Development and application of paints for controlling kiwifruit canker

The kiwifruit canker caused by Pseudomonas syringae pv. actinidiae (Psa) is a devastating disease in the kiwifruit industry. In field production, the water-based pesticide is often used to control the disease, but the control efficacy is poor because of its low adhesion and difficulty in forming films to protect plants. In order to develop a new technical measure to control kiwifruit canker, different fillers and thickeners were screened and mixed to obtain a film-forming assistant. Subsequently, the optimized penetrant was added into the mixture for preparing the basic paint (paint base^#), and its film-forming ability, tree adhesion, resistance to rainwater erosion and other properties were evaluated. The paint 1^# and paint 2^# were obtained by adding antibacterial combination 1^# (tetracycin and tebuconazole at the mass ratio of 2 : 1) and antibacterial combination 2^# (tetracycin and benziothiazolinone at the mass ratio of 5 : 1) into paint base^#, respectively. In vitro toxicities of paints base^#, 1^#, 2^# and their corresponding antibacterial combinations against Psa were determined by filter paper method, and their control efficacy was verified by field experiment. The results of formula screening showed that the optimal filler is nano bentonite and the optimal thickener is polyvinyl alcohol 2488. The film-forming assistant was obtained by mixing 3.00% (mass fraction, the rests were the same) nano bentonite and 10.00% polyvinyl alcohol 2488, and then the paint base^# was prepared by adding 1.60% of the optimal penetrant qigong into the paint. The paint base^# was a milky white viscous liquid with weak acidity, high viscosity, high ductility, high drawing degree and strong tree adhesion. After applying it on the glass plate for 123 minutes, a ductile film can be formed with a solid content loss rate of 6.77%, indicating that the film had strong resistance to rainwater erosion. In vitro toxicity results showed that paint base^# had no antibacterial activity against Psa, while the antibacterial activities of paint 1^# and paint 2^# were significantly higher than that of the corresponding single antibacterial combinations. The field trials showed that the control efficacy of paint base^# on kiwifruit canker was more than 30%, and the control efficacies of paint 1^# and paint 2^# both reached more than 65%, which were significantly higher than that of the corresponding single antibacterial combinations. The paints prepared in this study displayed good effects on controlling kiwifruit canker, which showed high application values and may be a new way for disease and pest management in the field.