Microparticles containing gallic and ellagic acids for the biological control of bacterial diseases of kiwifruit plants

Over the last decades, kiwifruit cultivation has gained increasing importance all over the world, but some bacterial diseases seriously threaten its cultivation. The most dangerous one is the bacterial canker caused by Pseudomonas syringae pv. actinidiae Takikawa et al., but also floral bud necrosis by Pseudomonas syringae pv. syringae van Hall and bacterial blight by Pseudomonas viridiflava (Burkholder) Dowson affect kiwifruit plants. Their control relies mainly on antibiotics, where allowed, and copper, although this adversely affects the environment, so that alternative control measures are needed. Here we investigate gallic acid and ellagic acid, substances easily obtainable from some plant tissues, for their antimicrobial activity aiming to use them as support in the biocontrol of kiwifruit bacterial diseases. These active principles demonstrated their effectiveness as pure substances in both in vitro and in vivo tests. Moreover, their encapsulation in methacrylate polymeric microparticles showed to improve their usefulness and to prolong remarkably their activity up to 14 days after the treatment, when applied in greenhouse or in field on artificially and naturally infected plants, respectively. The encouraging results obtained by this type of microformulation point the way to future alternative biological control strategies against kiwifruit bacterial diseases.