Greenhouse Pest Management

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Greenhouse Pest Management
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Three Types of Greenhouse Pest

• Insects

• Diseases

• Weeds

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Weeds
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Four Major Greenhouse Weeds
Oxalis

• Woodsorrel

Cardamine hirsuta

• Bittercress

Euphorbia maculata

• Spurge

Fatoua villosa

• Mulberry Weed

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Greenhouse weeds are adaptable . . .
have short lifecycles . . .
and are prolific seeders.
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Greenhouse weed control is important from an
aesthetic standpoint . . .
as well as from a pest control standpoint.
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Weeds can harbor insects as well as diseases.
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Preventative Measures
Sanitation is the most important control measure.

• Start with weed free plant materials.

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• Keep substrates sterile.

• Clean-up spilled media.

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• Control weeds outside the greenhouse.

Eliminate adjacent vegetation if possible.
Keep surrounding grassy areas mowed.
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• Reduce access for weed seed.
  

Screen vents and fans if possible.
Consider concrete floors.
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Cover earthen areas with geotextiles.
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If groundcloth is anchored with landscape
staples and left bare, it can be vacuumed free of
debris between crop cycles.
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Corrective Measures

• Remove weeds manually.
• Solarize the greenhouse for 1-2 months.
• Apply herbicides.

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Herbicides can be . . .

• Preemergent

Prevents the germination of weed seeds.
or Postemergent
Kills weeds after germination.

• Selective

Only controls certain types of weeds.
or Non-Selective
Kills everything.
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Only postemergent herbicides are registered for
greenhouse use.
Round-up Pro, Touchdown - (glyphosate)
Finale - (glufosinate-ammonium)
BareSpot Monobar-Chlorate -(sodium chlorate
sodium metaborate)
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It is recommended that non-selective herbicides
only be applied to empty greenhouses.
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When applying non-selective herbicides in a
greenhouse containing plants

• Spray in the coolest part of the day.
• Turn off all fans (exhaust and HAF).
• Close vents.
• Keep sprayer pressure low.
• Keep sprayer nozzle close to the ground.

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Insects
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Aphids
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Aphids Description

• Relatively Small (approx. 1/8 inch)
• Pear Shaped
• Various Colors
• Beak and Stylet
• Cornicles
• Winged Adults Produced when
• Population Pressure is High

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Aphids are often found on young growth or the
underside of leaves.
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Signs of Aphids

• Cast Exoskeletons

• Distortion of Shoots and Leaves

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Signs of Aphids

• Spots on Older Leaves
• (feeding damage)

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Signs of Aphids

• Honeydew and Sooty Mold

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Signs of Aphids

• Presence of Ants

Ants tend aphids and collect honeydew.
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Aphids sometimes fall prey to parasitic wasps and
become mummies.
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Aphids are also favorites of other predatory
insects, such as lacewings, ladybugs and ladybug
larvae.
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Thrips
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Thrips Description

• Very Small (approx. 1/16 inch)
• Long and Slender
• Tan, Yellow or Black in Color
• Damage Plants with
• Rasping Mouthparts

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Because they are very small, thrips can be
carried by air currents.
Thrip populations peak in early June.
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Thrips are often found in axils, buds and flowers.
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Signs of Thrips

• Streaks on Leaves and Flowers

• Brown or Black
• Droplets on Leaves

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Signs of Thrips

• Distortion of Leaves and Flowers

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Signs of Thrips

• Thrips can be Dislodged from Infested
• Plant Material

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Whiteflies
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Whiteflies Description

• Very Small (approx. 1/16 inch)
• Adults are Moth-like
• Adults are Covered with a White, Waxy Powder
• Piercing, Sucking Mouthparts

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Whiteflies are often found on the underside of
leaves.
They are weak fliers and often take off when
their foliage is disturbed.
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Signs of Whiteflies

• Visible Adults and Larvae

All stages of the whitefly lifecycle may be
present on the underside of leaves.
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Signs of Whiteflies

• Honeydew and Sooty Mold

• Stippling on Leaves

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Scales
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Scales Description

• Variable Size
• Variable Color
• Variable Shape
• (Flat, Oval, Rounded, Rectangular or
  Oyster-Shaped)
• Adults Legless with Hard Outer Shell
• Piercing-Sucking Mouthparts

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Scales are often found on stems and the underside
of leaves.
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Larvae (crawlers) emerge from underneath female
scales and travel for about 2 days. They lose
their legs during the first molt.
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Signs of Scales

• Yellow Spots on Leaves from Feeding

Scales have toxic saliva.
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Signs of Scales

• Honey Dew and Sooty Mold

• Attending Ants

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Mealybugs
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Mealybugs Description

• Approx. 1/8 to 1/4 Inch
• Oval
• White Waxy Coating
• Filaments
• Legs
• Piercing-Sucking Mouthparts

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May be found on leaves, in leaf axils and on
stems.
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Signs of Mealybugs

• Visible Adults, Nymphs and Egg Sacs
• Honey Dew and Sooty Mold
• Attending Ants

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Spidermites
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Spidermites Description

• Very Small (barely visible)
• Arachnids Adults have 8 Legs
• Piercing-Sucking Mouthparts

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Two-Spotted Spidermites (the most common
greenhouse mite) prefers high temperatures and
low humidity.
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Webbing is visible when populations are high.
Spidermites travel on air currents and can be
transported on clothing and tools.
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Signs of Spidermites

• Chlorotic Stippling

• Dessicated Leaves and Flowers

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Signs of Spidermites

• Webbing on Shoots and Under Leaves

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Fungus Gnats
Small gray flies with long legs and antennae.
Adults take flight when plants are watered or
moved.
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Egg clusters are laid on wet media. Larvae eat
organic matter and soil fungi. When populations
are high, roots may be attacked
Fungus gnat populations will decrease if media is
allowed to dry between waterings.
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Worms
Worms are the immature stage of moths.
Chewed foliage and frass are signs of worm damage.
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Snails and Slugs
Snails and Slugs are mollusks that feed at night
and hide during the day.
Chewed foliage and slime trails are symptoms of
feeding.
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Diseases
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Powdery Mildew
Powdery Mildew produces a white, powdery growth
on the surface of leaves, stems and petals.
On some plants, Powdery Mildew can cause severe
distortion.
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Powdery Mildew spores are carried by air currents.
Germination rate is higher and more rapid at
higher humidity levels.
Reducing humidity levels will help to control the
outbreak and spread of Powdery Mildew.
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Botrytis
Botrytis causes a brown rotting and blighting of
infected tissues.
It can be easily identified by the fuzzy, gray
spore masses on rotted tissues.
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High humidity is required for spore germination.
Water is required for spore germination and
infection
Maintain low humidity and reduce splashing of
water to help prevent or control Botrytis.
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Damping-Off
Damping-off is the decay of seedlings prior to
emergence or the rot of seedlings at the soil
line after emergence.
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Damping-Off can be caused by multiple fungal
pathogens.
It is spread by mechanical transfer. Unsterile
media, dirty tools, hands, water can all be modes
of pathogen transfer.
Attention to hygiene may help to prevent or
control Damping-Off.
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Root Rot
Root Rots are caused by various fungi.
Infected roots die-back and plants eventually
wilt and die.
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Root Rot is spread by mechanical transfer or by
the use of infected plant material.
Attention to hygiene may help prevent or control
the spread of Root Rot.
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Pest Control Measures
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The best pest control programs consist of three
components

• Preventative Measures
• Surveillance
• Corrective Measures

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Preventative Measures

• Practice Proper Sanitation
• Control weeds both inside and outside the
  greenhouse.
• Sterilize greenhouse benches between crops.
• Start with sterile planting media.
• Clean equipment such as pruners and trowels
  after each use.
• Remove diseased or unmarketable plants.
• Kill algae and remove excess media from bench
  and floor.

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Preventative Measures

• Maintain the Optimal Growing Environment
• Plants under stress are more susceptible to
  diseases and insects avoid temperature and
  water stress.
• Control greenhouse humidity.
• Maintain proper fertility.

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Preventative Measures

• Inspect All Plant Material Entering the
  Greenhouse
• Treat or dispose of plant material showing signs
  of disease or insect infestation.

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Surveillance

• Scout Greenhouse Crops for Insects and Diseases

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Surveillance

• Use Sticky Cards to Monitor Insect Populations

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Corrective Measures

• Select Appropriate Pesticides
• Read the label carefully.
• Rotate pesticides to prevent the build-up of
  resistant organisms.

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Corrective Measures

• Follow Proper Safety Precautions
• Wear appropriate protective equipment.
• Post appropriate notification signs on greenhouse
  prior to spraying. Lock and control reentry into
  the greenhouse until the Restricted Reentry
  Interval has passed.

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Corrective Measures

• Spray Plants Thoroughly to Obtain Optimal Coverage

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Pump sprayers work well for small applications.
Battery operated sprayers allow finer spray and
quicker application in large areas.
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Safety Issues
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Pesticide Safety

• Choose the Safest Pesticide for the Job
• Look for a pesticide with an appropriate REI.
• When possible, chose pesticides with high LD50s.
• In general, pesticides labeled Caution pose the
  least risk to human and environmental health,
  while pesticides labeled Danger pose the
  greatest risk. Pesticides labeled Warning are
  of moderate risk to human and/or environmental
  health.

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Pesticide Safety

• Ensure that Applicators have Proper Training
• A Private Pesticide Applicators License is
  required when restricted use pesticides are
  applied.

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Pesticide Safety

• Label Guidelines Should be Strictly Followed
• Follow all safety precautions listed on the
  pesticide label, including
• REI Periods
• Protective Equipment

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Pesticide Safety

• Post Appropriate Signage
• Fill-in and post pesticide application
  notification signs prior to spraying.
• Restrict Reentry Into Treated Areas
• If the greenhouse must be reentered prior to the
  expiration of the REI, follow the pesticide label
  guidelines regarding early reentry.

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Pesticide Safety

• Prepare for Emergencies
• Have an emergency shower nearby.

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Pesticide Safety

• Prepare for Emergencies (continued)
• Keep a spill kit readily accessible. Include
• Rubber aprons, chemical resistant suits,
  respirators, chemical proof gloves, rubber boots.
• Materials for soaking-up liquid spills
  (vermiculite, kitty litter).
• Plastic to cover-up dry materials.
• Broom and dustpan to collect spilled materials.
• Containers or bags to hold reclaimed material.

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Pesticide Safety

• Prepare for Emergencies (continued)
• Keep a list of emergency numbers readily
  accessible.
• Fire Department
• Hospital/Ambulance
• Police
• EPA
• Poison Control Information Center

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Pesticide Storage
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Pesticide Storage

• Store Pesticides Properly
• Pesticides should be locked in a cabinet in a
  well-ventilated area.
• Pesticide storage facilities should be posted
  with warning signs.
• All pesticides should have a label attached to
  the container.
• Pesticides should never be stored in food
  containers.

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Pesticide Storage

• Store Pesticides Properly (continued)
• Never store pesticides in the same cabinet with
  fertilizers and cleaning products.
• Store pesticides in the following order
• Dry pesticides (powders, granular formulations)
  on upper shelves.
• Wet pesticides (ECs, Flowables, Liquids) on
  lower shelves.
• Insecticides on upper shelves.
• Herbicides on lower shelves.

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Record Keeping
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Record Keeping

• Maintain Proper Records
• Keep copies of all MSDS information in a readily
  accessible location.
• Keep an updated inventory of pesticides in a
  readily accessible location.

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Record Keeping

• Maintain Proper Records (continued)
• Keep records of all pesticide applications,
  including the following information
• Brand/Product Name and Active Ingredient
• EPA Registration Number
• Total Amount Applied
• Size of Area Treated
• Crop or Site
• Location of Application
• Month, Day, Year
• Applicators Name and Certification Number