This document discusses the biotic and abiotic causes of plant diseases. The major biotic causes are fungi, bacteria, viruses, nematodes, and phytoplasmas. Fungi are the largest pathogen group and reproduce via spores. Bacteria are unicellular and reproduce by binary fission. Viruses can only be seen with an electron microscope and reproduce by taking over a host's reproductive machinery. Nematodes are parasitic worms that reproduce via eggs. Phytoplasmas are wall-less bacteria that live in the phloem and reproduce by binary fission.

1. Plant Health Care Bacteria, Virus and minor Pathogens

15. Bacterial Leaf Spot

17. Bacterial Soft Rot Erwinia carotovora

20. Bacterial Wilt

31. Fire blight

36. Bacterial ooze

39. Tulips with a virus

45. Mosaic

48. Mosaic Watermelon

49. Tobacco Mosaic Virus

50. Tomato Curly Top Virus

52. Tomato Curly Top Virus

59. Phytoplasma – Aster Yellows

60. Phytoplasma – Aster Yellows

63. Phytoplasma – Carrots

64. Phytoplasma – Fasciation in Maple

67. Root Knot Nematode

69. ID from Photographs Part I Bacteria