Garden Pests and Diseases – Pesticide Sprays

Garden Pests and Diseases – Best Spraying Practice

  • Choose an appropriate spray product, having first identified the problem.
  • Only use sprays for those applications mentioned on the product label.
  • Follow label instructions precisely.
  • Only make up the quantity you need.
  • Never store made-up spray.
  • Use a good-quality sprayer.
  • Spray only the relevant areas.
  • Spray in still weather to prevent drift.
  • Never spray where bees are working. If it is essential to spray a plant in flower, do this in the evening when bees have returned to their hives.
  • Always store pesticides in their original container in a safe, cool, dark place.

Organic Pesticide Sprays

best spraying practice - garden pesticide sprays A few sprays may be used to control pests and diseases in an organic garden. They should never be used on a regular basis, but only when necessary to prevent a particular problem getting out of hand. They may be less harmful or persistent than other pesticides, but they can still harm creatures other than those you want to kill. If regular spraying is required to keep a plant healthy, consider replacing it with a sturdier plant.

Traditionally, organic gardeners used a selection of home-made concoctions such as boiled rhubarb leaves to control pests and diseases. The use of such preparations is now illegal; all materials used as a pesticide must now be registered as such.

All the normal precautions to safeguard the environment should be taken when using the sprays described here. Read the label before you buy and use pesticides safely.

Bacillus thuringiensis (Bt)

This is a powder containing spores and protein crystals of the bacterium Bacillus thuringiensis, a naturally occurring disease of caterpillars. It is applied as a spray to protect brassicas and other plants against butterfly and moth caterpillars.

Cautions: Bacillus thuringiensis can kill a wide range of caterpillars; avoid spray drift to non-target plants.


A liquid or powder made from the roots of derris plants, for use against small pests including aphids, spider mite, sawfly larvae, raspberry beetles, or as directed on the product label.

Cautions: Poisonous to fish and some beneficial creatures including ladybirds, anthocorid bugs and worms.


Pyrethrum is made from pyrethrum Chrysanthemum cinerariaefolium flowers. It usually also contains piperonyl butoxide to increase efficacy. Use against aphids, small caterpillars, flea beetle or as directed on product label.

Cautions: Poisonous to fish and to some beneficial insects.

Insecticidal soap

A mixture of potassium salt soaps for use against aphids, whitefly, red spider mite and slugworm or as directed on the product label. Insecticidal soap is totally non-persistent so is suitable for spot spraying where biological control agents are used.

Cautions: It can harm beneficials, including ladybirds if they are sprayed directly. Some plants are sensitive to soap.

Bordeaux mixture

A mixture of copper sulphate and quicklime, Bordeaux mixture is used to prevent disease spread. It can be used against potato blight and a range of fruit diseases.

Cautions: Harmful to some plants; toxic to fish. Do not use on plants under stress.


Sulphur is sold as a dust or spray to prevent and control disease. Its main use is against powdery mildews and apple scab.

Cautions: Harmful to predatory mites and some other beneficial insects. Several varieties of apple and gooseberry are sensitive to sulphur.

Trichoderma (Binab T)

Spores of the fungus Trichoderma viride are sold in powder or pellet form. The powder is painted on to pruning wounds for protection against disease, especially silver leaf. Pellets are inserted into trees for protection against, and cure of, silver leaf.

Soft soap

This old-fashioned soap of vegetable origin is used as a “wetter” to help sprays to stick to waxy leaves of plants like brassicas and peas. It has some mild pesticide activity.

30. January 2011 by Dave Pinkney
Categories: Organic Gardening, Pests and Diseases, Plant Care | Tags: , , | Comments Off on Garden Pests and Diseases – Pesticide Sprays


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