Invasive Species Compendium

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Abstract

Cranberry dieback disorder: a new and emerging threat to cranberry production in British Columbia.

Abstract

In recent years, cranberry fields in the lower mainland of British Columbia (B.C.) have been affected by a severe vine decline and death, referred to as cranberry dieback disorder (CDD), resulting in substantial yield losses. Symptoms of CDD appear as patches of dying plants with copper to burgundy coloured leaves on dying uprights in spring and small to large blackened areas of dead vines in late summer. The most noticeable symptoms can be seen on diseased runners, where blackening of peripheral tissues and brown to dark-brown discolouration of pith tissue are distinguishable from healthy vines. A comprehensive field and grower survey in spring 2007 excluded insect pests, particularly cranberry girdler, weevil or Dearness scale damage, herbicide injury or poor field conditions as causes of CDD. To identify the possible casual agent(s), systematic field observation, sampling and laboratory analyses of roots, runners, uprights and soils from 32 affected cranberry beds belonging to 24 farms were carried out in spring and summer 2007. Phytophthora cinnamomi and a Phytophthora sp. were recovered from the soil of two separate fields, confirming for the first time their presence in cranberry soils in B.C. Although several fruit rot and foliar pathogens, including Allantophomopsis sp., Coleophoma sp., Colletotrichum acutatum, Pestalotia sp., Phomopsis vaccinii and Phyllosticta vaccinii, were encountered during microscopic examination and culturing of tissue samples, they may not be the cause of CDD. Among the several potential fungal pathogens isolated from the tissue samples, Coniothyrium sporulosum, Cylindrocarpon destructans and a Phomopsis sp., were consistently recovered at high frequencies from nearly 80% of the symptomatic fields, suggesting that these pathogens may be responsible for CDD, either acting solely or synergistically. Although the pathogenicity of C. sporulosum, C. destructans and Phomopsis sp. on cranberry is yet to be determined, they have been reported to be pathogenic on other plants. This preliminary investigation strongly suggests that CDD may be caused by a complex of pathogens, perhaps, including plant-parasitic nematodes, whose pathogenicity, epidemiology and association with CDD need to be investigated.