Master Gardener Class – Apples! April 11, 2018

Home , Malus prunifolia, Malus sieversii, Pollenizer

Ann. M. Chanon (OSU Extension, Lorain Co., [email protected]) Joseph C. Scheerens, OSU Horticulture and Crop Science, [email protected])

Note: Images in slide set that are not referenced are from PowerPoint clip art, or are my own images or those of Dr. Joszef Rascko.

Slide 1: Welcome and introduction! Additional contacts!

– Dr. Diane Miller, Dept. Horticulture & Crop Science, 330-263-3824, [email protected] – Dr. Melanie Ivey, Dept. Plant Pathology, 330-263-3849, [email protected] – Dr. Elizabeth Long, Dept. Entomology, 330-202-3556, [email protected] – Mr. Brad Bergefurd, OSU South Centers, 740-289-2071 (ext. 136) [email protected] Slide 2: Apples

– Apples are one of the earliest fruit trees under cultivation. – Improved over thousands of years of selection and breeding – Well over 10,000 named apple cultivars worldwide, many as the result of selected bud sports or root suckers with desirable characteristics – Marketed exclusively by cultivar or trademark name. Most other fruit crops are not. – Cultivated in temperate regions worldwide or at high elevation in the tropics. Grown on all continents except Antarctica – Apple fruit are classified as pomes. Apple carpels are surrounded by a accessory tissue called the hypanthium (cortex) which is derived primarily from calyx cells. This is the part we eat. The actual carpel material we refer to as “the apple core” – Apples have relatively long storage lives, perhaps fostering their use by indigenous cultures and their spread worldwide – Multiple uses -- used for fresh fruit, juice, hard and soft cider, vinegar, dried apples, canning, cooking and baking. – Health-beneficial values of apple consumption known for millennia "An apple a day keeps the doctor away", ‘‘Eat an apple on going to bed, and you’ll keep the doctor from earning his bread.” – Current taxonomic classification as Malus X domestica Older classifications now considered to be incorrect include Pyrus malus and Malus malus

Slide 3: Malus sieversii and the center of origin

– Turkey is considered to be the center of apple diversity but the center of origin now accepted to be in the apple forests of central Asia, predominantly Kazakhstan. relatively – Genetic evidence for M. sieversii as a prominent progenitor species of M. X domestica. Genotypes can be found that closely resemble the cultivated apple. – USDA germplasm collection trips. Material stored at the Apple Clonal Germplasm Repository in Geneva NY. Some Kazakhstan material being grown at Dawes Arboretum in Newark, OH. – Primary interest in Asian germplasm is to garner genes for late fruiting and scab (Venturia inequalis) resistance.

Slide 4: Other species important to M. X domestica

– Malus prunifolia: pear-leaf or plum-leaf crabapple, Chinese crabapple – Native to China in the following provinces: Gansu, Guizhou, Hebei, Henan, Liaoning, Nei Mongol, Qinhai, Shaanxi, Shandong, Shanxi, and Xinjiang – Grows from sea level to 1300 m – White flowers with yellow or red fruit – Primarily an ornamental, but some clones also used as rootstocks – Four botanical varieties are grown for edible consumption

– Malus baccata: Siberian crabapple, Manchurian crabapple, Chinese crabapple – Native to Siberia, Mongolia, Bhutan, India, Nepal and Japan – Trees 10-14 m – White flowers with yellow or red fruit; fruit small <1cm – Consumed in Asia as fresh or dried fruit; used as an ornamental or as a source of rootstocks elsewhere – Pest resistant and adapted to cooler temperatures

– Malus sieboldii: Toringo crabapple, Siebold’s crabapple – Native to China, Japan and Korea – Trees 2-6 m – Flowers pink to pale rose; flowers in spring and autumn – Fruit 6-8 cm in diameter; brownish yellow to red in color – Resistant to scab – Adapted to cold and drought conditions

– Malus sylvestris: European crabapple or forest crabapple. – Found widely throughout Europe as far north as Finland – Thorny trees up to 10 m in height; native habitat at forest’s edge – Tolerant of different soil types, but prefers a well-drained site – Flowers in May – Flowers are pale to deep pink and resistant to spring frosts – Red fruit are processed into jelly and confections, a few cultivars produce fruit sweet enough to eat fresh – Currently there is clear DNA evidence that European crabapple is one of the largest genetic contributors to the modern cultivated apple

Slide 5: Apple floral biology (introductory slide)

– Newly planted apples undergo a juvenility period before they are physiologically able to induce floral bud development. The length of juvenility is cultivar- and rootstock- dependent. Apples on dwarfing rootstocks may flower in 2-3 years whereas seedling apples (own-rooted) may take up to 8 years to bloom. – The juvenility period is affected by rootstock choice.

Slides 6 -7: Shoot-bearing vs. spur-bearing apples

– “Apple trees that bear fruit on flowering spurs are mutations of standard apple trees. Flowering spurs are short, leafy shoots with a terminal bud that grow from the base of leaves on 2-year-old shoots. Older, standard cultivars bear apples on the tips of shoots that began growing the previous year”. http://homeguides.sfgate.com/flowering-spurs- apple-trees-62477.html

– Apple floral buds form on short bearing shoots called spurs (at least two years old) and in axillary buds of elongated shoots (one year old). The tendency to produce spurs differs significantly among cultivars. – Spur-bearing cultivars tend to be smaller than shoot-bearing cultivars. – Pruning increases spurriness. – Spur-type apple trees produce fruit throughout the canopy whereas on tip bearing apples the fruit is borne on the canopy exterior. This has implications for pruning. – Yields tend to be higher.

Slide 8: Apple flower induction and development

– Floral induction occurs in July of the season preceding bloom. Induction involves the transition from vegetative bud to floral bud. Histological changes are evident.

– Floral development continues intensively until leaf fall, then slows precipitously throughout the dormant period, then accelerates again in early spring.

Slide 9: Hormonal interactions of developing fruit and floral buds – alternate bearing

– Seeds of developing fruit and vigorously growing shoots are inhibitors of flower bud differentation (flower formation). Gibberellins are the primary inhibiting substances. – Carbohydrate/nitrogen balance also plays a significant role in the competition between fruit/shoot growth and floral initiation – Overproduction of fruit (too many gibberellins) or underproduction of fruit due to biotic (insect damage) or abiotic stresses (freezes) causing the initiation of either too few flowers or too many flowers leading to an imbalance. – A pattern of alternate bearing can result causing the tree to have “on years” and “off years” – The tendency for alternate bearing is cultivar/rootstock specific – Alternate bearing is a particularly difficult problem to overcome. – Alternate bearing can be combated using specific cultural treatments such as judicious pruning or in “on years” aggressive fruit thinning (see below).

Slide 10: Apple chilling requirements (cultivar dependent, self explanatory)

Slide 11: Flowering phenology (temporal pattern)

– In Ohio, flowering occurs from mid-April to mid May with many cultivars blooming in the first few days of May. – The bloom period lasts about two weeks – In a flower cluster (inflorescence containing 4-7 flowers), the terminal or apical flower opens first followed by lateral buds. – Cultivar-specific flowering phenology is important to ensure pollen from pollenizers is available when stigmas of the desired cultivar are receptive.

Slide 12: The apple flower

– Apple flowers are typical of the Rosaceae with five petals and five sepals, an anther whorl with 20-40 stamens (4-5 K pollen grains per anther), 5 pistils (producing 10 seeds) – The flower is epigenous. The calyx tissue eventually forms the perianth. – Petals are often colored to attract pollinators – The flower also contains nectaries located on the inner surface of the sepals which also attracts pollinating insects. The volume of nectar and its sugar content are important because it serves as an energy source for bees.

– Stigmatic surface is receptive for 2-4 days depending on nutritional status of the tree and environmental conditions. Receptivity is curtailed by hot, dry weather as the surface must be moist to stimulate pollen germination. – Pollen is released from the anthers by spontaneous bursting of the anther when conditions are right (warm and sunny with low relative humidity)

Slide 13: Pollination requires insects

– Apple is predominantly cross-pollinated with pollination occurring in open flowers – Apple is entomophilous (pollinated by bees or other insects) – Activity of pollinating insects weather-dependent – Commercial orchard recommendations:

o 4 - 6 bee colonies (nuc-box sets) per acre are typically adequate for optimum pollination. 5-10 hives within a distance of 200 yards.

o Introduce bees immediately after flowering begins. If placed too early, the bees will move on to other species that are flowering; if placed too late, the effective pollination period may be too short to ensure an adequate crop

o Distribute evenly throughout the orchard – Provide food and water to pollinators – Attract pollinators with fragrances – Hand pollination is laborious; spray or dusting with pollen is not very effective. – Eliminate competitive weeds that have overlapping bloom periods [(dandelion (Taraxacum, top), stitchwart (Stellaria, middle), deadnettle (Lamium, bottom) – Wild bees [e.g., mason bees (Osmia, right) or bumble bees (Bombus, left)] have some advantages. They are often more efficient (in good weather, a half-dozen Osima females are adequate to pollinate all the flowers on an average tree). Both females and workers collect pollen. – Wild bees are available in limited supply. Some species (bumblebees) can be purchased.

Slide 14: Pollinizers

– Most cultivars are self-sterile and require pollenizers. – Judicious choice of pollenizing cultivars. If pollenizer pollen is in low supply or if pollenizers are not planted at optimized spacings, bouquets of pollenizer branches can be placed throughout the orchard. – Choose pollenizers that are similar to the main cultivar being produce with respect to growing conditions, growth habits, cultural needs and phytosanitary requirements. – At least a 60% overlap in bloom is recommended.

– Multiple pollenizer cultivars can be used but the number should be limited to avoid extra management headaches or increased cultural costs. Efficiency is not likely to be improved with more than 4 pollenizer cultivars. – Pollenizers can be placed at the head of each row. – If possible, choose a pollenizer cultivar that is also commercially important or desirable.

Slide 15-16: Flower and fruitlet thinning

– Trees produce an excessive number of flowers – 5-10% final fruit set is needed to produce a desirable crop – Thinning improves fruit quality and fruit size – Thinning promotes return bloom in the following year (see alternate bearing) – Thinning prevents overcropping and maintains adequate vegetative vigor and tree structure

– Types of thinning include: mechanical (dormant pruning and blossom thinning); chemical thinning at bloom with caustic materials and/or coating agents; chemical thinning after fruit set with natural or synthetic hormones and related compounds; and manual (hand thinning usually practiced as a follow-up to mechanical or chemical thinning.

– Several machines are available for mechanical thinning including those that spray jets of water at high pressure, those that have stiff brushes or tines to remove flowers (pictured) and those that shake the whole tree by its trunk. – The advantages of mechanical thinning include that it is inexpensive, fast and easy to use; the disadvantages include that it is damaging to remaining flowers or fruitlets, and it tends to remove fruit from the outer canopy and that it can result in disease spread, namely fireblight. – If used after fruit set shaking devices remove the largest fruit first. Also, it can result in damaged fruit which drop later during development.

– Chemical thinning can be accomplished during full bloom to prevent pollination from occurring – Typical agents are caustic compounds (lime sulfur) or coatings (clay, oil)

– Chemical agents can also be applied after bloom to thin developing fruit – Fruitlet thinners are typically hormone-based (See Midwest Fruit Pest Management Guide for information https://ag.purdue.edu/hla/Hort/Documents/ID-465.pdf – Advantages include reduced damage to leaves and other structures and less danger of post-treatment frost. Also, application occurs after a reliable estimate of initial fruit set can be made

– Early thinning results in best response, especially when return bloom is the primary object. A standard treatment for apple fruitlet thinning with hormones is best applied 40 days after full bloom; for pears it is 60 days and for peaches it is 70 days. Check to see what is known about your specific cultivar and the optimum timing for the compound you are applying. – However, thinning can be accomplished later if its goal is to increase fruit size.

Slide 17: Apple cultivars

– There are over 10,000 named cultivars; According to the US Apple Association, there are over 100 cultivars grown commercially in the US and only about 50 are commercially important worldwide. In the US. less than 20 cultivars account for 90% of the commercial production. The eighteen varieties listed on the slide are the top cultivars being produced in the US according to the US Apple Association – Currently important cultivars were bred or developed in temperate regions around the world. – The age of currently important cultivars spans two centuries – Cultivar information can be found at the following three websites

o http://usapple.org/all-about-apples/apple-varieties/ o http://en.wikipedia.org/wiki/List_of_apple_cultivars o http://www.orangepippin.com/apples – Important apple cultivars have resulted from the selection of chance seedlings, the discovery of useful bud sports (currently 100 strains of ‘Golden Delicious’) and through controlled crossing and selection by breeders. – Recent active university-led breeding programs in the Eastern US have included Minnesota, New York and Indiana – Freeman Howlett was Ohio State’s most successful apple breeder releasing the variety ‘Melrose’ (1944) – Midwest Apple Improvement Association (public-private partnership) established 1998. Their goal is to develop late blooming apples (spring frost avoidance) that produced fruit of exceptional quality for the Midwest for agrotourism and local markets. – ‘Evercrisp’ is their first named cultivar which has superb flavor and excellent keeping quality – MAIA also developing specialty apples for their members that have appeal in limited markets.

– Cultivars should be chosen for their environmental adaptation to a specific region (e.g., winter hardiness, chilling requirements, spring frost tolerance, bloom cycle, heat tolerance, etc.), for their resistance or tolerance to diseases and pests (e.g., apple scab – Venturia inaequalis, fireblight – Erwinia amylovora, for their storage or keeping quality,

and for their sensory characteristics (e.g., tart vs. sweet) and for their end use (fresh consumption, baking, cider production, etc.)

Slide 18: Cultivar sensory quality

– Data on slide depicts sensory evaluation results from an apple cultivar laboratory exercise in HCS 5460 Fruit Crop Physiology and Production. – Demonstration of important apple cultivars and opportunity for sampling will be available during the break in this presentation

Slide 19: Apple Rootstocks

– Rootstocks have been used in apple production for millennia – Most scion (apple fruit) cultivars do not root well from cuttings. – Rootstock development borne of need to clonally reproduce cultivars. – Trees from seeds are slow to bear – The most profound effect of rootstock choice is tree size (vigor) control – How dwarfing stocks dwarf is not yet known. How they cause the other effects that they do is also not yet known.

Slide 20: Rootstock effects

– Control of tree size and stature – Control vigor control (yield to tree size ratio) – Hasten precosity – Precocity may be independent of dwarfing effect because it is found in all rootstock vigor classes – Promote balanced flowering and fruit set – Can improve fruit quality – Smaller, more open trees let in more sunlight. Smaller trees may also have reduced fruit loads with more carbohydrates available for fruit development (not consistent with all rootstock scion combinations. Improved carbohydrate ability also promotes a more balanced sugar acid ratio. Fruit color is a function of light intensity and small, open trees promote darker colors. Harvest dates may be hastened. Pre- and postharvest calcium levels in fruit may be improved lessening the incidence of cork spot and bitter pit (see pictures Slide 23). – Affect cold hardiness – Most dwarfing rootstocks more susceptible to cold but some bred for resistance such as B.9. – Affect heat tolerance – Heat tolerance is variable among stocks. – Impart disease and insect resistance – Some dwarfing rootstocks and some invigorating rootstocks show resistance to Phytophthora spp. Some rootstocks show resistance to fireblight (Erwinia amylovora see pictures Slide 23) and woolly apple aphid (Eriosoma lanigerum see pictures Slide 23) where others are susceptible.

Slide 21: Rootstocks and vigor

– M.27 (superdwarfing) is used for very high density orchards in ideal locations (deep fertile soils adequate moisture, excellent fertility, etc) It is not suited to many soils and sites. It is very shallow rooted, sensitive to drought. It’s heavy fruit set requires thinning. The fruit are small (not necessarily disadvantageous in all markets). This rootstock is best used with very vigorous scions.

– M.9 (dwarfing) – M.9 produces the quintessential tree size most desired by growers. The ultimate size depends on scion, fertility and management practices. Trees on M.9 need to be staked. It is difficult to propagate. M.9A and M.9 EMLA are virus free versions (sub-clones). There are small differences among subclones with respect to scion vigor.

– M.26 (semi-dwarfing) is used when climate and soil conditions suggest M.9 to be potentially too dwarfing (i.e. climate and soil conditions that are not perfect). It imparts 15-30% more vigor to the scion. It is more winter hardy than M.9, Trees on M.26 also need to be staked. M.26 has several disadvantages including that it produces burr knots on above-ground portion that are potential pathogen entry points and result in uneven scion growth and a variable orchard, Uneven machine planting with variable graft union heights exacerbates this problem. Trees on M.26 should be planted all at one height as close to the soil line as possible while still preventing scion rooting. M.26 may not be as efficient at calcium uptake as other stocks, do not use with scions susceptible to cork spot or bitter pit. It is sensitive to fireblight

– Semi-vigorous to vigorous rootstocks M.7 and MM.106 – M.7 is adapted to a variety of edaphic conditions. It induces precocity and has a relatively good yield efficiency. It is resistant to collar rot and fireblight. It suckers badly and is not as winter hardy as others, – MM.106 excellent yields and precocity. – M.27 = 16 kg/tree – M.9 = 30 kg/tree – M.26 = 41 kg/tree – M.106 = 79 kg/tree

Slide 22: Interstocks (interstems)

– Act as the size-controlling factor between a vigorous rootstock and the desired scion – Overcome incompatibility problems between desired rootstock and scion – Act as intermediate to control vigor when environment (or pathogen level) is unsuitable for planting the desired rootstock – Improve cold hardiness (trunk-builders or staddles) – Hasten fruit ripening.

Slide 23: Rootstock History

– Rootstocks used to control apple tree size for 2000 yrs. – Romans used cuttings or suckers from existing trees. – Early English growers recommended the use seedling rootstocks. Apple pomace provided the source of seeds. They often used M. sylvestris for greater uniformity of performance. – First dwarfing rootstocks were described in 16th and 17th Century literature – The first named rootstocks were French ‘Paradise’ and ‘Doucin’ or English ‘Paradise’. French ‘Paradise’ was more dwarfing Eventually 14+ different clonal rootstocks were known as ‘Paradise’. – In the late 1800s East Malling Research Station UK researcher Ronald Hatton selected stocks for trueness and assigned each clonal line a number in order to eliminate confusion among rootstock names. He made 24 selections but his numbers were not in order of size control (e.g., M.9 creates smaller number than M.2) – In 1917 East Malling efforts were joined by researchers at John Innes institute in Merton, UK, began rootstock breeding program for resistance to woolly apple aphids. There clones bear the name MM. – In 1960 Long Ashton Research Station also joined the effort, developing virus-free rootstocks (e.g., M.9EMLA) – More recent efforts include: from Russia, the Budagovsky series; Poland (P-series) Germany (Pillnitzer supporter series) Canada (Vineland, Ottawa) and the US (MI, NY, geneva series) – Rootstocks evaluated for extended study by NC 140. Their results were published primarily in the Journal of the American Pomological Society (Fruit Varieties Journal)

Slide 24: Apple rootstock breeding and selection programs (self-explanatory)

Pennsylvania Tree Fruit Production Guide

Slide 25: Site preparation and planting

– Slope and exposure

o A = Young trees experience the warmest in winter and spring due to ample sun and air drainage

o B = Young trees subject to cold winter temps because of exposure o C = Young trees stay warmer than B in the winter but bud later in spring due to north face

o D = Young trees subject to coldest temperatures in winter due to air drainage o E = Also low in elevation but young trees are protected by windbreak o F = Undesirable because windbreak is to the south shading young trees – Deep, well-drained soil: a loam soil that is 3 to 4 feet deep is optimum

– Organic matter: Approximately 3% or higher. – pH: 6.0-6.5 – Remove unwanted vegetation: remove woody perennials and control weeds – Subsoiling: Use a subsoiler or deep plowing equipment if a hardpan impedes drainage – Level or contour the planting site – Soil test for native fertility and nematodes – Correct deficiencies – Plant sod-row middles – Purchase trees from a reputable nursery (PA Tree Fruit Production Guide has an exhaustive list of nurseries)

Slide 26: Introductory remarks on pruning and training

– Pruning and training are different operations that affect tree performance; each has a distinct function but they are used together in synergistic ways to maximize orchard efficiency – Pruning reduces undesired wood (unproductive, too vigorous or not vigorous enough) leaving specific branches that are most fruitful or advantageous to tree health. Overall, pruning is a “dwarfing” process, but it may stimulate growth in the area of the pruning cuts.

– Reasons for pruning and training include:

o Improve sunlight (& spray) penetration o Improve/develop specific tree shape and size o Promote tree vigor o Develop branches that are strong and more resistant to environmental stress o Balance vegetative vigor with fruiting potential o Optimize fruit quality o Reduce incidence of disease and insect infestations

– Training directs tree growth (i.e., development of tree framework, control of branching habit). Obviously some pruning is needed during training (one technique used). Branching habit affects fruit production with more horizontal branching being typically more fruitful. – Pruning is practiced throughout the life of the orchard. Training may also continue as trees mature, but it is mostly accomplished during the early life of trees. – Conversely, early training determines pruning practices in later years. A poorly trained tree will require substantial pruning to remain productive.

– Light and air penetration is a critical factor; shaded areas will produce small fruit of poor quality, develop spurs that become unproductive and eventually necrotic. Dense foliage acts as a carbohydrate sink and an excellent environment for plant pests.

Slide 27: Thinning vs. heading cuts (self-explanatory; primarily a function of apical dominance and auxin levels)

Slide 28: Bending to control vertical growth (self-explanatory; primarily a function of auxin accumulation in various portions of the branch)

Slide 29: Pruning of a six year old tree (self-explanatory)

YouTube Pruning Demonstrations http://www.youtube.com/watch?v=DVS4hNFwWUQ http://www.youtube.com/watch?v=h752aNtq_Xw&feature=endscreen&NR=1 https://www.youtube.com/watch?v=1SzDPmAOZKo https://www.youtube.com/watch?v=WZQfbGlzz90 http://www.youtube.com/watch?v=6nAIQfOLyeg http://www.youtube.com/watch?v=bM2fivRR4qY

Slide 30: Just a pretty and humorous picture

References for Today’s Discussion

Pennsylvania Tree Fruit Production Guide – http://extension.psu.edu/tree-fruit-production-guide

Byers, R. E. 2003. Flower and fruit thinning and vegetative : fruiting balance. (Chapter 16). In Apples: Botany Production and Uses, D.C. Ferree and I.J. Warrington, eds. CAB International, Wallingford, UK.

Dennis, F. Jr. 2003. Flowering, pollination and fruit set and development. (Chapter 7). In Apples: Botany Production and Uses, D.C. Ferree and I.J. Warrington, eds. CAB International, Wallingford, UK.

Ferree, D.C. and J.R. Schupp. 2003. Pruning and training physiology (Chapter 14). In Apples: Botany Production and Uses, D.C. Ferree and I.J. Warrington, eds. CAB International, Wallingford, UK.

Forshey, C.G. Training and pruning apple trees. Cornell Cooperative Extension Publication/Info Bulletin #112. http://eap.mcgill.ca/CPTFP_7.htm.

Jackson, K.E. 2003. The growing of apples and pears (Chapter 1). In Biology of Apples and Pears. Cambridge University Press, Cambridge, UK.

Jackson, K.E. 2003. Apples and pears and their relatives (Chapter 2). In Biology of Apples and Pears. Cambridge University Press, Cambridge, UK.

Luby, J.J. 2003. Taxonomic classification and brief history (Chapter 1). In Apples: Botany Production and Uses, D.C. Ferree and I.J. Warrington, eds. CAB International, Wallingford, UK.

Marini, R. P. Training and pruning apple trees. Virginia Cooperative Extension Publication 422-021. http://www.pubs.ext.vt.edu/422/422-021/422-021.html

Marini, R.P. Physiology of pruning fruit trees. Virginia Cooperative Extension Publication 422- 026. http://www.pubs.ext.vt.edu/422/422-025/422-025.html

Training and Pruning Fruit Trees (AG-29). North Carolina Cooperative Extension Service. http://www.ces.ncsu.edu/depts/hort/hil/ag29/html

Webster, A.D. and S.J. Wertheim. 2003. Apple rootstocks (Chapter3). In Apples: Botany Production and Uses, D.C. Ferree and I.J. Warrington, eds. CAB International, Wallingford, UK.