Transcript What are the major pests found in the greenhouse?

Horticulture Science
Lesson 37
Identifying and Managing
Plant Pests in the Greenhouse
Interest Approach
Bring one or more plants that are suffering from disease
or insect problems into the classroom. Also bring in one
healthy plant. Ask the students to explain why
the infected plants could cause a problem. Ask them if
the infected plants should be put in the greenhouse with
the healthy plants. Ask them to explain their answer.
Student Learning Objectives
•Identify the major pests found
in the greenhouse.
•Discuss the management of
greenhouse pests.
Student Learning Objectives
•Describe the different practices
of integrated pest management
used in the greenhouse.
Terms
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aerosols
aphids
aster yellows
biological control
botanical insecticides
Botrytis blight
caterpillars
chemical control
Terms
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cultural/physical control
damping–off
dip
drench
Erwinia
fumigants
fungus gnats
granular
horticultural oils
Terms
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insect growth regulators
insecticidal soaps
leaf miners
mealybugs
microbial organisms
mites
parasitic organisms
Phytophthora
plant health
powdery mildew
Terms
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predatory organisms
Pythium
Rhizoctonia
sanitation
scale
spray
Thielaviopsis
tobacco mosaic
Western flower thrips
whiteflies
What are the major pests found in
the greenhouse?
• The health of crops grown in a greenhouse
is challenged by a variety of pests and
diseases.
• The ability to identify major greenhouse
pests and diseases is the first step in a pest
management program.
• Insect pests can severely damage or ruin a
crop if their populations are not managed.
What are the major pests found in
the greenhouse?
• Aphids are pear-shaped, soft-bodied,
usually wingless insects.
• They are often green or yellowish in
color.
• Aphids have the ability to reproduce
very rapidly.
• Astonishingly, they give birth to live
young that are pregnant!
• Aphids use their mouthparts to pierce
the plant and suck out juices.
• Aphids attack a wide variety of
greenhouse plants.
What are the major pests found in
the greenhouse?
• Caterpillars are the larvae of various moth
species.
– They damage greenhouse crops by eating the
plants.
• Fungus gnats are long-legged, winged,
gray-black insects less than 1/8 inch long.
– The larvae of fungus gnats feed on root hairs
and tunnel into plant stems.
– They prefer a growing medium that is constantly
moist.
What are the major pests found in
the greenhouse?
• Leaf miners are small, stocky flies.
– The adult deposits eggs inside a leaf.
– The eggs hatch, and the larvae feed on the
interior of the leaf, making tunnels as they
move along.
– Chrysanthemums are subject to leaf miner
damage.
What are the major pests found in
the greenhouse?
• Mealybugs are slow-moving, oval-shaped,
whitish insects.
– They have a waxy finish and produce small
cottony masses.
– Mealybugs pierce plant leaves and suck the
plant juices.
– As with aphids, they give birth to living nymphs.
What are the major pests found in
the greenhouse?
• Mites have eight legs and are related to
spiders.
– Mites pierce leaf tissues and suck juices.
– Symptoms of damage include a yellow
speckled appearance to the leaves, and, in
severe cases, yellowing of the leaves and
defoliation.
– Two spotted spider mites and red spider mites
are among the most serious greenhouse pests.
– They appear as tiny specks on the plants and
are often found on the undersides of leaves
and near the apical meristems.
What are the major pests found in
the greenhouse?
– A two-spotted mite has two dark spots on its
back.
– Spider mites create a complex network of
webbing as they move about a plant.
– Cyclamen mites infest a broad range of plants
and are not visible to the naked eye.
– Bulb mites damage lily bulbs and the developing
shoots.
What are the major pests found in
the greenhouse?
• Many types of scale insects infest greenhouse
plants.
– Typically, they have flat, oval, often brown bodies.
– They may or may not be covered with armored shells.
– Scale insects pierce plant leaves and stems and suck
juices.
• Western flower thrips are small dark brown
insects with two pairs of fringed wings.
– They have rasping mouthparts that scrape plant tissue.
– The damage they cause to many kinds of plants often
appears as whitish discoloration.
What are the major pests found in
the greenhouse?
• Whiteflies are small white insects.
– They generally camp out on the undersides of
leaves, where they pierce the tissues and suck
juices.
– Their flat, scale-like larvae feed on the
undersides of the leaves.
– Whiteflies are major pests of poinsettias and
fuchsias.
What are the major pests found in
the greenhouse?
• Diseases affect roots, leaves, stems, and
flowers of floriculture crops.
1. Botrytis blight is a fungal disease that
can attack nearly all greenhouse crops and
is a common problem with cut flower
storage.
•It causes a brown rotting and
develops fuzzy, gray mold as it
produces spores.
•Botrytis blight is most common
when temperatures are between 60
and 70°F, air circulation is poor,
and humidity is high.
What are the major pests found in
the greenhouse?
2. Erwinia is a bacterial disease that
causes rotting of plant tissues.
– The bacterium enters the plant through wounds.
It is a common problem on Dieffenbachia,
Philodendron, chrysanthemum, and Cyclamen.
What are the major pests found in
the greenhouse?
3. Powdery mildew is a fungal disease.
– Characteristic symptoms include a white dusty
coating to leaves and flowers.
– Infected plants can become stunted.
– High humidity contributes to powdery mildew
problems.
What are the major pests found in
the greenhouse?
4. Pythium is a fungal disease
that attacks greenhouse plants
under cool, wet conditions.
– It is one fungus that can cause
damping-off.
– Damping-off is the early death
of seedlings that have
germinated.
– More mature plants can develop
root and stem rots as a result of
Pythium, particularly when the
growing medium has poor
aeration.
What are the major pests found in
the greenhouse?
5. Phytophthora is a fungal disease
similar to Pythium.
– It causes crown and stem rots in cool, wet
conditions.
What are the major pests found in
the greenhouse?
6. Rhizoctonia is a fungal disease common
in wet and warm conditions.
– It is a widespread disease problem in the
southeastern region of the country.
– Rhizoctonia causes damping-off, as well as root
and stem rots.
What are the major pests found in
the greenhouse?
7. Thielaviopsis is a fungus that causes
root and stem rots.
– It favors cool, moist conditions.
What are the major pests found in
the greenhouse?
8. Tobacco mosaic and
aster yellows are two
common viral diseases
associated with greenhouse
crops.
– Symptoms of infection include
discoloration of plant tissues,
stunting of growth, and
deformed growth.
– The spread from one plant to
another is primarily by feeding
greenhouse insects.
– Tobacco mosaic virus can be
spread to the plants from the
hands of workers who smoke.
What is involved in the management
of greenhouse pests?
• Healthy greenhouse crops are essential to a
successful greenhouse business.
– Plant health refers to the condition of plants.
– Healthy plants are free of pests and disease.
– They have clean foliage and flowers, along with
a good rate of growth.
– It is important that plants be healthy while they
are growing and developing.
– It is also important that their health be
maintained after they are sold.
What is involved in the management
of greenhouse pests?
• Healthy plants have a greater capacity to
defend themselves against plant pests than
plants under some type of stress.
• Plant stress is usually associated with
environmental conditions.
– Improper watering weakens a plant’s ability to
fight off infectious diseases, including root rots.
– High humidity in greenhouses is ideal for many
fungal diseases.
What is involved in the management
of greenhouse pests?
• Growers have control over many environmental
factors that can keep plants healthy.
1. Care can be taken to provide a growing medium
with the desired drainage, aeration, and pH.
2. Plants can be planted at the proper planting
depth.
3. Optimum nutrient levels can be maintained with
fertilizers.
4. One of the most important factors is to follow
recommended watering practices.
5. Temperature, light intensity, and air quality can
also be adjusted to meet the needs of the specific
crop.
What is involved in the management
of greenhouse pests?
• No matter how well crops are grown, pests
and diseases will become problems from
time to time.
– The very nature of greenhouse crop production
leads to some disease problems.
– In most cases, crops are of the same species,
variety, or cultivar.
– Being of identical genetic makeup, they are
vulnerable to infectious disease that can easily
spread from one plant to another.
• Greenhouses also tend to be humid, which
is ideal for many fungal diseases.
What are the different practices of
integrated pest management
used in the greenhouse?
• The IPM program for greenhouse crops
must be year-round.
• IPM control measures for a specific crop
(e.g., poinsettias) should begin before the
plants enter the greenhouse.
– Four broad areas of control include sanitation,
cultural/physical control, biological control, and
chemical control.
What are the different practices of
integrated pest management
used in the greenhouse?
• Many pest problems can be greatly reduced
or eliminated with greenhouse sanitation.
• Sanitation is simply the efforts made to
keep a greenhouse clean.
What are the different practices of
integrated pest management
used in the greenhouse?
1. Weeds should be removed from the
interior of the greenhouse and the
immediate area outside the greenhouse.
– Weed control is extremely important.
– Weeds harbor pests.
– Pests migrate from the weeds to the greenhouse
crop to cause damage.
– Some greenhouse ranges have been built with
concrete floors, in part to eliminate habitat for
pests.
– A few herbicides are labeled for use inside the
greenhouse.
What are the different practices of
integrated pest management
used in the greenhouse?
2. Plant debris and other debris should be
removed from the floors and benches.
– Debris often houses disease organisms and
pests.
– Also, severely infested or infected plants should
be removed and disposed of properly.
What are the different practices of
integrated pest management
used in the greenhouse?
• Cultural/physical control consists of those
methods that physically prevent activities of
pests.
• Major advantages to cultural/physical controls
are that they are safe to humans.
1. The first line of defense against plant pests is
to prevent their introduction to the greenhouse.
– All plants should be thoroughly inspected before
they are admitted into the greenhouse.
– Accept only clean plants purchased from
reputable suppliers.
What are the different practices of
integrated pest management
used in the greenhouse?
2. Another practice is to maintain the ideal
growing environment for the crops.
– As mentioned, plants that are healthy are better
able to fight disease organisms and pests. A
good analogy is people and colds.
– People who eat right, exercise, get plenty of
rest, and are under little stress are more
resistant to colds.
– People who eat poor diets, are out of shape, get
little sleep, and are “stressed out” are more
susceptible to colds.
What are the different practices of
integrated pest management
used in the greenhouse?
3. Good air circulation around the
greenhouse plants reduces the incidence of
fungal diseases.
– Fungal diseases grow and spread when moisture
covers plant leaves.
– Air circulation helps to keep plant leaves dry.
4. Screens can be used over greenhouse
openings.
– The fine mesh of the screens prevents pests
from entering the greenhouse environment.
What are the different practices of
integrated pest management
used in the greenhouse?
5. Yellow sticky traps used to monitor pest
populations also serve as a means of
physical control.
– Flying insect pests are attracted to sticky traps,
fly onto the traps, get stuck, and die.
What are the different practices of
integrated pest management
used in the greenhouse?
• Biological control
involves the use of
microbial, parasitic, and
predatory organisms to
control pests.
– Biological control
organisms are found in
nature and, therefore, are
considered environmentally
safe.
What are the different practices of
integrated pest management
used in the greenhouse?
1. Microbial organisms include bacteria
and fungi.
– A prime example is a bacterium, Bacillus
thuringiensis, which effectively controls
caterpillars.
– Some species of bacteria and fungi can be used
to control aphid and whitefly populations
because they are natural diseases of those
insects.
What are the different practices of
integrated pest management
used in the greenhouse?
• 2. Parasitic organisms help to control
some pests.
– The parasites are natural enemies of the pests
and live off the pest organisms.
– An example of a parasitic insect used in
greenhouses is a tiny parasitic wasp.
– It lays its eggs on whitefly larvae.
– The eggs hatch with the wasp larvae inside the
whitefly larvae.
– The wasp larvae slowly weaken and kill the
developing whiteflies from within.
– Each female wasp lays eggs in up to 200
immature whiteflies.
What are the different practices of
integrated pest management
used in the greenhouse?
• When the wasps mature, they emerge from
what is left of the whiteflies, mate, and look
for whitefly larvae on which to lay the next
generation of eggs.
– a. It should be noted that chemical pesticides
cannot be used in the greenhouse without killing
the beneficial parasites.
– b. The parasites are also not effective with
heavy infestations of plant pests.
What are the different practices of
integrated pest management
used in the greenhouse?
3. Predatory organisms can be
purchased and released in the greenhouse
to devour certain plant pests.
– Ladybugs eat aphids.
– A mite is an effective control of thrips.
– A specific beetle is freed to attack whitefly
larvae and adults.
– As with parasitic organisms, chemical pesticides
should not be used when predatory organisms
are introduced.
What are the different practices of
integrated pest management
used in the greenhouse?
• Chemical control is the use of pesticides
to control pests and diseases.
– Chemical control is often applied only when
absolutely necessary.
– Pesticide application must be done safely to
reduce potential injury to people and the
environment.
1. Pest control has been made safer with
the introduction of less toxic pesticides.
– This group of “soft” pesticides includes botanical
insecticides, horticultural oils, insect growth
regulators, and insecticidal soaps.
What are the different practices of
integrated pest management
used in the greenhouse?
• a. Botanical insecticides are natural
materials obtained from plants that are
toxic to insect pests.
• b. Horticultural oils are sprayed on the
insects to clog their breathing pores,
causing suffocation.
• c. Insect growth regulators disrupt the
growth and development of the insects.
• d. Insecticidal soaps dissolve the
protective membranes of insects, bringing
on death.
What are the different practices of
integrated pest management
used in the greenhouse?
2. There are several methods used to apply
pesticides in the greenhouse.
a. Aerosols consist of atomized spray or smoke
particles distributed through the air.
– Cans containing the pesticide can be set to
release the aerosol, thus creating a fog in the
greenhouse. Once the aerosol is started, the
applicator can safely leave.
b. A dip is a pesticide mixed with water for
the purpose of submerging plants.
– Easter lily bulbs are commonly dipped in a
miticide before planting to control bulb mites.
What are the different practices of
integrated pest management
used in the greenhouse?
c. Some materials are used as a drench,
which is a solution of pesticide mixed with
water that is simply poured into the pots.
– A common practice is to drench poinsettias with
a fungicide to control soilborne disease.
d. Fumigants are poisonous gases
distributed through the air to all parts of
the greenhouse.
– They are particularly effective with flying insects
and pests exposed to the gases.
What are the different practices of
integrated pest management
used in the greenhouse?
e. Some pesticides are in a granular or
pellet form.
– They are carefully measured and applied on the
surface of the growing medium.
– These pesticides are referred to as systemic.
When plants are watered, the roots absorb the
pesticides into their systems.
What are the different practices of
integrated pest management
used in the greenhouse?
f. Pesticides may be applied as a spray on
the plant.
– The small droplets of the spray cover the
surface of the plant.
– Care must be taken with a spray to cover parts
of the plant where the pest is found, such as the
underside of the leaves.
Review/Summary
•What are the major pests found
in the greenhouse?
•What is involved in the
management of greenhouse
pests?
Review/Summary
•What are the different practices
of integrated pest management
used in the greenhouse?