Diseases of Horticultural Crops. Shubin K. Saha D.P.M., Ph.D., Extension Vegetable Specialist Department of Horticulture University of Kentucky

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1 Diseases of Horticultural Crops Shubin K. Saha D.P.M., Ph.D., Extension Vegetable Specialist Department of Horticulture University of Kentucky

2 A disease can be Non-infectious (abiotic) P deficiency Infectious (biotic) Pythium aphanidermatum (Edson) Fitzpatrick

3 Non-Infectious Often too much or too little problems Factors include- water heat fertilizer/nutrients pesticides Leaves of a pepper plant affected by a somatic mutation are an example of a non-infectious problem.

4 Boron deficiency-muskmelon Non-infectious

5 Hollow Heart - Watermelon Non-infectious

6 Lightening strike

7 Ethylene damage Notice the epinasty (down turned leaf petioles)

8 INFECTIOUS DISEASES Living agent Biotic (parasites)

9 Susceptible Host Conducive Environment Pathogen

10 Susceptible Host Disease Conducive Environment Pathogen

11 Parasites-any organism that obtains nourishment at the expense of another living organism. Plant Pathogen-biotic agents such as fungi, bacteria or viruses that cause plant disease. Plant disease-interaction between host and the environment that results in an abnormal condition.

12 Infectious agents include: Fungi Bacteria Virus Nematodes Higher plants

13 Parasitic fungi Saprophytic fungi

14 Examples of fungal pathogens

15 Damping-off Infection versus infestation-seedling above is infected soilless mix above is infested.

16 Greenhouse sanitation-transplant trays Used unwashed Transplant tray Used washed Transplant tray

17 Downy Mildew Pseudoperonospora cubensis (Berkeley & Curtis) Rostovtsev

18 Downy Mildew on cucumbers

19 Late blight of tomato (and potato)

20 Late blight of tomato

21 hyphae spores Fungus that causes late blight of tomato

22 mycelia White mold of tomato

23 bacterium

24 Examples of bacterial pathogens

25 Bacterial Wilt Cucumbers

26 bacterial spot of tomato

27 Sanitation-bacterial canker

28 Virus particles

29 Examples of viral pathogens

30 Aphid vector Zucchini yellow mosaic virus pumpkin

31 Zucchini yellow mosaic virus pumpkin

32 Zucchini yellow mosaic virus pumpkin

33 Examples of nematode pathogens

34 A nematode has: Digestive organs Reproductive organs Excretory structures Muscles Nerves Tough skin or Cuticle

35 Root knot nematode muskmelon

36 Examples of parasitic higher plant

37 Dodder muskmelon Mistletoe

38 Integrated Pest Management (IPM) A multi-tactic approach to mitigate a crop disorder in the most economical manner using pesticides as a last option. Examples of IPM Scouting for pests Insect thresholds Weather based disease forecasting Variety Selection (Host Resistance) Planting Densities (air movement and leaf wetness) All of the above

39 Calendar-based schedule: every 7 days. 8 fungicide applications per year. Weather-based disease forecaster-apply fungicides according to weather conditions. 6 fungicide applications per year.

40 Insect thresholds-only apply insecticides when a the number of pests/damage reaches a specific number. Corn earworm larvae on sweet corn Example-apply treatment for corn earworm when more than 10/moths caught per night.

41 Disease management strategies using the disease triangle

42 Manage the host-disease resistance Watermelon hybrids vary in host resistance to Fusarium wilt

43 Manage the pathogen- Sanitation Clean propagation materials quarantines Seeds may harbor plant pathogens

44 Manage the environment- Fall tillage Crop rotation Planting date Rotate to an agronomic crop like field corn between horticultural crops.

45 Questions to ask. What is the crop and production system? Plasticulture? High Tunnel? What is the size of the planting? What is the age of the crop? What are the signs/symptoms?

46 Questions to ask. What percentage of the planting is showing symptoms/signs? What portion of the individual plant is affected? Fruit? Foliage? Roots? Have any fungicides already been used? If so, when and what? What kind of sprayer is available and what is max pressure (PSI)?

47 Questions? Contact: Shubin K. Saha

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