Abstract:
Identification and assessment of diseases of avocado, guayabano and mango was done in the municipality of Itogon barangay Dalupirip, Loacan, Poblacion and Tinongdan, Benguet from December 2015 to April 2016 to determine the causal pathogens of diseases associated with these trees and assess the severity of infection on the affected plant parts. Infected plant samples (10 leaves) were collected from three sample trees within plot size measuring 20 x 20 M in different sampling areas. Collected samples were rated accordingly after which brought to the laboratory for microscopic observations and pathogen identification.
Based on structures observed and identified under the microscope, there are four (4) fungal pathogens affecting avocado, three (3) in guayabano and four (4) on mangoes. The fungal pathogens causing leaf spot, leaf blight and anthracnose on avocado, guayabano and mango are Pestalotiopsis spp. and Colletotrichum spp. Algal leaf spot (red spot) is caused by Cephaleuros virescens and the brown wound like or brown spot on avocado fruit is caused by Curvularia sp. The same fungal pathogens except Curvularia sp. were noted to cause the same infection with similar symptoms on guayabano and on mango with the addition of Capnodium mangiferae.
Cultural characteristics on potato dextrose agar and light microscopy after seven days showed that Pestalotiopsis sp. on guayabano produced the widest colony of 71 mm that is pale yellow with the biggest conidia of 14.13 x 3.08 μm, straight to slightly curve. The conidia has two apical and the longest appendages of 11 μm and the longest basal appendages of 3.58 μm. Colletotrichum spp. infecting avocado in Tinongdan gave the widest colony of 90 mm. with gray color and a conidia of 7.63 x 2.50 μm. Meanwhile colony growth of Colletotrichum in guayabano from Poblacion is smaller in size of 65 mm, light orange in color but with the biggest conidia of 17.6 x 2.50; elongated falcate in shape and hyaline in color.
In terms of infection, severe anthracnose on avocado with 6 to 10% infection was recorded in Dalupirip and Loacan, while severe algal leaf spot of 1 to 10% on the same fruit tree was recorded in Dalupirip only. In guayabano, severe anthracnose and algal leaf spot was noted in Poblacion with 1 to 5 % and 1 to 10% infection. Severe anthracnose of 25% infection on mango caused by Colletotrichum gloeosporioides was noted in Loacan, while Pestalotiopsis leaf spot with 5% infection is severe in Loacan and Dalupirip.
