Management of bacterial speck of tomato in greenhouses under four individual polythene glazing materials

Most electromagnetic radiation can be detrimental to living organisms, especially for microorganisms. UV radiation is used as a strategy for microbial control to eliminate plant pathogens. The most effective wavelength for UV radiation is 250-60 nm (253.7 nm), as this wavelength is absorbed most efficiently by DNA. The tomato bacterial speck disease agent, Pseudomonas syringae pv. tomato, causes severe damage in nurseries, commercial greenhouses and several regions with highly rainy summers. In this study, the effects of four individual polythene (PE) glazing materials used in greenhouses for bacterial speck disease management were investigated. The study was performed from January to June 2015. Bacterial inoculum was sprayed onto 1-m-tall tomato plants and disease development was monitored. Disease severity was scored according to speck symptoms on the leaves using a 0-5 scale. Disease severity ranged from 22-33% in the four greenhouses. The most successful PE glazing, with enhanced red/infrared radiation, reduced disease development by 32.5%. This latter treatment was also analyzed in different statistical groups using ANOVA statistics. PE glazing with different UV transmittance filtering reduced disease symptoms by up to 9.20%, statistically significantly different. However, disease severity was high, up to 32%, in PE glazing with no UV radiation transmittance and in traditional PE glazing greenhouses.