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. malicorticis Fillbarrel, Finkenwerder Herbstprinz, acknowledged from Washington State University (Zang et al., 2011). Trees were nurs- Frequin Rouge, Granniwinkle, Harry Extension, Washington State Commission on Pes- ticide Registration, Northwest Cider Association, ery-budded in Aug. 2012, planted at Masters’ Jersey, Jouveaux, Kermer- Northwest Agricultural Research Foundation, WSU NWREC in Apr. 2014, and rien, Kingston Black, Major, Maude, and USDA NIFA Hatch projects 1000194 and were in their second growing season Mettais, Muscadet de Dieppe, Peau 1017286. in 2015. Trees were trained to a tall- de Vache, Reine des Hatives, Ross The mention of a trademark, proprietary product, or company does not constitute a guarantee or warranty spindle trellis system, spaced 6 ft in- Nonpareil, Roxbury Russet, Smith’s of the product by the USDA-ARS and does not imply row and 14 ft between rows. The Cider, Stembridge Jersey, Stoke Red, its approval to the exclusion of other products or diameter of the central leader was Sweet Alford, Sweet Coppin, Tay- companies that also may be suitable. 0.5 inch in 2015, 0.7 inch in lor’s, Vilberie, Yarlington Mill, and 1Department of Horticulture, Washington State Uni- versity Northwestern Washington Research and Ex- 2016, and 0.8 inch in 2017. Weather Zabergau Reinette. Five treatments tension Center, 16650 State Route 546, Mount data (mean air temperature, relative were applied only once, on 16 Dec. Vernon, WA 98273, humidity, total precipitation, and so- 2014: 1) BM only; 2) CE + 0.5% 2U.S. Department of Agriculture-Agricultural Re- lar radiation) were recorded every 5 s sodium hypochlorite (5.25% sodium search Service, Physiology and Pathology of Tree Fruits Research Laboratory, 1104 N. Western Ave- and summarized every 15 min by hypochlorite, household bleach; nue, Wenatchee, WA 98801 WSU AgWeatherNet, the monitored James Austin Co., Mars, PA); 3) 3Department of Mathematics and Statistics, Washing- Mount Vernon station located 0.4 CE + CAU; 4) CE + CAU + copper ton State University, Pullman, WA 99164 miles from the cider apple research hydroxide (Nu-cop 50 DF; Albaugh, 4Corresponding author. E-mail: [email protected]. orchard (WSU, 2017). Disease distri- Ankeny, IA); and 5) CE + copper https://doi.org/10.21273/HORTTECH04148-18 bution, as defined by appearance and hydroxide. The BM used in this
• December 2018 28(6) 729 RESEARCH REPORTS experiment was a 10–10–100 ratio, Table 1. Treatments applied to anthracnose cankers on cider apple trees in 2015, prepared by mixing 10 g of basic 2016, and 2017. copper sulfate (CuSO4) and 10 g of Treatmentz Yry calcium hydroxide [Ca(OH)2] with 100 mL water; 2 mL of the BM was 1. BM only 2015, 2016 x applied with a paint brush (1 inch) to 2. CE + 0.5% sodium hypochlorite 2015, 2016, 2017 the canker. A 0.5% sodium hypochlo- 3. CE + copper hydroxide 2015, 2016, 2017 rite solution was prepared by mixing 1 4. CE + CAU 2015, 2016 part household bleach with 9 parts 5. CE + CAU + copper hydroxide 2015, 2016 water, and 1 mL of the solution 6. CE + BM 2016, 2017 was applied with a hand-spray bottle. 7. CE only 2017 The copper hydroxide was mixed zBM = Bordeaux mixture, prepared as 10 g (0.35 oz) basic copper sulfate, 10 g calcium hydroxide, and 100 mL (3.38 fl oz) water; CE = canker excision, canker cut out with a pruning knife sterilized with sodium hypochlorite according to label directions, applied solution (0.5%), 1 part of sodium hypochlorite with 9 parts water applied to excised area with a hand-spray bottle; at 12 lb/acre with a hand-spray bot- copper hydroxide, mixed according to label directions, 12 lb/acre (13.45 kgÁha–1) applied to the excised area with a hand-spray bottle; CAU = cauterization, carried out with a hand-held propane torch (Worthington Industries, tle. For CE, the canker was cut out Columbus, OH), flame held to the excised area for 5 s. with a pruning knife that was steril- yTreatment application dates were 16 Dec. 2014 for the 2015 experiment, 11 Dec. 2015 for the 2016 experiment, ized with 0.5% sodium hypochlorite and 13 Dec. 2016 for the 2017 experiment. before each excision. Following Rahe (2010), healthy tissue beyond the perceived margin of infection was re- moved as the pathogen may reside in this tissue. The resulting excisions were 1 to 3 mm beyond the original canker margins, but cambium tissue was present throughout the excision zone. Excised material was removed from the orchard. The CAU treat- ment was carried out with a self- igniting hand-held propane torch kit (Bernzomatic TS3000 and TX9 14.1-fl oz cylinder; Worthington Industries, Columbus, OH). All treated tissue was flamed for 5 s with the full flamed torch held 6cm from tissue (Fig. 1). Per manufac- turer labeling, flame temperature in air was 3600 F. 2016 EXPERIMENT. Sixty trees of 36 cultivars were evaluated: Amere Forestier, Blanc Mollet, Bramley’s Seedling, Bramtot, Breakwell Seed- ling, Brown Thorn, Brown’s Apple, Campfield, Chisel Jersey, Fillbarrel, Frequin Rouge, Golden Russet, Grimes Golden, Jouveaux, Kermer- rien, Lambrook Pippin, Major, Medaille D’Or, Mettais, Michelin, Muscat De Bernay, Peau De Vache, Redstreak, Reine des Hatives, Reine des Pommes, Royal Jersey, Stem- bridge Jersey, Stoke Red, Sweet Alford, Sweet Coppin, Taliaferro, Taylor’s, Tom Putt, Whidbey, Yar- lington Mill, and Zabergau Reinette. Six treatments were applied only once Fig. 1. (A) Anthracnose canker on cider apple tree before treatment application; on 11 Dec. 2015: 1) BM only; 2) CE + (B) Bordeaux mix applied to excised canker (1 to 3 mm of tissue beyond the canker margin was removed); (C) cauterization applied to excised canker; and (D) arrows 0.5% sodium hypochlorite; 3) CE + illustrate the area that was measured pre- and posttreatment; 1 mm = 0.0394 inch. CAU; 4) CE + CAU + copper hy- droxide; 5) CE + BM; and 6) CE + copper hydroxide (control). Treat- canker was cut out with a sterilized 2017 EXPERIMENT. Forty trees of ments repeated from 2015 were for- pruning knife as described above and 26 cultivars were evaluated: Amere de mulated and applied identically. For the excised area was painted with BM Berthcourt, Ashmead’s Kernel, Bou- the new treatment, CE + BM, the (2 mL). teville, Brown Snout, Brown Thorn,
730 • December 2018 28(6) Bulmer’s Norman, Campfield, Chisel streaking; and 5 = more than 81% mixed procedure. To determine if Jersey, Doux Normandie, Fillbarrel, streaking. Each year, symptomatic there was a treatment effect for can- Finkenwerder Herbstprinz, Frequin tissue was collected from the selected ker size, data were analyzed as a re- Rouge, Golden Russet, Harrison, treated canker or the excised area peated measures analysis of variance Harry Masters’ Jersey, Hewe’s Vir- that was monitored for size in each (ANOVA). Treatment and weeks ginia Crab, Liberty, Major, Maude, experiment, five trees per treatment, were considered fixed effects and Puget Spice, Roxbury Russet, Royal for pathogen isolation and identifi- replicates considered random. The Jersey, Russet King, Stembridge Jer- cation. Tissue was surface sterilized assumptions of normality and homo- sey, Stoke Red, and Tom Putt. Four in 0.5% sodium hypochlorite and geneity of variances were assessed in treatments were applied only once on rinsed with sterile distilled water, then all cases using the Shapiro-Wilk test 13 Dec. 2016: 1) CE only; 2) CE + small sections were plated onto po- and the Levene’s test respectively 0.5% sodium hypochlorite; 3) CE + tato dextrose agar [PDA (Difco, (using a = 0.05). Canker size data BM; and 4) CE + copper hydroxide Betcon, Dickinson and Co., Sparks, were log transformed to meet nor- (control). Treatments repeated from MD)] amended with chlorampheni- mality and equal variance assump- the two previous experiments were col (Sigma-Aldrich Co., St. Louis, tions. Treatment effects by each year formulated and applied as described MO). Plates were incubated at 20 to were analyzed by ANOVA and com- above. ‘‘CE only’’ was added as a 22 C, and cultures were transferred pared using Tukey’s honestly sig- treatment, and no CAU treatments to fresh PDA weekly. nificant difference at a 5% level of were applied in 2017. STATISTICAL ANALYSIS. All data significance. For the number of new DISEASE SEVERITY. Two objec- were analyzed in SAS (version 9.3; cankers, which was a discrete count tive response variables were measured SAS Institute, Cary, NC) using proc variable, a generalized linear model in the three experiments to assess disease severity: 1) initial canker size followed by the size of the treated canker or the excised area, and 2) number of new cankers. Initial canker size (length and width) was measured immediately before treatment appli- cation, and then the size of the treated canker or the excised area was mea- sured 3, 5, 7, 9, 11, 13, and 15 (2017 only) weeks posttreatment (Fig. 1). The area was calculated using an equation for an ellipse [PI function (Excel 2013; Microsoft, Redmond, WA)], and the size posttreatment was compared with the pretreatment canker size. The number of cankers present on each tree was recorded before treatment application and at the time of the final size measure- ment of the treated canker or excised area each year. The number of new cankers observed was calculated by taking the difference between pre- and posttreatment measurements. A subjective response variable, brown streaking indicative of the disease (Byther, 1986; Rahe, 2010), was evaluated in the tissue below the treated canker or the excised area. The surface of the treated canker or the excised area was removed with a sterilized pruning knife, as described above, 15 months posttreatment, on 17 Mar. 2016, 14 Mar. 2017, and 15 Mar. 2018. The amount of cambium tissue that exhibited dark brown streaking was then visually rated on a scale of 0 to 5 where 0 = Fig. 2. Mean daily air temperature and relative humidity (RH) and precipitation at no streaking;1=1%to20%streaking; Washington State University Northwestern Washington Research and Extension 2 = 21% to 40% streaking; 3 = 41% Center in Mount Vernon, WA during the 2015 experiment on cider apple trees; to 60% streaking; 4 = 61% to 80% (1.8 · C) D 32 = F, 1 mm = 0.0394 inch.
• December 2018 28(6) 731 RESEARCH REPORTS with a Poisson distribution was used. For tissue streaking rating, an ordinal logistic model was used. Treatment means for the number of new cankers and tissue streaking were compared using Student’s t test at a 5% level of significance. The evidence in the literature regarding cultivar effect for anthrac- nose canker incidence or severity is limited and contradictory, and cur- rently all apple cultivars, including cider cultivars, are considered to be susceptible to N. malicorticis (British Columbia Ministry of Agriculture, 2016; Creemers, 2014; Pscheidt and Ocamb, 2017). Therefore, this study was not designed for testing a cultivar effect on canker size or treatment response, and cultivar effect was assessed post hoc by comparing data for each treatment across the cultivars where possible. Data were subset by each treatment and year and analyzed as a repeated measures design with replicates random. Similarly, to de- termine if there was a year effect, data for the two treatments that were applied all 3 years (CE + 0.5% sodium hypochlorite, CE + copper hydrox- ide) were analyzed as repeated mea- sures ANOVA, with year, treatment, and weeks as fixed effects and repli- cate as a random effect.
Results CLIMATE. Daily mean air temper- ature tended to be lower each con- secutive year, and was 7.7 C in 2015 Fig. 3. Mean daily air temperature and relative humidity (RH) and precipitation at and 4.2 C in 2017 (Figs. 2–4). Washington State University Northwestern Washington Research and Extension Center in Mount Vernon, WA during the 2016 experiment on cider apple trees; Relative humidity also was lower (1.8 · C) D 32 = F, 1 mm = 0.0394 inch. each year, and was 88% in 2015 and 81% in 2017. Daily mean precipita- tion was higher in the 2016 experi- of treatment and week for size of the CE only treatment (5-fold), and was ment (3.9 mm average) than in 2015 treated canker or excised area in 2015 lowest with the CE + BM treatment and 2017 (2.8 mm average). and 2016, and the relative response (3-fold) (Fig. 6). Cultivar effect on DISEASE SEVERITY. There was a to each treatment was similar both canker size pretreatment and the size year effect (P < 0.0001) for the two years (Fig. 5). The size of the excised of the treated canker or excised area treatments that were applied in all area increased over time compared posttreatment was not significant three experiments, CE + 0.5% sodium with the pretreatment area (P < (P > 0.05) for any treatments except hypochlorite and CE + copper hy- 0.0001), while there was no increase CE + 0.5% sodium hypochlorite [P = droxide. Size of cankers in 2016 was in the size of the treated canker. For 0.008 (data not shown)]. The CE smaller than in the other 2 years [P = treatments without CAU, the size of only treatment, evaluated solely in 0.001 (data not shown)]. However, the excised area increased on aver- 2017, had inadequate replicates to there were no differences in canker age 4-fold in 2015 and 3-fold in test for cultivar effect. Overall, there size among treatments within a year. 2016. For the two treatments that was not a cultivar effect to influence Initial mean canker size was 0.49 cm2 included CAU, the size of the excised the efficacy of the treatments. in 2015 (P = 0.92), 0.26 cm2 in 2016 area increased on average 16-fold in The number of new cankers (P = 0.17), and 0.38 cm2 in 2017 2015 and 40-fold in 2016. In 2017 recorded 13–15 weeks after treat- (P =0.88). there was only a significant effect ment application differed across ex- There were significant effects for due to treatment (P = 0.03). Increase periments (P = 0.03), but there were treatment, week, and the interaction in canker size was greatest with the no differences within the experiment
732 • December 2018 28(6) developing on the trees. This result was similar to observations of Rahe (2010) where CE did not limit the number of new cankers that de- veloped the following year. In the current study, CE followed by an application of 0.5% sodium hypochlo- rite had the lowest increase in size of the excised area compared with the other CE treatments, and the fewest number of new cankers. However, some cultivars appeared to show sen- sitivity to the solution by developing dark black tissue around the margin of the excised area, and this response likely accounted for the cultivar effect with this treatment. Other reports have indicated that sodium hypochlo- rite loses its disinfecting properties within 24 h of application (Ono, 2006), thereby reducing its ability to prevent infection of the wound. So- dium hypochlorite may be more ef- fective if it is applied to the excised area and then covered with BM (Zaiger, 1968; Zaiger and Zentmyer, 1965); however, this may exacerbate sensitivity to the sodium hypochlorite solution in some cultivars. There was also a relatively low expansion of the excised area when CE was followed by an application of copper hydroxide. The spray applica- tion of copper hydroxide was rela- tively quick and only required a small amount of product, which are impor- tant cost considerations. However, some cultivars developed dark black tissue surrounding the margin of the Fig. 4. Mean daily air temperature and relative humidity (RH) and precipitation at excised area, similar to that observed Washington State University Northwestern Washington Research and Extension with the CE + 0.5% sodium hypo- Center in Mount Vernon, WA during the 2017 experiment on cider apple trees; chlorite treatment. This may have (1.8 · C) D 32 = F, 1 mm = 0.0394 inch. been a phytotoxicity response or an effect of a host defense mechanism. The size of the excised area treated in 2015 or 2017 (P = 0.83 and 0.16, Discussion and conclusions with BM was similar to other CE plus respectively) (Table 2). In 2016, the The current recommendation chemical treatments in this study, but treatments BM only and CE + BM for managing established anthracnose more new cankers developed with had on average five more new cankers, cankers in the Pacific Northwest is BM than with other treatments. Only while the treatments CE + 0.5% so- excising symptomatic tissue during a single application of BM was used in dium hypochlorite and CE + CAU + this study (as the product was not dry weather (Pscheidt and Ocamb, copper hydroxide had two on average washed off by rain events), and either 2017; WSU, 2016). This study tested (P = 0.01). a different timing of the application or Fifteen months after treatment the treatments that are commonly more applications may be needed to application, dark brown streaks indic- applied to anthracnose cankers, and reduce new canker development. In ative of the disease were observed in measured disease severity when, in the current study, application of BM the cambium tissue below the treated theory, there was no new inoculum was by hand with a paint brush, which cankers and excised areas for all treat- present, as spores are released from was time consuming and laborious. ments each year (Table 2). Ratings cankers during the late summer and This application method is likely not ranged from 1 to 3 (1% to 60%) and fall (Pscheidt and Ocamb, 2017). The cost-effective, and it may be more did not differ due to treatment in any size of the excised area increased with efficient to spray BM on affected areas year (P = 0.21, 0.12, and 0.06, the CE only treatment, and CE alone or the entire tree, but efficacy would respectively). did not prevent new cankers from need to be tested. Some growers have
• December 2018 28(6) 733 RESEARCH REPORTS
did not limit canker disease incidence or severity in the year following treat- ment application. Thus, CAU can be eliminated from an anthracnose can- ker management plan. For all treatments in this study, 15 months after treatment applica- tion, brown streaking was observed in the tissue directly below treated can- kers and where cankers had been excised. Streaking occurred despite removing all visible symptoms of fun- gal infection in the cambium plus an additional 1 to 3 mm of healthy tissue at the time of treatment application. Others have reported that N. mali- corticis colonizes host tissue beyond the sites of visible symptoms (Byther, 1986; Rahe, 2010). Thus, it may be necessary to extend the excision even further to remove fungal mycelium that may be present. Although N. malicorticis was not successfully iso- lated from symptomatic cambium tis- sue in the current study, symptom morphology aligned with descrip- tions of N. malicorticis by Byther (1986) and Rahe (2010). While streaking may have been due to injury of the cambium cells caused by the treatments, symptoms were present even when cankers were not removed. Streaking also occurred when cankers where excised and no fungicide was applied. It is possible that toxicants may have diffused or were translo- cated downward from the site of treatment application, causing dam- age to the cambium tissue. Further studies are needed to determine the cause of the streaking found under the cankers and the excised areas. The climatic conditions were mildly cold and moist during the winter months when the current Fig. 5. Effect of Bordeaux mixture only, or canker excision (CE) with a subsequent study was carried out. These condi- application of cauterization (CAU) and/or chemical treatment, on the mean size tions mirrored those found to be of the treated canker or excised area on cider apple trees in 2015 (top) and 2016 favorable for disease incited by N. (bottom). Treatments were applied once each year (on 16 Dec. 2014 and 11 Dec. malicorticis as reported by Hortova 2015, respectively) to different trees that were naturally infested with anthracnose et al., (2014), Miller (1932), and canker. Each data point represents a mean of 10 replicates ± SE, pretreatment (Pre- Spotts (1985). The study period of trt) to 13 weeks posttreatment. Some error bars not visible due to masking by data 2016 tended to have the highest point symbols. NS indicates nonsignificant differences, and *, **, *** indicate significant differences among treatments at each measurement time at P £ 0.05, average precipitation and the greatest 0.01, and 0.0001, respectively, as determined by Tukey’s honestly significant number of new cankers, but the initial difference test; 1 cm2 = 0.1550 inch2. size of cankers was smaller than in the other 2 years of this study. Little is known regarding the impact of been cauterizing the excised area, number of new cankers was not re- weather conditions (temperature, although there is no evidence to duced. CAU of the excised area fol- precipitation, relative humidity, and support the efficacy of this treatment. lowed by copper hydroxide also did solar radiation) on N. malicorticis in- In the current study, CE plus CAU not reduce new canker development. cidence and severity. Measuring cli- caused the most damage to the area of This finding is similar to Byther mate data during future studies may the tree that was treated, and the (1986) that reported CE plus CAU help to explain treatment results.
734 • December 2018 28(6) appears to be active throughout the dormant season in the western Washington maritime climate. Thus, a year-round management plan is needed, potentially including apply- ing protectant fungicides in the au- tumn and/or winter. Future research should evaluate CE and fungicide ap- plications to the entire tree through- out the year, and additional fungicide chemistries should be evaluated to prevent pathogen resistance to copper- based products that are currently used extensively in some orchard spray programs. While results from this study for the most part indicate no cultivar effect on disease susceptibil- ity or incidence and severity, some cultivars displayed sensitivity to ap- plications of 0.5% sodium hypochlo- rite and copper hydroxide. Future studies should target cultivar effects Fig. 6. Effect of canker excision (CE) with and without a subsequent chemical for disease resistance and chemical application on the mean size of the excised area on cider apple trees in 2017. treatment. Treatments were applied once (on 13 Dec. 2016) to different trees that were naturally infested with anthracnose canker. Each data point represents a mean of 10 replicates ± SE, pretreatment (Pre-trt) to 13 weeks posttreatment. Some error Literature cited bars not visible due to masking by data point symbols. NS indicates nonsignificant Barss, H.P. 1925. Northwestern apple differences, and *, **, *** indicate significant differences among treatments at tree anthracnose canker and fruit rot each measurement time at P £ 0.05, 0.01, and 0.0001, as determined by Tukey’s (Neofabraea malicorticis). Oregon State honestly significant difference test; 1 cm2 = 0.1550 inch2. Agr. College Ext. Serv. Circ. 220. Barss, H.P. and D.C. Mote. 1931. Or- chard protection program for Oregon. Table 2. The mean number of new cankers on cider apple trees observed in 2015, 2016 (both 13 weeks posttreatment application), and 2017 (15 weeks Oregon State Agr. College Ext. Serv. posttreatment application), and mean severity rating of brown streaking 15 mo. Bul. 431. after treatment application in each experiment. Borecki, Z. and A. Czynczyk. 1985. Sus- New cankers (no.)y Brown streaking (1–5 scale)x ceptibility of apple cultivars to bark canker diseases. Acta Agrobot. 38:49–59. Treatmentsz 2015 2016 2017 2015 2016 2017 BM only 2 5 aw –v 23 –Braun, P.G. 1997. Distribution and se- verity of anthracnose canker and Euro- CE + 0.5% sodium 22b12 2 3 pean canker of apple in Kings County, NS. hypochlorite Can. J. Plant Pathol. 78:78–82. CE + copper hydroxide 3 3 ab 1 2 2 2 CE + CAU 2 4 ab – 3 2 – British Columbia Ministry of Agriculture. CE + CAU + copper 42b–3 3 – 2016. Anthracnose and perennial canker hydroxide of apple. 27 Mar. 2017.
• December 2018 28(6) 735 RESEARCH REPORTS
Creemers, P. 2014. Anthracnose canker Hortova, B., D. Novotny, and T. Erban. Spotts, R.A. 1985. Environmental factors and perennial cankers, p. 51–53. In: T. 2014. Physiological characteristics and affecting conidial survival of pear decay Sutton, H. Aldwinckle, A. Agnello, and J. pathogenicity of eight Neofabraea isolates fungi. Plant Dis. 69:391–392. Walgenbach (eds.). Compendium of ap- from apples in Czechia. Eur. J. Hort. Sci. ple and pear diseases, 2nd ed. APS Press, 79:327–334. Spotts, R., K. Seifert, K. Wallis, D. Sugar, St. Paul, MN. C.L. Xiao, M. Serdani, and J. Henriquez. Kienholz, J.R. 1939. Comparative study 2009. Description of Cryptosporiopsis Davidson, R. and R.S. Byther. 1992. Ap- of the apple anthracnose and perennial kienholzii and species profile of Neo- ple anthracnose: Bull’s-eye rot. Wash- canker fungi. J. Agr. Res. 59:635–665. fabraea in major pome fruit growing dis- ington State Univ. Ext. Bul. 0940. tricts in the Pacific Northwest USA. Miller, E.V. 1932. Some physiological Mycol. Res. 113:1301–1311. El-Hamalawi, Z.A. and J.A. Menge. studies of Gleosporium perennans and 1994. Effect of wound age and fungicide Neofabraea malicorticis. J. Agr. Res. Washington State University. 2016. Ap- treatment of wounds on susceptibility of 45:65–77. ple: Anthracnose (bull’s-eye rot). 23 Mar. avocado stems to infection by Phytoph- 2017.
736 • December 2018 28(6)