Control Of Pepper Blight Using Combination Of Trichoderma Spp. And Fungicides

Phytophthora capsici is the causal pathogen of phytophthora blight, the most important damaging root disease of pepper (Capsicum annuum), inflicting substantial economic losses worldwide. Trichoderma spp. have been studied for over80years and widely used as biological control agents against several soil-borne plant pathogens. However, no single biological control agent has proved capable of inhibiting the infection totally, especially when the explosive disease happened within short time. Nowdays, chemical control is still the main means against pepper blight. However, the exclusive and excess use of fungicides is not only expensive, but also is not totally effective and may lead to the appearance of resistant strains of pathogens. Furthermore, the difficult degradation of such chemicals increases risks to the environment and the accumulation of them in food chains lead to higher toxicity levels in animals. So it is necessary for looking for an effective solution,such as combination of Trichoderma spp. agents and dosage-reduced fungicides. The objective of this study was to determine the optimum fungicides and dosages without inhibiting Trichoderma spp. growth, and evaluate the control effect against pepper blight using combination of Trichoderma spp. and fungicides.We collected the diseased pepper plants infected by P. capsici and10P.capsici isolates were isolated. Meanwhile, resistance of21pepper vatieties,widely cultivated in Zhejiang Province to P. capsici were evaluated. The results showed that most of the varieties were susceptible or high-susceptible varieties, only Xinxiang-4, Hangxian-3were high-resistant varieties, Xianla-8and Qianli-1were middle-resistant varieties.By effect of13fungicides inhibiting Trichoderma spp on mycelial growth, conidial germination and sporangial production of two Trichoderma spp., we found that the suitable fungicides for Thz01were mandipropamid and eugenol, and the suitable fungicide for TZ1105was mandipropamid. So these two fungicides were choosed and divided into four combinations to go on with field experiments:Thz01+mandipropamid250SC, Thz01+eugenol0.3SL, TZ1105+mandipropamid250SC and Thz01×TZ1105+mandipropamid250SC.The combination of two fungicides and Trichoderma spp. isolates showed a greater synergistic control effect on the pathogen than single-fungicide treatment even at a low dosage (reduction up to25%-35%and10%, respectively). On the other hand, the inhibit experiments confirmed that the certain dosage are harmless to Trichoderma Spp. isolates and they are more effective when used together than individually in controlling pepper blight.The desirable effects of combinaing dosage-reduced fungicides with the tested isolates of Trichoderma spp. against P. capsici demonstrate that it is a promising synergistic disease control approach. However, this control method takes more time and labour as Trichoderma spp. agents and the fungicides are used at different period. It is suggests that Trichoderma spp.+fungicides components should be developed, thus, it opens up the direction of designing future strategies for developing the components and assaying the control efficiency.