include the 3 survival mechanisms of plant pathogens in the absence of the host

1. Survival Mechanisms of Plant
Pathogens
&
Disease Management

2. Disease Triangle
Source: http://www.finegardening.com/10-ways-keep-your-garden-healthy

3. Survival mechanisms of pathogens
1. Survival by means of specialized resting structures
2. Survival as saprophytes
3. Survival in vital association with living plants
4. Survival in association with nematodes and fungi
5. Survival in association with insects
6. Survival on agricultural materials
7. Survival on surface water

4. Survival on agricultural materials
• Some pathogens can survive,
• Inside air dried tissues of diseased plants, establishing
an epiphytic population
• as dried slime on machinery or containers.
• e.g. :
Clavibacter michiganensis subsp. michiganensis
(causative agent of bacterial wilt and canker of tomato)
• survive in air-dried conditions for 7
to 8 months on the surface of
wooden stakes and boxes or wires
• Survive for 15 months in air-dried
tissues of diseased tomato plants.
Source: http://bacmap.wishartlab.com/organisms/512

5. Clavibacter michiganensis subsp. Sepedonicus
(causative agent of potato ring rot)
• survive and remain
infectious on potato
bags, barn walls,
machinery and other
equipment.
• Survives inside of an
infected tubers
Source: http:// www.pinterest.com/pin/515169644851653467

6. Disease Management
• Using disinfectants ,such as quaternary ammonia, chlorine,
iodine or phenol-containing compounds applied to equipment
and other contaminated surfaces.
• Removing or isolating diseased crops debris can be helpful to
reduce the rate of infection
• Burial of diseased debris is often useful along with crop
rotation

7. Survival in association with insects
• Facilitate transmission from one host to another
• No harm to the insect act as carriers / vectors
• Lives in a symbiotic relationship
Pathogen protection from adverse weather
conditions
Insect supply digestive enzymes

8. Most of the pathogens do not reproduce inside the vector
e.g.
1) Erwinia amylovora honey bee
Fireblight
2) Pectobacterium & Dickeya sp. Fruit flies
soft rot plant tissues

9. Some pathogens multiply within the host
e.g.
Pathogen vector
1). Xylella fastidiosa
leaf hopper
2). Ca. liberibacter
psyllid

10. • Multiply in the gut & the salivary glands.
through wounds
Pathogens Plant
inside the insect due to biting, chewing, piercing

11. Disease management by controlling the
insect/vectors
Chemical control
• insecticides
• horticultural oils e.g. stylet oil
• insect repellents
Resistant crop varieties
• Resistance that prevents feeding or repels the insects can prevent
transmission of pathogens spread by feeding
cultural control
• elimination of weed hosts of vectors
• Adjusting planting dates can minimize crop exposure to vectored
pathogens

12. Survival of plant pathogens on surface water
• Till contact the specific host
• Inoculum-Individual itself
• Stage of life cycle (E.g.: Vegetative body, Dormant
mycelium, Asexual Spores, Sexual spores ) capable of
causing disease
• Vectors
 Bacteria
1. Erwinia carotovora
2. Xanthomonas campestris
Erwinia carotovora
Source:
http://www.usu.edu/westcent/microstructure_food/E
rwinia.htm

13. • Viruses
Tomato bushy stunt virus
zoospores of Olpidium virulentus - vector of the
lettuce big vein virus
• Fungi
Phytophthora species (oospores,
zoospores)
Olpidium virulentus (zoospores)
• Nematodes
Individuals Ditylenchus hemicycliophora
Cysts Heterodera
Olpidium virulentus
Source:
https://www.paceturf.org/phot
o/member-galleries/p1585-
olpidium.html

14. Management Of Pathogens
 Using Resistant crop varieties
 Treatment of waste water
 Treat the water - slow sand filtration ,
using Heat, ultraviolet light, ozone, and
chlorination
 Improve water drainage
 Using other varieties of crops
 Chemotherapy( E.g. fungicides)
Fungicides
Source:
http://pnwhandbooks.org/plantdisease/pesticide-
articles/fungicides-disease-control-home-landscape
Slow Sand filtration
Source: http://greendesert.org/sandfilter.html

15. Reference:
• Hong, X. C. and Moorman, W. G. (2005). Plant Pathogens in Irrigation Water. Challenges and
Opportunities-Critical Reviews in Plant Sciences.24-3: 189-208.
• http://pnwhandbooks.org/plantdisease/pesticide-articles/fungicides-disease-control-home-
landscape (18.09.2015)
• http://greendesert.org/sandfilter.html (19.09.2015)
• http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/pythium (19.09.2015)
• http://www.usu.edu/westcent/microstructure_food/Erwinia.htm (19.09.2015)
• https://www.paceturf.org/photo/member-galleries/p1585-olpidium.html (19.09.2015)
• http://www.apsnet.org/edcenter/intropp/pathogengroups/pages/bacteria.aspx
• (19.09.2015)
• http://www.eppo.int/QUARANTINE/bacteria/Clavibacter_m_sepedonicus/CORBSE_ds.pdf (
19.09.2015)
• Gleason,M.L., Barun,E.J., Carlton,W.M. and Peterson,R.H. 1991. Survival and Dissemination of
Clavibacter michiganensis subsp.michiganensis in Tomatoes. Journal paper J-14244 of the Iowa
Agriculture and Home Economics Experiment Station 81: 1519-1521.
• http://www.finegardening.com/10-ways-keep-your-garden-healthy (19.09.2015).