THERE’S a lot of confusion about using so-called ‘organic’ chemicals in the garden and their effect on bees, pets and pollinators.
It’s really up to you if and how you control pests in your garden, but many people think that a method derived organically is safe to use – it isn’t necessarily so.
One of these compounds is pyrethrum, extracted from the flower of a type of Chrysanthemum. The active ingredients are six esters (organic compounds that react with water to produce alcohols and organic or inorganic acids) known as pyrethrins.
Pyrethroids are synthetically-produced compounds with a similar chemical structure, but do not come from flowers.
Both organic and synthetic types are capable of killing off aphids and other pests on contact – and are toxic to bees.
Here’s the facts: Pyrethrum-based insecticides are less harmful than most chemicals to humans and mammals, but are still toxic to other creatures, including bees.
Pyrethrins are used in household insect sprays, outdoor and indoor herbicides, lice treatments, and flea and tick treatments. They’re often mixed with other chemicals to make them effective for longer, often pyrethroids, the synthetic version of pyrethrum.
Insecticides labelled as containing pyrethrum and one of these other chemicals are usually more toxic than pyrethrum-based insecticides alone.
Pyrethrum is classed as moderately toxic to bees and can kill them. To avoid harming them, apply pyrethrum insecticides only in the late evening, night or early morning – bees are not active then and are least likely to come in contact with the insecticide.
Do not apply to blooming plants on nights when dew is forecast or when temperatures are expected to be below 16C/60F. The residual effects are twice as hazardous to bees.
Liquid formulations are usually less hazardous to bees than dusts or granular forms. Pyrethrum dusts can be carried on the bees back to the hive, where the queen may be affected.
Pyrethrins are only mildly toxic to humans, but chemical enhancer piperonyl butoxide, is considered a human carcinogen.
If you do use them, wear eye protection, long trousers, a long-sleeve shirt and a respiratory mask to minimize your exposure.