1. After its first determination on grapes in 1914 Sclerotinia sclerotiorum has been identified on 18 different cultivated species in Chile, sunflower being its most important host.
2. In a cultural study with strains obtained from sunflower and carrot, apothecia development was observed between 53 and 56 days after the date of pot inoculation with those given by foreing workers on this species.
3. Patogenicity trials proved the resistance of Gramineae to S. sclerotiorum and the susceptibility to its attack of peas, beans, chickpeas, lettuce, sunflower, cucumber, clover and carrots.
4. In accordance with the trials carried out, fungus development in the soil is more rapid with more frequent irrigation and when the sclerotia are placed al lesser depths.
5. Concerning soil pH, apothecia formation is favored by soil pH aproaching neutral reaction (pH 7.28).