First Report of Powdery Mildew on Euryops pectinatus in Italy

Euryops pectinatus is grown in Italy for landscape use in parks and gardens. In 2001, severe outbreaks of a previously unknown powdery mildew were observed in commercial farms located in Albenga (northern Italy). All green parts (leaves, stems, and petioles) became covered with a white mycelium. Infections were particularly severe on the upper leaf surface. With progress of the disease, infected leaves turned yellow and died. The presence of powdery mildew infections on leaves and stems only rarely was linked to growth reduction. Conidia were hyaline, cylindric to slightly doliform, did not show fibrosin bodies, borne in chains, and measured 24 to 41 × 12 to 20 μm. Cleistothecia were not observed. The pathogen was identified as Oidium sp. subgen. Fibroidium (1). Pathogenicity was confirmed by gently pressing diseased leaves on leaves of healthy E. pectinatus plants. Inoculated plants were maintained in a growth chamber at 20 to 24°C. After 12 to 14 days, powdery mildew symptoms developed. A similar disease of E. pectinatus was observed in 1999 in California and identified as being caused by Podosphaera (Sphaerotheca) fusca (2). It is possible that the powdery mildew observed in Italy belongs to the same species, also considering that recently the two genera, Podosphaera and Sphaerotheca, have been unified in the genus Podosphaera (1). References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) G. S. Saenz et al. Plant Dis. 84:1048, 2000.

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First Report of Powdery Mildew on Asclepias curassavica in Italy

Plant Disease ◽

10.1094/pdis.2002.86.8.923b ◽

2002 ◽

Vol 86 (8) ◽

pp. 923-923

Author(s):

A. Garibaldi ◽

A. Minuto ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Lower Surface ◽

Northern Italy ◽

Causal Agent ◽

Growth Chamber ◽

First Report ◽

Leveillula Taurica ◽

Asclepias Curassavica ◽

Commercial Farms ◽

A Chain

Asclepias curassavica is grown in Italy for landscape use in parks and gardens. In 2001, severe outbreaks of a previously unknown powdery mildew were observed in commercial farms located in Albenga (northern Italy). Powdery mildew developed on the lower surface of leaves of container grown plants. The upper surface of infected leaves turned reddish and sometimes yellow. Infected tissues wilted, and leaves dropped prematurely. Conidiophores emerged through the stomata. Conidia were hyaline and had variable shape, mitrate when located at the apex of the conidiophore, and subcylindric when borne in the middle of a chain. Conidia measured 46 to 74 × 12 to 24 μm. Cleistothecia were not observed. The causal agent was identified as Oidiopsis sp. Pathogenicity was confirmed by gently pressing diseased leaves on leaves of healthy A. curassavica plants. Plants were maintained in a growth chamber at 20 to 24°C after inoculation. After 12 to 14 days, powdery mildew signs developed. Leveillula taurica has been reported as causal agent of powdery mildew on A. carassavica in India and on Asclepias sp. in Morocco (1). Also in our case, L. taurica should be the causal agent, since the genus Leveillula has as anamorph the genus Oidiopsis (2). In Switzerland, Phyllactinia suffulta has been described as incitant of a similar powdery mildew on A. syriaca. References: (1) G. Bergen. Ann. Epiphyt. Nuove Serie, IV, 1:21, 1938. (2) J. Palti. The Bot. Rev. 54:423, 1988.

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First Report of Powdery Mildew Caused by Erysiphe aquilegiae var. aquilegiae on Aquilegia flabellata in Italy

Plant Disease ◽

10.1094/pdis.2004.88.6.681a ◽

2004 ◽

Vol 88 (6) ◽

pp. 681-681

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

United States ◽

Powdery Mildew ◽

The United States ◽

Northern Italy ◽

American Phytopathological Society ◽

First Report ◽

Powdery Mildews ◽

The Family ◽

White Mycelium ◽

The University

Aquilegia flabellata Sieb. and Zucc. (columbine) is a perennial garden species belonging to the family Ranunculaceae. During the summer of 2003, a severe outbreak of a previously unknown powdery mildew was observed in several gardens near Biella (northern Italy). Upper surfaces of leaves were covered with a white mycelium and conidia, and as the disease progressed infected leaves turned yellow and died. Foot cell was cylindric and appressorium lobed. Conidia were hyaline, ellipsoid, and measured 31.2 to 47.5 × 14.4 to 33 μm (average 38.6 × 21.6 μm). Fibrosin bodies were not present. Cleistothecia were globose, brown, had simple appendages, ranged from 82 to 127 (average 105) μm in diameter, and contained one to two asci. Ascocarp appendages measured five to eight times the ascocarp diameter. Asci were cylindrical (ovoidal) and measured 45.3 to 58.2 × 30.4 to 40.2 μm. Ascospores (three to four per ascus) were ellipsoid or cylindrical and measured 28.3 to 31.0 × 14.0 to 15.0 μ;m. On the basis of its morphology, the pathogen was identified as Erysiphe aquilegiae var. aquilegiae (1). Pathogenicity was confirmed by gently pressing diseased leaves onto leaves of five, healthy A. flabellata plants. Five noninoculated plants served as controls. Inoculated and noninoculated plants were maintained in a garden where temperatures ranged between 20 and 30°C. After 10 days, typical powdery mildew symptoms developed on inoculated plants. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of the presence of powdery mildew on Aquilegia flabellata in Italy. E. communis (Wallr.) Link and E. polygoni DC. were reported on several species of Aquilegia in the United States (2), while E. aquilegiae var. aquilegiae was previously observed on A. flabellata in Japan and the former Union of Soviet Socialist Republics (3). Specimens of this disease are available at the DIVAPRA Collection at the University of Torino. References: (1) U. Braun. Nova Hedwigia, 89:700, 1987. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (3) K. Hirata. Host Range and Geographical Distribution of the Powdery Mildews. Faculty of Agriculture, Niigata University, 1966.

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First Report of Powdery Mildew Caused by Golovinomyces cichoracearum on English Daisy (Bellis perennis) in Italy

Plant Disease ◽

10.1094/pdis-92-3-0484a ◽

2008 ◽

Vol 92 (3) ◽

pp. 484-484 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Its Region ◽

Northern Italy ◽

Flowering Plant ◽

Pathogenicity Test ◽

First Report ◽

Golovinomyces Cichoracearum ◽

Blastn Analysis ◽

Commercial Farms ◽

Voucher Specimens

Bellis perennis (English daisy) is a flowering plant belonging to the Asteraceae and is increasingly grown as a potted plant in Liguria (northern Italy). In February 2007, severe outbreaks of a previously unknown powdery mildew were observed on plants in commercial farms at Albenga (northern Italy). Both surfaces of leaves of affected plants were covered with white mycelia and conidia. As the disease progressed, infected leaves turned yellow. Mycelia and conidia also were observed on stems and flower calyxes. Conidia were hyaline, ellipsoid, borne in chains (as many as three conidia per chain), and measured 27.7 × 16.9 (15.0 to 45.0 × 10.0 to 30.0) μm. Conidiophores measured 114.0 × 12.0 (109.0 to 117.0 × 11.0 to 13.0) μm and showed a foot cell measuring 78.0 × 11.0 (72.0 to 80.0 × 11.0 to 12.0) μm followed by two shorter cells. Fibrosin bodies were absent. Chasmothecia were not observed in the collected samples. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 415 bp obtained showed an E-value of 7e–155 with Golovinomyces cichoracearum (3). The nucleotide sequence has been assigned the GenBank Accession No. AB077627.1 Pathogenicity was confirmed through inoculations by gently pressing diseased leaves onto leaves of healthy B. perennis plants. Twenty plants were inoculated. Fifteen noninoculated plants served as a control. Plants were maintained in a greenhouse at temperatures ranging from 10 to 30°C. Seven days after inoculation, typical symptoms of powdery mildew developed on inoculated plants. The fungus observed on inoculated plants was morphologically identical to that originally observed. Noninoculated plants did not show symptoms. The pathogenicity test was carried out twice. To our knowledge, this is the first report of powdery mildew on B. perennis in Italy. The disease was already reported in other European countries (2). Voucher specimens are available at the AGROINNOVA Collection, University of Torino. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) U. Braun The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena, Germany, 1995. (3) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000.

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First Report of Powdery Mildew Caused by an Oidium sp. on Spiraea japonica in Italy

Plant Disease ◽

10.1094/pdis.2004.88.9.1045c ◽

2004 ◽

Vol 88 (9) ◽

pp. 1045-1045

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Ornamental Plants ◽

The United States ◽

Northern Italy ◽

Artificial Inoculation ◽

Conidial Suspension ◽

Sterile Water ◽

Growth Reduction ◽

White Mycelium ◽

The City

Spiraea japonica is an old-fashioned shrub widely grown in Italy in parks and gardens. In the summer of 2003, severe outbreaks of a previously unknown powdery mildew were observed in some parks and gardens in the city of Torino (northern Italy). Infected leaves became covered on both sides with a white mycelium. As the disease progressed, infected leaves turned reddish and eventually dropped prematurely. The presence of powdery mildew infections on leaves sometimes caused their distortion and growth reduction. Frequently, mycelium was observed also on the stem. Conidia were hyaline, ellipsoid, cylindrical, or dol iform, born in chains, measured 21.0 to 38.4 × 10.8 to 14.4 mm, and showed fibrosin bodies. Cleistothecia were not observed. The pathogen was identified as Oidium subgenus Fibroidium (1,2). Pathogenicity was confirmed by spraying leaves of healthy potted S. japonica plants with a conidial suspension (105 conidia per ml) prepared in sterile water from diseased leaves. Three plants were inoculated and three noninoculated plants served as control. The artificial inoculation was carried out twice. After artificial inoculation, plants were maintained in a growth chamber at 25°C. After 20 days, powdery mildew symptoms developed. Microsphaera alni and Podosphaera oxyacanthae were described as causal agents of powdery mildew on S. japonica in the United States (3), while Sphaerotheca spiraeae was considered the causal agent of a powdery mildew observed in Japan (4) and more recently in Poland. References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) R. T. A. Cook et al. Mycol. Res. 101:975, 1997. (3) P. Pirone. Diseases and Pests of Ornamental Plants. John Wiley and Sons, NY, 1978. (4) K. Sawada. Rev. Appl. Mycol. 31:577, 1952.

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First Report of Powdery Mildew on Tomato Caused by Oidium neolycopersici in Venezuela

Plant Disease ◽

10.1094/pdis-91-7-0910b ◽

2007 ◽

Vol 91 (7) ◽

pp. 910-910 ◽

Cited By ~ 1

Author(s):

J. O. Montilla ◽

M. S. González ◽

D. Renaud

Keyword(s):

Powdery Mildew ◽

Leaf Surface ◽

Distinct Species ◽

Oidium Neolycopersici ◽

First Report ◽

Physalis Peruviana ◽

Infected Tomato ◽

White Mycelium ◽

Foliar Tissue ◽

Plant Pathol

During 2004 and 2005, a powdery mildew was observed in tomato (Lycopersicon esculentum Mill. cv. Rio Grande) fields in several states in Venezuela. Symptoms included development of patches of dense white mycelium, predominantly on the upper leaf surface. Leaves in the middle and lower canopies were the most affected. Similar symptoms sometimes were observed on stems. The foliage of infected plants turned yellow and showed necrosis followed by desiccation and rapid defoliation. Microscopic examination revealed the presence of typical structures of the Oidium genus. Hyphae were hyaline and septate. Conidiophores were unbranched, erect, measured 51 to 108 (80) μm, and consisted of 3 or 4 cells. Conidia were hyaline, ellipsoidal to ovoidal, and measured 16 to 43 (30) × 12 to 22 (16) μm. Conidia were produced singly, without fibrosin bodies. Conidial polar germination was common. Appressoria were lobed. The sexual stage was not found. The fungus was identified as Oidium neolycopersici, recently recognized as a distinct species (1,2). Conidia from infected tomato leaves were shaken onto leaves of 10 plants of L. esculentum and L. pimpinellifolium (Jusl.) Mill. and five plants of a weed (Physalis peruviana L.). Noninoculated plants served as a control. Symptoms that developed on all inoculated plants were similar to those of plants naturally infected. Within 7 to 8 days, symptoms in L. esculentum consisted of small colonies that quickly covered large portions of foliar tissue. L. pimpinellifolium showed small and localized symptoms after 10 days and P. peruviana showed symptoms after 15 days. To our knowledge, this is the first report of O. neolycopersici in Venezuela. References: (1) H. Jones et al. Mol. Plant Pathol. 2:303, 2001. (2) L. Kiss et al. Mycol. Res. 105:684, 2001.

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First Report of Powdery Mildew Caused by Oidium Subgenus Pseudoidium on Lonicera caprifolium in Italy

Plant Disease ◽

10.1094/pdis.2004.88.9.1045b ◽

2004 ◽

Vol 88 (9) ◽

pp. 1045-1045

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

Growing Season ◽

Northern Italy ◽

First Report ◽

Leaf Surfaces ◽

Voucher Specimens ◽

Inoculation Procedure ◽

White Mycelium ◽

The University

Honeysuckle (Lonicera caprifolium L., family Caprifoliaceae) is a climbing shrub used in gardens to cover walls and supports. During the summer of 2003, severe outbreaks of a previously unknown powdery mildew were observed on this species in some gardens near Biella (northern Italy). The first symptoms included extensive chlorosis on leaves, followed by the appearance of white mycelium on the adaxial and abaxial leaf surfaces. As the disease progressed, infected leaves turned yellow and died. Conidia were hyaline, ellipsoidal, and measured 27.6 to 43.2 × 12.2 to 21.6 μm (average 35.7 × 17.6 μm). Foot cells were cylindric and appressoria lobed. Fibrosin bodies were not present. Cleistothecia were not observed during the growing season. The pathogen was identified as Oidium subgenus Pseudoidium (2). The inoculation procedure involved gently pressing diseased leaves onto leaves of healthy L. caprifolium plants. Three plants of L. caprifolium were used as replicates. Noninoculated plants served as control. Inoculated and noninoculated plants were maintained in a garden at temperatures ranging from 15 to 25°C. After 10 days, typical symptoms of powdery mildew developed on inoculated plants. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of powdery mildew on L. caprifolium in Italy. The presence of powdery mildew on different species of Lonicera has been reported in several countries, particularly, Microsphaera miurae U. Braun on L. morowii A. Gray in Germany (1), M. lonicerae (DC.) Winter on L. peryclimenum L. in England (3), and M. lonicerae-ramosissimae on L. ramosissima Fr. & Sav. in Japan (4). The conidia of M. lonicerae are smaller than those of the Oidium sp. reported on L. caprifolium. Voucher specimens are available at DIVAPRA Collection at the University of Torino. References: (1) U. Braun. Mycotaxon 16:417, 1983. (2) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (3) J. Robbins. Cecidology 15:15, 2000. (4) S. Tanda. Mycoscience 41:155, 2000.

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First Report of Powdery Mildew (Oidium sp.) on Akebia quinata in Italy

Plant Disease ◽

10.1094/pdis.2004.88.6.682d ◽

2004 ◽

Vol 88 (6) ◽

pp. 682-682

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Powdery Mildew ◽

The Netherlands ◽

Northern Italy ◽

Abaxial Surface ◽

First Report ◽

The Family ◽

White Mycelium ◽

The University ◽

Ornamental Species

Akebia quinata Decne., an ornamental species belonging to the family Lardizabalaceae, is used as a climbing species in gardens to cover walls as well as supports and is very much appreciated because of its dark red flowers. During the summer of 2003, severe outbreaks of a previously unknown powdery mildew were observed on established plantings in several gardens near Biella (northern Italy). The upper surfaces of leaves were covered with white mycelium, and the corresponding abaxial surface of infected leaves were chlorotic. Young, green stems also affected showed extended chlorosis. As the disease progressed, infected leaves turned yellow and died. Foot cell was cylindric and appressorium lobed. Conidia formed singly were hyaline, ellipsoid, and measured 26.4 to 45.6 × 10.6 to 15.6 μm (average 35.1 × 12.7 μm). Fibrosin bodies were not present. The pathogen was identified as Oidium sp. subgenus Pseudoidium (1) partially because cleistothecia were not observed. Conidial measurements are close to those reported for Microsphaera akebiae Sawada. Pathogenicity was confirmed by gently pressing diseased leaves onto leaves of healthy A. quinata plants. Three plants of A. quinata were used as replicates. Noninoculated plants served as controls. Plants were maintained between 20 and 30°C in a garden located 5 km from where the disease was originally found. After 10 days, typical symptoms of powdery mildew developed on inoculated plants. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of the presence of powdery mildew on A. quinata in Italy. The disease is currently restricted to the area of Biella. The presence of M. akebiae was recently reported in the Netherlands (2). Specimens of this disease are available at the DIVAPRA Collection at the University of Torino. References: (1) U. Braun and S. Takamatsu. Schlechtendalia, 4:1, 2000. (2) M. Scholler and W. Gams. Nova Hedwigia, 67:101, 1998.

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First Report of Bremia lactucae Causing Downy Mildew on Helichrysum bracteatum in Italy

Plant Disease ◽

10.1094/pdis.2003.87.3.315a ◽

2003 ◽

Vol 87 (3) ◽

pp. 315-315 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

A. Minuto ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Downy Mildew ◽

Morphological Characteristics ◽

The United States ◽

Northern Italy ◽

Plant Diseases ◽

Bremia Lactucae ◽

First Report ◽

Parasitic Fungi ◽

Commercial Farms ◽

Helichrysum Bracteatum

Helichrysum bracteatum, also known as strawflower, is commonly grown for the production of dried flowers and, more recently, as a potted plant. This latter cultivation system is becoming increasingly important on the Liguria Coast in northern Italy. During the spring of 2002, severe oubreaks of a previously unknown disease were observed in commercial farms in the area of Albenga (northern Italy) on several cultivars of H. bracteatum. Leaves of infected plants appeared curled and blistered; the infected portions of leaves turned chlorotic. On the lower leaf surface of chlorotic areas, a dense, whitish growth was evident. Infected leaves eventually wilted without dropping. Basal leaves with poor air circulation were the most severely affected. Certain cultivars of H. bracteatum (such as ‘Florabella Pink’) were most seriously affected, while others (‘Florabella Gold’ and ‘Florabella White’) had less disease. Microscopic observations revealed sporangiophores emerging from the stomata that were dichotomically branched, ending with 4 to 7 sterigmata. The sporangia were globose and measured 15.5 to 16.8 μm in diameter. The pathogen was identified as Bremia lactucae based on the morphological characteristics. Pathogenicity was confirmed by inoculating healthy H. bracteatum (100-day-old ‘Florabella Gold’) as well as Lactuca sativa (25-day-old ‘Salad bowl’) plants with a sporangial suspension (1 × 105 sporangia/ml). Five plants of H. bracteatum and 10 of lettuce were used as replicates. Noninoculated plants served as controls. Inoculated and uninoculated plants were maintained in a growth chamber at 20°C and 90 to 95% relative humidity. After 7 to 10 days, typical symptoms of downy mildew developed on H. bracteatum and lettuce plants artificially inoculated. Bremia lactucae was observed on infected leaves. Uninoculated plants did not show symptoms. To our knowledge, this is the first report of Bremia lactucae on H. bracteatum in Italy. B lactucae was previously reported as the causal agent of downy mildew on H. bracteatum in several countries including the United Kingdom (3), the United States (1), and Egypt (2). References: (1) S. A. Alfieri et al. Index of plant diseases in Florida. Bull No. 11, 1984. (2) H. Elarosi and M. W. Assawah. Rev. Plant Prot. Res., 39:583, 1959. (3) W. C. Moore. British Parasitic Fungi. Cambridge University Press, Cambridge, 1959.

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First Report of White Mold Caused by Sclerotinia sclerotiorum on Thymus × citriodorus in Italy

Plant Disease ◽

10.1094/pdis.2004.88.9.1044a ◽

2004 ◽

Vol 88 (9) ◽

pp. 1044-1044

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Sclerotinia Sclerotiorum ◽

Soil Surface ◽

White Mold ◽

First Report ◽

Potted Plants ◽

Inoculation Trial ◽

Initial Symptoms ◽

Commercial Farms ◽

Stem Necrosis ◽

White Mycelium

Thymus × citriodorus is well known for the citrus aroma released by its leaves and is grown as a potted plant in northern Italy. This species is widely used in gardens and landscapes and for culinary purposes. In the Liguria Region alone, 1.5 million plants are grown. In the winter of 2002, extensive chlorosis was observed on potted plants of Thymus × citriodorus cv. Silver Queen grown outdoors on commercial farms near Albenga. Initial symptoms included stem necrosis at the soil level and darkening of leaves. As stem necrosis progressed, infected plants wilted and died. Wilt, characterized by the presence of soft and watery tissues, occurred within a few days on young plants. Necrotic tissues became covered with whitish mycelium that produced dark sclerotia. Sclerotinia sclerotiorum (Lib.) de Bary (1) was consistently recovered from infected stem pieces of Thymus × citriodorus. The diseased stem tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm of streptomycin sulfate. Sclerotia produced on PDA were ellipsoid and measured 5.2 to 4.4 × 2.1 to 1.5 mm (average 3.5 × 3.0 mm). Pathogenicity of three isolates obtained from infected plants was confirmed by inoculating 30-day-old plants grown in 14-cm-diameter pots in a screenhouse. Inoculum that consisted of wheat kernels infested with mycelium and sclerotia of each isolate was placed on the soil surface around the base of each of 10 plants. Noninoculated plants served as controls. The inoculation trial was repeated once. All plants were kept at temperatures ranging between 5 and 26°C and watered as needed. Inoculated plants developed symptoms of leaf yellowing within 13 days, soon followed by the appearance of white mycelium, and eventually wilted. Control plants remained symptomless. White mycelium and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of white mold of Thymus × citriodorus caused by S. sclerotiorum. The economic importance of this disease for the crop can be considered low. Reference: (1) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 1949.

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First Report of Powdery Mildew Caused by Sphaerotheca fusca on Tomatillo in California

Plant Disease ◽

10.1094/pdis.1998.82.6.711c ◽

1998 ◽

Vol 82 (6) ◽

pp. 711-711 ◽

Cited By ~ 1

Author(s):

S. T. Koike ◽

R. F. Smith

Keyword(s):

Powdery Mildew ◽

Fungal Growth ◽

Premature Senescence ◽

First Report ◽

Powdery Mildew Disease ◽

Salinas Valley ◽

Germ Tubes ◽

Husk Tomato ◽

Sphaerotheca Fusca ◽

Commercial Field

Tomatillo or husk tomato (Physalis ixocarpa Brot.) is an annual Solanaceous bush grown for its fruit, which are harvested when the fruit fill the enlarged calyx and are used primarily in Hispanic cooking. In the summer of 1997, commercial field-grown tomatillo in the Salinas Valley (Monterey County) was severely affected by a powdery mildew disease. Fungal growth was found on leaves, petioles, and calyces and resulted in twisting, desiccation, and premature senescence of the tissues. The mycelium was white to gray, ectophytic, amphigenous, and effuse. Mycelial appressoria were indistinct. Conidiophore foot cells were straight, cylindric, measured 36.1 to 61.1 µm (mean 47.0) × 11.1 to 13.9 µm (mean 11.7), and were followed by 1 to 3 shorter cells. Doliform conidia were formed in chains and measured 25.0 to 50.0 µm (mean 32.5) × 11.1 to 22.2 µm (mean 17.7). The length-to-width ratios of conidia generally were less than 2.0, and fibrosin bodies were present. Germ tubes usually were laterally inserted, lacked conspicuous appressoria, and were of the pannosa-type. Cleistothecia were not observed. Based on these characters, the fungus was identified as Sphaerotheca fusca (Fr.) Blumer, Beitr. Krypt.-Fl. Schweiz (1). Pathogenicity was confirmed by gently pressing infected leaves onto leaves of potted tomatillo. Inoculated plants were kept in a chamber at 100% humidity for 48 h, and then maintained in a greenhouse. Powdery mildew developed on inoculated plants after 12 to 14 days, while uninoculated plants did not develop disease. The experiment was conducted a second time and the results were the same. This is the first report of a powdery mildew disease of tomatillo in California. Reference: (1) U. Braun. Nova Hedwigia 89:1, 1987.

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