Y. Mesika, A. Sztejnberg

The interaction between L. taurica and the biological control agents Trichoderma harzianum T39 (TRICHODEX) and Ampelomyces quisqualis (AQ10), alone or mixed with the mineral oils JMS Stylet-Oil and Add, respectively, were studied. The effect of the control agents on important life cycle stages of L. taurica (viability of conidia, conidial germination, leaf colonization by hyphae and disease severity on leaves) were studied under controlled conditions and in a greenhouse. In field experiments conducted in Israel, the above and other treatments were examined under various microclimatic conditions. The biological control agents were more effective in disease control at 15 and 25 degrees C than at 20 degrees C, and there was less colonization of the leaf by the mycelium of the pathogen. The mineral oils and TRICHODEX reduced conidial germination. Under commercial greenhouse conditions, disease control by the various agents and by a treatment of alternation of the control agents were more efficient under warm conditions, i.e. above 25 degrees C during the day (achieved by curtain closure) and 19 degrees C at night, than at lower temperatures (20 and 13 degrees C, respectively). A treatment of alternation of 'friendly' treatments (helio-sulfur, TRICHODEX, Neemgard and AQ10) in the warm greenhouse climate resulted in effective disease control, similar to that by the standard alternation and mixture of chemical agents. In colder greenhouses, the former treatment was inferior to the chemical treatment. In the greenhouse, the combination of high temperature with alternating sprays of the 'friendly' agents effectively controlled powdery mildew on pepper.