Efficacy of different chemical and biological products in the control of Pseudomonas syringae pv. actinidiae on kiwifruit

Abstract

The recent outbreak of bacterial canker on kiwifruit, caused by Pseudomonas syringae pv. actinidiae, has caused considerable damage to the international kiwifruit industry. Commercial products, and products under development, were evaluated over 2 years to assess their ability to control bacterial canker on kiwifruit under controlled conditions. The results were compared with two trials carried out in a kiwifruit orchard located in northern Italy during 2011 and 2012, to test the preventative efficacy of different copper formulations against P. syringae pv. actinidiae. In the greenhouse and orchard trials, copper hydroxide and the mixtures of copper hydroxide and copper oxychloride, significantly reduced the foliar symptoms by 70-80 % compared with the control, and showed low phytotoxicity. Similar efficacy was provided by acibenzolar-S-methyl, whose use has been temporarily extended to kiwifruit in Italy, with a maximum of four treatments per year. However, the product showed phytotoxicity on one-year old plants. The efficacy of fosetyl-Al was lower, particularly in the first orchard trials of 2012 and 2013. The efficacy of the other products tested never exceeded 30-40 %, and some products were not significantly different from the control. Kiwifruit plants grown in a steamed peat substrate mixed with compost obtained from digested organic matrices of municipal solid waste showed significantly fewer leaf spots compared with untreated controls. Copper compounds alternated with resistance inducers could be used in combination with compost, in order to develop new integrated control strategies to reduce the disease development and spread.

Biological control of bacterial plant diseases with Lactobacillus plantarum strains selected for their broad‐spectrum activity

“…However, with some plant, defence elicitors such as ASM (Reglinski et al, ) and commercial microbial biopesticides based on Bacillus spp. against Psa (Monchiero, Gullino, Pugliese, Spadaro, & Garibaldi, ), a lack of consistency in efficacy has been demonstrated under some limited conditions.…”

Isolation of bacterial endophytes from Actinidia chinensis and preliminary studies on their possible use as antagonists against Pseudomonas syringae pv. actinidiae

“…Several bacterial isolates present as epiphytes in kiwifruit orchards were confirmed to be copper resistant or copper tolerant [30]: among them, at least two isolates, collected in kiwifruit orchards, have been demonstrated to be copper resistant and their ability to transfer such resistance to Psa has been studied [30]. The choice of a prospective antagonist to be used as biocontrol agent for the inhibition of the inoculum build up on plant organs, especially on leaves, should be done by carefully testing and confirming its susceptibility to low (<30 ppm) copper treatment rates, since the concentration of Cu ++ sprayed in kiwifruit orchards during the chemical control of the bacterial canker implies the use of copper bactericides at a concentration starting from 30-50 ppm [37,38]. Altimira et al [39] reported the presence of copper resistant bacteria and bacterial communities in agricultural soils with the presence of high copper pollutants, and kiwifruit orchards are notoriously sprayed with copper compounds several times a year, to control both phytopathogenic bacteria and some fungi [38,40].…”

“…The choice of a prospective antagonist to be used as biocontrol agent for the inhibition of the inoculum build up on plant organs, especially on leaves, should be done by carefully testing and confirming its susceptibility to low (<30 ppm) copper treatment rates, since the concentration of Cu ++ sprayed in kiwifruit orchards during the chemical control of the bacterial canker implies the use of copper bactericides at a concentration starting from 30-50 ppm [37,38]. Altimira et al [39] reported the presence of copper resistant bacteria and bacterial communities in agricultural soils with the presence of high copper pollutants, and kiwifruit orchards are notoriously sprayed with copper compounds several times a year, to control both phytopathogenic bacteria and some fungi [38,40]. Therefore, the possibility of detecting copper resistance endophytes should not be excluded.…”

Kiwifruit under plastic covering: impact on fruit quality and on orchard microclimate

“…Psa started to infects severely Actinidia chinensis on orchards cultivated in Central Italy and since 2009 new outbreaks have affected orchards of both A. deliciosa (cv Hayward) and A. chinensis in the main kiwifruit producing areas of Italy (Armentano 2010). To date, the bacterial disease is limiting the possibility of cultivating kiwifruit, in particular in the areas of northern Italy, where the climate pattern, creates favourable conditions for the pathogen spread (Monchiero et al, 2015).…”

“…Psa is, at the moment the major source of losses in kiwifruit production because it is responsible for both economic losses in fruit production and plant mortality in the orchards (Monchiero et al, 2015). For these reasons, researchers and kiwifruit industry have done considerable works and progresses in understanding Psa.…”