Biological control of Botrytis gray mould on tomato cultivated in greenhouse.

Research was carried out to evaluate the effectiveness of the biological control of the Botrytis gray mould, caused by Botrytis cinerea Pers., one of the most important fungal diseases of the tomato (Lycopersicon esculentum Mill.). Biological control was performed by using Trichoderma harzianum Rifai, an antagonist that is a naturally occurring fungus found on some plants and in the soil worldwide. Trichoderma spp. are fungi diffused in nearly all agricultural soils and in other environments such as decaying wood. The object of this research is to find control strategies to reduce chemical treatments that cause damage to the environment and increase the pathogen resistance, applying the biological control by using T. harzianum against B. cinerea. A commercial product containing a natural isolate of T. harzianum is trichodex (Makhteshim Chemical Works, LTD). The research was performed in laboratory and in greenhouse. In laboratory, radial growth reduction of B. cinerea, in presence of T. harzianum, was calculated in relation to the growth of the pathogen control, by using a specific formula that measures the percentage of the inhibition of the radial mycelial growth. In greenhouse, starting from the tomato fruit setting, the research was carried out comparing, by a randomized complete block experiment design, replicated four times, the following treatments:1) untreated control; 2) pyrimethanil (400 g/L of a.i.), at 200 cc/hL of c.i. (pyrimidine fungicides); 3) trichodex at 100g/hL (1 kg/ha); 4) trichodex at 200 g/hL (2 kg/ha); 5) trichodex at 400 g/hL (4 kg/ha). Before fruit setting, the plots were all treated against Botrytis gray mould with iprodione 50% (100 g/hL), procymidone 50% (100 g/hL) and switch (Novartis plant protection) at 80 g/hL. In dual culture, the inhibition of B. cinerea radial mycelial growth was 76%. No inhibition halo was observed between B. cinerea and T. harzianum colonies but, after 3 days, the pathogen colony radius resulted no more than 1.8 cm (towards T. harzianum). T. harzianum grew quickly and after 5 days the medium surface was completely colonized covering the B. cinerea colony. The laboratory tests were confirmed in greenhouse trials. Trichodex at 400 g/hL gave the best results, decreasing the disease over 50% compared to untreated control and over 70% compared to chemical control. After fruit setting, T. harzianum was the best in the control of Botrytis gray mould, allowing to avoid the use of the chemical fungicides that can be applied only up to the fruit setting, obtaining high quality tomato fruits.