Disease development following infection of tomato and basil foliage by airborne conidia of the soilborne pathogens Fusarium oxysporum f. sp radicis-lycopersici and F-oxysporum f. sp basilici

Fusarium oxysporum f. sp. radicis-lycopersici, the causal agent of Fusarium crown and root rot of tomato, and F. oxysporum f. sp. basilici, the causal agent of Fusarium wilt in basil, are soilborne pathogens capable of produc ing conspicuous masses of macroconidia along the stem. The role of the airb orne propagules in the epidemics of the disease in tomato plants was studie d. In the field, airborne propagules of F. oxysporum f. sp. radicis-lycoper sici were trapped with a selective medium and their prevalence was determin ed. Plants grown in both covered and uncovered pots, detached from the fiel d soil, and exposed to natural aerial inoculum developed typical symptoms ( 82 to 87% diseased plants). The distribution of inoculum in the growth medi um in the pots also indicated the occurrence of foliage infection. In green house, foliage and root inoculations were carried out with both tomato and basil and their respective pathogens. Temperature and duration of high rela tive humidity affected rate of colonization of tomato, but not of basil, by the respective pathogens. Disease incidence in foliage-inoculated plants r eached 75 to 100%. In these plants, downward movement of the pathogens from the foliage to the crown and roots was observed. Wounding enhanced pathoge n invasion and establishment in the foliage-inoculated plants. The sporulat ion of the two pathogens on stems, aerial dissemination, and foliage infect ion raise the need for foliage protection in addition to soil disinfestatio n, in the framework of an integrated disease management program.