Ecological fitness of the fungal pathogens causing Mycosphaerella leaf spot diseases on bananas (Musa spp.)
2005
Catur Hermanto, Philippines Univ. Los Banos, College, Laguna (Philippines)
The general objective of the research was to study the fitness of Mycosphaeralla leaf spot pathogens on: 1) different banana varieties; 2) different climatic types, altitudes, seasons and cropping systems and 3) different fungicide pressures on the basic of their reproduction, survival capacity, and virulence. From the 42 banana varieties grown at the UPLB Banana Gene Bank, Mycosphaeralla spp. were mainly found on Ambon, Gros Michel, Giant Cavendish, Pisang Pelimbing and Señorita. Pisang Pelimbing and Señorita supported higher conidial density than Ambon, Gros Michel and Giant Cavendish varieties, while Ambon resulted in the highest survival capacity, followed by conidia in Pisang Pelimbing, Giant Cavendish, Señorita and Gros Michel. Type 1 climate resulted in more and longer conidia, lower YLS [youngest leaf spotted] and higher disease severity than the type 4. Lowland yielded more number and sensitive conidia, lower conidia germination, lower YLS and higher disease severity than the highland. Compared to dry season, wet season produced more number and sensitive conidia and lower YLS. Commercial banana orchard resulted in more and longer Mycosphaeralla spp. Conidia, lower YLS and higher disease severity than those collected from backyard planting. Azoxystrobin and/or mancozeb fungicide application reduced conidial germination and disease severity, significantly lower than plants with no fungicide application. Consecutive application of Azoxystrobin caused 5.1 fold increases in fungicide resistance as compared to the control. The case of resistance can be reduced through the alternating or mixing applications of the fungicide with mancozeb.
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