EFFECT OF ENVIRONMENTAL-CONDITIONS AND INOCULUM DENSITY ON INFECTION OF GUAVA FRUITS BY COLLETOTRICHUM GLOSOSPORIOIDES

The influence of environmental factors (temperature and humidity), ino culum density on infection by Colletotrichum glososporioides and devel opment of anthracnose lesions were determined on uninjured, sand-injur ed and punctured fruits. The optical temperature for severe infection was 30 degrees C, whereas the disease incidence was less at 20 and 35 degrees C. Inoculated guavas that received 1-60 h of continuous free m oisture developed lesions, but the disease was minimal (0-7%) after 1- 6 h free moisture. Infection rates of uninjured, sand-injured and punc tured fruits receiving 60 h of free moisture were 34, 70 and 100%, res pectively. Disease incidence increased as inoculum density increased f rom 10(1) to 10(6) conidia/ml. In field conditions, the development of anthracnose lesions was greater on punctured guavas than on uninjured or sand-injured ones, in both rainy and winter seasons. In general, t he number of lesions was highest in sand-injured fruits, followed by p unctured and uninjured fruits. In rainy season the number of lesions o n injured and uninjured fruits was greater than similarly treated guav as in winter.