There are a number of natural botanical sprays and powders available in garden centers. These are derived from plants and not made in a lab. We’ll look at a few of the more common ones available to you.
Insecticidal soap is sodium or potassium salts combined with fatty acids. If you use soap, it must come in direct contact with the insect and it must be wet. It is no longer effective once it has dried.
The fatty acids in the soap penetrate the insect’s outer covering and cause the cells to collapse. This is one of the safest organic pesticides to use because there is no residue, it is non-toxic to animals, and you can use it on your vegetables all the way up to harvest. Be cautious, however, soap can burn or stress plants, so don’t use it in full sun or high temperatures.
Bacteria spray is also commonly known as Bt (Bacillus thuringiensis). There are more than 80 types of Bt used as pesticides. It is a stomach poison that releases toxins in the stomachs of insects that causes them to stop eating and starve to death.
It is generally available in powdered form that is sprinkled or dusted on a plant. It must be eaten by the targeted insect. Bt strains are very host specific and will not harm people, pets, birds or bees, but it can be very slow acting taking days for the insect to completely stop eating and die. It can also kill some of the beneficial insects in your garden.
Neem is a spray that is derived from the seed kernels of the neem tree fruit. It is sprayed onto the plant’s leaves which will upset the insect’s hormonal system and prevents it from developing to its mature stage. Neem is most effective on immature insects and species that undergo complete metamorphosis.
Use caution with Neem as it can be damaging to pets, so keep them away from freshly sprayed leaves until the liquid dries. Neem is non-toxic to humans.
Horticultural Oil is highly refined petroleum oil that is mixed with water and sprayed onto foliage. It coats and suffocates insects or disrupts their feeding.
There is a low toxicity to humans, pets, and birds and does not leave behind any toxic residue. Be careful you don’t burn the leaves of your plants when you use this oil.
Rotenone and Pyrethrum are most readily available ones and are often used in combination. They are derived from the roots of tropical legumes. It generally comes in powder form that is dusted onto the plant. These will inhibit the cellular process thus depriving insects of oxygen in their tissue cells. This is a broad spectrum pesticide and can be used with many types of pests.
If you are using a spray, dilute it in water and use only as needed. Of course, follow application directions on the label. The best time to apply sprays and powders is in the evening or in early morning. And always read the labels of anything you buy commercially. Just because a pesticide is organic doesn’t mean it isn’t toxic.
You don’t HAVE to use anything on your plants if you depend on other animals to help you control pests.