Gardening News

The relatively dry weather last week certainly helped the garden. The lilies just starting to emerge brought flashbacks to last summer’s brilliant display but reminded me of the only serious pest I really need to deal with: the lily beetle.

I have been reading about how the Amish control pests, famously without the use of insecticides. Rather, they rely on the health of their plants and the use of natural predators. This is where the ladybird comes to the rescue, feeding on the lily beetle grubs and larvae. They plant an insectary strip to provide nectar, pollen and shelter for general predators that suppress many pests and increase beneficial insect biodiversity. Use a selection of plants to cover the whole year; this can include winter-flowering pansies, cosmos and a ladybird favourite, French marigolds.

Understanding the cycle of the lily beetle is the key to their eradication. Adults emerge in late March from their winter shelter and remain active until October, laying eggs from spring into late summer. They navigate to the plants by following chemical signals released by host plants. They can fly short distances between plants and neighbouring gardens, but their spread is mainly caused by human movement of plants, soil or garden waste. I would recommend buying quality bulbs rather than pot-grown plants. If you do buy pot-grown lilies, quarantine them for at least two weeks to make sure there is no infestation.

Natural predators do help, but there is no substitute for frequent inspection of the plant and the removal of beetles and larvae as they appear. You can resort to spraying if necessary—only the beetles feeding on the plant will be affected; never spray the flowers. Once under control, go back to manual removal, shaking them onto an old white sheet or pinching them as you find them, and let the ladybirds help. Removing all the food source for natural predators is like firing your whole defence team.

In the autumn, tidy and disturb the soil around lilies to reduce overwintering adults returning in spring. It may take a few years to eradicate them, but we will get there in the end. Deferred gratification!