AN INTRODUCTION TO PLANT DISEASES. Alan Windham Professor, Plant Pathology UT Extension

Transcription

1 AN INTRODUCTION TO PLANT DISEASES Alan Windham Professor, Plant Pathology UT Extension

2 PLANT PATHOLOGY, AN INTRODUCTION Introductory plant pathology is often taught as an undergraduate course at an university over a semester. This introduction to plant pathology is brief by necessity and meant to introduce Master Gardeners to the world of plant diseases. For more information on plant pathology visit our lab s Facebook page, UT Extension publications, and the books mentioned at the end of this presentation.

3 SOIL, PLANT AND PEST CENTER For all your diagnostic needs: soil and plant tissue testing, insect and disease identification ifi i.

4 FOLLOW US ON FACEBOOK Or search for: Soil, Plant Pest Center

5 INFORMATION ON SPPC FACEBOOK PAGE Info about new diseases and insect pests Info about diseases or pests that are active Images and illustrations ti

6 IMAGES Images from past posts. Keep abreast of plant pest activity.

7 WHY STUDY PLANT P PATHOLOGY?? Plant pathology is the study of plant diseases Life on earth as we know it, would not be possible without green plants Directly or indirectly plants provide all of the food onwhich the humanpopulation relies Plants are valuable for shelter, fiber, fuel, ornamentalandlandscape and landscape uses Plant diseases reduce the yield of principal food and cash crops by almost 20% worldwide

8 SOME INFAMOUS DISEASES It s impossible to separate plants from the history and culture of humans

9 IRISH POTATO FAMINE Millions died or emigrated to other countries as a result of the famine. The causal fungus was Phytophthora infestans.

10 POTATO FIELD DEVASTATED BY LATE BLIGHT 170 yrs after the Irish Iihpotato tt famine we still battle the same organism.

11 CHESTNUT BLIGHT Discovered in 1904 in the U.S. Devastating to the American chestnut Research in hopes of developing resistant trees continues Image: American Chestnut Foundation; acf.org

12 AMERICAN CHESTNUTS WERE KING OF THE APPALACHIAN FORESTS The American chestnut made up 1 or every 4 trees in the Appalachian forests. The wood was rot resistant and used for rail fences, poles and furniture. The nuts were invaluable to wildlife and livestock.

13 DUTCH ELM DISEASE Dutch elm disease was introduced on elm logs imported from Europe for furniture veneer in the 1920 s. Elm bark beetles are the vector for the fungus that causes Dutch Elm Disease.

14 DISEASE RESISTANT ELMS Princeton Valley Forge New Harmony * Lacebark elms are also resistant to DED

15 Dogwood Anthracnose Discovered in TN on Flowering Dogwood in the late 1980 s

16 DOGWOOD ANTHRACNOSE HAS BEEN DEVASTATING IN FORESTS Dogwood Mortality in the Appalachian Region, where up to 75% of flower dogwood have been killed in forests.

17 NEW DOGWOODS FROM UT AGRESEARCHR Disease resistant dogwoods released: Applachian Spring anthracnose resistant Appalachian Joy mildew resistant Appalachian Blush mildew resistant Appalachian Mist mildew resistant Appalachian Snow mildew resistant

18 CURRENT THREATS Citrus Greening Soybean Rust Sudden Oak Death Stem Rust of Wheat Citrus Canker Thousand Cankers Disease Boxwood Blight Downy Mildew of Impatiens

19 Thousand Cankers Disease of Black Walnut Wl The discovery of TCD in Knox Co. in 2010 represents the first find in the native range of black walnut in the Eastern U.S. It sent shockwaves through all industries that use walnut nuts and timber.

20 THOUSAND CANKER D DISEASE/WALNUT The TN Department of Agriculture has restricted movement of black walnut lumber and firewood from quarantine areas.

21 THOUSAND CANKERS DISEASE SYMPTOMS AND VECTOR The walnut twig beetle is the vector of the fungus that causes TCD. 1.5mm

22 UT AGRESEARCH UT AgResearch advances science in agriculture and food systems, natural resource management, and family and community sciences.

23 PLANT DISEASES- THE BASICS

24 HOW DO WE DIAGNOSE PLANT D DISEASES?? What is the host? Imagine a healthy plant What plant functions are being disrupted? What plant parts are affected? What are the signs and symptoms of disease?

25 W HAT PLANT PART IS AFFECTED? F UNCTIONS DISRUPTED? Root knot nematode injury on begonia. begonia Deformed roots are inefficient at transporting water and nutrients.

26 COMPARE A HEALTHY AND DISEASED PLANT Hosta August Moon infected with hosta virus X

27 SIGNS AND SYMPTOMS OF DISEASE Symptom damage to the plant eg e.g. leaf spots Anthracnose on switchgrass Signs can we see the pathogen? Brown structures in the leaf spot

28 SIGNS OF DISEASE Fungal structures and spores of Colletotrichum the causal agent of Fungal structures and spores of Colletotrichum the causal agent of anthracnose on switchgrass

29 SIGNS AND SYMPTOMS OF POWDERY MILDEW ON CRAPE MYRTLE Sign white fungal growth on leaves and flowers Symptoms distorted t d leaves and flowers

30 THE PLANT DISEASE STOOL Disease Manage by: Disrupting the pathogen Modifying the environment Altering the physiology or genetics of the host nme ent En nviro

31 PLANT DISEASE MANAGEMENT Avoidance Exclusion Eradication Protection

32 AVOIDANCE This landscape bed was modified by incorporating 4 inches of pine bark into the soil prior to planting azaleas as a means to avoid phytophthora root rot. Choosing a planting location where the pathogen is not present Choosing a planting site not conducive to disease

33 EXCLUSION Legal restrictions and quarantines Propagation of disease free cuttings Production of disease free seed in areas not favorable for disease

34 ERADICATION Removal of pathogens from infested soil and tools Removal of pathogens from infected seed or plant parts Removal of infected plants Steaming soil to eradicate root knot nematode

35 PROTECTION Cultural control Biological i l i lcontrol Chemical control Genetic resistance Knockout rose is resistant to black spot and cercospora leaf spot

36 DISEASE CONTROL WITH FUNGICIDES Fungicides protect healthy plants Fungicides protect new, flushes of shoots or roots Fungicides do not cure sick plants!

37 CONTROL OF POWDERY MILDEW ON DOGWOOD Dogwood on the right was sprayed once a week for six weeks prior to the onset of powdery mildew with copper octanoate (copper soap). Untreated Copper Soap

38 HOW DO WE KNOW WHAT ORGANISMS CAUSE D DISEASE?? Koch s Postulates Robert Koch was a German scientist that conducted breakthrough research on anthrax and cholera. Associate a pathogen with a diseased d plant Isolate the pathogen in culture Inoculate a healthy plant and reproduce symptoms Isolate the pathogen again

39 KOCH S POSTULATES FOR DOGWOOD ANTHRACNOSE

40 WHAT ARE THE CAUSES OF D DISEASE?? Fungi Bacteria Nematodes Viruses Parasitic plants Abiotic Factors