Diagnosing plant problems

1. Diagnosing plant problems Megan Kennelly Assistant Professor Plant Pathology Kansas State University January 2007 Garden center training Topeka www.ipmimages.org, Fetzer

2. Problems in the home garden *Environmentalstress *Nutritional deficiency *Chemical injury *Insect damage *Infectious Disease: fungi, viruses, bacteria, nematodes

3. Before you can manage it… … you need to know what it is Needless spraying costs time, money, and exposure to chemicals

5. Insects (arthropods) • Chewing • Beetles, caterpillars • Piercing/sucking • Aphids, leaf hoppers • Beneficials!

6. Infectious agents: pathogens Viruses Bacteria Fungi Nematodes most microbes are not pathogens

7. caused by noninfectious factors: weather stress nutrient deficiency chemical injury soil factors (pH, salts) Abiotic stress

8. These stressors are often related Some insects spread diseases Some insects are attracted to diseased plants Some insects are attracted to stressed plants Drought stressed plants more susceptible to wilt diseases

9. 1) Plant Diseases 2) Insects 3) Abiotic problems 4) Diagnostic Process

10. Diseases: Symptoms & Signs Symptom Expression of a disease by the plant Sign Visible presence of a pathogen

11. Cornell Symptoms Leaf spots Galls Branch dieback & Canker Wilt

12. Signs: pathogen structures

13. Microscopic signs

14. Pathogens attack different tissues • Leaves: spots, dieback • Root: rot • Crown: rot • Stem: rots, galls • Shoots: cankers, dieback • Whole: wilts • Wood: decay

15. Pathogen groups • Viruses • Bacteria • Fungi • Nematodes

16. Ring spots Viruses Veinal chlorosis Mosaic & distortion Mottling & distortion

17. Insect-vectored viruses • Have you seen insect damage? • Have you seen insects? • Did damage show up all at once, or gradually? • What is the spatial pattern?

18. Gerber Thrips damage: flecking, thrips, when blew into plant thrips came out Maybe a virus, might be just thrips damage

19. Hosta Virus X ‘Gold Standard’ ‘Sum and Substance’ ‘Striptease’ (hosta of the year in Wichita)

20. HVX Cultivars • Breakdance, Eternal Father, Kiwi Watercolours, Leopard Frog, Lunacy, Parkish Gold • Kansas Dept of Ag assumes these are ALL infected

21. Bacteria Many symptoms: leaf spots wilts rots galls blights cankers sticky ooze

22. Fungi and fungal-like • Most fungi dispersed by spores • Thread-like growth • Many kinds of symptoms

23. Rusts • Host specific • Often alternate between two hosts • Rust fungi produce millions of airborne spores hollyhock

24. Leaf Spots (can be bacterial or fungal) Bacterial: water soaked, yellow halo Fungal: grey/tan, with specks Sanitation, sprays Resistant cultivars

25. Botrytis (grey mold) Starts on dying tissue *Sanitation *Air flow *Sprays Roses at KSU garden

26. Powdery Mildews • Host specific • Reproduce by spores

27. Fruit Diseases Grape – black rot Apple – sooty blotch Apple - scab Peach - scab

28. On the “fruits” of vegetables, too

29. Wilt Diseases • Pathogen systemically colonizes water conducting system • Infections usually result in mortality • Whole plant affected

30. Insects can also cause wilting Look for boring holes, eggs, frass

31. Root Rots • Primarily caused by fungi and fungal-like organisms • Often found in wet soils/poor drainage

32. Wood Decay in Trees Usually tree stressed, injured

33. Trunk and branch cankers

34. Nematodes • Microscopic worms • Parasitic nematodes have stylet. • Most live in soil/roots. • Root deformity, stunting, yellowing, general decline • Present in all soil • Most are beneficial

35. Pine Wilt of Scots Pine Nematode

36. Management of diseases • Resistance • Cultural • Don’t plant in problem areas • Don’t plant difficult plants • Make site unfavorable to disease: spacing, staking, water management • Chemical: identify, treat early, choose appropriate material, read label carefully for rate, dilution, etc

37. Insects • All the good things they do: • Silk, honey, beeswax, pollination, eating weeds, controlling bad insects, part of food chain… • Damage: (less than 1%) • Eat plants! Spread viruses!

38. Leaf chewers Greenstriped Mapleworm, U of Missouri Tomato hornworm

39. Spider Mites: bronze color Clemson University - USDA Cooperative Extension Slide Series, , www.ipmimages.org Put down a piece of white paper, and tap branches, leaves Could resemble nutrient deficiency?

40. Fruit chewers Tomato fruitworm= corn earworm

41. Piercing, sucking insects Aphids Clemson University - USDA Cooperative Extension Slide Series, , www.ipmimages.org

42. Eggs, larvae, boring holes Will Hudson, University of Georgia, www.insectimages.org Use a knife or razor blade to cut into tissue. Cross sections and longitudinal

43. Frass

44. Eggs, hatched eggs From Tennessee Extension But, it could be a beneficial…

45. Leaf miner damage http://entweb.clemson.edu/cuentres/cesheets/veg/ce103.htm

46. Insect management • Proper ID • How many are there? • Physical removal • Chemical sprays: right chemical, right dose, right time

47. Abiotic stresses Don’t spread from plant to plant (not infectious) Causes • Adverse environment • Mechanical and chemical injury • Adverse soil conditions • Soil structure • Soil fertility **Can predispose to biotic disease, insect

48. Cold Damage • Early spring, late fall frosts • Low temperature injury during winter • Sunscald damage bark damaged by freezing/thawing in late winter

49. Heat and Drought

50. Transplant Stress Slope, no water