Smith, Leon R.

English

Texas A&amp;M Repository

L-1099METHODS FOR CONTROLLING PLANT FOLIAGE DISEASESLeon R. Smith*• Basic Suggestions for Disease Prevention• Plant Protectants and Formulations• EquipmentThe need for chemically controlling plant dis-eases around the home frequently raises questionsabout the kind of chemical best suited for the joband how, when and how often to apply. Failureto obtain satisfactory control generally is due tousing improper materials or application procedures.The following information outlines a dependableapproach with emphasis on methods of applyingplant protectants.Basic Suggestions for Disease Prevention1. Know your plants, their range of soil andclimate adaptation and other specific growthrequirements. Plants growing under en-vironmental stress are disease prone, oftendeveloping diseases that otherwise would notoccur.2. Establish plants highly susceptible to fOliagedisease in areas where air circulates freely.Avoid wetting foliage in late evening whenleaves may remain wet during night hours.High humidity and surface moisture favorsdevelopment of many foliage diseases.3. Consider using disease-resistant varietieswhen establishing new plantings. Localnurserymen and garden enthusiasts can sug-gest varieties best suited to the area thatoffer resistance or tolerance to commonfoliage diseases.4. Identify the cause of a disease problem beforeapplying chemicals. Some foliage diseasesare difficult to control except with specificfungicides. Also, certain non-pathogenicfoliage abnormalities caused by insects, root*Area Extension plant pathologist, Texas A&M University, Overton.7.3• Spraying Plant Foliage• Spraying Lawnsor stem diseases and mineral deficiencies areconfused easily with those caused by fungior bacteria, even though they require differ-ent treatment methods.Professional assistance for plant disease iden-tification is available through all countyExtension offices.5. Anticipate the occurrence of common foliagediseases and apply recommended plant pro-tectants before damage becomes serious. Mostfungicides and bactericides function pri-marily to prevent further disease develop-ment, with little or no ability to eradicatedisease-producing organisms already estab-lished in the host plant.Plant Protedants and FormulationsAll reputable fungicide products carry labelinformation including safety precautions, ingredi-ents and dosage recommendations. If the materialis cleared for use on edible plants or fruit trees, thelabel should give the minimum time limit betweenapplication and harvest. Chemical control recom-mendations often are made in terms of activechemical rather than trade name. When followingprofessional advice, check the label and insist thatproducts contain the suggested chemical ingredi-ents. For convenience in preparing spray mixes,choose products that give dosage information insmall measures such as tablespoons or ounces re-quired per gallon of water.Formulations- Fungicides and bactericides aremarketed in essentially four forms: (1) wettablepowders, (2) emulsifiable concentrates, (3) liquidsin pressurized containers and (4) dusts. Each hasTexas A&M University • Agricultural Extension Service • John E. Hutchison, Dir dor • College Stationits place for u e around the home. Sprays whenproperly applied provide more efficient and longerlasting protection than dusts, yet dusts are easy toapply and generally require less time for coverage.Pressurized cans, usually 1 pint or larger, are con-venient for spraying house plants or specimenplant that require frequent treatment. To preventfoliage burn, avoid spraying in excess or too closeto plants.Wettable powder and emulsifiable co~centrateformulations offer the widest variety of fungicidalmaterials at the greate t economy, but sprayingequipment is required for application. Types ofspray equipment are almost unlimited, but all re-quire thorough cleaning after each use to guardagain t corrosion of metal parts and nozzle stoppage.\Vettable powder formulations may cause cloggingof sprayers, particularly those with a s.mall nozzleorifi e, during the spraying operation. This gen-erally can be overcome by premixing the powderwith a small amount of water to form a thin,smooth paste before mixing in the spray tank.Adding a few drops of liquid household detergenthelps reduce clogging.EquipmentDusters-Dusting equipment is available in allpractical sizes ranging from Y2 to 25 pounds ormore in dust capacity. Small piston or plunger-type dusters are convenient when only a few plantsare involved, but for the most efficient applicationon a large area, continuous flow models of thebellows-operated or hand-crank, rotary type arepreferred. Regardless of type, extension tubes anddust-deflecting accessories are essential for coverageof hard-to-reach places and undersurfaces of lowgrowing plants.For best results and maximum personal safety,dust when air is calm and plant surfaces are damp,but not wet. Dusting wet surfaces causes unsightlydeposits on leaves. After dusting, remove excessdust from the hopper to prevent caking in storageand possible corrosion of metal parts.Hose-on sprayers-Of the many different typesof spray equipment on the market, the hose propor-tioner or hose-on sprayer proba.bly is the mostwidely used around the home. Its popularity isdue mostly to low cost, simplicity and versatilityin applying all kinds of spray materials. Thissprayer attaches to the end of a garden hose andmeters the pesticide out through a siphon to mixwith water from the hose. The chief differencebetween models of hose-on sprayers is the meteringsystem used to regulate dosage. The simplestmodels have a non-adjustable nozzle and siphonsystem calibrated so that a set volume of water isSelection of garden hosesprayers:. lVnn - breakablepesticide dispensers are pre-ferred.required to empty the pesticide conta.iner. Theseare available in sizes calibrated to deliver 3 to 15gallons of spray for each jar of chemical used.Sprayers with the lower delivery rates are bestsuited for spraying plant foliage; the 15-gallon sizeis best for lawns. Instructions for measuring pesti-cide amounts generally are provided with thesprayer, but correct dosage also can be calculatedby multiplying the gallon size of the sprayer by therecommended amount per gallon of water.For example: Product label information recommends 3 table-spoons (tbsp.) of the product per gallon ofwater; the sprayer to be used has a 3-galloncapacity.Therefore: 3 tbsp. X 3 gal. = 9 tbsp. (thecorrect amount to place in thepesticide iar).After placing the calculated amount of pesti-cide concentrate in the jar, fill the jar to capacitywith water to obtain the correct spray concen-tration. When only a few plants are to be prayed,smaller amounts may be prepared provided theamount of chemical and water are reduced pro-portionately. To prepare only one-third jar ofchemical mix, measure ~ of 9 (3 tbsp.) into thejar and fill to one-third capacity for corre~t dosage.This is based on the example recommendationgiven above.More versatile types of hose-on sprayers areequipped with an adjustable nozzle so that sprayvolume can be regulated. These work better withemulsifiable concentrates than with wettable pow-ders. Dosage is regulated by· a dial setting thatmeters out desired amounts of pesticide concentratefor each gallon of spray applied. Using the properdial setting, the amount of concentrate placed inthe pesticide jar does not affect dosage; therefore,do not dilute materials in the jar with water.Some disadvantages of hose-on sprayers are:(1) their use is limited to the area reached by hose,(2) difficulty in obtaining uniform spray coveragein large, dense shrubbery and on undersides oflow-growing plants and (3) water pressure may notbe sufficient to break. the spray into the fine mistneeded for good plant coverage.Compressed air sprayers-These sprayers operateon air pressure (20 to 80 psi) developed by a hand-operated air pump. They will handle wettable!vIediu1n size compressed air sprayer for gellerol use aroundthe home.powders as well as liquids, provided the spray tankis agitated frequently to keep materials in suspen-sion. Tank sizes range from 2 quarts to 5 gallonsor more with the largest sizes normally mounted onwheels for handling ease. Quality features for thistype of sprayer include a corrosion-resistant tankfitted with a large filler opening for cleaning ease,a pump equipped with replaceable parts and areasonably long extension tube fitted with a rotat-ing, adjustable nozzle.Trombone sprayers-These also are hand-operat-ed, but operating pressure is developed by theaction of a sliding rod or piston to force liquidthrough the spray nozzle. Pressures up to 180 psiare possible, and liquids can be sprayed up to 30Knapsack sprayer with hand-operated pump.feet depending on nozzle adjustment. This sprayermost commonly is fitted with a suction hose thatcan be dropped into any size container of spray mix.The larger models are the best choice of all hand-operated equipment for spraying large shrubs andfruit trees.Spraying Plant FoliageCoverage-Disease-producing organisms, unlikeother parasites, do not move around on plant sur-faces. Spray depositions, therefore, must be uniformon all foliage parts including the undersides ofleaves for maximum disease control. Particle sizeof sprays is important because materials applied ina fine mist may result in particle distribution onfoliage up to 100 times greater than that obtainedby coarse spray droplets. Generally, spray plantswith as fine a mist as possible without sacrificingpenetration ability on dense foliage. Apply enoughmaterial to reach the point of run-off.Spray additives- Certain materials, commonlycalled spreaders and stickers, may be added to spraymixes to improve coverage and sticking ability ofspray deposits. Spray particles when landing onglossy or waxy leaf surfaces tend to combine intolarge droplets and run off the plant. Rose, gar-denia, holly, iris and hairy-leaved plants such asLoquat especially are hard to wet. This problemcan be overcome by adding a small amount ofhousehold detergent or commercial spreader to thespray mix. Use Y2 to I teaspoon per gallon. Foliageof certain plants, such as the rose, may be sensitiveto detergents so use caution when adding to thespray ingredients.Use of a sticking agent may be desirable par-ticularly during prolonged periods of rainy weather.Several commercial stickers or spreader-sticker com-binations are available, although the use of 1 table-poon of wheat flour per gallon of spray mix maywork equally as well. Before using additives, checkthe pesticide label to see if these materials arealready in the product.Sp1'aying schedules-Because plant pathogens donot cause symptoms of damage until they are wellestablished within the plant, the most effectivespray program is one that starts early in the seasonbefore ymptoms normally appear. This is trueespecially for such universal diseases as Black Spotof Rose, fire blight of pear and certain ornamentalsand common leaf-spotting diseases. Each disease-producing organism, however, has some point inits life cycle when it is most susceptible to chemicalcontrol. Thus, preventive spray programs workbest when timing is based on a working knowledgeof the causal organisms involved.Regardless of when the first spray is applied,control generally will not be achieved withoutfollow-up treatments scheduled to provide protec-tion until the disease is no longer a threat. Thisperiod may vary with each disease, depending onstage of plant susceptibility, environment andpresence of the pathogen. Normally, apply spraysevery 7 to 14 days depending on weather conditions.During periods of fast growth when leaves enlargerapidly, or during rainy periods, the 7-day scheduleis most applicable.Spraying LawnsControl of lawn diseases requires high gallonagespray treatments for effective penetration of densegrass and thatch accumulations. Unless high pres-sure commercial equipment is available, the com-mon hose-on sprayer is the best choice for thiswork. Dosage recommendations for lawn sprayinggenerally are based on materials needed for each1,000 square feet of area. Apply 15 gallons of spraymix for each 1,000 square feet. To insure proper. coverage with the hose-on sprayer, stake off a 20x 50-foot area, then practice spray with water todetermine swath width and walking speed necessaryto empty the pesticide container within the speci-fied area. Use of a spreading agent or detergentin the spray mix will increase greatly spray pene-tration and treatment effectiveness.Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socio-economiclevels, race, color, sex, religion or national origin.Cooperative Extension Work in Agriculture and Home Economics, Texas A&M University and the United States Department ofAgriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, 1914, as amended, and June 30, 1914.lOM-2-73 PP

Methods for Controlling Plant Foliage Diseases.

Texas A&M University

L-1099
METHODS FOR CONTROLLING PLANT FOLIAGE DISEASES
Leon R. Smith*
• Basic Suggestions for Disease Prevention
• Plant Protectants and Formulations
• Equipment
The need for chemically controlling plant dis-
eases around the home frequently raises questions
about the kind of chemical best suited for the job
and how, when and how often to apply. Failure
to obtain satisfactory control generally is due to
using improper materials or application procedures.
The following information outlines a dependable
approach with emphasis on methods of applying
plant protectants.
Basic Suggestions for Disease Prevention
1. Know your plants, their range of soil and
climate adaptation and other specific growth
requirements. Plants growing under en-
vironmental stress are disease prone, often
developing diseases that otherwise would not
occur.
2. Establish plants highly susceptible to fOliage
disease in areas where air circulates freely.
Avoid wetting foliage in late evening when
leaves may remain wet during night hours.
High humidity and surface moisture favors
development of many foliage diseases.
3. Consider using disease-resistant varieties
when establishing new plantings. Local
nurserymen and garden enthusiasts can sug-
gest varieties best suited to the area that
offer resistance or tolerance to common
foliage diseases.
4. Identify the cause of a disease problem before
applying chemicals. Some foliage diseases
are difficult to control except with specific
fungicides. Also, certain non-pathogenic
foliage abnormalities caused by insects, root
*Area Extension plant pathologist, Texas A&M University, Overton.
7.3
• Spraying Plant Foliage
• Spraying Lawns
or stem diseases and mineral deficiencies are
confused easily with those caused by fungi
or bacteria, even though they require differ-
ent treatment methods.
Professional assistance for plant disease iden-
tification is available through all county
Extension offices.
5. Anticipate the occurrence of common foliage
diseases and apply recommended plant pro-
tectants before damage becomes serious. Most
fungicides and bactericides function pri-
marily to prevent further disease develop-
ment, with little or no ability to eradicate
disease-producing organisms already estab-
lished in the host plant.
Plant Protedants and Formulations
All reputable fungicide products carry label
information including safety precautions, ingredi-
ents and dosage recommendations. If the material
is cleared for use on edible plants or fruit trees, the
label should give the minimum time limit between
application and harvest. Chemical control recom-
mendations often are made in terms of active
chemical rather than trade name. When following
professional advice, check the label and insist that
products contain the suggested chemical ingredi-
ents. For convenience in preparing spray mixes,
choose products that give dosage information in
small measures such as tablespoons or ounces re-
quired per gallon of water.
Formulations- Fungicides and bactericides are
marketed in essentially four forms: (1) wettable
powders, (2) emulsifiable concentrates, (3) liquids
in pressurized containers and (4) dusts. Each has
Texas A&M University • Agricultural Extension Service • John E. Hutchison, Dir dor • College Station
its place for u e around the home. Sprays when
properly applied provide more efficient and longer
lasting protection than dusts, yet dusts are easy to
apply and generally require less time for coverage.
Pressurized cans, usually 1 pint or larger, are con-
venient for spraying house plants or specimen
plant that require frequent treatment. To prevent
foliage burn, avoid spraying in excess or too close
to plants.
Wettable powder and emulsifiable co~centrate
formulations offer the widest variety of fungicidal
materials at the greate t economy, but spraying
equipment is required for application. Types of
spray equipment are almost unlimited, but all re-
quire thorough cleaning after each use to guard
again t corrosion of metal parts and nozzle stoppage.
\Vettable powder formulations may cause clogging
of sprayers, particularly those with a s.mall nozzle
orifi e, during the spraying operation. This gen-
erally can be overcome by premixing the powder
with a small amount of water to form a thin,
smooth paste before mixing in the spray tank.
Adding a few drops of liquid household detergent
helps reduce clogging.
Equipment
Dusters-Dusting equipment is available in all
practical sizes ranging from Y2 to 25 pounds or
more in dust capacity. Small piston or plunger-
type dusters are convenient when only a few plants
are involved, but for the most efficient application
on a large area, continuous flow models of the
bellows-operated or hand-crank, rotary type are
preferred. Regardless of type, extension tubes and
dust-deflecting accessories are essential for coverage
of hard-to-reach places and undersurfaces of low
growing plants.
For best results and maximum personal safety,
dust when air is calm and plant surfaces are damp,
but not wet. Dusting wet surfaces causes unsightly
deposits on leaves. After dusting, remove excess
dust from the hopper to prevent caking in storage
and possible corrosion of metal parts.
Hose-on sprayers-Of the many different types
of spray equipment on the market, the hose propor-
tioner or hose-on sprayer proba.bly is the most
widely used around the home. Its popularity is
due mostly to low cost, simplicity and versatility
in applying all kinds of spray materials. This
sprayer attaches to the end of a garden hose and
meters the pesticide out through a siphon to mix
with water from the hose. The chief difference
between models of hose-on sprayers is the metering
system used to regulate dosage. The simplest
models have a non-adjustable nozzle and siphon
system calibrated so that a set volume of water is
Selection of garden hose
sprayers:. lVnn - breakable
pesticide dispensers are pre-
ferred.
required to empty the pesticide conta.iner. These
are available in sizes calibrated to deliver 3 to 15
gallons of spray for each jar of chemical used.
Sprayers with the lower delivery rates are best
suited for spraying plant foliage; the 15-gallon size
is best for lawns. Instructions for measuring pesti-
cide amounts generally are provided with the
sprayer, but correct dosage also can be calculated
by multiplying the gallon size of the sprayer by the
recommended amount per gallon of water.
For example: Product label information recommends 3 table-
spoons (tbsp.) of the product per gallon of
water; the sprayer to be used has a 3-gallon
capacity.
Therefore: 3 tbsp. X 3 gal. = 9 tbsp. (the
correct amount to place in the
pesticide iar).
After placing the calculated amount of pesti-
cide concentrate in the jar, fill the jar to capacity
with water to obtain the correct spray concen-
tration. When only a few plants are to be prayed,
smaller amounts may be prepared provided the
amount of chemical and water are reduced pro-
portionately. To prepare only one-third jar of
chemical mix, measure ~ of 9 (3 tbsp.) into the
jar and fill to one-third capacity for corre~t dosage.
This is based on the example recommendation
given above.
More versatile types of hose-on sprayers are
equipped with an adjustable nozzle so that spray
volume can be regulated. These work better with
emulsifiable concentrates than with wettable pow-
ders. Dosage is regulated by· a dial setting that
meters out desired amounts of pesticide concentrate
for each gallon of spray applied. Using the proper
dial setting, the amount of concentrate placed in
the pesticide jar does not affect dosage; therefore,
do not dilute materials in the jar with water.
Some disadvantages of hose-on sprayers are:
(1) their use is limited to the area reached by hose,
(2) difficulty in obtaining uniform spray coverage
in large, dense shrubbery and on undersides of
low-growing plants and (3) water pressure may not
be sufficient to break. the spray into the fine mist
needed for good plant coverage.
Compressed air sprayers-These sprayers operate
on air pressure (20 to 80 psi) developed by a hand-
operated air pump. They will handle wettable
!vIediu1n size compressed air sprayer for gellerol use around
the home.
powders as well as liquids, provided the spray tank
is agitated frequently to keep materials in suspen-
sion. Tank sizes range from 2 quarts to 5 gallons
or more with the largest sizes normally mounted on
wheels for handling ease. Quality features for this
type of sprayer include a corrosion-resistant tank
fitted with a large filler opening for cleaning ease,
a pump equipped with replaceable parts and a
reasonably long extension tube fitted with a rotat-
ing, adjustable nozzle.
Trombone sprayers-These also are hand-operat-
ed, but operating pressure is developed by the
action of a sliding rod or piston to force liquid
through the spray nozzle. Pressures up to 180 psi
are possible, and liquids can be sprayed up to 30
Knapsack sprayer with hand-operated pump.
feet depending on nozzle adjustment. This sprayer
most commonly is fitted with a suction hose that
can be dropped into any size container of spray mix.
The larger models are the best choice of all hand-
operated equipment for spraying large shrubs and
fruit trees.
Spraying Plant Foliage
Coverage-Disease-producing organisms, unlike
other parasites, do not move around on plant sur-
faces. Spray depositions, therefore, must be uniform
on all foliage parts including the undersides of
leaves for maximum disease control. Particle size
of sprays is important because materials applied in
a fine mist may result in particle distribution on
foliage up to 100 times greater than that obtained
by coarse spray droplets. Generally, spray plants
with as fine a mist as possible without sacrificing
penetration ability on dense foliage. Apply enough
material to reach the point of run-off.
Spray additives- Certain materials, commonly
called spreaders and stickers, may be added to spray
mixes to improve coverage and sticking ability of
spray deposits. Spray particles when landing on
glossy or waxy leaf surfaces tend to combine into
large droplets and run off the plant. Rose, gar-
denia, holly, iris and hairy-leaved plants such as
Loquat especially are hard to wet. This problem
can be overcome by adding a small amount of
household detergent or commercial spreader to the
spray mix. Use Y2 to I teaspoon per gallon. Foliage
of certain plants, such as the rose, may be sensitive
to detergents so use caution when adding to the
spray ingredients.
Use of a sticking agent may be desirable par-
ticularly during prolonged periods of rainy weather.
Several commercial stickers or spreader-sticker com-
binations are available, although the use of 1 table-
poon of wheat flour per gallon of spray mix may
work equally as well. Before using additives, check
the pesticide label to see if these materials are
already in the product.
Sp1'aying schedules-Because plant pathogens do
not cause symptoms of damage until they are well
established within the plant, the most effective
spray program is one that starts early in the season
before ymptoms normally appear. This is true
especially for such universal diseases as Black Spot
of Rose, fire blight of pear and certain ornamentals
and common leaf-spotting diseases. Each disease-
producing organism, however, has some point in
its life cycle when it is most susceptible to chemical
control. Thus, preventive spray programs work
best when timing is based on a working knowledge
of the causal organisms involved.
Regardless of when the first spray is applied,
control generally will not be achieved without
follow-up treatments scheduled to provide protec-
tion until the disease is no longer a threat. This
period may vary with each disease, depending on
stage of plant susceptibility, environment and
presence of the pathogen. Normally, apply sprays
every 7 to 14 days depending on weather conditions.
During periods of fast growth when leaves enlarge
rapidly, or during rainy periods, the 7-day schedule
is most applicable.
Spraying Lawns
Control of lawn diseases requires high gallonage
spray treatments for effective penetration of dense
grass and thatch accumulations. Unless high pres-
sure commercial equipment is available, the com-
mon hose-on sprayer is the best choice for this
work. Dosage recommendations for lawn spraying
generally are based on materials needed for each
1,000 square feet of area. Apply 15 gallons of spray
mix for each 1,000 square feet. To insure proper
. coverage with the hose-on sprayer, stake off a 20
x 50-foot area, then practice spray with water to
determine swath width and walking speed necessary
to empty the pesticide container within the speci-
fied area. Use of a spreading agent or detergent
in the spray mix will increase greatly spray pene-
tration and treatment effectiveness.
Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socio-economic
levels, race, color, sex, religion or national origin.
Cooperative Extension Work in Agriculture and Home Economics, Texas A&M University and the United States Department of
Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, 1914, as amended, and June 30, 1914.
lOM-2-73 PP


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Methods for Controlling Plant Foliage Diseases.

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Texas A&M Repository

Texas A&M University

Methods for Controlling Plant Foliage Diseases.

Abstract

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Full text

Available Versions

Texas A&amp;M Repository

Texas A&M University

Texas A&M Repository