Plant Diseases and Insect Pests

1. Plant Diseases and Insect Pests • Disease - any kind of injurious abnormality • Physiological (environment) • Other living organisms (pathogens) • Pathogen - biological agent that causes the injury • Insects • Bacteria • Fungi • Viruses • Nematodes • Miscellaneous

2. Plant Diseases and Insect Pests • Parasite - an organism that derives nourishment from another living organism • Host - an organism that provides nourishment to another • Obligate parasite - organism that can only survive on the living host • Host range - list of several different plants that some parasites can feed off of

3. Plant Diseases and Insect Pests • Bacteria - one-celled organisms that enter through wounds and cause rot • Fungi - multi-celled organisms that either are saprophytes or parasites. Ex: molds, mildew. Cause decay of plants

4. Bacterial rot/wilt

5. Fireblight on an apple

6. Bacterial disease control? • Start with clean pots & potting media & tools • Start with clean seed or healthy transplants • Use drip irrigation or water in the morning so the extra water on the surface of the leaves evaporates by evening • Antibiotics now exist for injecting into trees but treatment is costly and the effects temporary. There are no antibiotic spray treatments.

7. Fungal rots

8. Fungus on foliage

9. Fungal disease control? • Start with clean pots & potting media & tools • Start with clean seed or healthy transplants • Use drip irrigation or water in the morning so the extra water on the surface of the leaves evaporates by evening • Fungicides do exist. They can be used as a liquid drench, spray or powder.

13. Captan & Thiram = synthetic fungicides

15. Plant Diseases and Insect Pests • Viruses - infectious particles made-up of nucleic acids (typically RNA in plants) with a protein coat. In the plant cell, the protein coat comes off and the RNA uses the plant cell to reproduce itself. These are obligate parasites.

16. Virus Tobacco Mosaic Virus

24. No control methods!

25. Plant Diseases and Insect Pests • Nematodes- unsegmented worms that feed on roots and create wounds for bacteria and fungi to enter

26. Nematode damage on tomato

27. Nematode damage on tomato

29. Nematode damage on carrot

30. Foliar nematodes Hosta Zinnia

31. How Plants are Damaged • Damage by: • Direct feeding • Secretion of toxic substances • Secondary organism enters the wound • Symptom- plant’s response to attack (wilt) • Sign- structures produced by the attacking organism (webs, tunnels, etc.)

32. Symptom = wilt

33. Webbing = sign

34. Spread of Insects and Disease • Diseases and insects are spread to plants by: • Water • Wind • Insects • Animals (including people) Ex: TMV • Machinery • Plants are more susceptible to disease and insect attack when they are stressed (water or temperature)