1. 2 To identify plant diseases common to horticulture and agronomic crops. To reveal the impact...
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Transcript of 1. 2 To identify plant diseases common to horticulture and agronomic crops. To reveal the impact...
Objectives
• To identify plant diseases common to horticulture and agronomic crops.
• To reveal the impact plant diseases can have on fruits, plants and agricultural crops.
• To analyze methods of plant disease control.
Disease• Is any condition interfering with normal
growth and development• Is caused by living or non-living agents• Can affect any area on a plant
Disease: Living Agents• Are referred to as plant pathogens
o anything causing harm to plants• Include microorganisms, such as:
o fungio bacteria
Fun Fact : Another term for living agent is biotic agent.
Fungal Diseases• Spread from plant-to-plant via
wind, insects, rain, soil and machinery
• Can be transmitted by seeds• Can be waterborne• Are most common and easiest to
treat• Treatment can include:
o sanitationo reduce wateringo increase air flow
Fungal Diseases• Usually start with spotted or discolored
leaves and stems o dry, brown margins and dead tissue
or necrotic lesions• Are controlled with dusts or sprays• Are nearly impossible to eliminate if not
treated immediately, especially soil-borne disease
Mildews• Are a form of mold• Are commonly found in damp, moist,
shaded places• Affect leaves, stems, buds, flowers and
fruitso leaves will turn pink, blue or purple
and drop prematurely• Are usually white, gray, green or black
Life Cycle of Fungi• Includes four stages:
o spore productiono sporeo spore germinationo hyphal growth
Bacterial Diseases• Are easier to prevent rather than cure• Enter plants through wounds or natural
openings, such as the stomata• Easily occur under the following
conditions:o high humidity o poor air circulationo irregular wateringo poor soil drainageo fluctuating temperatures
Bacterial Diseases• Spread by:
o infected seedso animals and birdso irrigation water and raino machinery
• Have symptoms such as:o leaf spotso blightso wilting
Disease: Non-Living Agents• Include:
o environmental stress on plants, such as:
• air pollution• drought• hail• wind
o cultural careo toxic chemicalso viruses
Fun Fact : Non-living agents are also referred to as abiotic agents.
Viruses• Are microscopic, infectious agents
consisting of a protein coat surrounding nucleic acid
• Multiply in cells of living hosts• Are recognized by the following
symptoms:o leaf curlingo leaf discolorationo ring spots on leaveso stunted growth
Viruses• Can be prevented by:
o planting disease-resistant varieties
o controlling pests carrying viruses
o removing and destroying infected plants
o controlling weedso handling foliage when dry
• Can be spread by:o infected insects, plants and
microorganisms
Fungicides• Are specific pesticides for fungal diseases
in plants• Are used to:
o control fungi in crop standso increase productivity of cropso increase storage life of plants and
produce
Fungicides• Should be applied as soon as symptoms
occur or with coated seeds• Can be applied in the following forms:
o dusto gaso granuleo liquid
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Assessment1. Which area of a plant can be affected by disease?
A. All areasB. Only the stemC. Only rootsD. Only leaves
2. What is another term used when referring to a living agent?
A. Living specimenB. Bacterial agentC. Fungal agentD. Biotic agent
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Assessment3. All but which of the following are treatment methods for fungal diseases?
A. Increasing air flowB. Increasing waterC. Reducing waterD. Sanitation
4. Which of the following can NOT spread bacterial diseases?
A. WindB. Infected seedsC. BirdsD. Machinery
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Assessment 5. What type of disease is the easiest to treat?
A. BacterialB. FungalC. VirusesD. All are equally treatable
Angular Leaf Spot • Scientific Name: Pseudomonas
lachrymans• Characteristics:
o infects cucumbers, melons and squash
o usually appears on fruit in middle stage of development
Angular Leaf Spot o causes small, saturated areas to
develop on stems and fruit• areas appear tan, but turn
gray and white as disease progresses
o forms holes in leaf as dead tissue falls off
o causes lesions between water-saturated veins
Angular Leaf Spot • Environmental conditions:
o humidityo strong windo splashing watero infected irrigation water
Angular Leaf Spot
• Prevention methods:o choose plant varieties suitable for
climateo practice crop rotationo destroy infected plants o avoid overhead watering systemso provide proper amounts of fertilizer
Angular Leaf Spot • Treatment methods:
o fungicides which contain:• copper hydroxide-based, such
as Champion®, Kocide® 101 and Bordeaux® mixture
Bacterial Blight
• Scientific Name: Xanthomonas campestris
• Characteristics:o affects a variety of crops, such as:
• lima beans• soybeans• snap beans
o forms saturated spots on leaves• spots turn pale-green or yellow
then dark-brown
Bacterial Blight o causes leaves to die and fallo causes stems to wilt as disease
progresses• Environmental conditions:
o high humidityo wet weather
Bacterial Blight • Prevention methods:
o use crop rotationo provide space for air circulationo use seeds from non-infected plantso avoid handling plants when wet
Bacterial Blight • Treatment methods:
o fungicides which contain:• copper hydroxide, as found in
Champ® or Kocide® 200
Bacterial Leaf Scorch • Scientific Name: Xylella fastidiosa• Characteristics:
o commonly affects trees, such as:o elmo mapleo walnut
o dries leaves outo turns margins browno affects outer leaves severely
Bacterial Leaf Scorch • Prevention methods:
o deep root systemso prune regularlyo water regularly
• soil should be deeply watered
• fertilize trees of low vigor
Bacterial Soft Rot
• Scientific Name: Erwinia carotovora• Characteristics:
o affects many vegetable plants, such as:
• carrots• corn• onions• potatoes
Bacterial Soft Rot
o affects potatoes in the following ways:
• tissue becomes saturated and wet
• rotten tubers acquire odor in later stages of disease
Bacterial Soft Rot
o affects onions in the following ways:• symptoms occur inside onion
during storage• infected bulbs are soft and
pale-brown• contaminated onions produce
a foul odor• infected onions have a soft
neck o causes taproots of carrots to decay
and become soft
Bacterial Soft Rot
o affects corn in the following ways:• uppermost leaf tips dry out • decay starts at top of plant and
moves down• stalks turn brown, become
water-soaked and eventually fall over
• produces an odor
Bacterial Soft Rot • Environmental conditions:
o warm weathero humidityo high level of soil moistureo insect wounds
Bacterial Soft Rot • Prevention methods:
o use crop rotationo handle gentlyo mix compost with soil to increase
beneficial bacteria populations• Treatment methods:
o seed treatments which contain:• thiophanate-methyl or
thiophanate-methyl, with the addition of mancozeb, such as Tops® MZ®
Bacterial Spot • Scientific Name: Xanthomonas
campestris pv. vesicatoria• Characteristics:
o irregular spots on tomato plants and pepper leaves
o younger leaves more susceptibleo weakens plantso causes decayo common in midwestern and eastern
United States
Bacterial Spot • Prevention methods:
o use disease-free seedso remove weedso fertilize o use crop rotationo provide space for air circulationo use drip irrigation and soaker hoses
to maintain dry foliageo cover soil with mulcho remove infected plants
Bacterial Spot • Treatment methods:
o fungicides which contain:• mancozeb and copper, such as
Yates™
Bacterial Wilt
• Scientific Name: Ralstonia solanacearum• Characteristics:
o leaves turn brown as disease spreads
o streaking in vascular tissueo causes cucumber and squash leaves
to droopo effects young plants firsto results in plant deatho bacteria clogs vascular system
Bacterial Wilt • Environmental conditions:
o infected insects feed on leaves• Prevention methods:
o plant wilt-resistant varietieso sustain proper plant healtho remove infected plants
Blackleg • Scientific Name: Pectobacterium
carotovorum var. atrosepticum• Characteristics:
o forms dark spots on base of stems and roots in cabbage plants
o plants turn yellow, wilt and dieo spread by rain, wind and human
activity
Blackleg • Prevention methods:
o provide space for air circulationo remove weeds o remove infected plantso use crop rotationo prevent injury to cropo choose resistant cultivars
Crown Gall • Scientific Name: Agrobacterium
tumefaciens• Characteristics:
o occurs on roots and stems of many plants
• most destructive in fruit trees and shrubs
• commonly seen in roses
o forms galls at crown and lateral roots
• galls are one-quarter inches to one foot in diameter
• young are tan and have a soft surface
• mature are black and have a very hard surface
o stunts plant growtho turns leaves yellow or brown
Crown Gall
Crown Gall • Prevention methods:
o avoid plant injuryo avoid contaminated toolso inspect plants carefully and
regularlyo destroy infected plantso plant gall-resistant varieties
Fireblight
• Scientific Name: Erwinia amylovora• Characteristics:
o destroys trees and shrubso common among fruit treeso identified by tan liquid seeping out
of branches and twigs• liquid darkens with air
exposure, called “bacterial ooze”
Fireblight o causes infected flowers to wilt and
turn black or brown • dead, blackened leaves will
cling to branches during springo forms orange-red streaks on barko dries out and kills wood
Fireblight • Prevention methods:
o avoid heavy pruningo monitor trees regularlyo remove infected plants o plant resistant varietieso provide adequate fertilization
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Galls• Characteristics:
o known as cecidiao abnormal tissue growthso formed by microorganisms and
insects• insects cause galls when laying
eggs or feedingo form on buds, leaves, flowers, twigs,
bark and rootso unattractive, but causes no harm
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Gallso appear in two forms: open or closed
• open are formed by insects with piercing mouthparts
• closed are formed by insects with mandibles
• Environmental conditions:o cool, humid weather
Potato Scab • Scientific Name: Streptomyces scabies• Characteristics:
o appears on skin of potato tubers• turns dark brown or black
o forms large circular scabs on potatoes, called “scab lesions”
o usually noticed after harvest or late in growing season
o reduces marketability of potatoes o transmitted by wind and water
Potato Scab
• Environmental conditions:o soil with high organic mattero coarse, textured soilso warm, dry weathero wounded plants
Potato Scab • Prevention methods:
o use crop rotationo do not use compost mixeso keep soil cool and moisto plant disease-resistant varieties
• Treatment methods:o before planting, treat seed tubers
with a seed fungicide which contain:• captan or mancozeb
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Assessment1. On which plant does angular leaf spot NOT occur?
A. CucumbersB. SquashC. MelonsD. Corn
2. Under which environmental conditions does bacterial blight spread?
A. High humidityB. Low humidityC. High temperaturesD. High winds
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Assessment3. Which prevention method is NOT used to prevent bacterial blight?
A. Crop rotationB. Proper irrigationC. Use non-infected seedsD. Provide space for air circulation
4. Which of the following can be used to treat bacterial spot?
A. CopperB. SulfurC. ZincD. Lime
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Assessment5. Which region of the country is bacterial spot most prevalent in?
A. NorthwestB. MidwestC. SouthwestC. South
6. Which environmental conditions are best for blackleg to occur?A. Cool, moist weatherB. Warm, wet weatherC. Cool, dry weatherD. Warm, dry weather
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Assessment7. Which part of the plant is affected by crown gall?
A. LeavesB. ThornsC. RootsD. Fruit
8. Which plant is crown gall commonly seen in?
A. RosesB. Bermuda grassC. Oak treesD. Pine trees
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Assessment9. How does gall harm the plant?
A. Wilts leavesB. Destroys fruitC. Removes fluidsD. Causes no harm
10. Potato scab is usually noticed when?
A. Before plantingB. During plantingC. During growthD. After harvest
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Final Assessment1. Which type of diseases can be waterborne?
A. FungalB. BacterialC. ViralD. Non-living
2. Environmental stress on a plant is what type of pest?
A. Non-livingB. ViralC. FungalD. Bacterial
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Final Assessment3. Which type of disease is commonly found in damp, moist and shaded areas?
A. BacterialB. FungalC. VirusesD. Mildews
4. Which symptom is NOT caused by bacterial diseases?
A. BlightsB. Leaf spotsC. MildewsD. Wilting
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Final Assessment5. Under which environmental condition does angular leaf spot occur?
A. Dry climatesB. Strong windC. Cold weatherD. Standing water
6. Which tree is NOT commonly affected by bacterial leaf scorch?A. ElmB. PecanC. MapleD. Walnut
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Final Assessment7. Which of the following is NOT a characteristic of bacterial soft rot?
A. Foul odorB. Tissues become saturatedC. Leaf tips dry outD. Bacteria clogs vascular system
8. How can bacterial wilt be treated?
A. FungicidesB. Proper irrigationC. Crop rotationD. No treatment available
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Final Assessment9. On which part of the plant does fireblight cause orange-red streaks?
A. LeavesB. FruitC. BarkD. Roots
10. How can galls be treated?
A. Remove by handB. Herbicides C. FungicidesD. No treatment available
85
ResourcesBiggs, A. R. & Hickey, K. D. (1997). Apple Scab. Retrieved from http://www.caf.wvu.edu/kearneysville/disease_descriptions/omapscab.html
North Dakota State University. McMullen, M. & Stoltenow, C. (May 2002). Ergot. Retrieved from http://www.ag.ndsu.edu/pubs/plantsci/crops/pp551w.htm
Cranshaw, W.S. (August 29 2011). Insect and Mite Galls. Retrieved from http://www.ext.colostate.edu/pubs/insect/05557.html
National Arborists. (2011). Apple Scab. Retrieved from https://natlarb.com/html/apple_scab.html
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ResourcesVann, S. Ph.D.(2006) Plant Diseases. Retrieved from http://www.aragriculture.org/diseases/image_library/default.htm
United States Department of Agriculture. Retrieved from http://www.ars.usda.gov/is/graphics/photos/
Kansas Department of Agriculture. Retrieved from http://www.ksda.gov/plant_protection/
Broome, J. C. & Ingels, C. A. Produced by UC Statewide IPM Program, University of California. (January 2011). Peach Leaf Curl. Retrieved fromhttp://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7426.html
87
ResourcesGrove, Gary, Ph.D., Washington State University Extension. Apple Scab. Retrieved from http://gardening.wsu.edu/library/tree005/tree005.htm
Rosenthal, S., Grau, C. & Hudelson, B. (December 28, 2005). Ergot. Retrieved from http://pddc.wisc.edu/factsheets/Full%20Color%20PDF%20Format/Ergot.pdf
Schuster, J. (2011). Cedar Apple Rust. Retrieved from http://urbanext.illinois.edu/focus/cedarapplerust.cfm
Oklahoma State University. Entomology and Plant Pathology. Retrieved at http://entoplp.okstate.edu/ddd/
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ResourcesUniversity of Illinois. Field Crop Diseases. Retrieved from http://cropdisease.cropsci.illinois.edu/index.html
Stack, R. W. & Lamey, H. A. (November 1995). Deciduous Tree Diseases. Retrieved from http://www.ag.ndsu.edu/pubs/plantsci/hortcrop/pp697-1.htm
Lamey, H. A., Ash, C. L., & Stienstra, W. C. (July 1996). Lawn Diseases. Retrieved from http://www.ag.ndsu.edu/pubs/plantsci/landscap/pp950w.htm#fairy
PAN Germany, OISAT. Retrieved from http://www.oisat.org/pests/diseases/viral.html
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ResourcesMcGrath, M.T. (2004). What are Fungicides. The Plant Health Instructor. Retrieved from ://www.apsnet.org/edcenter/intropp/topics/Pages/Fungicides.aspx
Iowa State University, Entomology Department. Retrieved from http://www.ent.iastate.edu/imagegal/plantpath/
University of Kentucky, Department of Plant Pathology. Retrieved from http://www.ca.uky.edu/agcollege/plantpathology/extension/links.html
Byers, J. A. (2006). Gall-Making Insects. Retrieved from http://www.chemical-ecology.net/insects/gallmake.htm
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