SUPPRESSION OF SCLEROTINIA SOFT-ROT OF LETTUCE WITH ORGANIC SOIL AMENDMENTS

The incidence of sclerotinia soft rot of lettuce and survival rate of sclerotia of Sclerotinia sclerotiorum were reduced by the addition of organic amendments to field plots at the Frankston Research Station, Seaford, Vic. Of the 6 materials tested, stable manure, fowl manure, and lucerne hay were the best, and all except brown coal significantly reduced disease compared with control. Composting of the already mature materials (as supplied) made no difference to their effectiveness. Incorporating the amendments into soil increased the number (to 229% of the control) and fresh weight (to 202% of the control) of marketable lettuce. Stable manure provided the greatest number of marketable heads (270% of the control), while fowl manure gave the greatest increase in head weight per plot (268% of the control). These benefits were less evident following the first applications of amendments (experiment 1) than the second to the same soil plots (experiment 2).