Effects of Temperature and Moisture on Conidia Germination, Infection and Acervulus Formation of Apple Marssonina Leaf Blotch Pathogen (Diplocarpon mali) in China

Apple marssonina leaf blotch (Diplocarpon mali) is a severe disease of apple that mainly causes premature leaf defoliation in many apple growing areas in the word. Its epidemic development is closely related to temperature and rainfall. The effects of temperature and moisture on conidium germination, infection on leaves, and acervulus production were investigated under controlled environments. Temperature required for conidium germination and infection ranged from 5 oC to 30 oC with the optimum around 23 oC, and temperature required for acervulus formation was slightly wider with the optimum at 24.6 oC. Wetness was needed for conidia to germinate and infect; only few conidia germinated at RH=100%. However, lesions can produce acervuli in dry conditions. The minimum duration of leaf wetness required for conidia to complete the entire infection process were 14, 8, 4, and 6 hours at 10, 15, 20, and 25°C, respectively. A model describing the effect of temperature and leaf wetness duration was built. The model estimated that conidial infection has the optimum temperature at 22.6°C and the minimum wetness duration required of 4.8 hours. The model can be used to forecast the conidial infection of D. mali to assist in disease management in commercial apple production.

Prvi nalaz zvjezdaste pjegavosti (Diplocarpon mali) na jabuci u Hrvatskoj

U Hrvatskoj je tijekom 2015. godine istraživana eventualna prisutnost fitopatogene gljive Diplocarpon mali, uzročnika zvjezdaste pjegavosti jabuke. Od kolovoza do studenog provedena su 23 vizualna pregleda jabuke u intenzivnim i ekstenzivnim nasadima, okućnicama i na javnim površinama u deset županija. Sakupljeno je 50 uzoraka listova jabuke koji su laboratorijski analizirani. Gljiva D. mali utvrđena je u 21 uzorku. Zvjezdasta pjegavost utvrđena je u uzorcima sakupljenima u Zagrebačkoj, Sisačko – moslavačkoj, Varaždinskoj i Međimurskoj županiji te u Gradu Zagrebu. Na svim lokacijama gdje je bolest nađena uočeno je žućenje zaraženih listova i rana defolijacija. Zvjezdasta pjegavost jabuke po prvi je puta utvrđena u Republici Hrvatskoj.

Diplocarpon mali. [Distribution map].

A new distribution map is provided for Diplocarpon mali Harada & Sawamura. Ascomycota: Letiomycetes: Helotiales. Hosts: apple (Malus spp.), flowering quince (Chaenomeles spp.). Information is given on the geographical distribution in Europe (Austria, Germany, Italy, Mainland Italy, Romania, Switzerland), Asia (China, Anhui, Gansu, Hebei, Heilongjiang, Henan, Hubei, Jiangsu, Jilin, Liaoning, Nei Menggu, Shaanxi, Shandong, Sichuan, Xinjiang, Yunnan, India, Himachal Pradesh, Jammu and Kashmir, Uttar Pradesh, Japan, Honshu, Kyushu, Korea Republic, Taiwan), North America (Canada, New Brunswick, Nova Scotia, Ontario, Prince Edward Island, Quebec, USA, Wisconsin), Central America & Caribbean (Panama), South America (Brazil, Rio Grande do Sul).

Determinação do início da proteção das macieiras 'Fuji' para racionalização do controle químico de Diplocarpon mali

O objetivo do trabalho foi avaliar um nível de controle para determinar o início do uso dos fungicidas no manejo da Mancha Foliar de Marssonina (MFM). O método proposto consistiu no monitoramento semanal de 20 macieiras e, quando em quatro plantas foi detectada a presença de sintomas da doença, foi iniciada a aplicação dos fungicidas com intervalos de 10 dias. Na avaliação do experimento se verificou que todos os tratamentos controlaram a incidência e a severidade da MFM nas folhas. A utilização do nível de controle para MFM reduziu o número de aplicações de fungicidas em 23% quando comparado com os tratamentos realizados pelo método convencional pelos produtores.