The Green Thumb Almanac

YOUR ONLINE GARDENING INFORMATION CENTER

Pest Control

Garden pests come in all shapes and sizes.  As lovers of nature, most gardeners would like to live in harmony with these creatures.  However, when they destroy your lawn, eat your prized roses or attack your favorite houseplant most gardeners patience runs out.
 

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  • Pests of Indoor Plants
  • Insect Pests in Home Gardens
  • Organic vs Synthetic Pesticides
  • Controlling Large Pests

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Pests of Indoor Plants

Aphids are small, soft-bodied insects with piercing/sucking mouthparts.  There are many species which may appear yellow, green, pink or black.  As they feed they produce a sticky 'honeydew' that may attract other insects, such as ants.  A black sooty mold can also grow on the honeydew.  Damage symptoms may include yellowing, stunting, or wilting of the affected plant parts.  Aphids also are responsible for the spread of many plant diseases.  CONTROL: Insecticidal soaps and oils are effective for adults found on the plant.  Systemic insecticides containing imidacloprid will eliminate severe infestations however will also kill beneficial insects.  Hosing off insects, use of beneficials and good plant culture can be useful for minor infestations.
Mealybugs are fuzzy white insects which often appear as masses of white, cottony growths hiding under leaves, along stems or sometimes on the roots of plants.  Like aphids they have piercing/sucking mouth parts and produce 'honeydew' as they feed.  Adults and nymphs crawl slowly, while the adult males fly from plant to plant.  CONTROL:  Neem oil is the best remedy for mealy bug infestations.  Mealy bugs can also be removed by wiping them off with a q-tip dipped in rubbing alcohol.  Mealy bugs are VERY difficult to eliminate.  Often the cure will cost more than the plant itself.  Dispose of plants with severe infestations.
Scale insects are small pests with hard or soft shells, like a turtle.  They may appear tan or brown in color.  Scale insects only move soon after hatching and are otherwise immobile.  They also have piercing/sucking mouthparts and secret 'honeydew.'  Their hard outer shell makes them difficult to kill.  They are most often found along stems and under leaves.  Symptoms include stunted growth, yellowing or death of plant parts.  CONTROL:  Scale is best controlled using either Neem or horticultural oil sprays as these smother the insect.  Other insecticides are less effective in penetrating their hard outer shell.  Systemic insecticides can be used with varying levels of effectiveness depending on the species of scale found on your plant.
Whiteflies are tiny powdery-white insects.  They are active and highly mobile.  Immature whitefly appear as scale-like and are often found on the underside of leaves.  They also have piercing/sucking mouthparts and secret 'honeydew.'  The adults are difficult to kill since they usually fly away when disturbed.  Whitefly may cause distorted, yellow foliage.  CONTROL:  Use of insecticidal soaps or oils such as neem oil may reduce but not eliminate populations. Systemic insecticides may be more effective but can have negative impacts on beneficial insects and pollinators.  Minor infestations can be controlled with the use of whitefly sticky traps.
Thrips are very tiny, slender insects which feed on flowers, buds and leaves with their rasping mouthparts.  Leaves or flowers may appear silvery, or dried out.  They are difficult to control because they hide deep inside the flower and they deposit their eggs into leaf tissue.  They fly from plant to plant and are responsible for tomato spotted wilt virus.  CONTROL:  Insecticides containing Spinosad are the most effective means of controlling thrips especially if horticultural oil is added to the spray mix.  Generally thrips are hard to control because by the time damage is noticed the thrips have moved on.
Spider mites are extremely difficult pests to identify and control.  They are relatives of the spider and are microscopic in size.  Spider mite colonies appear along the stem and under leaves and can be identified by the fine webbing they produce.  Leaves may appear stippled from their feeding.  They thrive in warm, dry indoor conditions and reproduce very rapidly.  CONTROL:  Spider mites frequently become a problem after applying insecticides.  This is because insecticides kill the mites natural enemies.  Neem and horticultural oil sprays are acceptable as are the use of plant based acaricides found in products such as garlic, clove, mint, rosemary and cinnamon oils.

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Insect Pests in Home Gardens

Home gardens can be attacked by a myriad of insect pests.  The proper line of defense should be two-fold:  good gardening practices coupled with chemical pest control.  Use the following guidelines to prevent problems before they occur.  (photo at right: tomato hornworm)
  • Start Healthy:  Transplant only strong healthy plants.  Stressed plants are more susceptible to pests and disease.
  • Sanitation:  Many pests over-winter in old plant material.  Keep your garden clear of last years foliage.
  • Weed Control:  Many weeds actually attract insect pests.  Weeding your garden will make it less attractive to them.
  • Water Early:  Some pests prefer moist areas.  Water early in the day and space plants to provide good air circulation.
  • Physical Removal:  Examining your plants regularly and physically removing pests early will prevent their populations from getting out of control.
  • Physical Barriers:  The use of floating row covers over your plants and wrapping stems with foil or cardboard can prevent infestations.
  • Biologicals:  Release beneficial predator insects such as ladybugs into your garden.
  • Use Pesticides:  Pesticides, whether organic or synthetic, should be used as a last resort.  Only spot spray affected plants.  Remove plants with serious infestations.
  • Consult Professionals:  Take a sample of the plant and pest to your local garden center or extension service for proper identification of the pest and advice on the most effective chemical control for you.

Pill Bugs, Sow Bugs, & Roly-Polies are the names commonly given to separate, but related, species of isopods (land dwelling crustaceans).  These minor nuisance pests can be found living in damp areas where they primarily feed on decaying matter.  Large populations may feed on young seedlings and their plant damage is similar to slugs resulting in holes in leaves.

CONTROL:  Eliminate their preferred habitats around the exterior of your home.  Seal door thresholds and windows to prevent entry.  Spray the foundation of your home with cyfluthrin or permethrin or use diatomaceous earth. 

Slugs & Snails can wreak havoc on the garden.  Both prefer damp areas and both primarily feed at night.  CONTROL:  The first step in eliminating them is to remove anything from your garden that they can hide under...boards, rocks, leaves.  The second is to water only in the morning so that your garden can dry out over night.  There are many home remedies for slug infestations:  placing a dish of beer out for them to drown in and the use of copper barriers around plants can also be effective.  Commercial slug baits can also be used.  Use baits containing iron phosphate.  Baits containing metaldehyde are poisonous to pets.  Encouraging slug predators will help as well.  Nothing is better than a hungry toad!

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Organic vs Synthetic Pesticides

Are organic pesticides safer than synthetic pesticides?  Not necessarily.  The term 'organic' merely means that the deadly chemical was derived from natural sources as opposed to being created in a lab.  Organic pesticides may break down quicker in the environment than synthetics but they can be equally, or more, toxic.  A recent study compared the environmental impact quotient (EIQ) of several pesticides with the higher number being the most toxic.  Here are some results:
Bt (organic)          13.5
Acephate (synthetic)         17.9
soap (organic)       19.5
Carbaryl (synthetic)        22.6
Malathion (synthetic)      23.2
Rotenone (organic)        33.0
Sabadilla (organic)         35.6
Many organics are also broad spectrum pesticides meaning that they will kill beneficial insects as well.  So use caution when spraying ANY pesticide and please read all product labeling prior to use!

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Controlling Large Pests

Controlling large garden pests can be challenging.  Physical barriers, such as fencing and netting, are a good first step.  The next line of defense are animal repellents.  These products come in either dusts, pellets or sprays which usually  have a scent that is  unappealing to animals.  Most need to be applied frequently, especially after rains. 
 
The Green Thumb Almanac recommends the I Must Garden line of animal repellents.  Finally you can enjoy your garden and stop worrying about deer damage and damage from other garden pests. I Must Garden offers protection for your garden with products that are safe, eco-friendly and pleasant to use.
 
Moles & Voles are destructive little creatures that tunnel underground disrupting plant roots.  Moles are primarily consumers of worms and grubs.  Voles often attack plant roots and stems.  CONTROL:  Traps are the most effective method of controlling moles.  Poison baits are also effective but can be dangerous if you have a pet.  Repellents containing Thiram or Castor Oil can also be used.

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