Things to know before using insecticides
Do your homework and make wise choices. All insecticides should be used only when necessary and plant based compounds are safer for people, pets and the environment than chemical ones.
Insecticidal oils disrupt insect growth. Today ultra-refined horticultural oils are used that are less harmful to your plants than the old, heavier dormant oils and kill on contact. Oils are very effective on sucking insects as once sprayed they remain on leaves a bit longer than soap sprays. Spray outside if possible, never in direct sunlight and away from ornamentals that may have bees pollinating or food crops, children and pets. Be sure to spray stems, flowers, and both the tops and undersides of the leaves. Use this spray if the temperature is less than 90°F (32°C) or more than 40°F (4°C) or leaf damage may occur. If it is too hot, cold or too windy you can use a gentle spray of clear water to knock insects off and wait for a better day. A follow up spray of clear water the following day is recommended as oils can clog leaf stomata.
Homemade insecticidal oils, while harmful to both good and bad insects on contact, have minimal effect on plants, pets, and the environment.
Natural plant based oils made from neem (oil is pressed from the seed of the evergreen neem, Azadirachta indica, tree native to India), pyrethrum, or nicotine extracts are less harmful to plants and animals so try to use these before resorting to synthetics or chemicals. They have a shorter residual life and breakdown relatively quickly for good insects that may appear after spraying.
Pyrethrum or pryrethrins are controversial with environmentalists and nicotine has been banned in Canada.
Some plants like ferns and plants with bluish colored leaves are very sensitive to oils on their leaves. Do a test on a small part of your plant before a full treatment.
There are sometimes specific warnings not to use a product on a particular plant. e.g. Areca and other palms, ferns and succulents are extremely sensitive to chemicals. Do a test on part of a plant the day before a full treatment if unsure.