Effect of temperature and humidity on germination and infection of Colletotrichum gloeosporioides (Penz.) Sacc. on carabao mango (Mangifera indica L.) [Philippines]
1990
Estrada, A.B. | Ilag, L.L. (Philippines, Univ., Los Banos, College, Laguna (Philippines). Dept. of Plant Pathology)
Results of these experiments together with actual field weather data were used to evaluate the worthiness of the scheduled spray program employed in a mango orchard in Dasmarinas, Cavite [Philippines]. Germination and growth of Colletotrichum gloeosporioides were found highly sensitive to temperature and atmospheric humidity. The optimum temperature range for germ tube formation and growth was from 25 to 30 deg C. Spore germination and fungal growth increased as the RH was increased from 90 to 100% with profuse growth observed at 97.5 and 100% RH. Germination on glass slides was inhibited at humidities 90% and below even after 36 hours at 30 deg C. A higher germination percentage and more profuse growth were observed on leaves and fruit peels than on glass slides. There was no relationship between the stage of fruit development and germination, mycelial growth and appressorial formation. Appressorial formation increased with increasing temperature and humidity. No appressoria were formed at 90% RH irrespective of the temperature of incubation. Very few were formed at 20 deg C even after 38 hours of incubation at 100% RH. Less appressoria were observed on peels compared to leaves. No appressoria were formed on glass slides. Increased appressorial formation resulted in increased severity of anthracnose infection in mango leaves. Lesions appeared earlier and were more severe under 97.5 and 100% RH at 25 and 30 deg C. Evaluation of the standard spray program revealed that majority of the scheduled fungicide sprays in the program were made during low anthracnose-risk periods.
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