Epidemiology of apple leaf spot

Abstract

Apple leaf spot (ALS) caused by Colletotrichum spp. is a major disease of apple (Malus domestica) in Southern Brazil. The epidemiology of this disease was studied in experiments carried out in the counties of Passo Fundo and Vacaria, State of Rio Grande do Sul, from February 1998 to October 2000. The disease was found in all the six apple orchards sampled in the growing seasons of 1997/98 and 1998/99. The fungus isolates associated with ALS fit the characteristics of C. gloeosporioides (75%), C. acutatum (8%), and Colletotrichum sp. (17%). The pathogen overwintered in dormant buds and twigs but not in dropped leaves or fruit mummies. Two sprays of copper oxychloride (at 0.3%) reduced the fungus initial inoculum by 65-84.6% in buds and 85.6-93.7% in twigs, but had no effect on the early season progress of the disease. Disease severity increased proportionally to elevation of temperature from 14 to 26-28 °C. At 34 °C, however, infection was completely inhibited. The duration of leaf wetness required for infection ranged from two hours at 30 °C to 32 h at 16 °C. The relationship of temperature (T) and leaf wetness (W) to disease severity (Y) was represented by the model equation Y = 0.00145[((T-13)1.78)((34.01-T )1.09)] * 25/[1+14 exp(-0.137W)], R² = 0.73 and P < 0.0001. Currently, this information is being used to manage the disease and to validate a forecast system for ALS.

Investigation and genetic mapping of a Glomerella leaf spot resistance locus in apple

“…This was then later discovered in six other apple‐producing areas in Brazil and was then considered a major disease, with the most widely grown cultivar, ‘Gala’, being highly susceptible to GLS (Crusius et al. , Velho et al. ).…”

“…The causative agent had been designated as G. cingulata (Leite et al 1988, Gonz alez 2003 and the disease was named apple GLS. This was then later discovered in six other apple-producing areas in Brazil and was then considered a major disease, with the most widely grown cultivar, 'Gala', being highly susceptible to GLS (Crusius et al 2002, Velho et al 2013). The disease resulted in up to 70% of leaf defoliation of 'Gala' (Camilo and Denardi 2002).…”

Avaliação de formulações de fosfito de potássio sobre Colletotrichum gloeosporioides in vitro e no controle pós-infeccional da mancha foliar de Glomerella em macieira

“…Os sintomas iniciais da doença são manchas vermelho-arroxeadas, já visíveis 48 h após o inicio da infecção e que evoluem para manchas necróticas. As folhas lesionadas amarelecem e caem precocemente, entre oito a dez dias (Crusius et al, 2002). A MFG é causada por Colletotrichum gloeosporioides (Penz.)…”

Fungicidas associados ou não a fosfitos no controle da mancha foliar de glomerela em macieira

“…A menor quantidade de sintomas pode ser devida à menor precipitação observada no início da brotação das plantas, na safra 2005/2006, em relação à anterior, interferindo na disseminação dos esporos no início do ciclo vegetativo da cultura; entretanto, são imprescindíveis maiores esclarecimentos sobre a forma de sobrevivência deste patógeno visto que no Brasil o único estudo a este respeito foi realizado por Crusius et al (2002) no Rio Grande do Sul, que afirmam que o patógeno sobrevive de um ano para outro em ramos e gemas dormentes de macieira.…”