DISPERSAL OF CONIDIA OF ASCOCHYTA-FABAE F SP LENTIS FROM INFECTED LENTIL PLANTS BY SIMULATED WIND AND RAIN

Splash was shown to be an effective mechanism for short-range dispersa l of conidia of Ascochyta fabae f. sp. lentis, the cause of ascochyta blight of lentil. The dispersal gradients were well described by the p ower law model in its linear form, 1ny = 1na - b 1nx. In still air the slope of the linearized dispersal gradient, b, ranged from 2.83 to 4. 07 and was steeper for 4.9 mm than for 3.9 mm incident drops. Neverthe less, for all drop sizes tested, fewer than 50% of the conidia were sp lashed more than 15 cm from the source. The pattern of conidium disper sal was similar for both drop sizes when horizontal windspeeds were 2. 5 or 5 mis. Wind significantly decreased the value of b (range 2.35-2. 43 at 25 m/s, 1.71-1.91 at 5 m/s) and increased by about 2 m the maxim um distance that conidia in ballistic droplets were deposited. In addi tion, the experiments suggested two other potentially important mechan isms for dispersal of the pathogen over longer distances, namely conid ia in small air-borne droplets and windblown leaflets.