Common Peach Diseases. Jane E. Stewart Plant Pathologist Colorado State University

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1 Common Peach Diseases Jane E. Stewart Plant Pathologist Colorado State University

2 Colorado climate inhibits some pathogens, and other pathogen behave differently Foliar Peach Diseases Brown rot Peach leaf curl Shot hole* Powdery mildew* Stem/Root Peach Diseases Armillaria root rot* Phytophthora root rot Cytospora* *Important Colorado Diseases

3 Brown rot Fungal pathogen: Monilinia fructicola No. 1 disease in Southeast, but widespread in US Hosts include: Prunus spp. Typically occurs in areas with high moisture Polycyclic disease Chavez, UGA

4 Brown Rot Symptoms Blossom blight, twig and dieback and fruit rot Some infections are symptomless until fruit ripens Symptoms may occur while in storage PNWhandbooks.org

5 Identification of Brown Rot Mummy berries Sporulation Look for apothecia in winter/early spring in moist areas If found, infections are likely to be high Intermountainfruit.org APSnet.org; Sanoamuang & Ganut

6 Disease Cycle of Brown Rot Protective fungicides to prevent new infections Spring Summer and Fall Protective fungicides to prevent new infections Protective fungicides to prevent new infections Winter M. Ellis, OSU

Control insect damage and wounding Post harvest: cool

7 Management for Brown Rot Sanitation: Remove infected fruits Limits inoculum current and next growing season Control insect damage and wounding Post harvest: cool fruit rapidly after harvest Short soak in 122F water APSnet.org

8 Chemical Management for Brown Rot Fungicides are the best option Sterol Inhibitors: Indar, Elite, Pristine and Gem Iprodione: Rovral Spring application Copper or sulfur Spray at full rate and coverage at pink bud, full bloom and petal fall Wet conditions: 7-10 days post Rotate fungicide classes Populations are becoming resistant to sterol inhibitor fungicides

9 Peach Leaf Curl Fungal pathogen: Taphrina deformans Hosts: Peach, plum, nectarine, almond Can defoliate trees early in the season Found throughout the US

10 Symptoms of Peach Leaf Curl M.A. Hansen, VA Tech

buds or twigs New Infections on young leaves Summer and Fall Healthy

11 Disease Cycle of Peach Leaf Curl Protective fungicides to prevent new infections Spores penetrates host tissues Spring Spores overwinter on buds or twigs New Infections on young leaves Summer and Fall Healthy and diseased peach Spores on infected leaf and fruit Winter Spores Agrios

12 Management for Leaf Peach Curl Fungicides are the most effect method of control A single application before buds begin to swell can control disease for a season Can also apply chemicals in dormant season Ferbam, Ziram, Chlorothalonil, or copper

13 Shot hole blight Fungal pathogen: Thyrostoma carpophilum (Wilsonmyces carpophilus) Hosts: Peach, apricot, cherry Common in Intermountain West Intermountainfruit.org Polycyclic disease

14 Symptoms of shot hole Intermountainfruit.org

Disease cycle for shot hole Fungus overwinters in infected buds and lesions on small

survives in buds and twigs until wet weather returns In fall and winter, spores are

Utah State University Extension Summer In spring, spores are disseminated via wind/rain

15 Disease cycle for shot hole Fungus overwinters in infected buds and lesions on small shoots Protective fungicides to prevent new infections Fall In warm, dry weather fungus survives in buds and twigs until wet weather returns In fall and winter, spores are produced during wet condition s Winter Spores can infect healthy tissues. Utah State University Extension Summer In spring, spores are disseminated via wind/rain Protective fungicides to prevent new infections Spring Later in spring, spores infect fruit Utah State University, Extension

16 Cultural Controls Summer rain and sprinkler irrigation promote fruit infections, when fruit is wet for longer periods of time If orchard is sprinkler irrigated, reduce canopy wetness by adjusting sprinklers Prune cankers and remove/burn infected branches

17 Chemical controls for shot hole Similar to leaf peach curl and brown rot Bordeaux mixture, Boscalid, Chlorothalonil, Azoyxstrobin In orchards with a history, spray at leaf fall to protect against twig infections Spring applications during bloom and wet conditions to prevent fruit and leaf infections.

18 Powdery Mildews on Peaches Fungal pathogens: Podosphaera pannosa Infects peach and rose Podospharea leucotricha Infects apples and peaches Polycyclic disease Obligate pathogen Utah State University, Extension

19 Symptoms of Powdery Mildew Yellowing or distorted leaves Stunted shoot growth Reduced yield Powdery residue on leaves and fruit Utah State University, Extension

20 Identification Conidia Cleistothethia Apsnet.org

21 Disease cycle of Powdery Mildew Overwinters on in buds, as buds expand, infection occurs on young leaves Sporulation occurs usually at night with relative humidity is higher Spore germination occurs when temperatures are between F. H. Larson APSnet.org

22 Management of Powdery Mildews Provide good circulation by pruning for increase airflow between trees Full sun exposure Use lower levels of nitrogen less succulent, young growth Remove nearby rose for peach powdery mildew Do not plant peaches next to susceptible apple varieties Gala, Jonathan, MacIntosh, Rome Beauty H. Larson

23 Chemical Control for Powdery Mildew Conventional: Azoxystrobin (Abound), boscalid + pyraclostrobin (Pristine), thiophanate methyl (Topsin) Organic: Potassium bicarbonate + horticultural oil, sulfur based Spray early spring (7-10 days) until symptoms are moderate Alternate chemicals to prevent fungicide resistance H. Larson

24 Stem/Root Peach Diseases Armillaria root rot* Phytophthora rot Cytospora* *Important Colorado Diseases

25 Armillaria Root Rot Fungal pathogen: Armillaria mellea Hosts: Many hardwoods Persists on decaying roots and debris, infects new Occupies large areas Guido Schnabel

26 Humongous fungus

27 Symptoms Height growth is reduced Thin crown Yellow leaves Sap on the root collar Reduced root system Circle of diseased trees

28 Identification Honey mushrooms Mycelial Fans Rhizomorphs

29 Conditions that promote disease Poorly drained soils and excess irrigation Furrow irrigated orchards Areas of lower elevation a field Planting new stock in the same areas Rootstock Working Group, rootstocks.net

Cultural Management Options Avoid excess watering Armillaria can exists for many years; Sanitize to remove diseased roots before replanting Avoid

30 Cultural Management Options Avoid excess watering Armillaria can exists for many years; Sanitize to remove diseased roots before replanting Avoid wounding roots; Shade exposed crowns from sunburn Root collar excavation to expose crowns to air and to limit spread to the stem Keep trees healthy

31 Root collar excavation Guido Schnabel, Clemson University

32 Phytophthora Root Crown and Collar Rot Caused by pathogens: Phytophthora cactorum and Phytophthora spp. Hosts: Peach, apple, cherry, apricot T. Burr, Cornell Soilborne pathogens

33 Symptoms of Phytophthora Root Rot Stunted growth Scorched leaves, dry leaves that remain on tree Reduced root system Circle of diseased trees T. Burr, Cornell

34 Identification of Phytopththora root rot Oospores of P. cactorum, Cating et al M. Murray, UT

35 Disease cycle of Phytophthora root rot Optimum temperature 50-60ºF Several hundred oospores can be produced per inch length of infected root!! Penetrate root Swim to the root tips optimum temperature 50-64ºF In soil and roots resistant structure Wolfgang Oßwald et al. 2004

36 Management of Phytophthora Root Rot Avoid excess watering, especially in the fall and spring. Good temperatures for fungal infection and less use by the tree Plant trees on a good site. Good drainage and evenly sloped Plant trees shallow on a mound Move easily on nursery stock so ensure clean material Select resistant root stocks Soil drenches of mefenoxam (Ridomil Gold)

37 Cytospora Canker Caused by Cytospora spp. Common on all stone fruits and many other tree species (urban and forests) Associated with stress (drought, ph, cold damage) Most significant disease in Colorado peaches

Cytospora Disease Cycle Fungus grows in bark tissue open wounds, buds Kills by girdling branches or trunk of tree through and can can also enter Alan Biggs Attacks tree during conditions when

38 Cytospora Disease Cycle Fungus grows in bark tissue open wounds, buds Kills by girdling branches or trunk of tree through and can can also enter Alan Biggs Attacks tree during conditions when temperatures are warm and moisture is available Trees affected by drought, late spring frosts, insect and fungi defoliation, sunscald, herbicides, or mechanical injury are susceptible to Cytospora infection

39 Survey of Orchards Estimated incidence and severity of Cytospora in major peach production areas of Western Colorado March/April 2015 Conducted in Grand Valley, North Fork and Olathe areas Focus on gathering data from a widespread area and range of orchard management

40 Methods Surveyed by orchard and variety Recorded presence/absence for every 10 th tree Counted and rated infection severity for every 50 th tree Interviewed growers Collections of Cytospora isolates K. Kimbrough

Surveyed: Results 200 acres 42 varieties 2-32

2 (range 0-27) Potential relationships between

41 Surveyed: Results 200 acres 42 varieties 2-32 year old orchards (11 yr mean) 100% of orchards surveyed infected (mean 75% infected) Ave number of infections per tree was 5.2 (range 0-27) Potential relationships between practices and infection, but are inconclusive at this time

42 Species differ biologically Three species have been identified on peach within the US: Cytospora leucostoma Cytospora paraleucostoma Cytospora cinctum Only 1 species has been identified in Colorado Cytospora leucostoma

43 Symptoms of Cytospora canker Larson & Pokharel

44 Identification of Cytospora

45 Disease cycle Leaf scars, damaged buds Crotches with narrow branch angles Unhealed pruning stub Shaded winter damaged twig Humid, wet Conidia spread by rain; germinate and infect injured and dead tissues, expands as cankers Poorly healed wound Fungus persists and forms fruiting structures in dead wood and cankers Canker rings formed by infection and host callus formation Biggs and Grove 2006.

46 High inoculation levels correlated with high rainfall events (Watapo, WA) Grove and Biggs Plant Disease

47 Spread of spores from cankers Maximum spread 2 ft from rain splash More inoculum further at angles higher than 90 degrees from canker Rain splash is important for inoculum spread Are there long distance spread mechanisms? Wind Insects Humans Grove and Biggs Plant Disease

48 Healthy trees To help a tree resist infection: Prepare soil before planting Fertilize, water properly for winter and summer Avoid injury to the trunk and limbs Prune correctly Slow growth in Fall: Fertilize in late winter or early spring Avoid excessive nitrogen fertilization, which causes vigorous growth Trees need to harden off in fall to prevent cold-injury

49 Management Tools Manage tree stress Remove cankers Pruning Reduce inoculum levels Pruning Chemical treatments

50 Chemical Management options Stephan will present these!

51 Summary foliar fruit diseases

52 Summary soil borne pathogens Armillaria Root Rot Avoid excess watering, sanitize sites before replanting, avoid wounding roots, root collar excavation method, keep trees healthy Phytophthora Root Rot Avoid excess watering, plant trees on a good site, plant shallow on a mound, use clean nursery stock, resistant cultivars in available, drench with mefenoxa T. Burr, Cornell

53 Questions?

Optimizing Peach Disease Management

Optimizing Peach Disease Management David Ritchie, 2015 North Carolina Peach and Nectarine Disease and Pest Management Guide Information = data, facts, news, Example: tree growth stages, disease, when