limited and contradictory (Borecki Efficacy of Excision, Cauterization, and and Czynczyk, 1985; Braun, 1997), Fungicides for Management of Apple and currently all cider apple cultivars are considered susceptible (British Anthracnose Canker in Maritime Climate Columbia Ministry of Agriculture, 2016; Pscheidt and Ocamb, 2017). 1 2 3 Neofabraea malicorticis can di- Whitney J. Garton , Mark Mazzola , Nairanjana Dasgupta , rectly infect intact bark tissue, with Travis R. Alexander1, and Carol A. Miles1,4 most infections occurring through the lenticels (Kienholz, 1939). Stem and trunk infections appear to occur ADDITIONAL INDEX WORDS. Bordeaux mixture, copper hydroxide, Malus ·domestica, primarily in the autumn but can take Neofabraea place throughout the winter and early SUMMARY. This study was designed to determine the efficacy of canker excision (CE) spring during mild, moist conditions followed by a subsequent application of cauterization (CAU) and/or fungicide (Davidson and Byther, 1992; Rahe, treatment to the excised area for the management of anthracnose canker (caused by 2010). Cankers develop during the Neofabraea malicorticis) on cider apple (Malus ·domestica) trees. Three experiments autumn and to a lesser extent in the were conducted from 2015 to 2017, with one experiment each year, in an winter. In the following spring, can- experimental cider apple orchard in western Washington where trees were naturally kers resume development, reaching N. malicorticis infested with . Treatments were applied once in December and data full size in the summer, and pycnidia were collected January through March. Treatments in the 2015 experiment were D D D D that form on the canker margin are CE CAU, CE CAU copper hydroxide, CE 0.5% sodium hypochlorite, the source of inoculum for new in- Bordeaux mixture (BM) only, and CE D copper hydroxide (control). The 2016 experiment included the same treatments as in 2015 plus one additional treatment, fections (Barss, 1925; Creemers, CE D BM. In 2017, one additional treatment was added, CE only, and CAU 2014; Rahe, 1997). In midsummer treatments were removed as they caused significant injury to the trees. Canker size to late autumn, conidia (asexual) are was measured pretreatment, and the treated canker or excised area was measured disseminated by rain and wind to posttreatment every 2 weeks for 13–15 weeks. Compared with pretreatment, other parts of the tree as well as to cankers treated with BM did not increase in size, while the excised area treated with surrounding trees and fruit, causing CAU increased 28-fold in size on average, and the excised area treated with 0.5% new infections (Creemers, 2014). sodium hypochlorite or copper hydroxide increased up to 4-fold in size. Each year Cankers that overwinter may produce new cankers developed in all treatments 13–15 weeks after treatment application, at ascospores (sexual) in the spring, a time of year when there should not be any spores present to cause new infections. which can be carried over substantial Dark brown streaking, indicative of the disease, was observed in the tissue below the intact or excised cankers 15 months after treatment application all years. Although distances and may also incite new N. malicorticis was not isolated from symptomatic tissue, symptoms were observed infections (Powell et al., 1970; Rahe, in all treatments including where cankers had not been excised and there was no 1997). wounding of the cambium tissue. Findings from this study indicate that of the Current recommendations for treatments evaluated, the application of copper hydroxide after CE was the most managing anthracnose canker in- effective for limiting the number of new cankers, but it did not limit expansion of clude 1) excising cankers, and 2) the excised area. Additional physical and fungicidal strategies need to be tested for applying fungicides to minimize the effective management of anthracnose canker. occurrence of new infections (Pscheidt and Ocamb, 2017). The reported efficacy of canker excision in manag- n recent years there has been years can kill newly planted trees and ing disease incidence and severity a rapid expansion of cider apple structurally weaken established trees (appearance of new cankers, and ex- Iproduction in Washington state, (Davidson and Byther, 1992; Garton pansion of existing cankers) on trees is with many new plantings occurring et al., 2018; Rahe, 2010). Informa- limited and variable. Byther (1986) west of the Cascades where there is an tion on cultivar susceptibility and host reported a 45% reduction in the oc- average reported yield of 36,000 lb/ resistance to anthracnose canker is currence of new cankers 1 year after acre and crop value of $12,960/acre, assuming a fruit price of $0.36/lb (Galinato et al., 2014; Northwest Cider Association, 2016). A major Units obstacle to long-term orchard pro- To convert U.S. to SI, To convert SI to U.S., ductivity and continued expansion in multiply by U.S. unit SI unit multiply by western Washington is the wide- 0.4047 acre(s) ha 2.4711 spread occurrence of anthracnose 29.5735 fl oz mL 0.0338 0.3048 ft m 3.2808 canker on apple, caused by Neofab- 2.54 inch(es) cm 0.3937 raea malicorticis (Rahe, 2010; Zang 25.4 inch(es) mm 0.0394 et al., 2011). In the absence of effec- 6.4516 inch2 cm2 0.1550 tive management of N. malicorticis, 0.4536 lb kg 2.2046 1.1209 lb/acre kgÁha–1 0.8922 anthracnose canker can spread with- 1.6093 mile(s) km 0.6214 in an entire western Washington or- 28.3495 oz g 0.0353 chard in 1 or 2 years, and within 3 or 4 (°F – 32) O 1.8 °F °C(°C · 1.8) + 32 728 • December 2018 28(6) canker excision (CE) treatment, while Bordeaux mixture (BM) (basic copper number of anthracnose cankers, was Rahe (2010) observed no reduction sulfate and calcium hydroxide) after uniform across cultivars in the or- in the number of new cankers. The CE (Cordley, 1900; Zeller, 1926). chard with 77% of trees in the orchard reported efficacy of applying cauter- There are no published data on the infested with three or more cankers ization (CAU) and/or fungicidal efficacy of CE plus BM or other per tree at the beginning of the study treatments to cankers or excised copper-based products to control an- each year; this level of infection is areas is also quite variable. Studies of thracnose canker. representative of the severity of this pathogens that incite similar canker Anthracnose canker is an eco- disease in this region. Trees selected diseases on fruit trees, such as nomic threat to cider apple produc- for the experiment each year bore bacterial canker (Pseudomonas syringae), tion in western Washington and anthracnose cankers of similar size, phytophthora canker (Phytophthora growers are in need of an effective and different trees were included in citricola), and botryosphaeria canker management plan. Cider apple growers the experiment each year. The exper- (Botryosphaeria sp.), have demon- in the region are currently using imental design did not block the strated that CAU or chemical treat- several physical and fungicidal treat- treatments by cultivar as it was not ments applied directly to cankers or ments alone and in combination in feasible given the orchard design, and to the excised area following CE can an attempt to control anthracnose there is no evidence in the literature reduce or prevent infections (Brown- canker during the winter, although that there is any cultivar effect on Rytlewski and McManus, 2000; there is no evidence of treatment disease incidence or severity. Treat- El-Hamalawi and Menge, 1994; efficacy. The objective of this study ments were assigned to trees in a com- Fawcett, 1915; Hawkins, 1976). Stud- was to assess the efficacy of various pletely randomized fashion with 10 ies on anthracnose canker specifically treatments on existing cankers on single-tree replicates per treatment. have reported that the effect of CAU cider apple trees in western Wash- All cankers on each tree received the treatments in limiting disease progres- ington,andtoassistgrowerstoelim- assigned physical and/or fungicidal sion does not last more than 1 year inate the application of ineffective treatment, but only one randomly after application (Byther, 1986; Rahe, and costly treatments. selected canker on the central leader 2010). Chemical treatments to control of each tree was monitored in each Neofabraea species are predominantly Materials and methods experiment. All cankers on the trees copper-based fungicides (Barss and Three experiments that included were new each year; that is, they Mote, 1931; Childs, 1927; Henriquez a total of seven treatments were car- appeared within a few months before et al., 2006; Spotts et al., 2009). ried out over 3 years, from 2015 to each experiment was initiated. Treat- Byther (1986) found that basic copper 2017, in an experimental cider apple mentswereappliedonceeachyear, sulfate reduced the number of new orchard at Washington State Univer- inDecember;assporesarereleased cankers on trees by 50% when an sity (WSU) Northwestern Washing- from cankers during the late summer application was made once in mid- ton Research and Extension Center and fall (Pscheidt and Ocamb, October followed by a second dor- (NWREC) in Mount Vernon, WA. 2017), this time of year was selected mant application in mid-February. Five treatments were applied in 2015 for this study to test efficacy of In contrast, an in vitro study found and 2016, and the 2016 experiment treatments when there likely was no that copper-based fungicides were included one additional treatment new inoculum present to cause new ineffective to control N. malicorticis (Table 1). In 2017, three of the same infections. (Rahe, 1997). Early 20th century treatments were applied as in 2016 2015 EXPERIMENT. Fifty trees of recommendations for managing an- plus one additional treatment. The 30 cultivars were evaluated: Blanc thracnose canker included applying 1-acre orchard included three to six Mollet, Brown Thorn, Bulmer’s trees each of 60 cultivars that were Norman, Chisel Jersey, Domaines, Funding and support for this project are gratefully naturally infested with N.