D.A. Rosenberger, Cornell's Hudson Valley lab, Highland, NY
About four years ago, the Northeast SARE Apple Production Project published descriptionsof the most promising scab-resistant apple cultivars in the Management Guide for Low-Input Sustainable Apple Production. Since then, we have accumulated extensiveobservations with some of these cultivars, and additional selections have been named orreleased for limited testing. This update provides a synthesis of published andunpublished information concerning the characteristics, qualities, and availability ofscab-resistant cultivars and advanced selections (SRCs).
Some of the new SRCs have been evaluated in more locations than others. Advancedselections from Cornell's Geneva breeding program, for example, are frequently evaluatedby numerous researchers because trees have been available through the Fruit TestingAssociation Nursery (formerly New York State Fruit Testing Cooperative). Weaknesses in newselections generally become apparent as selections are evaluated in differentenvironmental settings. Thus, the SRC descriptions which follow are probably biasedagainst cultivars which are older or have been more widely tested. Where relatively littleinformation is provided, most of the strengths and weaknesses remain to be discovered.
GoldRush, Enterprise, and Pristine are new cultivars which were released fromthe PRI (Purdue-Rutgers-Illinois) breeding program during the past four years and are nowavailable from commercial nurseries.
Advanced selections released by the PRI program for grower testing include Co-op 27, Co op29, Co-op 31, Co-op 32, Co-op 33, Co-op 34, Co-op 35, Co-op 36, Co-op 37. Trees of theseadvanced selections are available only by special arrangements with the University fruitbreeders or by special order (50 tree minimum) from Ed Fackler of Rocky Meadow Nursery,New Salisbury, Indiana (tel. 812-347-2213).
Advanced selections available from Cornell University's apple breeding program at Genevainclude NY 65707-19, NY 73334-35, NY 74840-1, NY 75413-30, NY 75414-1, NY 81204-42. Treesof these selections are available from the Fruit Testing Association Nursery, Inc., P.O.Box 462, Geneva, NY 14456 (tel. 315-787-2205; fax 315-787 2216). After spring of 1995, theFruit Testing Association Nursery, Inc. will go out of business and numbered selectionswill be available only by special arrangements with the apple breeder, Dr. Susan Brown.
Some of the SRCs developed in Nova Scotia and Quebec are available in the U.S. or can beshipped from Canadian nurseries whereas other cultivars cannot yet be imported. Canadiancultivars available in the US include Novamac and Nova Easygro. Cultivars that are not yetavailable include Novaspy, Richelieu, Rouville, Trent, and BelMac. However, Novaspy wascleared for importation into the U.S. in 1994 and commercially-propagated trees may beavailable within several years.
SRCs have not been widely planted by commercial growers because of potentialdifficulties in marketing new cultivars. However, some of the new cultivars and selectionsproduce fruit of acceptable commercial quality. Growers who retail some of their fruitdirectly are encouraged to experiment with marketing these newer scab-resistant cultivars.
Many of the SRCs reportedly have a better flavor after storage than they do at harvest.Thus, those experimenting with new SRCs should evaluate eating quality both at harvest andafter fruit are stored. With some cultivars (Liberty is an example), eating quality at harvest may be better in northern areas with coolgrowing seasons. Acidity at harvest seems to be greater when these cultivars are grownunder hot conditions.
Storage potential for SRCs has not been widely investigated. SRCs maturing in Augustgenerally have only 2-3 weeks of storage life. Moira, Prima, and Priscilla wereextensively tested at Nova Scotia and were judged suitable only for short-term storage of2 months in regular (air) cold storage. Liberty, Novamac, Nova Easygro, Macfree were judged suitable for 2-4 months of regular storagewhereas Novaspy and Trent were held well for > 4 months in regular storage. GoldRush,Enterprise, and some of the advanced selections from the PRI and Cornell programs havealso held up well in long-term storage in other more limited tests.
Although scab-resistant cultivars will need less fungicide than highly susceptiblecultivars such as McIntosh, Delicious, and Empire, we now know that some fungicideprotection will be needed almost everywhere these cultivars are grown. Flyspeck can causeextensive fruit blemishing as far north as Maine on fruit which are not protected withfungicides during summer. In addition, we have discovered that none of the cultivarsevaluated to date are completely immune to cedar apple rust. Cultivars and advancedselections which have been listed as resistant to cedar apple rust still develop smallpin-point lesions when exposed to heavy rust inoculum. The rust fungus in these lesions isunable to grow into normal rust lesions as one would see on rust-susceptible cultivars.However, the pin-point rust lesions provide entry sites for weak pathogens such asPhomopsis, Botryosphaeria, and Alternaria. These weak pathogens sometimes enlarge thepin-point rust lesions and cause a leaf-spotting similar to frog-eye leaf spot.Rust-induced leaf spotting is sometimes severe enough to cause premature defoliation.Thus, even rust-resistant cultivars will need fungicide protection from cedar apple rustif they are planted adjacent to cedars which harbor cedar apple rust.
Co-op 27 - (Illinois #2 X PRI 1042-100): Late-season dark red apple comparingfavorably to Winesap and matures one week after Delicious. Fruit have moderatelythick skin, with firm, crisp to slightly tough flesh texture. Fruit ripen uniformly, butmay be slightly woody at harvest, mellowing in storage. Tree has moderate vigor,upright spur-type habit similar to spur-type Delicious, is resistant to rust andfireblight, moderately resistant to mildew.
Co-op 29 - (Golden Delicious X 1050NJ1): Late-season apple pink blush over pale yellowsmooth skin. Fruit matures 2.5 weeks after Delicious. Flesh is cream to white, very crisp andbreaking, moderately coarse-grained, juicy, full-flavored and slightly spicy. Fruit areborn in clusters and develop some stem-end russet. Good quality winter storage apple. Treeis moderately vigorous, slightly upright, with leggy branches and some blind wood.Resistant to cedar apple rust, moderately resistant to mildew and fire blight.
Co-op 30 - See Enterprise
Co-op 31 - (Rock 41-112 X PRI 841-103): Late-seasonapple with potentially rough appearance, but good spicy flavor and good storage potential.The fruit may be splashed, striped, or mottled medium red to purple red with green groundcolor . Scarf skin has been noted some seasons. Very susceptible to cedar apple rust.
Dayton - (NJ 123249 X PRI 1235x100): Early-seasonred apple maturing in the Paulared season. Very susceptible to rust (as bad as Prima).Some reports suggest it is not cold-hardy enough for northern growing areas. Fruit qualityconsidered mediocre in Vermont.
Enterprise (formerly Co-op 30; PRI 1661-2 X PRI 1661-1): A smooth, glossy,90-100% red apple with yellow-green ground color. Fruit mature the same time as RomeBeauty, are round to elongated in shape, occasionally lopsided. Lenticels can beconspicuous. Flesh is medium grained, firm, crisp and breaking at harvest; remains firmand crisp in storage. Flesh color is pale yellow to cream. Flavor is very spicy, rich and sprightly acidat harvest, improves after one month in storage. Retains quality and texture for over 6months when stored at 1°C. Fruits hang well on the tree even when overripe. Tree isspreading, round topped, vigorous, with a standard bearing habit, highly resistant to fireblight, resistant to cedar apple rust, and moderately resistant to powdery mildew.Relatively thick skin makes this apple more palatable when peeled. Lenticel spotting ofunknown etiology (possibly bitter pit or a similar disorder) has been a problem on fruitfrom young trees in some locations. Late maturity may limit its northern adaptability.
Freedom - (NY 18492 X NY 49821-46): Mid-season orangish-redfruit ripens with Delicious. Fruit have prominent lenticels. When grown withoutfungicides, fruit quality varies considerably from year to year. In bad years, fruit maybe very rough in appearance with numerous superficial blemishes and some black rotinfections at lenticels. Rated as fair or poor-quality cultivar in Vermont and Maryland,but some peoplereally like the unique spicy flavor. If picked too early, storage scald is a major problem. Onlymoderately resistant to fire blight.
peoplereally like the unique spicy flavor. If picked too early, storage scald is a major problem. Onlymoderately resistant to fire blight.
Jonafree - (855-102 X NJ 31): Thismid-season red apple ripens with Delicious. Fruit color well and trees are annuallyproductive. Rated as fair fruit quality in Vermont. Fruit have very hard flesh; skin isslightly thick, tough, dry, waxy .May be more acceptable in areas where Jonathan is apreferred cultivar. Susceptible to cedar apple rust, but moderately resistant to mildewand fire blight.
Liberty - (PRI 54-12 X Macoun): Mid-season red applematuring with Empire. Probably one of the best scab-resistant cultivars for the McIntoshgrowing region. Trees are consistently productive (equal to Empire) with good winterhardiness. Flavor and quality are excellent when picked at the right time, but harvestwindow may be narrow. Fruit left on the tree too long soften rapidly, develop anoff-flavor, and may drop. After hot growing seasons, fruit are very acid at the optimumharvest date but eating quality improves after several weeks of storage. Fruit tend to besmall if trees are not adequately thinned. Mature trees on M.9 have been difficult to thinin eastern NY , but adequate thinning was achieved with 10 ppm NAA at 4-5 mm fruit size inVermont. Fruit may develop brown core if held more than 3-4 months in regular coldstorage.
Macfree - (McIntosh X PRI 48-177): Mid-season red apple. Trees are susceptible to mildewand cedar apple rust. Tendency to be biennial. Fruit coloring is a problem in southernareas just as with McIntosh.
Nova Easygro - (Spartan X PRI 565): Early-mid season darkred fruit matures with Mclntosh. Rated fair quality in Vermont; eating quality improveswith storage. Some fruit russetting has been noted in older trees. Fruit coloring is aproblem in southern areas just as with Mclntosh. Only moderately productive.
Novamac - (McIntosh X PRI 1018-3): Early-mid season redapple maturing with Mclntosh and sharing flavor, texture, and premature dropcharacteristics with Mclntosh. Considered only fair quality in Western NY.
NY 73334-35 - (Liberty X Delicious): Very large dark redfruit maturing after Delicious. Many fruit develop parthenocarpically. Some irregularlyshaped fruit. Not as precocious as Liberty or Empire. Unusually large size may make fruitattractive for direct-market sales.
NY 65707-19 - (Spartan X NY 140-9): Late-seasonred fruit maturing after Delicious. Fruit is extremely attractive, very "typey";resembles Delicious in appearance and texture. Fruit stores very well, but flavor isconsidered too mild by some.
NY 66305-139 - (NY 55140-9 X NY 45500-3): Good quality, mid-August red apple, but maynot be highly productive.
NY 75414-1 - (Liberty X Macspur): Mid-season red applematuring between Mclntosh , and Delicious. The Macoun appearance, flavor, and fruitcrispness of this selection have attracted attention, but a "chalky" afterta~tehas been noted under certain growing conditions. Tree habit is very upright; branches onyoung trees break out relatively easily during spreading. Scarf-skin and the conspicuouslight-colored lenticels may reduce attractiveness of fruit. Fruit retains flavor andcrispness during 5-6 months of regular cold storage, but fruit may shrivel like GoldenDelicious if relative humidity of storage is too low. Fruit are susceptible to moldy core.Trees are less precocious than Empire and Liberty.
NY 74840-1 - (NY 58524-1 X Empire): Mid-seasonred apple matures with Delicious. Fruit resemble Empire in appearance, but are somewhatlarger and considerably more acid at harvest. Eating quality is best after fruit have beenstored for a month or two. Trees have been highly productive at Geneva, only modestlyproductive in Vermont. May be biennial if not thinned.
Prima - (PRI 14-510 X NJ 123249): Early-seasonred-orange apple matures with Jonamac. Rated as a fair to good-quality SRC in Vermont,poor quality (soft, rough finish) in Maryland. Requires multiple harvests. Highsusceptibility to cedar apple rust limit its usefulness where rust is a problem. Lackswinter hardiness required for some northern climates.
Priscilla - (Starking Delicious X PRI 610-2): Mid-season dark red applematures with Empire. Fruit develops 70-90% red blush over pale yellow background. Flesh isfirm, pale creamy colored, medium grained, crisp, juicy, with sweet, aromatic, somewhatlicorice-like flavor. Resistant to rust, mildew, and fire blight.
Redfree - (Raritan X PRI 1018-101): Earlyseason red cultivar matures with Paulared, has good eating quality for an August apple,and is generating increased interest among commercial growers. Redfree is sweeter, lessacid than Paulared; unusually crisp for a summer apple, though quality may vary from yearto year. Trees are low in vigor; small fruit size may be a problem. Resistant to cedarapple rust, but only moderately resistant to mildew and fire blight.
Sir Prize - (Tetraploid Golden Delicious X PRI 14-152): Late mid season yellowapple matures with Delicious; bruises very easily and therefore is unsuitable for standardcommercial packing. Triploid. Susceptible to cedar apple rust, but moderately resistant tomildew and fire blight.
Williams Pride -(PRI 1018-101 X NJ50): Early-season red-purple apple ripens before Paulared; somewhat uneven ripening withfruit sometimes showing water core or bitter pit. Fruit quality may vary with the summergrowing conditions. Resistant to cedar apple rust, moderately resistant to mildew and fireblight.
NY 61345-2: No longer recommended for trial because of inferior fruit quality,problems with fruit cracking.
NY 66305-289: Discontinued because of rather unattractive appearance, average performance,and susceptibility to mildew.
NY 74828-12: Attractivepale red fruit with good flavor ripening with or slightly before Mclntosh. Reported tomake an excellent pink applesauce in Vermont. Trees set heavy annual crops and requirethinning. Discontinued because the fruit softened very quickly after harvest and because ahigh proportion of the fruit developed symptoms of sunburn during the last few weeksbefore harvest. Sunburn symp- toms may be virus-induced (dapple apple virus?) and wereless severe in Vermont than in eastern NY .Susceptible to one race of scab.
NY 75441-67: Discontinued because fruit developed severe net russetting and cracking atmany locations where this selection was evaluated.
Co-op 28 - (PRI 1982 X Prima): Variable butmedium-sized red apple matures with Mclntosh. Tree is vigorous, upright and spreading,somewhat limber, with blind wood in basal portions of branches. Fruit are oblate-round toround or short conic, slightly striped 50-90% medium red over yellow ground color. Fleshis cream- colored, very crisp and breaking, with medium to slightly coarse grain,moderately juicy, mildly subacid to sweet, slightly spicy. Flavor, flesh, and appearanceare similar to Prima, but with less acid. Fruit retains firm crisp texture throughoutstorage. Very susceptible to fire blight and has a tendency toward biennial bearing.
Co-op 32: Medium sized, yellow apple maturing in early August; pleasant, mild summer applewith a smooth, attractive finish; quality and shelf-life is significantly better than'Lodi' or 'Yellow Transparent'.
Co-op 33: Small-sized red apple maturing one week before Delicious. Exceptionally crisp,breaking flesh texture and excellent flavor at harvest.
Co-op 34: Medium-sizedred apple maturing one week after Delicious. Annually productive. Conic-shaped fruit has'Jonathan'-like quality and appears well adapted to the mid-west.
Co-op 35: Yellowapple maturing with Rome. Flavor is mild and pleasant with crisp breaking flesh. Fruitsize is smaller than 'Golden Delicious' but storage-Iife is superior .
Co-op 36: Yellowapple maturing with Rome. Flavor is mild and pleasant with crisp breaking flesh. Fruitsize is smaller than 'Golden Delicious' but storage-Iife is superior .
Co-op 37: Yellow fruit matures with Rome; fruit has a full rich, complex flavor; crisp andbreaking yet melting flesh type; fruit size is smaller than 'Golden Delicious' but storagelife is superior.
GoldRush (formerly Co-op 28; Golden Delicious X Co-op 17): Medium-sizedyellow- bronze apple maturing after Rome and 3-4 weeks after Delicious. Fruit are ovateand regular, greenish yellow at harvest turning to deep yellow in storage, sometimes witha fine net-Iike russet. Skin is nonwaxy, tender, thin to medium in thickness withconspicuous russetted lenticels. Flesh is pale yellow, medium coarse-grained, firm, verycrisp with a complex, spicy flavor. Eating quality is very good at harvest and improves toexcellent in storage. Stores at least 7 months at 1 C, but may shrivel slightly. Trees aresusceptible to cedar apple rust, slightly upright, moderately vigorous, with limitedbranching, semi-spur bearing habit, and some biennial tendency. Fruits hang well on thetree even when over-ripe. Late maturity may limit its northern adaptability.
Moira - (McIntosh X DG22-81): Late-season dark redapple maturing after Delicious. Released from the Agriculture Canada breeding program inTrenton, Ontario. Fruit are moderate in size, round to round-conic, lightly ribbed, mediumto dark red over a greenish-yellow ground color. Flesh is cream-white and slightly coarse.Tree is moderately vigorous, resistant to cedar apple rust, but susceptible to mildew,fire blight, and quince rust.
Nova Spy: Fruitare similar to Northern Spy, with red blush or stripes on greenish- yellow background.Flesh is creamy yellow, fine-grained, very firm, crisp, juicy, and moderately acid.Considered a promising new SRC. Moderately resistant to mildew, but susceptibility to fireblight and rust diseases is unknown.
NY 75413-30 - (Liberty X Starking): Very large dark redapple reported to mature with Delicious at Geneva, but maturing slightly ahead of Empirein the Hudson Valley in 1994. Fruit are slightly oblate in shape. Flesh is cream colored,firm crisp and juicy. Flavor is slightly astringent, but may mellow with storage. Storeswell. Trees are vigorous and productive. Many fruit develop parthenocarpically, and someunevenness in fruit shape has been noted. Considerable fruit drop has occurred during windstorms when fruit are left on the tree too long. Not as precocious as Liberty or Empire.
NY 79529-7 - (NY 66305-259 X Empire): Late-season red apple maturing with GoldenDelicious. Fruit resembles Empire, but with a more acid flavor.
NY 81204-42 - (Empire X NY 65707-19): A large fruited McIntosh type that is productive andgood quality. Will not color well in low light conditions.
Priam: Redfruit maturing about a' week before Delicious. Fruit .moderate to large in size,round-conic, with a moderately tough skin, flush red over a greenish-yellow ground color.Flesh is fine-textured, crisp, acid. Eating quality is better afteI storage. Of interestin Europe where a late-ripening, highly acid cultivar was desired. Susceptible to mildew.Not available in the US.
Pristine-(formerly Co-op 32; Co-op 10 x Camuzat): Medium-sized, yellow apple maturing with Lodi inlate July to early August. Pleasant, mild flavor with a smooth attractive finish. Qualityand shelf-life is significantly better than Lodi or Yellow Transparent. Wood is limber,resulting in drooping tree habit. Susceptibility to other diseases is unknown.
Richelieu - (Ottawa 521 X 11-51): Medium sized fruit, 60-65% red on light greenbackground, mature one week before McIntosh. Fruit are oblong conical with crisp, juicy,white flesh, mild to sub-acid with high sugar and aroma. Tree is medium vigor, spreading,precocious, annually productive, moderately resistant to mildew and fire-blight, but verysusceptible to cedar apple and quince rust.
Rouville - (52-05-312 X 69-52): Large, 75% red fruit with pale green-yellow ground color.Fruit are oblate, symmetrical, somewhat ribbed with white to cream-colored, juicy,slightly coarse flesh. Flavor is sub-acid with high sugar and tannin content. Fairquality, dual purpose-fruit. Tree is vigorous, semi-spreading, precocious, annuallyproductive, cold hardy, but susceptible to race 5 of apple scab.
Trent: Darkred, very late maturing cultivar from the Agriculture Canada program in Ontario. Flesh isfirm, juicy, cream colored with greenish tinge, and slightly, coarse.Tree is vigorous,upright, susceptible to cedar apple rust and quince rust. Fruit are moderate to large,round to slightly conic, medium to dark red with faint striping over a greenish-yellowground cover. Prone to bitter pit.
The author appreciates the information and insightful comments provided by the following:Jon Clements, University of Vermont; Susan Brown and Ian Merwin, Cornell University; SaraWolfgang, Rodale Institute Research Center; Jennifer DeEll, Ag Canada, Kentville; andRaymond Granger, Ag-Canada, Quebec.
TheNortheast SARE Apple Production Project has published eight issues of The NortheastSustainable Apple Production Newsletter since 1989. Some of the more recent newsletterarticles relating to SRC culture and quality are cited below:
Brown, S. 1990. Anoverview of the best scab-resistant cultivars from New York. Northeast LISA AppleProduction Newsletter 1(2):1-2.
Clements, J. Cowgill, W.,Costante, J. Heleba, D., Berkett, L., Granger, R.L. 1993. Scab resistant apple cultivarshave the right stuff in Canada and the U. S. Northeast Sustainable Apple ProductionNewsletter 4(1): 22.
Clements, J., Cowgill,W., Costante, J., Heleba, D., Berkett, L., and Granger, R. L. 1993. Scab resistant applecultivars have the right stuff in Canada and the US.
Northeast SustainableApple Production Newsletter 4(1):22-23. Costante, J. F., Berkett, L. P., and Clements, J.1990. Scab-resistant cultivars: the good, the bad, and the ugly. Northeast LISA AppleProduction Newsletter 2(1):4-5.
Costante, J. F., Berkett,L. P., and Clements, J. 1992. Liberty tops in taste!. Northeast LISA Apple ProductionNewsletter 2(3):10.
Costante, J., Berkett,L., and Clements, J. 1994. Liberty thinning experiment yields positive results. NortheastSustainable Apple Production Newsletter 5(1):9-11.
Crosby, J. A. 1990.Five new disease-resistant apple selections released by Purdue, Rutgers and Illinois.Northeast LISA Apple Production Newsletter 2(1):1-3.
Polk, D. F., Durner, E.F., and Rizio, E. F. 1994. Reduced spray trials for scab resistant apples in New Jersey.Northeast Sustainable Apple Production Newsletter 9(1):4-6.
Polk, D. F., Durner, E.F., Goffreda, J. C., and Rizio, G. F. 1992. Consumer acceptance trials with named andnumbered disease resistant cultivars in 1991. Northeast LISA Apple Production Newsletter2(3):3,11.
Prokopy, R. J., Mason, J.Duan, J. J., Elliott, R., and Cooley, D. R. 1993. Second-level IPM in orchards ofscab-resistant cultivars. Northeast Sustainable Apple Production Newsletter 4(1):13-15.
Rosenberger, D. A.,Meyer, F. W ., and Engle, C. A. 1993. Sooty blotch and flyspeck on 'Liberty' apples:Impacts of the diseases on projected value of the crop and unexpected impacts of summerfungicides. Northeast Sustainable Apple Production Newsletter 4(1):1-5.
Rosenberger, D. A.,Meyer, F. W., and Engle, C. A. 1994. Are apple fungicides providing more benefits thangenerally recognized? Northeast Sustainable Apple Production Newsletter 5(1):6-9.
Rosenberger, D. A., Meyer, F. W ., and Engle, C. A. 1994. Rust-induced leaf spots andpowdery mildew on scab-resistant apple cultivars are affected by planting location.Northeast Sustainable Apple Production Newsletter 5(1):1-3.
An Explanation forReports of Apple Scab Infection on Fruit ofNY 74828-12. S. K. Brown and L. P. Berkett.
Disease Management of Scab-ResistantCultivars. L. P.Berkett, J. F. Costante, K. N. Bower, J. M. Clements, and D. Schmitt.
Super-Marketing andTasting 'Liberty' Apples in Vermont. J. M. Clements, J. F.Costante, and L. P. Berkett.
Seven DiseaseResistant Apple Selections Released for Grower Testing. J. A. Crosby, J. Janick, P. C.Pecknold, S. S. Korban, S. M. Hies, J. Goffreda, and A. Voordeckers.
Promising ScabResistant Apple Selections for Quebec, Canada. H. L. Granger, S.Khanizadeh, and 0. Carisse.
'Enterprise' and'GoldRush,' Two New Disease-Resistant Cultivars. J. A. Crosby, J. Janick, P. C.Pecknold, S. S. Korbcin, S. M. Hies, J. Goffreda, and A. Voordeckers.
Arthropod PestPressure Among Several Disease-resistant Apple Cultivars. D. F . Polk, E. F. Durner and E.F. Hizio.
Using Disease-ResistantApple Cultivars to Reduce Fungicide Applications for Disease Control. W. H. Shaffer .
Non-Target Effect of aFungicide Spray Program on Phytophagous and Predacious Mite Populations in a ScabResistant Apple Orchard. K M. Bower, L. P.Berkett, and J. F. Costante.
Disease Resistant Apple Cultivars:Twelve Years of Observations. R. F. Heflebower and C. S. Walsh.
A Maturity and StorageStudy of Scab-Resistant Cultivars. J. R. DeEll, and R. K.Prange.
Early-Season DiseasesOccurring on Scab-Resistant Apple Cultivars and Advanced Selections Grown in SoutheasternNew York State. D. A. Rosenberger, F. W.Meyer, and C. A. Engle.
Evaluation of Four NewScab-Resistant Apple Varieties Compared with 'Empire' in New York Orchards. I. A. Merwin, D. A.Rosenberger, and C. Engle.
Summer FungicidesApplied to 'Liberty' Apple trees Affect Timing of Autumn Leaf Drop and Effectiveness ofFruit Thinning with NAA the Next Year. D. A. Rosenberger, F.W. Meyer, and C. A. Engle.
Anonymous. 1994. Acatalog of new and noteworthy fruits. New York State Fruit Testing CooperativeAssociation, Inc.
Autio, W. R. andCostante, J. F. 1992. Ripening and storage of the 'Liberty' apple. Fruit Var. Jour.46:235-244.
Bonn, W. G. 1993.Response of apple and crabapple cultivars and lines to fire blight, 1992. Biological andCultural Tests for Control of Plant Diseases 8:3.
Crosby, J. A., Janick,J., Pecknold, P. C., Goffreda, J.C., and Korban, S. S. 1994. 'Enterprise' apple.HortScience 29:825-826.
Crosby, J. A., Janick, J., Pecknold, P. C., Goffreda, J.C., and Korban, S. S. 1994.'GoldRush' apple. HortScience 29:827-828.