The cultivation of Hydrangea in the summer, placing the plants pot thick in the field gives rise to frequent attacks of Botrytis cineria given plant density, rain and other irrigation methods used. By the autumn, Botrytis has effectively colonized the plants and resides in the tissue of mature leaves and the lower shaded parts of the plant. At this stage, signs of Botrytis attack are not particularly eveident. However wehen the plants are brought inside the greenhouse for forcing, the pathogen can cause very serious and violent attacks, mostly of the swelling bud. Because of this, chemical control of Botrytis should be started while the plants are still outside before waiting to observe the first signs of attack later under greenhouse conditions. Experiments at the Experimental Centre of Albenga demonstrate that a mixture of dicarbossimidico with a ditiocarbammate (e.g. procymidone + thitam) or benzimidazolico with a tionailide (e.g. tiofanate-metyl + cichlorofluanide) guarantee a good protection. of the flower buds. Proper control of humidity and adequate ventilation and heating is needed to bring the moisture from the stems to the leaves for evaporation, especially the case during the nght. Oidium can also damage the mother plants and young plants between March and October, mainly attacking the mature leaves near the top of the vegetative apex. Infected leaves become flacid and eventually will dry-up and fall. Suitable plant chemicals can be applied to contain such infection in particular those belonging to the group of inhibitors of the biosynthesis of steroli. Such products should be used in combination with Sulphur to avoid that the disease develops resitance. Giovanni Minuto "Colture Protette" Fax 051 6575856, E-mail cp@gce.it