only when applied 2 or 4 days after inoculation. Ammonium acetate, calcium chloride, sodium benzoate, sodium citrate, and sodium formate reduced disease severity by at least 50% when applied 2 days after H. solani inoculation. With the exception of calcium chloride and sodium formate, these salts also were shown to strongly inhibit H. solani mycelial growth or spore germination in vitro. Results of this study further demonstrate the possibility of using selected salts for the control of potato silver scurf.
Rates of Transmitting Erwinia stewartii from Seed to Seedlings of a Sweet Corn Hybrid Susceptible to Stewart's Wilt
Authors: Michener P. M. , Pataky J. K. , White D. G.
Published: May 2007

Rates of transmitting Erwinia stewartii from seed to seedlings were estimated from field grow-outs of seedlings grown from seed infected with E. stewartii. Infected seed were produced in 1998, 1999, and 2000 on a Stewart's wilt-susceptible sweet corn hybrid, Jubilee. Seedlings were inoculated repeatedly with pinprick inoculators and suspensions of E. stewartii were injected into ear shanks of the primary ears of each adult plant. Seed from inoculated plants were harvested and bulked. Single kernels were assayed for E. stewartii to estimate the proportion of kernels infected with E. stewartii. Estimates of E. stewartii-infection were 15.6 ± 4.3, 49.4 ± 3.9, and 12.5 ± 2.4% for seed produced in 1998, 1999, and 2000, respectively. Approximately 61,800 seedlings were grown in DeKalb, IL in 1999 and 83,400 and 60,000 seedlings were grown in Plover WI in 2000 and 2001, respectively, from infected seed lots produced the previous year. Approximately 10,000, 12,200, and 29,400 seedlings of susceptible sweet corn hybrids also were grown each year from commercial seed produced in Idaho where Stewart's wilt does not occur. Based on estimates of kernel infection in each seed lot and plant populations in each grow-out trial, about 9,600, 41,200, and 7,500 seedlings were grown from infected kernels in 1999, 2000, and 2001, respectively. Seedlings at the two- to three-leaf stage were examined for symptoms of Stewart's wilt. Infected plants were confirmed by microscopic observations of bacterial ooze and by enzyme-linked immunosorbent assay. When data were combined from all three trials, 59 of approximately 58,300 seedlings grown from infected seed were infected with E. stewartii based on symptoms of Stewart's wilt and E. stewartii-positive leaf tissue samples. Of these 59 seedlings, 22 probably were infected from seed-to-seedling transmission of E. stewartii and 37 probably were the result of natural infection due to the presence of flea beetles in DeKalb in 1999. Twenty-two infected seedlings from 58,300 infected kernels corresponds to a seed-to-seedling transmission rate of 0.038%. This rate of seed-to-seedling transmission of E. stewartii is substantially lower than seed transmission rates reported in the first half of the twentieth century; however, it is similar to seed-to-seedling transmission rates reported from other recent research.
Quality of Harvested Seed Associated with Soybean Cultivars and Herbicides Under Weed-Free Conditions
Authors: Bradley C. A. , Hartman G. L. , Wax L. M. , Pedersen W. L.
Published: May 2007

Different herbicides were applied to soybean plants in field plots planted to different soybean cultivars located at four locations in Illinois between 1997 and 2000. Treatments varied from hand weeded to preemergence herbicides to postemergence herbicides. Soybean seeds were harvested and evaluated for different seed quality parameters. The percentage of seeds infected with Phomopsis spp. ranged from 1 to 40%, and the percentage of seeds infected with Cercospora kikuchii was low, ranging from 0 to 4%. Herbicides had little or no effect on seed quality parameters such as percent germination and incidence of seed pathogens or on protein and oil concentrations. Soybean seed quality was affected by Phomopsis spp. in that there were significant (P ≤ 0.05) inverse correlations between Phomopsis spp. incidence and percentage seed germination. It appears that Phomopsis spp. may be a more prevalent seed pathogen than C. kikuchii for soybean fields in central to northern Illinois.
First Report of Phytophthora cactorum on Strawberry Plants in Spain
Authors: Santos B. de los , Porras M. , Blanco C. , Barrau C. , Romero F.
Published: May 2007

Crown rot of strawberry (Fragaria × ananassa Duch. cv. Camarosa) was observed in three and two production fields in 2000 and 2001, respectively, in Huelva, southwestern Andalucia, Spain. Affected plants did not exhibit typical symptoms of red stele. Instead, there was an internal red-brown discoloration of the upper crown, a bluish discoloration of leaves, and the plants were wilted. Eventually, plants collapsed and died. Fungi were isolated from surface-disinfested necrotic crown tissue on P5ARPH medium (1). Plates were placed at 21°C for 5 to 10 days. One species was isolated consistently from symptomatic tissue. Microscopic observations revealed spherical oogonia with thin walls. Antheridia were paragynous and were attached to the oogonium near the oogonial stalk. Single oospores were spherical and had double-layered, yellow-brown walls (20 to 25 μm in diameter). Sporangia were usually borne terminally and were colorless and papillate (22 to 30 μm in diameter). Based on these characteristics, the causal agent was identified as Phytophthora cactorum (Lebert & Cohn) J. Schröt. (2). The fungus was transferred to V8 juice agar and maintained at 21°C in the dark. Disks (9-mm diameter) were removed from 7-day-old cultures of P. cactoru and used to inoculate five 2-month-old ‘Camarosa’ strawberry plants grown in sterilized peat in the greenhouse. Three disks were placed in the crown of each plant at soil level. Five noninoculated plants were similarly treated with sterile V8 juice agar disks only. After 2 weeks, the pathogen was reisolated from red-brown lesions visible on crowns of all inoculated plants. Noninoculated plants did not show any symptoms. To our knowledge, this is the first report of P. cactorum attacking strawberry plants in Spain.

References: (1) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986. (2) G. M. Waterhouse and J. M. Waterston. No. 111 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, UK, 1996.
Chrysomyxa weirii on Colorado Blue Spruce in Wisconsin
Authors: Stanosz G. R. , Cummings-Carlson J.
Published: May 2007

In early June 2002, yellow spots and bands with erumpent telia on previous year's needles of Colorado blue spruce (Picea pungens) were noted in landscape tree nurseries in both northern (Sawyer County) and southern (Dane County) Wisconsin. Many 1 to 2 m tall trees were symptomatic at each location. Based on the age of affected needles, time of year of telium development, and telial characteristics including the size and shape of teliospores, the pathogen was identified as Chrysomyxa weirii, the cause of Weir's cushion rust (1,2). Identification of the pathogen was confirmed by Dale Bergdahl, (School of Natural Resources, University of Vermont), who also observed basidiospores. C. weirii is an autoecious microcyclic rust pathogen known to affect P. englemanii, P. glauca, P. mariana, P. pungens, and P. sitchensis. Although this fungus has been reported in the western United States from the Black Hills of South Dakota to Washington State, in the eastern United States from the southern Appalachian Mountains (Tennessee and West Virginia) to Vermont, and in most Canadian provinces and territories (1,2), to our knowledge, this is the first report from the Great Lakes Region of the United States. The occurrence of Weir's cushion rust in Wisconsin has direct implications for the economically important nursery and Christmas tree industry in this region.

References: (1) D. Bergdahl and D. Smeltzer. Plant Dis. 67:918, 1983. (2) W. Ziller. The Tree Rusts of Western Canada. Canadian Forestry Service, Victoria, BC, 1974.
First Report of Charcoal Rot of Sugar Beet Caused by Macrophomina phaseolina in Greece
Authors: Karadimos D. A. , Karaoglanidis G. S. , Klonari K.
Published: May 2007

During the summer of 2000 in the Amyndeon area of northern Greece, sugar beet (Beta vulgaris L.) roots with rot symptoms were observed in many fields. Initially, the plants wilted, and leaves soon turned brown and died. Diseased plants appeared in patches in the field. Brown-black lesions were observed in the external part of the root crown while yellow-mustard colored lesions occurred internally. In advanced stages of decay, masses of sclerotia formed in rotted cavities and roots became mummified. Macrophomina phaseolina (Tassi) Goid. (1) was isolated on potato dextrose agar (PDA) from 30 rotted roots collected in five fields. Cultures produced dark multi-septate mycelium and sclerotia, which were black, smooth, spherical to irregular in shape, and varied in size from 100 μm to 1mm in diameter. Five isolates were evaluated for pathogenicity on surface-sterilized 16-week-old sugar beet roots (cv. Rizor) by placing a 5-mm-diameter PDA plug of actively growing mycelium in wounds made with a sterile knife. Sterile PDA plugs were placed in wounds made in control beet roots. Ten roots were inoculated per isolate. Roots were kept at 25°C in the dark for 10 days. Extensive decay of inoculated roots developed, similar to decay observed in the field, and M. phaseolina was reisolated from rotted tissue. Control roots showed no decay. This pathogen has been previously reported as a root rot pathogen of sugar beet in California, India, and countries of the former USSR. Charcoal rot is of minor economic importance since M. phaseolina attacks mainly weakened plants under conditions of high temperature (2). To our knowledge, this is the first report of charcoal root rot of sugar beet in Greece.

References: (1) Anonymous. Macrophomina phaseolina. No. 275 in: Descriptions of Plant Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1970. (2) J. E. Duffus and E. G. Ruppel. Diseases. Page 347 in: The Sugar Beet Crop. Science into Practice. D. A. Cooke and R. K. Scott eds. Chapman and Hall, NY, 1993.