Abstract

In this paper, a survey of pathogens on Japanese quince (Chaenomeles japonica) plants is reported. The main part of the study was performed in South Sweden, in experimental fields where no pesticides or fungicides were applied. In the fields shoots, leaves, flowers and fruits were collected, and fruits in cold storage were also sampled. It was concluded that Japanese quince is a comparatively healthy plant, but some fungi were identified that could be potential threats to the crop, which is currently being developed for organic growing. Grey mould, Botrytis cinerea, was very common on plants in the fields, and was observed on shoots, flower parts, fruits in all stages and also on fruits in cold storage. An inoculation experiment showed that the fungus could infect both wounded and unwounded tissue in shoots. Studies of potted plants left outdoors during winter indicated that a possible mode of infection of the shoots could be through persisting fruits, resulting in die-back of shoots. Fruit spots, brown lesions and fruit rot appeared in the field. Most common were small red spots, which eventually developed into brown rots. Fungi detected in these spots were Septoria cydoniae, Phlyctema vagabunda, Phoma exigua and Entomosporium mespili. The fact that several fungi were connected with this symptom indicates that the red colour may be a general response of the host, rather than a specific symptom of one fungus. Fungi found in brown lesions and rots were Botrytis cinerea, Phlyctema vagabunda, Penicillium expansum, Colletotrichum gloeosporioides and Cryptosporiopsis curvispora. Phlyctema vagabunda was often found in brown rots and also in red spots, indicating that this was the most common fungus. Leaf spots were also a common symptom in the fields. The spots varied in size, shape and colour, and it was obvious that they were caused by several different fungi. From leaves sampled in Latvia, Septoria cydoniae, Phoma pomorum, Asteromella sp. and Ramularia sp. were detected. Phoma pomorum and Alternaria alternata were isolated from leaves sampled in Sweden. However, most of the fungi recorded were widely distributed saprophytes or secondary invaders and leaf diseases were not considered severe. On flowers, the most commonly observed fungi were Cladosporium sp. and Botrytis cinerea but Penicillium expansum, Alternaria alternata and Fusarium sp. were also recorded. Pests found were leaf weevils, Phyllobius spp., larvae of Operophtera sp., Yponomeuta sp., and Caliroa sp. Aphids and red spider mites were also observed, but these were not identified to species. Differences in susceptibility to fruit spots were detected between populations derived from controlled cross-pollination. Plant breeding programmes aimed at developing varieties with resistance to fruit spots should therefore be successful.

Keywords

Chaenomeles; Pathogens; Botrytis

Published in

ISBN: 91-631-3765-8
Publisher: Department of Crop Science, Swedish University of Agricultural Sciences

Permanent link to this page (URI)

https://res.slu.se/id/publ/124471