Reducing plant stands and killing plants. Reduce photosynthesis, destroy leaf foliage. Damage destroy root systems. Feed of the plant.

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Chad Bridges
5 years ago
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2 Reduce yield potential. Reducing plant stands and killing plants. Reduce photosynthesis, destroy leaf foliage. Damage destroy root systems. Feed of the plant. Reduce end use quality. Visual appearance. Particularly with fruits and tuber rots. Also related to seeds. Impact export potential.

3 Early Blight

4 Scab on apple

5 Plant Diseases

6 Susceptible Host Pathogen No disease No No disease disease Disease Favorable environment No disease No disease No disease

7 The elements Wind Water Soil Infected plant parts Crop residue Seed Insect Vectors Man and other animals Farm equipment Irrigation

8 Seed borne Diseases Bean seed mottle Ergot in barley Soybean mildew Seed potatoes

9 Seed Treatments Germination enhancement Fungicides Insecticides

10 Bacteria Air-borne fungi Soil-borne fungi Viruses Insects Mammals, etc Plant Parasitic Nematodes (Eelworms)

11 Most damaging of all crop diseases, yet easiest to control. Over 100,000 fungal species identified, over 8,000 of these cause disease in plants. Unable to photosynthesize fungi live parasitically. Obligate saprophytes, live only on dead plants. Obligate parasites, live only on live plants. Facultative saprophytes, live on live plants, but can live on dead tissue. Facultative parasites, live on dead plants, but can live on live ones.

12 Disease spread is by spores. Spores are wind spread and can cause epidemics quickly. Spread is usually related to temperature and humidity. Infect through wounds or direct through epidermis. Spores germinate and produce structures called hyphae. Hyphae grow and branch into fungal bodies called mycelia.

13 Downey Mildew (Peronospora parasotica)

14 Key symptoms of airborne fungal disease include: Necrotic symptoms, leaf spots (localized lesions), blights (leaf browning and death), die back (stating at leaf tips), and scab (localized raised lesions). Reduced plant growth, hypertrophy and hyperplasia including clubfoot (enlarged wilts), galls (enlarged plant parts), witches broom (profuse branching), leaf curling. Other symptoms, wilts (vascular), rusts, and mildew.

15 Examples of airborne fungi: Potato early and late blight, wheat, barley & maize rusts, powdery mildew (many crops), cereal smuts, rice blast. Relatively easy to control. Seed fungicide treatments. Foliar applied fungicides. Sanitation to minimize initial inoculation. Resistant cultivars. Crop rotation.

16 Late Blight

17 Barley Powdery Mildew Wheat stripe rust Potato early blight Corn common rust

18 Soil borne fungi are usually of lesser importance compared to airborne fungi. Have all the features of airborne fungi but can be microscopic to large. Their spread through crops is slow and is usually assisted by man. Examples: Potato wart, Brassica club root, many Vertillilium and Fusarium wilts, cereal take-all.

19 Potato - Common scab Sclerotinia Stem Rot Wheat - Take all Banana - Panama

20 Microscopic, prokaryotic organisms. Plant parasitic bacteria usually active in moist and warm conditions. Responsible for decay of plant tissues. Little pathotype differentiation. Slow moving mainly through the soil, usually manassisted. Examples: Potato ring-rot; vascular wilts of many crops; ratoon in sugar cane; cotton blackarm

21 Potato Ring rot Bacterial wilt in corn Bacterial shothole on Prunus Erwinia on potato

22 Viruses are obligate parasites and hence need a host plant to stay alive. Most plant viruses are single strand RNA viruses. Many plant viruses enter the plant via a wound or injury and are vectored and slow moving. Mostly systemic, occurring in the host s phloem fluids. Symptoms include mosaics (light patches on leaves). Seldom kill plants. Examples: Potato virus LR, X, Y; tobacco mosaic, barley yellow dwarf, many clonal fruit viruses.

23 Barley Yellow dwarf Potato Leaf Roll Pea early Browning Blueberry mosaic virus

24 Plant nematodes live parasitically on living plants. Microscopic organism and mostly inhabit the soil. Specific, obligate pathogens with some pathotype differentiation. Important nematodes in crops include: Root knot nematodes (Meloidogyne ssp.) where infected plants develop knots or gals at the infection site. Secondary infection from other diseases is common. Cyst nematodes (Globodera Spp. and Heterodera Spp.) Examples: Potato cyst nematode, cereal stem & root eelworms, sugar beet nematode, wire worms.

25 Potato cyst nematode Root knot nematode Soybean cyst nematode Sugar beet nematode

26 Many insects have wings and so can have a long range. Include both general feeders (several aphids) and specific feeders (wheat Hessian fly, cabbage seedpod weevil). Seasonal, can be limited to a few miles. Defoliate plants, kill whole plants, secondary damage by many insects is later infection by other diseases. Virus vectors.

27 Colorado potato beetle Corn Root worm Cabbage seedpod weevil Aphids

28 Voles & Mice Elk Elk Others

29 Minimize initial inoculation. Disease resistant cultivars. Crop rotation. Seed treatments. Foliar applied pesticides. Green manure crops Soil fumigants.

30 Disease-free Seed Bean seed mottle Ergot in barley Soybean mildew Seed potatoes

31 Final infection Final infection Harvest date

33 Million acres Broadcast Aircraft Soil Placement Fumigation Broadcast Ground

34 Vertical resistance Controlled by a single gene. Results in distinct resistance classes. Resistance is usually absolute (yes or no). Horizontal resistance. Controlled by multiple genes. Results in continuously variable levels of resistance. Usually resistance is not absolute.

35 Black pod spot Alternaria alternata

36 Downey Mildew (Peronospora parasotica) Susceptible Resistant

37 Russian wheat aphid Resistant varieties combine both, antibiosis and tolerance. Resistant plants exhibit less leaf rolling, slower aphid population increase and less reduction in plant biomass.

38 Final infection Final infection Harvest date

39 Using genes from Bacillus thuringiensis to product Bt Toxin in the plant itself.

40 Bacillus thuringiensis (Bt) is a soil bacterium whose spores contain crystalline (Cry) protein. In the insect gut this protein breaks down to a toxin called delta-endotoxin. Toxin creates pores in intestine, an ion imbalance, and paralysis of digestive system.

42 Insect and Virus Control Transgenic potatoes that combine resistance to CPB and leafroll virus or potato virus Y have been developed. Colorado potato beetle

All either Roundup Ready or Liberty Link Resistant Insect Pest Mode Insect Pest Mode EU corn borer *** SW corn borer *** Northern corn borer ** Western corn borer ** Corn earworm ** Full army worm

43 All either Roundup Ready or Liberty Link Resistant Insect Pest Mode Insect Pest Mode EU corn borer *** SW corn borer *** Northern corn borer ** Western corn borer ** Corn earworm ** Full army worm *** Western bean cutworm * Black cut worm * * = single mode; ** = double mode; *** = triple mode RIB = Refuge in bag = % seeds with only herbicide resistance to confuse insects. RIB ranges from 5% in north to 20% in south.

45 Published 1962 by Rachal Carson. Outlined the toxic and environmental effects of pesticides (mainly DDT). Major cause of EPA replacement of DDT by organophosphate and carbamate products.

46 Toxins

48 Environmental

49 Air. Drift dusts, spray droplets. Vapors fumigants (ozone depletors). Water. Leaching, runoff Spills, leaks & back-siphoning. Improper disposal. Other, incl. plants, animals & machinery. Stick to work cloths, shoes, or machinery. Stick to harvested fruits etc.

50 Pesticide Disposal

51 Crop Fungicide Insecticide Herbicide Corn 5% 30% 97% Wheat 9% 3% 97% Soybean 2% 1% 98% Cotton 12% 79% 92% Potato 89% 83% 87% Vegetable 78% 82% 79%

52 Biological control: Encourage natural predators and parasites. Biopesticides. Cultural control: Resistant cultivars; trap crops; intercropping. Cultivation & tillage; crop rotation, timing. Mechanical & Physical control: Screens; traps. Reproductive & Genetic control: Introduce harmful pest genes; mass release of sterile insects. Chemical control: Pesticides used in an appropriate manner; hormones.

53 Harvest & Storage

BREEDING OBJECTIVES DISEASE AND PEST RESISTANCE

BREEDING OBJECTIVES DISEASE AND PEST RESISTANCE 2010 Reduced use of Agricultural Chemicals Must develop biological resistance to pests & diseases BREEDING OBJECTIVES DISEASE AND PEST RESISTANCE Which pests