Abstract
The fungus Neonectria fuckeliana has become an increasing problem on Norway spruce (Picea abies) in the Nordic countries during recent years. Canker wounds caused by the pathogen reduce timber quality and top-dieback is a problem for the Christmas tree industry. In this study, four inoculation trials were conducted to examine the ability of N. fuckeliana to cause disease on young Norway spruce plants and determine how different wound types would affect the occurrence and severity of the disease. Symptom development after 8–11 months was mainly mild and lesion lengths under bark were generally minor. However, N. fuckeliana could still be reisolated and/or molecularly detected. Slow disease development is in line with older studies describing N. fuckeliana as a weak pathogen. However, the results do not explain the serious increased damage by N. fuckeliana registered in Nordic forests and Christmas tree plantations. Potential management implications, such as shearing Christmas trees during periods of low inoculum pressure, cleaning secateurs between trees, and removal and burning of diseased branches and trees to avoid inoculum transfer and to keep disease pressure low, are based on experiments presented here and experiences with related pathogens.
Highlights
Neonectria canker, caused by the fungus Neonectria fuckeliana
Neonectria fuckeliana needs an open wound as an entry point for causing disease on Norway spruce
Data from our inoculation trials showed that larger wound treatments resulted in larger lesion length under bark as well as higher detection frequencies of the fungus
Summary
Neonectria canker, caused by the fungus Neonectria fuckeliana & Rossman, is a disease of Norway spruce (Picea abies (L.) Karst.) and other spruce species. For the Nordic forestry sector, Norway spruce is of great economic and ecological importance. Norway spruce is the dominant Christmas tree species in Sweden, accounting for more than 50% of sales. Neonectria canker can diminish the value of Norway spruce by causing stem defects of timber trees or top-dieback of several branch whorls (Figure 1), the latter being especially destructive in Christmas tree fields [1]. In addition to dark canker wounds and dying tops (Figure 1), symptoms caused by N. fuckeliana on Norway spruce often include heavy resin-flow [2,3]. Mortality of young trees may occur but, more commonly, the terminal leader shoots along with the top 3–4 whorls die [1]
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