EPIDEMIOLOGY AND PREVENTION OF DIPLODIA STEM-END ROT OF RIPE MANGO FRUITS

The stem-end rot of mango fruits caused by Diplodianata - lensis Pole Evans in transit and storage is a serious problem which has received relatively limited attention in this country. The disease manifests only in the ripe mangoes. In the initial stage, the epicarp darkens around the base fo the pedicel. Later, the affected area enlarges to form a circular, brownish-black patch which under humid atmosphere extends rapidly and turns the whole fruit black within 2–3 days. The pulp of the diseased fruits becomes brown and somewhat softer. The pedicel, if present, becomes dry. Sporulation does not occur unless the fruit is left over under humid condition for over a month. Under dry condition, the blackened fruit get mummified.

The stem-end rot is quite distinct from the lateral rots caused by Colletotrichum gloeosporioides, Aspergillus niger, Macrophoma mangifereae and certain other fungi.

Although this disease was reported and investigated in Burma, Ceylon, the Philippines, Mauritius and the U.S.A., it was first recorded in India 1964 (1). These studies were undertaken to ascertain the pathogen, mode and source of infection, stage of infection and secondary infection in the fruit, if any.

Cultures of isolates of Diplodia from orange peal, bark of Syzigiumsp, and mango, rose and Cajanus cajan shoots were all pathogenic when inoculated on fruits of mango (var. 'Langra').

The only natural avenues of infection of the uninjured fruit were the exposed end of the pedicel or the pedicel scar. Infection did not occur through the uninjured epicarp even when the fruit was fully ripe.

The sources of primary inoculum were dead mango twigs and bark of the tree. Aeroscope slides exposed in the orchard showed that the atmosphere gets charged with spores of the fungus during June to August.

Fruit with and without pedicels, left uncovered in the orchard after harvest, developed 9 and 24 per cent stem-end rot, respectively on ripening. When such fruits were covered immediately after harvest, none of them developed the disease.

There was no secondary dissemination of the disease from diseased to healthy fruits when kept together for a long time.

On the basis of these results, the following preventive measures are suggested: 1) fruits should be covered and removed to the ripening houses immediately after harvest; 2) it would be of additional value to