For many, these delicate flying insects will be a joy to watch, often trailing through the sky in little groups that resemble snaking kite tails. But for others, the sight of cabbage white butterflies will probably cause concern, as it heralds the time they’ll be laying eggs on brassica plants. Eggs that soon hatch into their leaf-eating larvae.

However, it’s the yellowy green and black speckled larvae of the large white that’ll be most damaging to brassica plants since, after they hatch from the clusters of 50 or so yellow eggs, they feed gregariously, reportedly consuming around 27,000 times their final body weight of leaf material before they pupate.

Firstly, killing the adults should always be avoided since other white-coloured butterfly species could be mistaken for cabbage whites. However, if brassica plants are unprotected from the larvae, their feeding could invariably cause significant levels of leaf damage and potentially destroy crops.

Despite the potential for using chemical pesticides on the larvae, it wouldn’t be an environmentally friendly option, and should be a last resort. The reason being that these products will most likely contain a broad-spectrum toxin such as Pyrethrin (organic Pyrethrum), a Pyrethroid (e.g. Deltamethrin, Lambda-Cyhalothrin), or a Neonicotinoid (Acetamiprid), which could all harm non-target insects and beneficial wildlife, a fact that is not always on the product’s label.

However, a simple and environmentally safe alternative, would be to securely enclose susceptible plants within a netting large enough for water and light to pass through, but not the adult butterflies. 

Always ensure there is at least a gap of two inches from the plants; otherwise the butterflies could push their abdomens through the netting and lay their eggs on to the leaves. Another option would be to regularly check the underside of leaves for butterfly eggs and remove as many as possible by rubbing them off the leaf with a finger.

Any missed eggs will soon hatch into larvae, which could then be deterred from feeding on the leaves by spraying with a non-toxic, organic deterrent such as Grazers G3, leaving them to be predated on naturally by social and parasitic wasps. 

For those who do not need to control cabbage white butterflies and enjoy watching ‘summer snowflakes’ in their gardens each year, grow Nasturtiums for the butterflies to lay their eggs on and for their larvae to eat.