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Since greenhouse heating is abandoned by most Israeli growers of lisianthus (Eustoma grandiflorum), gray mold caused by Botrytis cinerea, severely affects the base of the stems of whole plants as well as cut stems that are left after flower harvest. We studied B. cinerea infections of lisianthus plants under laboratory and commercial greenhouse production in a moderately arid Mediterranean area typical of Israel. We evaluated cultural methods that use least energy for manipulating disease development in commercial greenhouses. The development of infection along lower leaves toward the stem was found important in stem infection. It was significantly less at 26 degrees C compared to 18 or 20 degrees C, and was highest at relative humidity (RH) close to saturation. B. cinerea infection developed in all of the stem wounds exposed to 65 to 99% RH and at temperatures ranging from 12 to 29 degrees C. Severity of infection in stem cuts on whole plants was least at 26 degrees C, and was high at 99% RH. Similarly, severity was greatest at temperatures of 15 to 22 degrees C and RH levels of 85 to 99%. Under commercial conditions, applications of supplemental calcium in spray or fertigation led to some reduction in disease incidence. Treatments of polyethylene soil cover, the use of buried drip irrigation instead of surface drip irrigation, plant spacing and blowing air inside plant canopy, each alone or in combinations suppressed gray mold on stem bases and plant cuts. Flower yield quantity and quality were increased by these treatments.