First Report of Glomerella cingulata on Common Guava in Argentina.

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 Artichoke Downy Mildew Caused by Bremia lactucae in Argentina.

In 1999, downy mildew was detected on artichoke (Cynara scolymus L.) plants from La Plata, Buenos Aires Province. The disease was observed on various commercial varieties. Symptoms were angular interveinal chlorotic spots less than 3 cm in size. These infected areas, although not confluent, covered a wide surface and caused early death of the leaves. On the undersides of these lesions, white-grayish sporulation was abundant, consisting of sporangiophores with dichotomous branches, widened in their peaks with 2 to 7 terminal sterigmata. Sporangia were ellipsoidal, hyaline and 14 to 30 × 12 to 25 µm in size. Oospores were not observed in leaf tissues. The pathogen was identified as Bremia lactucae Regel (1). Pathogenicity was confirmed with the inoculation of healthy artichoke plants. They were incubated in a humidity chamber at 10 to 15°C, and after 16 days chlorotic spots and downy mildew colonies developed. The presence of B. lactucae was confirmed by macro- and microscopic observation and Koch's postulates were fulfilled. This is the first report of downy mildew on artichoke in Argentina. Because it is widespread in the most important artichoke-growing area in Argentina (2), downy mildew should be considered in the cultural and sanitary management of the crop. References: (1) P. Corda. Hypermedia Prot. Plantes, INRA, 1995. (2) A. Ricceti et al. Bol. Hortic. 4:4, 1996.

First Report of Anthracnose Caused by Glomerella cingulata on Passion Fruit in Argentina.

Passion fruit (Passiflora edulis Sims.) is a subtropical fruit recently cultivated in Misiones Province, Argentina. In spring 1997, a severe epidemic of anthracnose was observed. Disease incidence was ≍95%, causing high yield losses. Sunken, gray lesions on the whole surface of young fruits were observed. Under humid conditions, acervuli containing masses of spores and dark setae were found within lesions. On leaves, tendrils, and twigs, circular and irregular brown spots with darker edges were observed. Abortion of flowers also was recorded. Cultures on potato dextrose agar yielded abundant, gray aerial mycelium and one-celled, hyaline, oblong conidia with obtuse or rounded ends (11.2 to 15.0 × 3.8 to 4.6 µm). Perithecia were scarce (90.2 to 220.0 µm). Asci were not conspicuous, and ascospores measured 10.8 to 23.4 × 3.5 to 7.0 µm. Based on morphological characteristics, the fungus was identified as Glomerella cingulata (anamorph Colletotrichum gloeosporioides) (2). Fruits and leaves of P. edulis with and without wounds were sprayed with a conidial suspension (106/ml) and incubated in plastic bags for 48 h. Lesions similar to original symptoms were observed after 2 weeks only on wounded leaves and fruits. G. cingulata was reisolated, confirming Koch's postulates. This disease has been recorded in Brazil and Japan (1). This is the first report of G. cingulata on passion fruit in Argentina. Reference: (1) E. Francisco Neto et al. Summa Phytopathol. 21:25, 1995. (2) J. A. von Arx. Phytopathol. Z. 29:413, 1957.

First Report of Pestalotiopsis guepini on Loquat in Argentina.

Loquat, Eriobotrya japonica (Thunb.) Lindl., is used as an ornamental plant in home gardens in the La Plata area of Buenos Aires, Argentina. During spring 1998, loquat branches with spotted leaves and fruits were submitted to the Plant Disease Diagnostic Laboratory. Symptoms on leaves consisted of small (2 to 5 mm in diameter), circular to oblong, greenish brown lesions that expanded to amphigenous, isolated, or confluent, dark brown spots. On fruits the disease appeared as circular to elongated, sunken spots. Advancing lesions spread over the surface resulting in the death of the fruit. Acervuli were observed within lesions. Isolations from symptomatic tissue onto acidified potato dextrose agar medium consistently yielded white fungal colonies of sparse aerial mycelium with acervuli containing black, slimy spore masses. The fungus was initially identified as Pestalotiopsis guepini (Desmaz.) Steyaert based on conidial and cultural characteristics (1), and the identification was confirmed by Institute Spegazzini, La Plata, Buenos Aires, Argen-tina. Loquat branches with fruit and 3- to 6-month-old loquat plants were mechanically injured and sprayed with a conidial suspension of one of the P. guepini isolates (4.5 × 105 per ml). Plants were incubated in a moist chamber for 48 h and then maintained in a greenhouse. After 6 days, lesions similar to the original symptoms were observed on the inoculated plant and P. guepini was reisolated, confirming Koch's postulates. Control plants sprayed with distilled water remained symptomless. This is the first report of P. guepini causing leaf and fruit spots on loquat in Argentina. Reference: (1) J. B. H. J. Desmazières. Ann. Sci. Nat. Ser. 2. 13:181, 1840.