Integrated Management for the Reduction of Calonectria Infections in Ornamental Nurseries

Chemical control represents the main effective strategy for managing Calonectria diseases in ornamental nurseries. The occurrence of fungicide-resistant strains and the European Directive on "Sustainable Use of Pesticides" has forced ornamental plant growers to establish effective integrated pest management strategies to control Calonectria infections. Here, three nursery experiments were performed to detect the best combinations of fungicides and biological control agents (BCA) to control both leaf spot, caused by six Calonectria spp. on bottlebrush and metrosideros, and stem rot, caused by Calonectria morganii on Dodonaea plants. Overall, the cyprodinil + fludioxonil mixture alone or combined with bioformulates containing Bacillus, Trichoderma, and Streptomyces spp. provided the best performance in reducing leaf spot and stem rot caused by Calonectria spp., followed by the mixture of boscalid + pyraclostrobin. Although BCA alone provided disease suppression significantly lower than the controls in most cases, these treatments were, on average, the least effective in controlling Calonectria infections. Otherwise, there were no significant increases in efficacy with fungicides plus BCA over fungicides alone. Thus, the application of boscalid + pyraclostrobin and cyprodinil + fludioxonil mixtures may also be used in large-scale applications to reduce Calonectria diseases because they effectively managed leaf and stem infections. Our comprehensive research applied previously acquired information on Calonectria disease management in nurseries, resulting in important data that affects integrated plans to fight these pathogens in accordance with European legislation.