Are shelter belts potential inoculum sources for Neonectria ditissima apple tree infections?

Abstract

The susceptibility of plants around apple orchards to Neonectria ditissima infections in the Tasman region was determined during summer 2013/14. Shelter belt and other neighbouring plants (in the absence of shelter trees) surrounding 20 apple orchards (approximately 51 km shelter length) were identified and compared with known European canker hosts. One-third of all neighbouring plants identified were either species known to be European canker hosts or shared a genus with a known host. Nine non-pomaceous plant species were selected for inoculation studies. Two rasp wounds were created (July 2014) and one was inoculated with N. ditissima conidia, the other with mycelium. Symptoms were recorded and the pathogen re-isolated. In February 2015, all symptomless inoculation sites were harvested to determine potential latent infections. Neonectria ditissima was reisolated from 38% of inoculations including from symptomless inoculation sites. The fungus could be re-isolated from all species inoculated.