Investigation on survival and viability of cankers of Nectria galligena following removal from apple trees and pulverisation on the orchard floor
Abstract: The risk of pulverised excised canker prunings to apple trees was evaluated in two orchard trials. Cankers (Nectria galligena) on one year shoots were collected from apple trees cv. Gala in two orchards and distributed among sprout net bags. Cankers on two, three or older wood were similarly collected and pulverised with a tractor-trailed standard orchard pulveriser before placing in sprout net bags. Both sets of bags were pegged out in two orchard sites, either in the tree row or the grass alley way between trees in February 2005. The bags were sampled at monthly intervals and the state and viability of the cankers assessed. The pruned out cankers whether pulverised or unpulverised continued to produce perithecia for at least 16 months after removal from the trees. Conidia were only found in the first two samples. Perithecia were produced more abundantly on pruned out cankered one year shoots. Pulverised prunings decayed more rapidly in the grass alley way than in the tree row. This study shows that pulverised canker prunings could be a source of inoculum of N. galligena and hence a risk to apple trees for more than a year after pulverising.