bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence of Five Thrips Species on Flue-Cured Tobacco and Impact on Spotted Wilt Disease Incidence in Georgia
Authors: McPherson R. M. , Pappu H. R. , Jones D. C.
Published: May 2007

Thrips-vectored tomato spotted wilt tospovirus (TSWV) infection is a major constraint on tobacco production in Georgia. Flue-cured tobacco fields were surveyed throughout the season from 1989 to 1991 and 1996 to 1998 to determine spotted wilt disease incidence and seasonal abundance and species composition of thrips populations. Five species were commonly found that accounted for more than 95% of the 17,000 thrips collected, including Frankliniella fusca, F. occidentalis, F. bispinosa, F. tritici, and Limothrips cerealium. F. fusca, F. occidentalis, and F. bispinosa are vectors of TSWV. F. fusca was the most common foliage thrips collected during all years, except 1989, when L. cerealium was the most abundant species. During 1989 to 1991, 22 to 68% of the foliage and flower thrips identified were TSWV vector species. The 1996 to 1998 foliage collections had much higher percentages of vector species (95 to 97%). The 1996 flower samples also had a very high percentage of vector species (94%); however, the percentages were much lower in 1997 (3%) and 1998 (32%). A trend toward higher incidence of TSWV occurred during the last three seasons studied, when thrips vector species were more abundant.
First Report of Clover Yellow Edge Phytoplasma in Corylus (Hazelnut)
Authors: Jomantiene R. , Postman J. D. , Montano H. G. , Maas J. L. , Davis R. E. , Johnson K. B.
Published: May 2007

During investigations into the cause of a stunt syndrome affecting cultivated European hazelnut trees (Corylus avellana L.) in Oregon, the clover yellow edge (CYE) phytoplasma was detected for the first time in this crop. The cause of hazelnut stunt syndrome (HSS) is unknown, but the disease has been transmitted by grafting and apparently has moved within orchards through root grafts (1). Severely affected trees persist for many years, but their nut production is greatly reduced. Previous attempts to detect viruses, bacteria, and other pathogens have been unsuccessful. HSS has been observed only in Oregon and already had been present for more than 10 years when it was first reported in 1970 (1). In June, 1999, leaf samples were collected from two affected and two apparently healthy (symptomless) hazelnut trees in a field plot at Oregon State University, Corvallis, and from a healthy greenhouse-grown tree. Leaf samples were sent to the USDA Beltsville, MD, laboratory, where they were assessed for phytoplasma infection, using nested polymerase chain reactions (PCRs). PCRs were primed by phytoplasma universal primer pairs P1/P7 and F2n/R2 (3) for amplification of phytoplasma 16S ribosomal (r) DNA (16S rRNA gene) sequences according to the procedures of Gunderson and Lee (2). Phytoplasma-characteristic 1.2-kbp DNA sequences were amplified from all field-tree samples. No DNA sequences were amplified from samples of the greenhouse-grown tree. Restriction fragment length polymorphism patterns of rDNA digested with AluI, KpnI, HhaI, HaeIII, HpaII, MseI, RsaI, and Sau3A1 endonucleases indicated that all diseased hazelnut trees as well as symptomless field trees were infected by a phytoplasma classified in group 16SrIII (peach X-disease group), subgroup B (III-B, type strain CYE phytoplasma). No phytoplasmas were detected in samples from the greenhouse-grown tree. Nucleotide sequences were determined for 16Sr DNA fragments amplified from the hazelnut CYE phytoplasma in nested PCRs primed with F2n/R2. The sequences were deposited in GenBank under Accession no. AF189288. Sequence similarity between 16Sr DNAs of the hazelnut CYE strain (CYE-Or) and the Canadian clover yellow edge strain (CYE-C, GenBank Accession no. AF175304) phytoplasma was 99.9%. Decline and yellows disorders of hazelnut in Germany and Italy have been associated with infections by apple proliferation, pear decline, and European stone fruit yellows phytoplasmas (4). These phytoplasmas are classified in 16Sr group X, the apple proliferation group of phytoplasmas. This is the first report of the CYE phytoplasma infecting Corylus.

References: (1) H. R. Cameron. Plant Dis. Rep. 54:69, 1970. (2) D. E. Gunderson and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (3) R. Jomantiene et al. HortScience 33:1069, 1998. (4) C. Marcone et al. Plant Pathol. 45:857,1996.
Natural Infection of Alstroemeria brasiliensis with Lily Mottle Virus
Authors: Bouwen I. , van der Vlugt R. A. A.
Published: May 2007

During a survey for a European Union-funded project on viruses of Alstroemeria, two A. brasiliensis plants were found expressing virus-like symptoms, including leaf chlorosis with deep-green oval spots and flower color breaking. In enzyme-linked immunosorbent assays (ELISA), no positive reaction was obtained with antisera to Alstroemeria mosaic, Alstroemeria carla, Cucumber mosaic, Freesia mosaic, or Tobacco rattle virus or potyvirus-specific monoclonal antibodies (Agdia, Elkhart, IN). ELISA reactions were positive with antisera to Lily mottle (LMoV) and Rembrandt tulip breaking viruses (1). In electron microscopy preparations of A. brasiliensis, potyvirus-like particles were observed. Using sap-inoculation, the virus was transferred to a range of host species. Chenopodium quinoa, Nicotiana occidentalis accession 37B, and N. occidentalis subsp. obliqua (P1) expressed local lesions; N. clevelandii expressed local and systemic mottle; and N. benthamiana expressed local lesions, systemic vein yellowing, and leaf crinkling. Isolated total RNA from infected N. benthamiana was used for initial cDNA synthesis and polymerase chain reaction amplification with a potyvirus-specific primer set (2). The amplicon (≈670 bp) was cloned and sequenced. The sequence showed 92% homology with the corresponding region of LMoV RNA (GenBank accession no. S44147). The results confirm the infection of A. brasiliensis with LMoV. This is the first report of natural infection of Alstroemeria by LMoV.

References: (1) E. L. Dekker et al. J. Gen. Virol. 74:881, 1993. (2) R. A. A. van der Vlugt et al. Phytopathology 89:148, 1999.
A New Disease of Parthenium hysterophorus Incited by an Undescribed Species of Cryptosporiopsis
Authors: Kumar P. Sreerama
Published: May 2007

Fungal pathogens of parthenium (Parthenium hysterophorus L.), an invasive weed in India, have been under intensive investigation at our Directorate since 1996 for development of mycoherbicides. During the southwest monsoon month of August 1997, a severe foliar disease of the weed was observed near Hunsur (12° 16′N; 76° 18′E; 779.37 masl) in Mysore district of Karnataka State. The primary symptoms consisted of circular to irregular, light brown leaf spots with a diameter up to 8 mm and surrounded by a diffuse chlorotic margin. Isolations on potato dextrose agar (PDA) yielded a relatively fast-growing (approximately 11.4 mm/day) white fungus. The same fungus was isolated consistently from diseased leaves but not from symptomless leaves collected from the vicinity. The mycelium of the fungus on PDA was immersed, branched, septate, and hyaline to pale brown. Conidia (approximately 10.50 × 2.75 µm) were hyaline, thin-walled, smooth, straight, and ellipsoid with obtuse apex and base abruptly tapered to a distinct truncate scar. Pathogenicity was assessed by inoculating healthy, surface-sterilized, mature detached leaves and whole plants (40-day-old) with spore (1 × 106 conidia/ml) or mycelial (0.2 g/ml) suspensions. For both kinds of inoculation, 10 replicates each for detached leaves and whole plants were maintained with equal number of uninoculated controls. Inoculated leaves and plants were incubated at ambient temperature (28 ± 2°C) and 48 h of continuous leaf wetness. Lesions resembling symptoms that occurred in the field were observed on all detached leaves and whole plants within 3 weeks of inoculation. The same fungus was recovered from the diseased tissues excised from all the inoculated material, satisfying Koch's postulates. All the controls remained symptomless and were negative for the fungus. A virulent isolate of this fungus was referred to CABI Bioscience, UK Centre (Egham) and was identified as Cryptosporiopsis sp. (IMI 378270). Although there are at least 12 described species of Cryptosporiopsis Bub. & Kabát (1), no species has been described on parthenium. This pathogen is being studied for its usefulness as a mycoherbicide for parthenium.

Reference: (1) B. C. Sutton. 1980. The Coelomycetes. Commonwealth Mycological Institute, Kew, Surrey, England.
First Report of Leaf Rust Caused by Uredo cajani on Pigeonpea in South Africa
Authors: Swart W. J. , Mathews C. , Saxena K. B.
Published: May 2007

Pigeonpea (Cajanus cajan [L.] Mills.) is an important legume with potential as a dryland crop with multiple uses in the semi-arid areas of South Africa. Approximately 150 tons of dry, split seeds are imported monthly to meet the needs of South Africa. In May 2000, field trials and farmer's plots with plant ages varying from 1 to 3 years old were visited in Mpumalanga and Kwazulu-Natal to assess problems associated with pigeonpea cultivation. Rust was prevalent on more than 80% of plants on young and old leaves at all sites but was most severe at sites in Mpumalanga, where severe rust was observed on all 17 ICRISAT varieties evaluated. Leaf lesions began as chlorotic flecks that expanded and developed into necrotic spots with several orange red to brown uredinia present mostly on the abaxial sides of leaves. Urediospores were 1-celled and initially hyaline, turning dark orange, minutely echinulate, spherical with 2 to 4 circular germpores and measured 20–27 × 17 to 21μ. No telia were found and all morphological characteristics therefore correspond with the CMI description of Uredo cajani Syd. (1). In Africa, pigeonpea rust has been reported from Kenya, Nigeria, Sierra Leone, Tanzania, and Uganda. In South Africa, rust, described as Uromyces dolicholi Arthur (2), has only once been reported on pigeonpea. In the United States, U. dolicholi has also once been reported on pigeonpea (3). However, since U. dolicholi, unlike U. cajani, produces telia and occurs only on Rhyncosia spp. (4), these reports can be considered incorrect. This is therefore the first report of U. cajani on pigeonpea in South Africa.

References: (1) K. H. Anahosur and J. M. Waller. 1978. No. 590: Descriptions of Plant Pathogenic Fungi and Bacteria. Commonw. Mycol. Inst., Kew, England. (2) E. M. Doidge. Bothalia 5:1-1094, 1950. (3) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN, 1989. (4) A. Sivanesan. 1970. No. 269: Descriptions of Plant Pathogenic Fungi and Bacteria. Commonw. Mycol. Inst., Kew, England.
Effects of Coating, Deployment Angle, and Compass Orientation on Performance of Electronic Wetness Sensors During Dew Periods
Authors: Lau Yewah F. , Gleason Mark L. , Zriba Narjess , Taylor S. Elwynn , Hinz Paul N.
Published: May 2007

Response of electronic, printed-circuit wetness sensors was compared to visual observations of free water on processing-tomato leaflets during 13 dew-onset and 11 dew-dryoff events. Deployment angle and painting of the sensor surface significantly (P < 0.01) influenced the mean absolute time difference between observation of the first wet or dry leaflet at the top of the tomato canopy and the start of sensor response (kΩ) to dew onset or dryoff, respectively. Compass orientation of painted sensors deployed at 45° to horizontal had no significant effect on response to dew onset or dryoff. For sensors deployed at 45° during dew onset, mean absolute time difference between the first observed wet leaflet and the start of unpainted sensor response was 4.00 h, compared to 0.58 and 1.09 h for sensors with three and nine coats of paint, respectively. At deployment angles of 30 or 0°, paint coating had a lesser influence on time differences between visual observation and sensor response to dew onset. During dew dryoff, absolute time differences between visual confirmation of the first dry leaflet and the start of sensor response were ≤1.03 h for all sensors. Trends were similar when the visual observation criterion was 50% wet or dry leaflets during dew onset or dryoff, respectively, rather than first wet or dry leaflet. Standard deviation of sensor response during dew onset was generally larger for unpainted sensors than for sensors with three coats of paint, especially when deployed at a 45° angle. The apparent temperature of unpainted sensors at 0 or 30° deployment angles decreased much more rapidly during the period preceding dew onset than for painted sensors at the same deployment angles, whose apparent temperatures cooled at rates similar to those of tomato leaflets positioned at these angles. The results indicate that deployment angle can significantly affect accuracy and precision of dew-duration measurements by unpainted, but not painted, electronic wetness sensors.
Dactuliophora Leaf Spot of Pearl Millet in Niger and Mali
Authors: Wilson J. P. , Hess D. E. , Kumar K. A.
Published: May 2007

Pearl millet (Pennisetum glaucum (L.) R. Br.) fields and cultivar trials in Sadoré, Niger, and Samanko, Mali, were surveyed in late August 1999 Most plants were in the late stem elongation to panicle exertion stage Local open-pollinated cultivars, experimental hybrids, and inbreds had disease severities of up to 10% of foliage diseased, with most severe disease on lower leaves. Individual, young, brown necrotic lesions averaged 2 × 1 mm and were surrounded by circular to irregular purple watersoaked margins 1 to 7 mm wide. Lesions expanded in irregular concentric rings, with zones of necrosis often separated by zones of green tissue Mature, individual lesions averaged 4.3 × 1.9 cm. Entire leaves could be blighted by coalescing lesions. No sclerotia were observed in young lesions, but sclerotia consistently developed and were macroscopically visible in necrotic tissues of older lesions. Sclerotia were oblong to pyriform (averaging 178 × 124 mm) and borne on erumpent, cup-shaped sclerotiophores. When incubated under high humidity, sterile gray mycelia grew rapidly from necrotic lesions up to a distance of ≈5 mm on the lower leaf surface, which likely resulted in the large concentric zones necrosis. Fungal characteristics and symptoms were consistent with disease caused by Dactuliophora elongata Leakey (1,2). Based on observations at the International Pearl Millet Downy Mildew Virulence Nursery in Mali, it is likely that resistance to D. elongata exists. Leaf spot of pearl millet caused by D. elongata has been reported only in Nigeria (1,2). Our observations confirm that the pathogen also is present on pearl millet Niger and Mali.

References: (1) C. L. A. Leakey. Trans. Br. Mycol. Soc. 47:341, 1964. (2) P. D. Tyagi Proc. Ind. Acad. Sci. (Plant Sci.) 94:407, 1985.
First Report of Alternaria Leaf Spot of Spathiphyllum sp. in Argentina
Authors: Cheheid A. L. , Wright E. R. , Lopez S. E. , Rodríguez Codazzi A. M.
Published: May 2007

Brown necrotic spots surrounded by chlorotic areas have been observed on the leaf margins of Spathiphyllum sp. in many nurseries in and near Buenos Aires, Argentina, since 1997. Spots reached 0.7 × 2 cm and appeared mainly on older leaves of stressed plants. To determine the causal agent of the leaf spot, small pieces of diseased tissue were surface-sterilized for 2 min in 2% sodium hypochlorite and plated on potato dextrose agar. Gray olivaceous to almost black colonies developed in 3 to 4 days. Dark conidiophores, which formed singly or in small groups, were short, less than 100 μm, sometimes flexuous, and occasionally geniculate. The brown to black, obclavate, pyriform, or rostrate conidia were 20 to 25 μm long × 10 to 15 μm wide, with three to four transverse septa and one to three longitudinal or oblique septa. Chains of conidia 5 to 10 spores long were sometimes branched, appearing bushy. The foliage of 15 healthy potted plants previously injured with sterile needles and 15 healthy potted plants without injuries was inoculated with a suspension of 2.8 × 104 conidia per ml. Plants were maintained at 23°C and 100% relative humidity under fluorescent light (12 h light/12 h darkness) for 3 days. Chlorotic and necrotic spots began to develop on the apex and margins of injured and inoculated leaves after 10 days. Lesions tended to coalesce, finally measuring 2.2 × 0.7 cm after 26 days. Control plants, with and without injuries, sprayed with distilled water remained symptomless. Koch's postulates were satisfied after reisolating the fungus. Cultures in potato carrot agar and V8 agar after 7 days exhibited typical characteristics of Alternaria alternata (2–4). An Alternaria sp. has been found previously in the United States on Spathiphyllum sp. (1). This is the first report of Alternaria leaf spot of Spathiphyllum in Argentina.

References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN. (2) E. G. Simmons. Alternaria themes and variations (226–235): Classification of Citrus pathogens. Mycotaxon 70:263, 1999. (3) E. G. Simmons. Alternaria themes and variations (236–243): Host specific toxin producers. Mycotaxon 70:325, 1999. (4) E. G. Simmons and R. G. Roberts. Alternaria themes and variations (73). Mycotaxon 48:109, 1993.
Molecular and Biological Characterization of a Trackable Illinois Isolate of Barley yellow dwarf virus-PAV
Authors: Moon Jae Sun , Allen Richard G. , Domier Leslie L. , Hewings Adriana D.
Published: May 2007

In consecutive annual statewide surveys of the incidence of Barley yellow dwarf viruses (BYDVs) in Illinois wheat and oat fields, 27 BYDV-PAV-like isolates were identified. Using polymerase chain reaction (PCR), the coat protein regions of all 27 isolates were analyzed for restriction fragment length polymorphisms. The PCR products of two isolates, one from each year, had restriction fragment profiles after digestion with HaeIII that differed from the other isolates. The nucleotide sequences of the coat protein regions of a laboratory isolate, BYDV-PAV-IL (PAV-IL), two of the isolates with the common restriction profile, and the two isolates with polymorphic profiles were more than 98% identical. The relatively rare isolate identified during the first year was designated BYDV-PAV-DK1 (PAV-DK1) and further characterized biologically. PAV-DK1 and PAV-IL did not differ significantly in symptom expression, but did differ significantly in rates of transmission by two of the three biotypes of Rhopalosiphum padiexamined. Since PAV-DK1 does not occur in high levels in the state of Illinois, and its PCR products have a unique restriction enzyme profile, it has the potential to be used as a traceable isolate in field epidemiological experiments.
New Natural Hosts of Tomato spotted wilt virus
Authors: Jordá C. , Font I. , Lázaro A. , Juarez M. , Ortega A. , Lacasa A.
Published: May 2007

Tomato spotted wilt virus (TSWV) has caused epidemics in recent years in many crops throughout the Mediterranean Region. Tomato, pepper, and lettuce are the crops most affected in Spain. To determine the reservoir hosts for the virus in the area, 210 samples from 95 species of plants were collected and tested for TSWV by double-antibody sandwich enzyme-linked immunosorbent assay with commercial antisera (Loewe Biochemica, Germany: BR-01, serogroup I or TSWV-L). Twenty-one species tested positive, and among them were thirteen newly identified hosts for TSWV (1). Weed species were among the 13 new hosts and included Diplotaxis erucoides (L.) DC., Beta maritima L., Phragmites communis Trin., Malva sylvestris L., Sonchus arvensis L., Sorghum halepense L., Panicum repens L., Atriplex patula L., Coronopus squamatus (Forssk.) Ascherson, Cuscuta sp., Xanthium spinosum L., Suaeda vera J.F., and Ecballium elaterium (L.) A. Rich. Most of these plants were asymptomatic hosts, but the Sonchus sp. showed typical symptoms of TSWV, such as yellows, bronzing, ring spots, necrosis, curling of young leaves, and growth reduction. D. erucoides, B. maritima, M. sylvestris, X. spinosum, and E. elaterium showed chlorosis and growth reduction.

Reference: (1) C. Jorda et al. 1998. Anexo no. 3. Pages 381–386 in: The Health of Tomato Crops. Phytoma-España S. L., Valencia, Spain.
Optimal Fungicide Management of Purple Spot of Asparagus and Impact on Yield
Authors: Meyer M. P. , Hausbeck M. K. , Podolsky R.
Published: May 2007

Purple spot disease of asparagus, caused by the fungus Stemphylium vesicarium, results in lesions on spears and ferns and defoliation of ferns. In two newly established commercial asparagus fields (cvs. Jersey Giant and Jersey Knight), chlorothalonil or mancozeb was applied every 7, 10, or 14 days or according to Tom-Cast with a threshold of 15 disease severity values, and not applied to the control. Tom-Cast prompted four sprays, resulting in a 60% reduction in the number of fungicide applications when compared with the 7-day-interval treatment. When disease pressure was severe, lesions on ferns were significantly less for both cultivars when fungicides were applied according to Tom-Cast or every 7 days compared with spray intervals of 10 or 14 days. Applying fungicides according to Tom-Cast or every 7 days resulted in an increased Jersey Giant fern stand compared with applying fungicides every 10 or 14 days. Unsprayed control plots yielded 77 to 83% (depending on cultivar) of those plots treated according to Tom-Cast using chlorothalonil. Significantly higher yields of Jersey Knight were obtained for chlorothalonil versus mancozeb. When mancozeb was used, Jersey Knight yield was significantly increased with a 7-day versus Tom-Cast application regime. Using chlorothalonil in a Tom-Cast program provided a benefit per hectare (BPH) of $1,005.24 (Jersey Knight) to $2,057.69 (Jersey Giant). In comparison, using mancozeb in a Tom-Cast program provided a BPH of -$484.27 (Jersey Knight) to $1,030.55 (Jersey Giant) over a 2-year period.
Effects of Host, Inoculum Concentration, Wetness Duration, Growth Stage, and Temperature on Anthracnose of Lentil
Authors: Chongo G. , Bernier C. C.
Published: May 2007

The effects of concentration of conidia, duration of the wetness period, plant growth stage, and temperature on the development of anthracnose (Colletotrichum truncatum) on lentil (Lens culinaris) were assessed in growth-chamber and greenhouse studies using cv. Indianhead and line 458-57, which have partial resistance, and susceptible cv. Eston. Each genotype was assessed for incubation period (IP), latent period (LP), number of lesions (LN) per stem, and disease severity (DS). Both IP and LP decreased linearly with increasing conidial concentration, wetness duration, and temperature. Both IP and LP also became progressively shorter as the plants aged between 2 to 6 weeks and increased between 6 to 8 weeks after seeding. Both LN and DS increased linearly with increasing inoculum concentration, wetness duration, and temperature. Both LN and DS also increased with plant age between 2 to 4 weeks and decreased between 4 to 8 weeks. The growth stage and temperature required for optimal disease development ranged, respectively, from 4 to 6 weeks and 20 to 24°C when plants were inoculated at a concentration of 4 × 104 conidia/ml and provided with a wetness period of 24 h. Generally, cv. Indianhead and line 458-57 had significantly longer IP and LP and lower LN and DS than cv. Eston.
First Report of White Pine Blister Rust in Nevada
Authors: Smith J. P. , Hoffman J. T. , Sullivan K. F. , Arsdel E. P. Van , Vogler D.
Published: May 2007

White pine blister rust, caused by Cronartium ribicola Fisch., was found in 1997 infecting white pines (genus Pinus, subgenus Strobus) at two locations in the Carson Range of western Nevada. Rust incidence, infection age, damage to trees, rust phenology, and host distribution were evaluated at one of these locations and a nearby location in California in 1998. At the first location (39.3°N, 119.9°W), C. ribicola was found infecting 24 of 49 whitebark pines (P. albicaulis Engelm.) near Mt. Rose Summit on Highway 27 at 2,710 m elevation, ≈6 km northeast of Incline Village, Washoe County, NV. Among infected trees, 33% had only branch cankers, 54% had live stem cankers, and 12% had stem cankers that had killed portions of trees distal to cankers. No trees had died from infection. At the second location (39.1°N, 119.9°W), we found only 6 of 50 (12%) infected western white pines (P. monticola Dougl.) near Genoa Peak (≈2,750 m elevation), 3 km east of Lake Tahoe, Douglas County, NV; however, stem cankers occurred on 4 of the 6 infected trees. In September 1998, whitebark pines at Mt. Rose and Tahoe Meadows (2,550 m elevation, 1.5 km southwest of Mt. Rose Summit) were examined, and the following was observed: (i) aeciospore production was at its peak, indicating that sporulation can occur exceptionally late in the season in this region; (ii) signs of blister rust infection were absent on the telial hosts of C. ribicola (Ribes cereum, R. montigenum, and R. nevadense) at both locations; (iii) ≈80% of the cankers occurred on host wood produced in 1978 and 1979; and (iv) the oldest cankers originated on wood produced in 1968 and the youngest on wood produced in 1980. In October 1998, infected western white pines were examined at a location (2,650 m elevation) ≈30 km north of Lake Tahoe on Babbitt Peak, Sierra County, CA (39.6°N, 120.1°W). At this location, no trees had died from infection, fresh aeciospores were abundant on live cankers, R. montigenum and R. cereum were present but did not show signs of infection, and 19 of 20 cankers examined were on wood produced between 1978 and 1980. White pine blister rust was not found at any of 10 other locations examined throughout Nevada from 1995 to 1997. This is believed to be the first documented report of C. ribicola infecting white pines in Nevada and the easternmost extension of blister rust in the Sierra Nevada Region. These observations suggest that our understanding of blister rust spread and infection dynamics east of the Sierra Nevada crest is incomplete and that future surveys and research in this region must address, among other issues, timing of aeciospore production on pine, and the possibility of blister rust spread into the Great Basin.
Occurrence of Cowpea aphid-borne mosaic virus in Peanut in Brazil
Authors: Pio-Ribeiro G. , Pappu S. S. , Pappu H. R. , Andrade G. P. , Reddy D. V. R.
Published: May 2007

Surveys of peanut crops in northeastern Brazil since 1995 showed the occurrence of a hitherto unreported virus disease. Characteristic leaf symptoms were ring spots and blotches. The virus was seed transmitted in peanut (1/610) and cowpea (47/796). Local and systemic symptoms were observed in cowpea (cv. TVu 3433) known to be susceptible to most Cowpea aphid-borne mosaic virus (CABMV) isolates. The virus was transmitted by aphids Toxoptera citricidus and Aphis gossypii. Using degenerate primers, the 3′ terminal region of the viral genome was cloned and sequenced. Sequence analyses of the coat protein and the 3′ untranslated region indicated that the potyvirus was most closely related to CABMV isolates from South Africa, Zimbabwe, and the United States. On the basis of genome analysis, the virus was identified as CABMV. The natural occurrence of CABMV on peanut has so far not been reported. The significance of this finding especially for germ plasm exchange is discussed.
Management of Botrytis Fruit Rot in Annual Winter Strawberry Using Captan, Thiram, and Iprodione
Authors: Legard D. E. , Xiao C. L. , Mertely J. C. , Chandler C. K.
Published: May 2007

The management of Botrytis fruit rot on annual strawberry by fungicides was evaluated in Florida during the 1995-96, 1996-97, and 1997-98 seasons. Weekly applications of captan or thiram, bloom applications of iprodione applied twice during each of two peak flowering periods, and weekly applications of captan combined with iprodione bloom applications were evaluated. Significant treatment effects (P ≤ 0.05) on the incidence of Botrytis fruit rot were detected for the early, late, and whole-season periods each season. Weekly applications of captan or thiram controlled Botrytis fruit rot, reducing disease incidence by more than 41% compared to the untreated control. These treatments also affected marketable yield during two seasons, with a 42 to 127% increase in yield compared to the control. Weekly fungicide applications did not reduce the incidence of Botrytis fruit rot until at least the fourth week of harvest, 9 to 10 weeks after applications began. Bloom applications of iprodione alone reduced the incidence of Botrytis fruit rot during the second peak bloom period, and the reductions in incidence occurred 1 to 3 weeks after the start of bloom applications. This suggests that iprodione applications control infections at flowering or early stages of fruit development. However, early-season bloom applications did not reduce the incidence of Botrytis fruit rot. The control of Botrytis fruit rot by weekly captan applications was not improved by the addition of iprodione bloom applications. These data suggest that early-season fungicide applications for the control of Botrytis fruit rot in annual winter strawberry are of limited efficacy, and that bloom applications of Botryticides such as iprodione should be focused on the second peak bloom period.
Weeds in Greenhouses and Tobacco Fields Are Differentially Infected by Tomato spotted wilt virus and Infested by Its Vector Species
Authors: Chatzivassiliou E. K. , Boubourakas I. , Drossos E. , Eleftherohorinos I. , Jenser G. , Peters D. , Katis N. I.
Published: May 2007

A survey was conducted in the Macedonia region of Greece to determine the reservoir hosts of Tomato spotted wilt virus (TSWV) in three tobacco fields and in a greenhouse complex in which lettuce and the ornamentals chrysanthemum, gerbera, aster, and anemone were grown. Assays for TSWV infection were made by enzyme-linked immunosorbent assay on 6,172 plant samples, 3,909 from tobacco fields and 2,263 from the greenhouse complex, comprising plants of 208 species in 137 genera of 42 families. Plants of 86 species out of 63 genera of 27 families were infected of which 39 species are newly reported hosts of TSWV. An infection index was developed to evaluate the relative potential of each weed species as a virus source in both systems. Seventeen species in the tobacco fields and nine in the greenhouses had an infection index higher than one. Most species with infected plants were found in the Compositae family. Plants of some species occurring both in tobacco fields and in greenhouses were infected at only one of these sites. Frankliniella occidentalis was the common thrips species on weeds and crops in the greenhouses, while Thrips tabaci was the only vector on tobacco plants and weeds in the tobacco fields. This observation strongly suggests that the occurrence of species with infected plants and their number have to be attributed to the vector species prevailing in the greenhouse complex or tobacco fields, supporting the conclusion that TSWV is spread in two different epidemiological processes in Greece.
Evaluation of Agar and Grain Media for Mass Production of Conidia of Dactylaria higginsii
Authors: Wyss Gabriela S. , Charudattan Raghavan , DeValerio James T.
Published: May 2007

Growth and sporulation of Dactylaria higginsii were quantified on complex agar media containing biological materials (group 1) and chemically defined agar media (group 2), as well as on grains, and the inoculum produced on these various substrates was tested for virulence on Cyperus rotundus. The fungus grew well between 25 and 30°C on potato dextrose agar (PDA), with 27°C being the optimum temperature. Generally, conidial production was highly variable and lower on complex agar media than on chemically defined media. Addition of purple nutsedge leaves to PDA did not increase colony growth or conidial production when compared with una-mended PDA. Conidial production was lowest on brown rice compared with white rice or white rice with nutsedge leaves. Peak production on grain media occurred from day 12 in test 1 (2.4 × 106 spores/g of grain) and on day 16 in test 2 (2.5 × 106 spores/g of grain). Germination rate of conidia produced on white rice was 50% compared with the near 100% germination of conidia produced on PDA or on white rice amended with potato dextrose broth (PDB). Conidia produced on white rice or PDA, when tested fresh or after two washings, were less virulent on C. rotundus than conidia from white rice amended with PDB. After four washings, conidia from all three media produced the same level of disease severity. White rice supplemented with PDB and PDA in trays were suitable for mass production of conidia of D. higginsii.
Occurrence and Virulence of Bipolaris hawaiiensis on Bermudagrass (Cynodon dactylon) on Poultry Waste Application Sites in Mississippi
Authors: Pratt R. G.
Published: May 2007

Bipolaris hawaiiensis has been reported on bermudagrass (Cynodon dactylon) and other Cynodon spp. from subtropical areas around the world (2). This pathogen has not previously been reported on bermudagrass in North America (1) nor has its virulence been compared with that of other Bipolaris spp. on this host. In July and October 1999, frequencies of dematiaceous hyphomycetous pathogens in live but symptomatic leaves of bermudagrass were determined on two poultry waste application sites in Smith and Covington counties, MS, where foliar disease symptoms were widespread. Common bermudagrass was being grazed in Covington County, and cv. Alicia was being grown for hay in Smith County. At each date and site, 100 stems with leaves exhibiting symptoms of chlorosis and necrosis were collected, and a single leaf with well-developed symptoms from each stem was assayed for pathogens by surface-disinfesting, plating on water agar, and observing fungal sporulation. Multiple species of pathogens were detected on most leaves. Identities and mean frequencies of observed pathogen species across both sites and sampling dates were Exserohilum rostratum (62%), Bipolaris cynodontis (98%), Curvularia lunata (28%), C. geniculata (20%), B. spicifera (3%), and B. hawaiiensis (3%). B. hawaiiensis was detected at both sites and on both sampling dates. It was distinguished from B. cynodontis by smaller conidia (14 to 28 μm long) and from B. spicifera by more than three pseudosepta per conidium. Virulence of B. hawaiiensis on bermudagrass, compared with B. cynodontis and B. spicifera, was assessed in two identical inoculation experiments using three pathogen-inoculated treatments plus an uninoculated control. In each experiment, foliage of 12-week-old plants in five replicate pots per treatment was sprayed with 4 × 104 conidia per ml of water of each pathogen. The pots were incubated under 12-h plant-growth lights at 25°C for 3 days in a water-saturated atmosphere to initiate infection and then grown for seven additional days in ambient air under plant-growth lights at 25°C. All three pathogens induced symptoms of chlorosis and necrotic lesions. Symptoms induced by B. hawaiiensis were similar in severity to those produced by B. spicifera and less severe than those produced by B. cynodontis. To our knowledge, this is the first report of B. hawaiiensis on bermudagrass in North America. The site in Smith County also apparently represents its northernmost known point of occurrence on this continent (2).

References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) A. Sivanesan. Graminicolous Species of Bipolaris, Curvularia, Drechslera, Exserohilum and their Teleomorphs. Mycol. Pap. No. 158, CAB International Mycological Institute, Wallingford, U.K., 1987.
Identification of an Isolate of Potato virus Y-Tuber Necrotic Strain on Clary Sage (Salvia sclarea)
Authors: Bellardi M. G. , Rubies-Autonell C. , Cerato C.
Published: May 2007

In 1999, clary sage plants (Salvia sclarea L.) at the Herb Garden of Casola Valsenio (Emilia-Romagna Region, northern Italy) exhibited malformed leaves with yellow spots and line patterns. Sap from leaves of symptomatic sage plants caused symptoms in inoculated Chenopodium amaranticolor Coste et Reyn. plants (local chloro-necrotic lesions developed 7 to 10 days after inoculation) and Nicotiana tabacum L. ‘White Burley’ and ‘Samsun’ plants (systemic veinal necrosis developed ≈ 2 weeks after inoculation). Leaves from symptomatic sage plants tested positive for Potato virus Y (PVY) based on immunoelectron microscopy, gold-labeled decoration, and protein A sandwich enzyme-linked immunosorbent assay (ELISA), using antiserum to PVY (PVAS 50a, American Type Culture Collection, Manassas, VA). Double-antibody sandwich-ELISA, using specific monoclonal antibodies (BioReba AG, Reinach, Switzerland) to the tobacco veinal necrosis strain group of PVY (PVY-N), revealed that the PVY isolate from sage belonged to this group. Immunocapture-reverse transcription-polymerase chain reaction, using specific primers for PVY and the tuber necrotic strain of PVY (PVY-NTN), further classified the sage isolate as PVY-NTN (1). PVY-NTN causes serious damage to potato in Europe. Clary sage, one of the most important aromatic plants cultivated worldwide as a source of essential oils, represents a new natural host of PVY-NTN.

Reference: (1) H. L. Weidemann and E. Maiss. J. Plant Dis. Prot. 103:337, 1996.
Formulation of Binucleate Rhizoctonia spp. and Biocontrol of Rhizoctonia solani on Impatiens
Authors: Honeycutt E. W. , Benson D. M.
Published: May 2007

Isolates BNR621 and P9023 of binucleate Rhizoctonia spp. (BNR) in Pesta and rice flour formulations were evaluated for control of preemergence damping-off of impatiens caused by R. solani. Amendment of a soilless potting mix with the formulations at 0.47% (vol:vol) 3 days prior to seeding and infesting did not improve control compared to amendment 1 day prior to seeding and infesting regardless of whether the moistened amended potting mix was stored in closed plastic bags or in plug trays under a mist system. BNR fungi were no more effective in biocontrol of R. solani in formulations amended at 0.9%. Control of damping-off was comparable but not consistent between formulations of BNR fungi and the fungicide thiophanatemethyl. Damping-off was controlled better with formulations of BNR fungi than with SoilGard based on Trichoderma virens. Shelf life of Pesta and rice flour formulations at 4°C was determined by assessing viability of BNR isolates over time. Viability of the BNR isolates, measured as CFU/g of formulation, declined to approximately 68 to 79% of the original propagule concentration after 6 months in Pesta and rice flour formulations, with the greatest decline in the first 2 months. Shelf life of BNR isolates in formulation significantly affected control of preemergence damping-off but was isolate dependent. Preemergence damping-off was only 5 to 7% with fresh formulations but increased to 30 to 50% with 4-month-old formulations. Controlled atmospheres, maintained with saturated salt solutions, were established to measure the effect of water activity on shelf life of formulations. Water activities (aw) of 0.12 and 0.33 aw enhanced BNR survival in formulations by approximately 2 to 3 months compared with aw of 0.53 and 0.75 aw. Storage of Pesta and rice flour formulations at 4°C significantly improved BNR survival by 4 to 5 months compared with storage at 25°C. These results suggest that improved shelf life of BNR isolates is needed before formulated products can be developed for biocontrol of preemergence damping-off.
Cryptodiaporthe Canker of Pagoda Dogwood in North Dakota
Authors: Redlin S. C. , Stack R. W.
Published: May 2007

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

Reference: (1) S. C. Redlin and A. Y. Rossman. Mycologia 83:200, 1991.
First Report of Pepino mosaic virus on Natural Hosts
Authors: Jordá C. , Pérez A. Lázaro , Martínez Culebras P. V. , Lacasa A.
Published: May 2007

Pepino mosaic virus (PepMV) is a potexvirus recently identified as the causal agent of a new disease occurring in protected tomato (Lycopersicon esculentum Mill.) crops in the Netherlands (2). PepMV has been subsequently identified in England, Germany, Italy, Morocco, Portugal, and Spain. The new disease has become a serious problem for tomato production in Europe. Most infected tomato plants expressed leaf distortion, chlorosis, and yellow mosaic. Other plants expressed mosaic and bubbling of the leaf surface. Tomato fruits showing severe discoloration and mosaic were observed in protected tomato crops. Symptoms attenuated in tomato plants as the ambient temperature increased. At present, only Solanum muricatum Ait. (Peruvian pepino) and L. esculentum are affected by PepMV.To determine possible reservoir hosts for this virus, 70 samples from Amaranthus sp., A. viridis (L.) Britton et al., Chenopodium murale L., Convolvulus arvensis L., Malva parviflora L., Nicotiana glauca Grah., Polypogon monspeliensis (L.) Desf., Senecio vulgaris L., Sisybrium sp., Solanum nigrum L., and Sonchus oleraceus L. were analyzed. The plants were collected around greenhouses affected by PepMV from different regions in Spain (Murcia and Canary Islands). The samples were analyzed for PepMV by double-antibody sandwich enzyme-linked immunosorbent assay with a commercial antiserum (DSMZ AS-0554, Biologische Bundesantstal, Braunschweig, Germany). Only Amaranthus sp., M. parviflora, N. glauca, Solanum nigrum, and Sonchus oleraceus tested postive. The presence of PepMV in these weed species was confirmed by electron microscopy and reverse transcription-polymerase chain reaction using degenerate primers for potexvirus (1). All the hosts analyzed were asymptomatic. However, symptoms were reproduced by mechanically inoculating tomato plants with sap from naturally infected weeds. To our knowledge, this is the first report of natural infection of weeds by PepMV.

References: (1) A. Gibbs et al. J. Virol. Methods 74:67, 1998. (2) R. A. A. Van der Vlugt et al. Plant Dis. 84:103, 2000.
Effect ofBarley yellow dwarf virusInfection on Yield and Malting Quality of Barley
Authors: Edwards Michael C. , Fetch Thomas G. , Schwarz Paul B. , Steffenson Brian J.
Published: May 2007

Barley yellow dwarf virus (BYDV) infection occurs frequently in barley in the Upper Midwest region of the United States; however, the impact of this disease on the yield and quality of malting cultivars has not been adequately addressed. Studies were conducted at Fargo, North Dakota (from 1989 to 1990) to determine the effect of BYDV infection on yield and malt quality parameters in barley. Three malting cultivars varying in yield potential and malting characteristics were artificially inoculated at the seedling stage with a North Dakota BYDV isolate of the PAV serotype. Overall yields were reduced 32.5 to 38% in 1989 and 8.5 to 19.8% in 1990 by BYDV infection. Thousand-kernel weight (3.2 to 14.9%) and kernel plumpness (11.9 to 38.9%) also were reduced. Kernel color and three malt quality parameters (α-amylase, malt recovery, and wort viscosity) were not affected by BYDV infection. Increases in wort protein (2.5 to 14.5%) and diastatic power (3.8 to 12.6%), and decreases in malt extract (1.1 to 5.6%) were found. Most notably, total protein increased 4.6 to 17.5% with BYDV infection. Higher proportions of thin seed, as a result of BYDV infection, contributed to the effects on several quality parameters. In summary, the negative effect of BYDV infection on overall quality is significant and should be considered when assessing the impact of this disease. Although annual BYD disease-related losses are typically not extensive in the Midwestern malting barley region, the incorporation of host resistance into recommended cultivars would ameliorate the negative effects of BYD disease on crop quality as well as on yield.
Alternaria alternata Causing Flower Stem Blight of Lupinus havardii
Authors: Colbaugh P. F. , Mackay W. A. , Davis T. D.
Published: May 2007

Lupinus havardii Wats., commonly known as Big Bend or Chisos bluebonnet, is a showy winter annual that can reach 1.0 to 1.5 m in height and produces blue, fragrant inflorescence (racemes). L. havardii is native to a narrow geographic range along the Mexican border in southwest Texas. The inflorescence of L. havardii has considerable potential in the cut flower industry where there is a need for high-quality, durable flowers with a blue color (1). Several crops have been produced in the greenhouse to determine production and post-harvest characteristics of the cut inflorescence. Under greenhouse growing conditions during March through June 1999, numerous plants of L. havardii cv. Texas Sapphire grown in raised beds and in containers in both Dallas and El Paso, TX, were observed with blighted flower racemes with light brown to gray lesions ranging from 1 to 5 cm in length. The racemes were attacked at varying ages and eventually assumed a hooked appearance where the terminal 15 cm of the raceme was bent downward. Isolations from symptomatic lesions removed from L. havardii flower stalks consistently yielded cultures of an Alternaria sp. on potato-dextrose agar. Typical conidia measured 27 μm length and 11 μm width with 3 to 5 transverse septa. The fungus was identified as A. alternata (Fries) Keissler consistent with the description in Ellis (2). Pathogenicity tests were conducted in the laboratory by inoculating cut inflorescences with agar disks containing the fungus. Inoculations produced light brown lesions on the racemes that were typical of disease symptoms observed on greenhouse crops. In addition to the blue-flowered Texas Sapphire cultivar, we also observed the disease symptoms on pink and white flowered breeding lines of L. havardii. This disease is important as a flower stem blighting pathogen and could severely restrict production of cut flowers during the growing season. This is the first report of Alternaria sp. attacking L. havardii.

References: (1) T. D. Davis. HortScience 29:1110, 1994. (2) M. B. Ellis. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute Kew, England.