1	Plant Health Management for Backyard Apple Plantings
2	"Prepared by" Prepared by Mike Ellis Professor and Extension Specialist and Omer Erincik Graduate Research Assistant Department of Plant Pathology The Ohio State University OARDC/OSUE Wooster, OH, 44691
3	Early Season Diseases of Apple Apple scab Cedar apple rust Powdery mildew These diseases develop in the orchard between bud break and early to mid summer. Control measures for these diseases need to be conducted during this period.
4	Apple scab Symptoms: On leaves: Velvety olive-green spots with unclear margin appear on the leaves. Later, the lesions enlarge, and become darker with more distinct margins. Heavily infected leaves become distorted and drops early in the summer. On fruit: Spots are similar to those found on leaves. Spots darken with age and become black and “corky” or “scabby”. Scabs are only skin deep. Cracks often develop on these scabby areas.
5	Apple scab Disease Development: Caused by the fungus Venturia inaequalis. The fungus overwinters in the previous year's diseased leaves that have fallen under the tree. In the April, May and June, the fungus produces millions of spores in the old leaves on the ground. These spores are shot into the air and carried by the wind or splashing rain to young leaves, flower parts and fruits. A free film of water on leaves and fruit is required for the spores to germinate and infection to occur.
6	Cedar-apple rust Symptoms: On upper side of the leaves: Pale yellow or orange spots appear during May or June. Small black fungal fruiting bodies (pycnia) form within the spots and may exude an orange fluid. On lower side of the leaves: During late spring and early summer,yellow spots develop on the underside of the leaf. Within these spots a number of small, orange-yellow tubular projections (aecia) appear. Infected leaves may turn yellow and drop. Defoliation of rusted leaves is most common in dry summers.
7	Cedar-apple rust Symptoms: On Fruit: Similar yellow-orange spots appear, usually at or near the calyx end. These spots are much larger than the spots on leaves. The tube-like aecia may form on the slightly raised fruit lesions. Infected fruits are often stunted and misshapen, and may drop early.
8	Cedar-apple rust Disease development: Caused by the fungus Gymnosporangium juniperi-virginianae. The fungus overwinters as mycelium in galls on juniper or cedar. Large yellow to orange gelatinous sporehorns are formed on the galls in the spring and spores (teliospores) are produced. Each teliospore germinates and produces four to eight sporidia or basidiospores.
9	Cedar apple rust Disease development: Sporidia are carried by wind to nearby apple leaves, fruits, and twigs where they penetrate the cuticle and lesions develop on the upper leaf surface and on fruit. After 10 to 14 days, the orange to black pycnia develop in the spots on the upper leaf surface. Several weeks later, the aecia form on the under leaf surface. The aecia produce another type of spore (aeciospores) that are carried by wind to junipers or cedars, where they cause infections resulting in galls; thus, completing the disease cycle.
10	Powdery mildew Symptoms: Small, whitish patches of fungal growth appear and quickly cover the entire leaf. Diseased leaves become narrow, crinkled, stunted and brittle. Infected blossoms shrivel and produce no fruit. By mid-summer, tiny, black round specks (fungal fruiting bodies) show up on the surfaces of the infected areas. Fruit symptoms are not usually seen unless the disease has built up to high levels on susceptible cultivars. Diseased fruit have a fine network type surface blemish called russetting.
11	Powdery mildew Disease development: Caused by the fungus, Podosphaera leucotricha. The fungus overwinters as mycelium in terminal buds and twig tips infected during the previous year. As buds break dormancy, the powdery mildew fungus resumes growth and colonizes developing shoots causing primary infections. The powdery white appearance on infected shoots consists of many thousands of spores which are responsible for spreading the fungus later in the growing season. Powdery mildew infections occur when the relative humidity is greater than 90% and the temperature is between 50-77 degrees F. Free water is not required for infection.
12	Management of Early Season Apple Diseases Free water (wet conditions) is required for most fungal pathogens to infect plants. Any practice that promotes faster drying of fruit and foliage is beneficial for disease control. Site selection Select a site with good air movement all-day sun light, and good soil drainage. Do not plant trees in shaded areas.
13	Management of Early Season Apple Diseases Canopy management Control timing and amount of nitrogen fertilizer to prevent excessive growth. Prune out and destroy all dead or diseased shoots and limbs while trees are dormant (mid-March is usually a good time). Prune healthy growth to improve air movement and sunlight penetration, to minimize shading and decrease drying time of leaves and fruit during the growing season.
14	Management of Early Season Apple Diseases Sanitation Apple scab-Rake and destroy fallen leaves including those from nearby crabapple, before growth starts in the spring. Cedar-apple rust-Remove nearby infected cedars or junipers. If infected plants are not removed, remove all galls in winter or early spring before sporehornes form. These sanitation measures will reduce the number of spores that can initiate these diseases. Fungicides On susceptible varieties, fungicides may be required to obtain an acceptable level of disease control.
15	Management of Early Season Apple Diseases Use of disease resistant apple varieties Several apple varieties have high level of resistance to apple scab, cedar-apple rust and powdery mildew. The following varieties have good resistance to all three diseases and are ideal for backyard production. Using these cultivars should eliminate the need for fungicides to control the early season disease complex. Early season varieties: Redfree, Prima, Jonafree, Sir Prize Mid-season varieties: Novamac, Liberty, Freedom Late-season varieties: Enterprise, Goldrush Other disease resistant varieties are available.
16	Management of Early Season Apple Diseases Use of disease resistant apple varieties Most other apple varieties, including most commercially grown varieties are susceptible to all three early season diseases; however, they differ in their degree of susceptibility. Information on these varieties and their level of susceptibility to various diseases is available in “selected literature for backyard fruit production and plant health management” provided at the end of this presentation. Use of varieties with high levels of susceptibility will probably require some level of fungicide use for control of the early season diseases. Avoid using highly susceptible varieties.
17	Late Season or “Summer” Diseases of Apple Sooty blotch Fly speck Black rot White rot These diseases develop in the orchard from shortly after petal fall through harvest; therefore, they are often referred to as “summer diseases”. Control measures for these diseases need to be conducted during this period.
18	Sooty blotch and Fly speck Symptoms: Sooty blotch: Brown to dull black, sooty blotches form on the fruit surface. The fungus is restricted to the outer surface of the fruit, and in many cases the blotches can be easily rubbed off. Fly speck: Groups of 6 to 50 or more black and shiny round dots appear on the surface of the fruit. Like sooty blotch, fly speck infections are superficial; however, they are usually harder to rub off than sooty blotch.
19	Sooty blotch and flyspeck Disease development: Pathogens: Sooty blotch ….Caused by a complex of several fungi Fly speck… Caused by the fungus Zygophiala jamaicensis Both pathogens overwinters on wild plants, especially brambles in or near to the orchard. In spring, they produce large numbers of spores on their wild hosts. The spores are then spread by splashing water or wind blown mists into orchards from late May or early June until fall. The conidia infect apple twigs and fruit under cool, humid weather conditions (optimum 65 degrees F).
20	Black Rot and Frogeye Leaf Spot Symptoms: On fruit: Black Rot At first, a light brown spot form on the fruit. With time, the spots enlarge and commonly develop a series of brown and black concentric bands or rings. The rotted fruit finally turns black. The decayed tissue remains firm to leathery, and holds its original shape until the entire fruit is rotted.
21	Black Rot and Frogeye Leaf Spot Symptoms: On leaves: Frogeye leaf spot Round to irregularly lobed spots develop a light brown-to-gray center surrounded by one or more dark-brown concentric rings and a purple margin giving it a "frogeye" appearance. Black pycnidia may develop on the upper surface in the centers of the older leaf spots. On branches: Small, slightly sunken, reddish-brown areas develop in the bark. These areas slowly enlarge and darken to form cankers. Cankers may continue to expand a little each year, and may extend down the limb for 3 feet or more.
22	Black Rot and Frogeye Leaf Spot Disease development: caused by the fungus, Physalospora obtusa. The fungus overwinters in cankers, mummified fruits, and the bark of dead wood. In the spring, the fungus produces spores on these previously infected plant parts. The heaviest release of spores occurs around blossom time, but the production of spores may continue during wet periods throughout the summer. Leaf infection usually occurs during the petal-fall period. Fruit infection can occur as early as petal fall; however, symptoms are usually not visible until mid to late-summer as the apple approaches maturity. A film of free water on plant surface and temperatures of 75-80 degrees F are favorable for spore germination and host infection.
23	White Rot Symptoms: On fruit: At first, small, reddish-brown spots appear around the lenticels. The spots enlarge and become slightly depressed. On yellow-skinned varieties, these spots may be bordered by one or more red "halo" rings. The tissue under the spots is soft and the rotted area is egg shaped. On branches: Small, circular spots or "blisters" appear on the twigs in June and July. The spots enlarge, become somewhat sunken, and fill with a watery fluid. Infected areas are slightly sunken and eventually form dark colored cankers.
24	White Rot Disease development caused by the fungus Botryosphaeria dothidea. The fungus overwinters on living and dead cankered limbs and in rotted fruits. In the spring, the fungus produces spores in these previously infected plant parts. The spores are rain-splashed or blown to other parts of the tree during rainy periods. Wounds or breaks in the epidermis are necessary for the fungus to penetrate. Apple fruits may become infected fairly early in the season, but fruit rot does not develop much until the fruit is almost mature. At temperatures above 75 degrees F, mature fruit may rot completely within a few days after infection.
25	Management of “Summer” Diseases (Sooty blotch, Fly speck, Black rot, and White rot) Free water (wet conditions) is required for these fungal pathogens to infect plants. Any practice that promotes faster drying of fruit and foliage is beneficial for disease control. Site selection Select a site with good air movement all-day sun light, and good soil drainage. Do not plant trees in shaded areas.
26	Management of “Summer” Diseases Canopy management Control timing and amount of nitrogen fertilizer to prevent excessive growth. Prune trees annually during the dormant season (mid-March is usually a good time). Opening up to tree canopy results in improved air movement and sunlight penetration . This reduces shading and decreases drying time of fruit and foliage. Remove wild hosts Remove and destroy nearby wild or neglected apple trees. Wild brambles (raspberry and blackberry) serve as a reservoir for sooty blotch and fly speck and should be removed.
27	Management of “Summer” Diseases Sanitation – Black rot and White rot Prune out and destroy all dead wood, cankers, and black rot mummies. Fungicides Especially if fruit rots are a problem, fungicides may be required to obtain an acceptable level of disease control. Special Note: Since sooty blotch and fly speck are superficial and rarely affect fruit quality, removal of the fungus by washing, rubbing, or pealing fruit results in fruit that is acceptable for cooking or eating fresh.
28	Other important Diseases of Apple Phytophthora Crown and Root Rot Symptoms: Above ground Infected trees may decline slowly over one or more years, or they may collapse and die rapidly. On declining trees, leaves are small and chlorotic (yellow) when compared to leaves on healthy trees. On trees that decline gradually, a reddish or purple discoloration of the leaves often occurs in autumn, while leaves on healthy trees remain green.
29	Phytophthora Crown and Root Rot Symptoms: Below ground A diagnostic reddish-brown discoloration of the inner bark and wood can be observed on the crown or main roots of infected plants. A sharp line separates the reddish-brown (diseased) and white (healthy) portion of the crown.
30	Phytophthora Crown and Root Rot Disease development: caused by several species of the fungus Phytophthora. The fungus overwinters and persists in soil for many years. The fungus requires extremely wet or saturated soils in order to infect and cause significant damage; thus good soil drainage is important for control. When soils are saturated, the fungus produces spores, called zoospores. Zoospores use flagella to swim to susceptible plant tissue where they cause infection. The longer the period or periods of soil saturation, the greater the risk of infection. Some species may also be introduced to the orchard on contaminated planting stock or through movement of contaminated soil.
31	Management of Phytophthora Crown and Root Rot Proper site selection Plant in well-drained soil. Select a site that does not have a previous history of problems with collar rot. Use disease resistant rootstocks Pears are resistant to collar rot. Collar rot resistance in various apple rootstocks: Resistant…………………M-2, M-4, M-9, Ottawa Moderately resistant…….M-7, M-11 Susceptible……………….M-26, MM-106 Highly susceptible………..MM-104
32	Fire Blight of apple and pears Symptoms: Blossoms become water-soaked and turn brown. Infected twigs become blighted, turning brown on apple and black on pear. The end of the branch may bend over, resembling a shepherd's crook . Blighted leaves remain attached to the dead branches throughout the summer. The bark sometimes cracks along the margin of the infected area on longer branches causing a distinct canker. Fruit may be blighted. Rotted areas turn brown to black. Droplets of milky tan-colored bacterial ooze may be visible on the surface of diseased tissue.
33	Fire Blight Disease development: Caused by the bacterium, Erwinia amylovora. The bacteria overwinter in living tissue at the margins of cankers on the trunk and main branches. The bacteria become active in the spring . Their growth is favored by rain, heavy dews, and high humidity. A single active canker may produce millions of bacteria, enough to infect an entire orchard. The bacteria in droplets of ooze are spread by splashing rain or insects (mostly bees, flies, and ants) to open blossoms. Invasion can occur directly through natural openings, such as lenticels and stomata, under conditions of prolonged rain and high humidity.
34	Management of fire blight Pruning Prune out blighted twigs and cankers during the dormant season. This may decrease the pathogen inoculum level for the following season. If blighted twigs are pruned out during summer, cuts should be made l2 to l5 inches below diseased wood and pruning tools should be disinfested by dipping in a 2:10 solution of household bleach in water after each cut. Proper fertilization Excessive nitrogen fertilizer and heavy pruning will promote vigorous growth of succulent tissue which is more susceptible to fire blight. Avoid excessive use of nitrogen fertilizer and apply fertilizer only in the spring. Control insects Sucking insects create wounds through which fire blight bacteria can enter.
35	Management of fire blight Apple Moderately resistant: Jonafree, Melrose, Northwestern Greenings, Nova, Easygro, Prima, Priscilla, Quinte, Red Delicious, Redfree, Sir Prize, Winesap. Moderately susceptible: Dutches, Empire, Golden Delicious, Haralson, Jonagold, Jonamac, Jerseymac, Liberty. McIntosh, Minjon, Northern Spy, Novamac, Spartan Highly susceptible: Beacon, Cortland, Fuji, Gala, Granny Smith, Idared, Jonathan, Lodi, Monroe, Mutsa (Crispin), Paulared, Roma, Beauty, Wayne, Wealthy, Yellow Transparent.
36	Using Fungicides For Apple Disease Control Fungicides are very important for disease control in commercial apple production, and may be required in backyard apple production if highly susceptible varieties are grown; however, the emphasis for disease control in backyard apple production should be placed on the use of disease resistance and the various cultural practices previously mentioned.
37	Using Fungicides For Apple Disease Control If diseases such as apple scab, cedar-apple rust, powdery mildew or fruit rots become established in the planting, fungicides may be required in order to obtain acceptable fruit quality. There are a few fungicides available for homeowners that should be useful in backyard apple plantings.
38	"For backyard growers that do..." For backyard growers that do wish to use fungicides in the disease management program, fungicide recommendations are available for apples in Bulletin 780 “Controlling Disease and insects In Home Fruit Planting”.
39	Selected literature for backyard fruit production and plant health management: Bulletin 591. “Growing and Using Fruit at Home” Bulletin 780. “Controlling Diseases and Insects in Home Fruit Planting” “Midwest Tree Fruit Pest Management Handbook” These can be obtained through your county extension agent or the Extension Publications Office, The Ohio State University, 385 Kottman Hall, 2021 Coffey Road, Columbus, Ohio, 43210-1044
40	"To get more information about..." To get more information about plant diseases visit the websites below. http://www.ag.ohio- state.edu/~plantdoc/extension.php http://www.ohioline.ag.ohio-state.edu