To spray or not to spray Part II

Part I of Natural pest control suggested alternative methods of pest control that don’t require any pesticides.  Natural methods should be the first course of action because you are targeting the pest and there are no side-effects.  If you are gardening to attract butterfly’s or other wildlife… I say “just let nature take its course”… don’t spray anything.

Part II offers some suggestions if you do decide a situation calls for a pesticide.  Always look for the least toxic.   Soap’s and oils are the only two pesticides I use.  I also carry a bottle of alcohol for Mealy.  Know that organic pesticides can kill beneficial insects if they get hit with the spray, so check the area around your target.

Read the label so you know what the ingredients are and know the side-effects.  Look for signal words such as Caution, Warning of Danger.

Insecticidal Soap

What’s in it:  Specially formulated soap with fatty acids – some are natural, others are synthetic.

How it works:  The fatty acids break down the protective cutical of soft-bodied insects causing them to dehydrate and die.

  • Aphids
  • Mealybug
  • Spider mite
  • Thrips
  • Whiteflies

To be effective, spray soaps directly on the insect. Be sure to thoroughly wet both  sides of leaves and all crevices. Repeat applications may be needed every five  to seven days. Always follow label directions  for diluting insecticidal soap concentrates. Using too much and applying to often can cause injury to  leaves. 

If you have hard water, use bottled water when mixing insecticidal soap, or use an already-diluted product. Minerals in hard water can greatly reduce the effectiveness of insecticidal soap.

Soap sprays can be made at home by mixing 1 tablespoon of dishwashing liquid (not detergent) per quart of water. Insecticidal soaps are purer, however, and therefore less likely to injure foliage.

Horticultural Oil

What’s in it:  Highly refined mineral oils combined with emulsifying agents.  Vegetable oils used in home remedies don’t work as well because they’re not as refined and don’t mix well with water.  Manufactured oils are more refined and easier to apply.

How it works:  When applied directly to the pest horticultural oil interferes with respiration, suffocating the insect.

  • Aphids
  • Mites
  • Scale
  • Oils also are used to prevent powdery mildew and black spot on roses.

Follow directions carefully.  Best when applied in cool weather.  Too much oil applied in excessive heat or cold can burn foliage.  Insects need to be thoroughly coated to be effective Oil can kill beneficial mites and frequent use can reduce yield in crop trees.


What’s in it:  Oil from the seeds of the neem tree (Azadirachta indica)

How it works:  When ingested, it interferes with hormones, preventing eating and growth.

  • Broad spectrum
  • Aphids
  • Mites
  • Whiteflies
  • Beetles
  • Scale

Some studies show people can have an allergic reaction to neem.  Toxic to fish and aquatic life.


What’s in it:  The soil-born fungus Bacillus thuringiensis.

How it works:  It makes the pest sick.  When eaten, it destroys the insect’s digestive system.  Used most often for lawns, vegetables, water gardens and ornamentals.

  • Bt kurstaki controls leaf-eating caterpillars
  • Bt tenebrionis Beetle larvae
  • Bt israelensis can be useful in controlling fly, mosquito and gnat larvae.  For fungus gnats in greenhouses or houseplants, or for  preventing mosquito problems in standing water that cannot be drained or  controlled with fish.

Bt will also kill butterfly caterpillars also.  It breaks down quickly in sunlight so apply late in the day.  Re-apply as needed every 7 – 10 days.


What’s in it:  The seeds of Dalmation chrysanthemum (Chrysanthemum cinerariaefolium)

How it works:  When it’s eaten or absorbed, it affects the transmission of impulses to and from the brain.  It works as a repellent.  Used most often on ornamentals, fruit trees and vegetables.

  • Broad spectrum
  • Aphids
  • Beetles
  • Caterpillars
  • Wasps
  • Whiteflies

Breaks down quickly in sunlight so may need to reapply about every week.  Some insects have developed resistance.  Highly toxic to fish, tadpoles, bees, wasps and other beneficial insects.  It can cause allergic reactions.  One of the oldest pesticides known, pyrethrum is also the strongest insecticide  allowed under National Organic Standards guidelines and should be used only as a last resort.

Don’t confuse the two… Pyrethroids are synthetic forms of Pyrethrum and are more toxic. 

Read more:

Use pesticides carefully and only as a last resort

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