Mal Secco

(from the Italian malsecco), a very dangerous disease of citrus crops, caused by the fungus Deuterophoma trachelphila.

Mai secco occurs in many eastern Mediterranean countries. It was first discovered in the USSR in 1939 in Adzharia, where it was brought in with planting stock from Italy. Subsequently, it spread to Western Georgia. The pathogen enters the plant through mechanical injuries, leaf scars, stomata, and roots, usually in early spring or autumn. It affects all above-ground organs at all stages of development.

The disease is spread by spores. The sources of infection are fallen leaves and branches, dead and dying trees, seeds, and planting stock. The symptoms include leaf fall, fruit fall, browning of the bark, and drying (at first of the shoots and later of the branches and the whole tree). The affected wood acquires a reddish orange color, which is noticeable on cuts. A mass of black corpuscles (the spore-bearing organs, or pyknids, of the fungus) forms on the leaf scars, in the bark of branches, and on fallen fruits. The disease is controlled by proper farming practices, by spraying the trees with fungicides (after spring pruning, in September, and either after the harvest or before covering the trees for the winter), and by the quarantine of planting and grafting stock.