Note: In order to minimize harming honeybees we recommend that all spraying be conducted at times when bees are not actively foraging, such as late evening or very early morning
There are so many insect control options available to the organic gardener, that it’s impossible to list them all. The products we carry at Heyden’s Gardens in Cedarburg fall into a few general categories:
Oils pose a very low risk to people or to most beneficial insect species, and they quickly dissipate, thereby leaving little or no residue. They may need to be applied multiple times throughout the season to control new populations of damaging insects. Oils should not be applied on hot sunny days as to do so can cause burning of plant tissue.
- Mineral oil and Cottonseed oil
These oils suffocate damaging insects by blocking the air holes through which they breathe.
- Clove Oil, Garlic Oil & High-Scent Essential Oils
These oils act primarily as an insect repellent/deterrent but many also are toxic to harmful insects.
Neem oil is derived from the seed of the Neem tree, which is native to Asia and India. This oil is relatively new on the natural insecticide scene and is actually rather amazing in that it acts not only as an insecticide but also as a miticide and a fungicide! Neem oil is usually sprayed on new foliage but can also be applied as a soil drench and will be taken up systemically by the plant tissue to control chewing & sucking insects. Neem is non-toxic to beneficial insects since insects need to ingest it to be affected. Neem oil acts in a different way than many insecticides and it is important for the gardener to understand that you will not see an immediate knockdown of insects but rather a slow but significant decline in populations. Rather than being a simple poison, Neem enters the system and interferes with the insect’s hormones, causing them to stop feeding and stop breeding.
Insecticidal soap works in a similar action as horticultural oil in that it effectively suffocates soft-bodied insects such as aphids, spider mites, thrips, whiteflies, and caterpillars. It is ideal for houseplants and edible crops as it does not persist in the environment and may be used up to the day of harvest.
BT (Bacillus thuringiensis)
BT is a naturally occurring bacterium that is an effective biological insecticide for use on caterpillars, mosquito larvae, and fungus gnats. The bacteria interfere with the digestive processes of the caterpillars, causing death.
Spinosad is a relatively new insect killer that is especially effective against caterpillars and thrips, which are the two most common pests on annual and perennial flowers. Spinosad is derived from the fermentation of a naturally occurring soil bacterium and is safe for adult butterflies, most insect predators & parasites and is in the safest human health category. Care should be taken, though, to apply when bees are not active as it is toxic if sprayed directly on them but safe for bees once it dries. Spinosad has been awarded the Presidential Green Chemistry Challenge Award for products that reduce negative impacts on human health and the environment.