Managing Tree Diseases in a Changing Climate. Michelle Grabowski

Transcription

1 Managing Tree Diseases in a Changing Climate Michelle Grabowski

2 Recent Climate trends in Minnesota Temperature: Warmer winters Higher minimum temperatures Longer growing season. ~2 weeks longer since Last spring frost occurs earlier

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5 Plant Hardiness Zones

6 Recent Climate trends in Minnesota Dewpoints: Increase in dewpoint Water settles out of air at higher temperatures Longer leaf wetness period

7 Dewpoint Temperatures Greater than or equal to 80 degrees F Since 1996 Dewpoints of 80 F or higher since No history of dewpoints of 80 F or higher prior to or more days - at least one day State Climatology Office - DNR Waters

8 Recent Climate trends in Minnesota Precipitation: increase annual precipitation Up to 20% increase in some areas Rain comes in heavy rain events Flood or drought common 71% more extreme storms in last decade

9 MN Counties designated for federal disaster assistance in 2012 All are associated with drought except those with which designates for flood or severe storm

10 WHY IS THIS IMPORTANT FOR TREE DISEASES?

11 Plant Disease Triangle Environment

12 Effect on the Pathogen Higher temperature = Longer growing season = potential for more life cycles Higher dewpoint = longer leaf wetness periods = increase pathogen reproduction and infection

13 Which Pathogens are Affected? Fungal and bacterial leaf spots and blights Many are polycyclic many lifecycles per year Need free moisture to reproduce and start new infections Longer periods of leaf wetness allow infection over a greater temperature range High temperature and drought can decrease disease

14 Apple Scab Infection At optimal temp. need 6 hours dew hours wetness infection occurs at higher and lower temps Temperature F Hours of leaf wetness Days until symptoms

15 Anthracnose Cool & Wet Fire Blight Warm & Wet Leaf Spots & Blights have Different Temperature & Moisture Requirements Powdery Mildew Dry with High Humidity

16 Make Management Decisions Based on Biology of the disease What conditions favor the pathogen What plant parts are susceptible Current weather Current plant phenology

17 Dothistroma Needle Blight USDA Forest Service, Forest Insect and Disease Leaflet from 1982 recommends: spray pine trees with a fungicide in Mid May and again in July Will this recommendation be effective with climate change?

18 Dothistroma Needle Blight Disease biology Mature needles are susceptible New needles are resistant Need several days of wet, cool (41-77 F) weather to infect Recommendation: If cool wet weather is present, apply a fungicide at bud break and when new needles have reached full length.

19 Year to Year Variability Average temperature is increasing Average growing season is increasing High variability from year to year

20 Hodson s Phenology Records : Dr. A.C. Hodson : Dr. Roger Moon and grad students Recorded flower and leaf emergence for Elm Aspen Apple Serviceberry Lilac Bur Oak Silver Maple P. Wray, ISU M. Pooler, Bugwood.org

21 Fungicide sprays protect susceptible tissue Begin apple scab sprays at half inch green tip Green tip on wealthy apple Avg April 25 Avg April 15 March 17, 2012 earliest on record April 27, 2013 May 4, th latest on record April 12, 2015 UMASS Extension Fruit Advisor

22 HOW DOES CLIMATE CHANGE AFFECT THE TREE?

23 Variable Effect on the Host Plant Northern, boreal species Picea glauca Abies balsamea Pinus banksiana Betula papyrifera Southern, temperate species Populus tremuloides Acer saccharum Acer rubrum Quercus macrocarpa Quercus rubra Pinus strobus

24 Testing Climate Change Dr. Rebecca Montgomery Warmed forest 6F with heat lamps and metal coils in soil Studied 10 native trees and buckthorn Measured growth and photosynthesis

25 White Spruce Balsam Fir Species at WARM range limit grow 20-40% less

26 Maple Oak Buckthorn Species at COOL range limit grow 20-60% more

27 Tree Growth and Climate Change Spruce and Fir grow poorly Oak, Maple and Buckthorn grow better Aspen, Paper Birch, Jack and White Pine had intermediate growth Does not take into account drought stress!

28 HOW DOES THIS AFFECT TREE DISEASES?

29 Opportunistic Pathogens and Stress Related Disease Organisms unable to cause disease in unstressed plants Often survive as a saprophyte or in latent infections Ubiquitous in nature

30 Decline Spiral Stress alters tree Reduced energy available for defense Pathogen uses tree for increased growth Tree becomes attractive to opportunistic pest or pathogen Trees often can recover from a stress event Repeated stress or infection with opportunistic pests = chance of survival May take years for tree to decline

31 J. O Brien, USDA Forest Service ARMILLARIA ROOT ROT J. O Brien, USDA Forest Service

32 Unstressed Oak Produces enzymes that degrade fungal cell walls Produces Gallic Acid inhibits Armillaria growth Keeps reserves as starch Armillaria spp. Infects wounded or dead roots Cannot infect healthy roots Survives as a saprophyte

33 Drought Stressed Oak Reserves changed to glucose and fructose Produces amino acids Defense enzymes fail Armillaria spp. Eats glucose and amino acids like candy Grows 3x faster Eats defense compound Gallic Acid for breakfast Invades and kills healthy root tissue

34 Diplodia Blight Caused by Diplodia pinea Infects 2-3 needle pines Austrian & Scots pine most common in MN Different phases of the disease depending on stress level of tree

35 Diplodia Shoot Blight Expanding shoots, needles, & cones can be infected Conidia released with wet weather Pycnidia form on infected plant parts Rapid development of symptoms

36 Diplodia Shoot Blight In unstressed tree, fungus does not invade 2 year old tissue Not a serious health problem Protect tree from shoot blight with fungicides applied at: bud break when candles are half length when needles emerge from sheath Copper, thiophanate methyl, chlorothalonil

37 In Stressed Trees, Diplodia causes Branch Cankers Stress may be continuous like drought, poor site Or sudden like hail or insect attack Stress allows progression of shoot blight, but also brings out latent infections L.Haugen, USDA FS Bugwood.org J.O Brien USDA FS Bugwood.org

38 Diplodia in Landscape Pines Diplodia pinea found in: 39% of healthy Austrian pines 70% of healthy Scots pines Flowers et al. 2001

39 Management of Diplodia Canker Reduce stress on trees Water, mulch, protect from wounds, manage insect pests Fungicides are ineffective against Diplodia canker USDA FS NC Research Station, Bugwood.org

40 Opportunistic Pathogens of Spruce USDA NCFS, Bugwood.org P. Bachi, UKY D. Fulbright, MSU Rhizosphaera Needle Cast R. kalkhoffii Cytospora Canker L. Kunzei Phomopsis Canker Phomopsis sp.

41 Stress cankers of deciduous trees Valsa Canker Valsa spp. Nailhead Canker Biscogniauxia marginata Coral-spot Canker Nectria cinnabarina

42 Recommendations Fungicides will NOT protect trees from stress related pathogens Prune out cankers before they reach the main stem Pruning Cut

43 Recommendations Plant trees adapted to site conditions and that grow well south of your location Mulch around the base of the tree preferably to drip line with 2-4 layer of woodchips

44 Recommendations Water all trees in times of drought If there has been no rain that week, test soil for moisture Root zone is inches deep Top half of root zone is dry add water Use a lawn sprinkler to water mature trees Water until a metal rod easily goes into soil inches

45 Recommendations Protect trees from wounds Prune out storm damaged limbs promptly Manage insect pests Manage defoliating leaf or needle diseases

46 Summary Use information about disease biology to make management decisions Water trees in times of drought Reduce stress on trees Cityofsalem.net

47 THANKS! Questions? Candeefick.com