Development of Neonectria ditissima infections initiated at grafting of apple trees
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Infections of Neonectria ditissima, the cause of European fruit tree canker, may be initiated during propagation. In a survey of 19 commercial apple orchards in southern Norway in the year of planting or the following year, the graft-union area of 15,270 trees was examined. The disease was found in 53% of the orchards, at a low incidence (<10%) with two exceptions (13 and 42%). Scion wood from mother trees with no, a few or several cankers were used to propagate trees that were surveyed for up to 38 months. In total 20 out of 1116 (1.8%) trees developed canker. The higher the number of cankers was on the mother trees, the higher was the number of trees developing canker after grafting. Infections developed on both cultivars (Discovery, Summerred) and all three rootstocks (Antonovka, B9, M9), but more so on grafted than T-budded trees, and more in 2015 than in 2014. When the scion wood was inoculated at the time of T-budding or grafting, disease development went faster and to a higher incidence on T-budded (94%) than on grafted trees (50%). Dipping the scion wood end in a spore suspension prior to grafting resulted in more infections than when a suspension droplet was placed on the bud and bark surface of the scion wood after grafting. The present investigation documents that scion wood may harbour inoculum of N. ditissima. Furthermore, infections may be initiated at time of propagation, and management practices of both scion wood production and nurseries should encounter that fact.
KeywordsCultivars Malus × domestica Nectria galligena Nursery Scion wood production
The authors thank the technicians at NIBIO Ullensvang and Fjeld Hagebruk for help with the experiments.
Funding was made available through the Research Council of Norway and Skattefunn. The Norwegian Elite plant station provided rootstocks and scion wood for the experiments.
Compliance with ethical standards
The study was funded by the Research Council of Norway and Skattefunn.
This article does not contain any studies with human participation or animals performed by any of the authors.
Conflict of interest
The authors declare that no known conflicts of interest exist.
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