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Thanatephorus cucumeris is a ubiquitous fungus responsible for many types of plant diseases worldwide. All isolates from infected Hevea brasiliensis trees secreted pectolytic enzymes; polygalacturonase (PG), pectin lyase (PL) and cellulolytic enzymes; beta-glucosidase and cellobiase in culture. The extracts of the rubber tree leaf tissues, inoculated with T. cucumeris did not show any PG activity. However, PL activity was detected in tissue with the establishment of the infection. The levels of beta-glucosidase, an inherent enzyme in Hevea spp. increased rapidly following infection. However, cellobiase was detected only with the initiation of infection. Molecular weights of PG in all isolates were similar and in the range of 53,000 to 58,000. PL also followed the same pattern showing a molecular weight around 39,000.

The fungus Corynespora cassiicola causes the very destructive Corynespora leaf fall disease of Hevea brasiliensis. The present population of C. cassiicola from Sri Lanka includes highly, moderately and poorly sporulating isolates. The fungus sporulated freely on potato dextrose agar at 10-35 ºC with a peak at 30 ºC. Cultures showed maximum conidia production after an incubation period of 12 days. Conidia produced well-branched germ tubes from both apices. The percentage germination reduced significantly at 1.5 × 10 6 conidia / mL. Germination of conidia occurred at temperatures between 5-40 ºC with the optimum between 15-35 ºC. Free water was not essential for germination but promoted germination. Conidia remained viable when the relative humidity was above 90 % and the ultraviolet radiation (254 nm) inactivated conidia. The most favourable temperature conditions for germination of C. cassiicola conidia described above has been observed to be prevalent in the main rubber growing areas in Sri Lanka, particularly during the period of refoliation, making it favourable for the establishment of the disease.

Colletotrichum acutatum is known to have a wide host range and has become an increasingly important pathogen on many economic crops worldwide. This is the first report of Colletotrichum acutatum on mango in Sri Lanka. Colletotrichum gloeosporiodes together with C. acutatum are considered as causal agents of this disease. Colletotrichum acutatum was characterized by fusiform conidia and white to orange colonies with slight shades of light mouse grey aerial mycelia. Colletotrichum gloeosporioides produced grey colonies with a dark mouse grey centre and conidia were cylindrical. The other differences between the mango isolate of C. acutatum and C. gloeosporioides were the slower growth rate and extremely high tolerance of C. acutatum to the fungicide carbendazim.

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