PLPA 301
Abiotic pathogen
- non-living pathogen cause non-infectious (not transmissible) diseases. - caused by: 1) Too high or too low temperatures. 2) Soil moisture (too much or too little). 3) Lack or excess of light (too much or too little). 4) Air pollution. 5) Nutrient deficiencies. 6) Mineral toxicities. 7) Soil acidity or alkalinity (pH). • note: soils around us are around 8.3 and the water is about 8.6 8) Toxicity of pesticides (soil pollution). 9) Improper cultural practices.
what needs to occur for disease to happen
- susceptible host - pathogen capable of causing disease (virulent) - environment that will aid disease development
plant disease
- the malfunctioning of host cells and tissues that results from their continuous irritation by a pathogenic agent or environmental factor and leads to the development of symptoms - a harmful deviation from the normal functioning of the physiological processes. - note: says nothing about specific cause, symptom, or loss of money
Phytophthora infestans deatails
- this pathogen produces both sexual and asexul • sexual: oospore • asexual: zoospores and sporangium spores (one is produced from another) - two mating types one is male and ones is female - only when male and female occur together can they reproduce sexually - antheridium (male) and oogonium (female)
Mycoplasmas
- type of prokaryote that lacks a nucleus, some organelles, and a cell wall (cell wall is present in bacteria but its very different from fungi) and were confused with viruses until the mid 1960s - phloem inhabiting
how many people are estimated to be on the planet by 2050 and how much more food will we need to satisfy the population?
- 9 billion - we will need to produce 40-60% more food
Last recorded epidemic of late blight
- Germany, 1916. (700,000 dead): WW1 is going on and copper fungicides had been discovered but coppers was being used for weaponry (copper bullets) instead
Koch's postulates (est a causal role for a microorganism in disease): overview
- Robert Koch (1843-1910) German microbiologist, awarded Nobel Prize in Physiology or Medicine for his tuberculosis findings - worked on Anthrax disease of sheep (anthrax bacterium is large and could be seen w/ microscopes back then) - wanted to prove anthrax bacterium was the cause of disease - developed a scientific method to test the role of a specific microorganism as a casual agent of disease
The greater the scale of agriculture production
- The easier it is for pathogens to spread and cause epidemics. - The more difficult to apply technologies of plant protection.
plant pathology
- The study of the organisms and the environmental factors that cause plant diseases. - The study of the mechanisms by which these factors induce disease in plants. - The study of interactions between the disease-causing agents and the diseased plant. - The study of methods to prevent or control disease or minimize the crop loss. • Plant pathology for plants is what medicine is for humans or veterinary medicine is for animals.
Approaches used in Studying plant pathology
1 ) Basic: Study of diseased and resistant plants to determine: - The effects of disease - The nature of disease. 2) Applied: Identify the most effective control techniques such as development of new pesticides or more resistant germplasm. - Diagnosis, treatment, and cure - Prevention of plant disease.
Modern civilization wants a food or plant products that are:
1) Cheap: low cost of production 2) Abundant: high yielding varieties 3) High quality: taste, color, size, ability to store for as long as possible.
Modern agriculture practices demand (constraints)
1) Dense cropping systems: we still do this even though we know its bad because we want the most yield. 2) Over large areas: "Economy of scale", the bigger the field the easier to manage, huge tractors which you need space to maneuver 3) Genetic uniformity: Monoculture, all plants that you plant in the field are of the same genetic background, it is a problem because they are more susceptible to losing the entire crop
Categories of diseases based on:
- Types of organs they affect and symptoms. - Types of crops they affect - Types of pathogens.
disease agents
- abiotic stress - biotic stresses (pathogenic organisms): viruses, bacteria, fungi, nematodes and parasitic plants.
What is easier to kill a eukaryote or a prokaryote
- complex eukaryotes have many different organelles within the cell so there are many things to target which makes them easier to kill (the more sophisticated you are the more susceptible you are) - simple prokaryotes have virtually nothing but ribosomes and DNA so its harder to target something to kill
Major Principles and concepts in plant pathology
- establishing a causal role for a microorganism in disease (Koch's postulates) - most important definitions in plant pathology - the nature of plant disease (concept of disease triangle)
New encounter diseases
- introduced new host to native pathogens OR native host to new pathogen. Have caused many of the most destructive epidemics - the most infamous example of New encounter diseases are human diseases: measles and chickenpox (devastated the American Indians when introduced by Europeans - plant examples include: Chestnut blight (fungal) and Fire Blight of Pear (bacterial), and downy mildew of grape (fungal) - the reason customs is so animate about what you can and can't bring to and from countries
Koch's Postulates
1) Describe the symptoms in detail. - Example = (symptoms) wilting or necrosis. 2) Isolate and purify the suspected pathogen. (culture all pathogens) Describe it, - Example: colony color, how fast growth, spore shape and size. 3) Inoculate healthy plants with purified pathogen. This must reproduce the disease symptoms as described in #1. 4) Reisolate the pathogen. It must be the same as that in #2. - note: some pathogens can not use Koch's Postulates bc they can not be cultured (viruses and obligate parasites)
Categories of diseases based on: types of pathogens
1) Fungal diseases 2) Prokaryotes 3) Parasitic higher plants 4) Viruses and viroids 5) Nematodes
The significance of historical developments in plant pathology
1) Man is completely dependent on plants 2) Every plant species is potentially subject to its particular disease (every plant species is potentially susceptible) 3) causes of plant diseases and methods to manage them has been recognized just recently (within the last 150 years) - most significantly since 1860, since Pasteur and others discovered that pathogens are causes of disease and not its consequence (the causes of pathogens are living microscopic organisms_
Types of interactions
1) Parasitism: one organism takes its nutrients from another, and in doing so causing disease. 2) Mutualism: two organisms living together, in close association, both benefiting from the interaction. 3) Commensalism: two organisms living together, where one derives benefit and the other is not affected. (college student to parents)
Categories of diseases based on: types of organs they affect and symptoms
1) Root diseases 2) Stem diseases 3) Vasculature diseases 4) Foliage diseases 5) Fruit diseases
Plant diseases and human history
1) The Irish potato famine 2) Ergot of wheat and rye 3) Coffee rust in Sri Lanka (Ceylon) 4) Southern corn leaf blight 5) Chestnut blight*
Categories of diseases based on: types of crops they affect and their symptoms
1) field crop diseases 2) vegetable diseases 3) fruit tree diseases 4) forest diseases 5) turf diseases 6) diseases of ornamentals - note: this is how you know who to call if you have diseases, highly specialized fields are often not interchangeable
Types of parasites
1) obligate parasite 2) non-obligate parasite 3) facultative parasite 4) facultative saprophyte
qualities of a pathogen
1) pathogenicity (pathogenesis) 2) Virulence 3) Host specificity (host range) 4) compatible interactions 5) incompatible interactions
Two historically competing theories of causes of diseases
1) spontaneous generation: we have no control over the disease because it is god that is punishing the people for sinning 2) germ theory: first proposed by French scientist Prevost diseases are caused by germs
Types of organisms
1) symbiont: an organism involved in a symbiotic relationship (see mutualism, above). 2) saprophyte: an organism that derives its nutrients from dead organic matter. 3) parasite/pathogen: an organism that derives its nourishment from another, and in doing so causes disease.
Test question: Why is it that if you grow the same tomato strained year after year and it grows just fine until it all of your tomato's are suddenly destroyed. What is the reason for it?
You should never grow a single variety bc if you do and a pathogen infects one of your plants you will lose them all because their is no genetic variance. It also will put pressure on the pathogen if the strain you plant is resistant it is better to have tolerant plants that don't necessarily put pressure on the pathogen to evolve and cause a bust of all your plants that are now susceptible to the evolved strain.
Symptom
a visible abnormality
Irish potato famine, late blight of potato: why was it so severe? -- Lessons learned/summary
Caused by man 1) Imported crop. 2) Imported pathogen. 3) Limited genetic base, therefore, uniform susceptibility. 4) Vegetative propagation: problematic because all propagated tubers and infected tubers were planted and spread the disease 5) Dependent population. - All of it combined with disease conducive environment
Interesting historical facts about ergot wheat and rye
Plant diseases and human history: 1) Witchcraft: accusations correlated with conducive weather, and were concentrated in areas where rye is grown as a staple food. 2) Peter the Great: halted on his way to capture Constantinople when his troops and horses ate ergotted grain. 3) Potato replaced rye as the major food crop of the poor.
Irish potato famine, late blight of potato: why was it so severe? -- Environmental conditions
Plant diseases and human history: A) Cool, moist conditions accelerate the rate of disease development. B) Summer of 1845 started out hot and dry C) Weather changed: 1.5 to 7°C degrees below normal D) Continuous overcast and rain for 6 weeks. E) Accelerates pathogen life cycle by nearly 10X F) Within a few weeks the potato crop of Ireland was destroyed.
Irish potato famine, late blight of potato: why was it so severe? -- Genetically uniform crop (agricultural practices)
Plant diseases and human history: A) Few potato species collected in South America. B) Fewer yet returned to Europe in an intact state. C) Selections were made from the limited variation. D) Vegetative propagation: - Potato seed pieces were used instead of true seeds. The pathogen survives winter in stored potatoes and is therefore comes back in the following year.
Irish potato famine, late blight of potato: why was it so severe? -- The pathogen Phytopthora infestans
Plant diseases and human history: A) Imported form S. America B) Hosts: potatoes and close relatives but in S. America, the broad genetic base of the host provides natural resistance. (because there was a larger variety of pathogens and hosts in S. America the devastation was never as bad as it was seen in Ireland)
Irish potato famine, late blight of potato: why was it so severe? -- Host, potato
Plant diseases and human history: A) Native to Andean highlands (Peru and Bolivia). - Staple food for Indians since 400 BC. - Native Indians cultivated it, and the Incan city of Matsupitsu, a potato breeding station. B) Imported to Europe by Spanish conquistadors (approx. 1570). C) Widely Accepted in Europe by 1800's. - Highly nutritious. - Easy to grow. - Higher yield compared to cereals.
Irish potato famine, late blight of potato: why was it so severe? -- Dependent population in IRELAND (social conditions)
Plant diseases and human history: A. Potatoes grew well in cool moist climate...similar to climate of the Andean Highlands. B. Similar nutrition value as grain crops but only on half the land. Peasants paid their rent in grain crops and ate the potatoes. C. By 1845, no significant food alternative existed. - note: (peasants consumed 8-14 lbs a day)
Coffee rust in Ceylon (Sri Lanka): Host and Pathogen
Plant diseases and human history: Host: Coffee = Coffea arabica Pathogen: Fungus and know its an obligate parasite
Southern Corn Leaf Blight: Host and Pathogen
Plant diseases and human history: Host: Corn = Zea mays Pathogen: Cochliobolus heterostrophus - Race T
Ergot of wheat and rye: host and pathogen
Plant diseases and human history: Host: Wheat, rye oats Pathogen: Claviceps purpurea
Irish potato famine, late blight of potato: impact on the science of plant pathology
Plant diseases and human history: Proving that the oomycete caused the disease 1) The P. infestans pathogen: visible as a white mildew on the leaves and stems of infected plants. - Common perception: excess water caused the disease. 2) Anton de Bary experiments
Coffee rust in Sri Lanka (agricultural conditions)
Plant diseases and human history: economy of scale: coffee grown over 400,000 acres (no effective control) - can't cultural fungus in petri dish so theres no control
Tillet 1755
Scientist in France showed that he could increase smut on wheat plants if he added smut dust to seed and reduce it if he pretreated the seed with copper sulfate - he believed incorrectly that smut dust was poisonous but copper sulfate was a major breakthrough
Host specificity (host range)
The ability to cause disease on only a limited number of plant hosts. In crop species, _______ ______ of the pathogen can be very specific, and even restricted to certain cultivated varieties.
virulence
The degree of pathogenicity.
ergot
french word for spur. It reduces yield because seeds or kernels are replaced by sclerotia
sclerotium
fruiting fungus body, is host plant dependent. Tend to be 1-5x larger than the host seed. Thus the largest ergots are found in large seeded plants such as cereal rye
pathogenicity (pathogenesis)
the ability of the parasite to interfere with one or more of the essential functions of the plant and thereby to cause disease.
Robigus
the rust god that the early Romans and Robigalia sacrifice red dogs and sheep to to prevent rust diseases of grain crops such as wheat
condispores
windblown or splashed by water to fresh plant tissue in the spring (penetrate the tissue directly, producing enzymes or will look for natural opening like stomata
Obligate parasite
A parasite that can grow only in association with a living host. Can not be cultured (can't be used in Koch's postulates)
non-obligate parasite
An organism that can survive either as a parasite or a saprophyte (an organism that consumes dead organic material for food).
facultative saphrophyte
An organism that is primarily a parasite but can be a saprophyte
Pathogen
Anything that causes disease: 2 types - Abiotic (non-living) ___________ cause non-infectious (not transmissible) diseases. - Biotic (living) ____________ are infectious (transmissible). - note: may also be called a causal agent, but environmental factors are not casual agents
Stem diseases
Disease based on types of organs they affect and symptoms: - Cankers: localized necrotic (dead, usually dark brown to black) areas associated with death of the phloem - Galls: hyperplasia (increase in numbers of cells). - Witch's broom: parasitic plants
Foliage diseases
Disease based on types of organs they affect and symptoms: - Chlorosis: vein clearing, mottling - Leaf blights, leaf blasts, leaf spots
Root diseases
Disease based on types of organs they affect and symptoms: - Rots: discoloration and decay due to disintegration and decomposition of tissues. • the plants are normally susceptible to pathogens, bc they have a single gene that is hijacked by the pathogen, the pathogen can not attack the gene if the gene is gone (need to look at both resistance genes and susceptibility genes) - Damping-off: seedling death just prior to (pre- emergence) or just following emergence (post- emergence) from the soil. Don't over water
Vascular diseases
Disease based on types of organs they affect and symptoms: - Wilt: when transpiration exceeds absorption of water and turgor in cells is lost - note: potatoes normally come from Idaho because they are susceptible to fungal wilts
Fruit diseases
Disease based on types of organs they affect and symptoms: - rots - spots, scurf, sunscald, etc
Fungal diseases
Disease based on types of pathogens: - Eukaryotes that have membrane bound nucleus and mitochondria - by far the largest category of disease-causing agents in plants (in humans its bacteria) - They are living organisms that do not have chlorophyll and cannot utilize the energy of the sun to manufacture their own food. - Must obtain food from a substrate. • has to be living in living or dead organism - Most are microscopic, usually filamentous, branched, and produce spores. • only group of pathogens that produce spores and fungi - Have cell walls that contain chitin, glucan, cellulose. • if you want to kill it you need to know what its made of - Number is huge, and they are grouped in a complex classification system.
Nematodes
Disease based on types of pathogens: - May be defined as unsegmented roundworms - soil inhibiting and microscopic nearly, internal organs, muscular systems, nerve centers, and digestive systems • note: they move in water by their muscles but can't move more than a meter per year - not related to other worms, classified uniquely
Viruses and viroids
Disease based on types of pathogens: - Most viruses consist of a single strand of RNA surrounded by a protein sheath (=nucleoprotein), a few are double stranded RNA or DNA. - Usually designated by the disease symptom they cause and plant they effect, e.g., tobacco mosaic virus. - Can only multiply in living cells, measured in nanometers. - viroids are low molecular weight RNA without a protein sheath
Prokaryotes
Disease based on types of pathogens: - Two types: bacteria and mycoplasmas, lack nucleus and some organelles - More important as pathogens of man and animals, but there are a number of serious plant bacterial diseases. - All are microscopic and most are unicellular (some form chains). - No nuclear membrane, no mitochondrial DNA or visible endoplasmic reticulum. - Some are limited to growing in the vascular tissues, phloem or xylem = fastidious bacteria. • note: can't culture these bacteria
Parasitic higher plants
Disease based on types of pathogens: - dodder, mistletoe - Degree of parasitism varies, some have chlorophyll and require only water and inorganic nutrients while others lack chlorophyll and require sugars from plants.
inbreeding depression:
continued selfing of the hybrid progeny gives declining yield (if you continue to inbreed the yield will eventually decrease) -- how inbred lines are developed
Why do we study plant pathology?
Estimated 36.5% of crops worldwide are lost annually ($550 billion) due to diseases, insects and weeds: -14.1% are caused by diseases (total annual crop loss of $220 billion) - 10.2% are caused by insects - 12.2% by weeds • this doesn't include losses from environmental factors
Irish potato famine: Late blight of potato: host and pathogen
Plant diseases and human history: - Host: Solanum tuberosum (potato: not the only host to this pathogen: tomato, eggplant, pepper) - Pathogen: Phytopthora infestans (oomycete) • phyto=plant; pthora=killer
Anton de Bary
German botanist that proved a pathogen was the cause for Irish potato famine (first person to show that is was a microbial organism to cause disease) - experiment: the infected plant appeared to have mold on the leaf (note: every part of the plant can be effected). It was thought that over watering caused for mold to grow easier. In Anton's experiment he grew both healthy and infected plants in a control environment (moist and cool), then collected the white mildew from the infected plant and was able to infect the original healthy plant. - known as the father of modern plant pathology - Major break through for understanding how plant and animal diseases are initiated: set the stage for Pasteur's Germ Theory in 1863 - experiment: it was believed that cold temp and a lot of water caused the mildew like structures so he had to prove the environment wasn't the cause so he isolated fungus on petri dish and created favorable environment (low temp high humidity) had a control plant (not infected) and infected plants and was able to tell prove that
Theophrastus
In 300 BC he wrote a book about diseases of trees, cereals, and legumes. Didn't know what the causes were but though it had to do with a greek god
Germ Theory
One of the two historically competing theories of causes of diseases: - first proposed by French scientist Prevost diseases are caused by germs - 50 years later he repeated Tillet's experiment and found: - microscopic fungal spores infect the plant - reduction of smut after seed treatment with copper sulfate results from inhibition of spore germination - Idea was wildly rejected: people continued to believe that mildews, rusts, rots, and microorganisms found on diseased plants were products of disease rather than the cause
Ergot of wheat and rye
Plant diseases and human history: (Agricultural conditions): not cleaning the seed prior to eating - Consuming infected grain resulted in human disease called the "Holy Fire" or "St. Anthony's Fire" (now called ergotism) - Middle Ages - Hospitals dedicated to St. Anthony took in the sick. • (social conditions) Common among rural poor who used rye for bread. Folk cure was to eat white bread instead of rye bread. (only rich people could eat wheat bread and rye was infected the most - sclerotium was much larger) • Not contagious. Victims: Young and feeble were most susceptible.
is ergot of wheat and rye still a problem?
Plant diseases and human history: (What we learned from this historical plant disease) not anymore because modern seed cleaning methods remove ergots from grain before it is used for consumption
Coffee rust in Ceylon (Sri Lanka): time line
Plant diseases and human history: - 1600's: coffee became popular in England, produced in Ceylon, Java, and Sumatra and imported to England - 1825: British developed all of Ceylon for coffee plantations
Coffee rust in Sri Lanka: Problem
Plant diseases and human history: - Coffee grown over 400,000 acres. - Both pathogen and host were introduced to new location. - No effective control for the fungus. (can't culture it bc its an obligate parasite) - One rust pustule (a little colony) on leaf can contain 150,000 spores. - One leaf can have hundreds of pustules.
Coffee rust in Sri Lanka: result
Plant diseases and human history: - Coffee production dropped: 100 million pounds in 1870 vs 5 million pounds by 1889. - The plantations were replanted to tea. - The English drink tea.
Chestnut blight
Plant diseases and human history: - New Encounter Disease (only 1 one the historical events that is bit this one is due to fungi the other is due to bacteria) 1) Destroyed the American Chestnut: 30 million acres 2) chestnut was economically important for wood, food and natural products. - Early 1900's. 1/4 of trees in the Appalachian forests was a chestnut. It was important for rot-resistant wood (most expensive furniture due to resistance against rot), food for humans and animals, and tannins in the tanning industry. 3. The fungus was in N.Y. with chestnut varieties from Asia. Over a 40-year period, the chestnut population was devastated.
southern corn leaf blight: races of the fungus
Plant diseases and human history: - Race O: old race that isn't virulent • Race O is nonspecific to TMS and is produced in small amounts - Race T: virulent on corn containing TMS • produces phytotoxins that specifically affects corn containing TMS - note: both produce phytotoxins
Southern corn leaf bight: environmental conditions
Plant diseases and human history: - Race T is extremely aggressive and has a reproductive cycle of 51 hours - it infects the leaves, husks, and ears - the southern states were hot and moist which was a more conducive environment for the disease to develop - asexually develops when not hot and moist so you avoid spreading spores
Southern corn leaf blight: the genetic weakness
Plant diseases and human history: - all those TMS (Texas Cytoplasm) were susceptible to infection by race T of the fungus and since 80% of all crops were TMS it had devastating effects
Southern Corn leaf blight: how it startedS
Plant diseases and human history: - farmers wanted hybrid corn so they wanted to make the male portion of the plant sterile (less work if they didn't have to manually remove the pollen by detasseling) - in order to make the plant sterile they wanted to use cytoplasmic male sterility: a genetic mutation that causes sterility in the male part of the corn - they ended up getting Texas male-sterile (TMS) cytoplasm: controlled by a mutated gene in the mitochondria (transmitted through female germ line) -- not genetically modified but it was a mutation - no longer a need for detasseling - 1970 80% of US corn crop was TMS
Southern corn leaf blight: agricultural conditions
Plant diseases and human history: - genetic uniformity of crop: planting of a disease susceptible crop variety - (Social conditions) in 1930 we realized that hybrids have higher yields (hybrid vigor) - inbreeding leads to corn varieties
Marshall Ward
Plant diseases and human history: - student of Anton de Bary, sent by british to save the coffee (he couldn't) - Made 2 important contributions 1) Distinguished the most susceptible stage for germinating spores - Disease Forecasting: spray crops based on the weather, not after the spores have already been spread and infected (apply fungicide on leaves before fungus arrives, anticipate) 2) Monoculture over large territories is problematic (agricultural condition)
Irish potato famine, late blight of potato: social and economic impact
Plant diseases and human history: 1) 1 million people dead (1 yr) 2) 1.5 million immigrated to US. (1 million immigrated to Australia) 3) Deepened the rift between Irish and British: British landlords refused to believe that the famine was serious. They still demanded the crop as payment of rent. (Ireland was apart of the English empire, they already didn't like each other to begin with) 4) Protectionist trade laws against imports of US corn repealed. • Import of American corn was allowed to feed the starving Irish with boiled corn mush, 1st time import of corn was allowed - note: late blight is still one of the major diseases of potato today (20% global potato losses) Potatoes are one of the major sources of nutrition in developing countries
Ergot of rye: causes
Plant diseases and human history: 1) Environmental Conditions: cool wet climate of Europe was conductive to disease development 2) Fungal mass, ergot or sclerotia (a grain-like structure or fungal growth), replaces rye grain 3) Fungus produces chemicals that are toxic: Alkaloids 4) Still a problem with domestic cattle 5) disease control- - clean seed, crop rotation (plant a crop that not susceptible to ergot of wheat and eye to prevent it from constantly being present), and deep tillage - sclerotia do not survive more than one year and do not produce spores if they are buried more than 4 inches deep
Irish potato famine, late blight of potato: why was it so severe?
Plant diseases and human history: 1) Host (potato) 2) Dependent population in IRELAND 3) Genetically uniform crop 4) The Pathogen: Phytopthora infestans 5) Environmental conditions
alkaloids produced through ergot wheat and rye
Plant diseases and human history: 1) LSD - Lysergic Acid Diethylamide: Discovered by Dr. Albert Hofmann, a chemist working in Switzerland in 1938. He was looking for circulatory stimulants in extracts from ergot. His book "LSD, My problem child"- story of this discovery and its impact on the world. Was first derived from Ergot mass, used as a treatment for psychiatric disorders and proclaimed as a wonder drug. Medical use became illegal in 1968. Tested by the CIA - revives memories of past experiences, was used as a way to "control mind". 2) Ergotamine: causes muscular contractions and spontaneous abortions - pharmaceutical uses: prevents hemorrhage after birth (contraction of blood vessels) and migraine headaches - some other famous alkaloids: morphine and caffeine
Ergot of wheat and rye: symptoms
Plant diseases and human history: 1) Mental aberrations 2) Hallucinations: feelings of burning skin or insect crawling under skin (thus name "Holy Fire" 3) Women often had Spontaneous abortions 4) Gangrene infections (due to constriction of blood vessels). People lost limbs (fingers, arms, and legs)
southern corn leaf blight: disease control
Plant diseases and human history: 1) Resistant hybrids: available to both races of the pathogen and should be used as the primary means of controlling plant health. 2) Residue Management, crop rotation to a non-host crop: - Pathogen survives in plant debris and burial of this material has proven effective in some instances. - However, there are parts of the country where the fungus can survive on buried debris so a rotation to a non-host crop would be most effective. 3) Fungicide Application. - There are fungicides labeled for the control of southern corn leaf blight and stalk rot. The list includes mancozeb and propiconazole, labeled for field corn, popcorn and sweet corn. Maneb and maneb plus zinc are also labeled for control on popcorn and sweet corn (1997).
compatible interactions
an interaction between a susceptible host and a virulent pathogen that result in disease.
parasite
an organism that has a close relationship with its host and is dependent on its host for its life functions
Facultative parasite
an organism that is primarily a saprophyte but can be a parasite under the appropriate conditions
pathogen
any organism that is capable of producing disease, even if the symptoms can not be felt (or directly witnessed)
whats the most promising control measure?
genetic resistance, but it is time consuming due to reproduction
hybridized corn
higher yielding corn no variety
Biotic pathogen
living pathogen are infectious (transmissible).
inbreed corn
makes variety of corn not as high yielding
challenges for plant pathology
reduced food losses while improving food quality
hybrid seed production
requires preventing self fertilization. Usually done by hand: remove male inflorescence (tassel) from the plant that will serve as the female in the cross
what does Plant Pathology study as a science?
studies plant disease