Gardeners growing lilies have been told to “watch out” for one common problem that could arise in the coming days and weeks. With another heatwave on the horizon, temperatures are set to hit 34C this weekend, according to weather maps WXCharts.
Experts at Which? Gardening have suggested cutting back early-flowering perennials, harvesting veg and feeding the lawn in July, as well as regularly watering anything you’ve planted in the past few months. For those who have lilies in their garden, the experts recommend that you keep an eye on them. Lilies are easy summer-flowering bulbs for pots and borders. They are usually planted in spring in either pots or borders, but you can also buy potted plants for spring and summer. Ceri Thomas, editor at Which? Gardening, says there is one common problem that you should “watch out” for: Lily beetles.
“Lily beetles are at their peak in July, as many new adults emerge. Watch out for the red adult beetles and the black grubs, both of which will eat your lily leaves and flowers,” she said.
Lily beetles are bright red beetles around 7mm long with black heads, legs and undersides. They can deter predators by squeaking, and you can hear them if you hold them close to your ear.
“Adults and larvae eat the leaves, flowers and seed pods of lilies, fritillaries and nomocharis and can do severe damage,” Ceri says. “Adult beetles nibble irregular holes in the leaves and petals, while the larvae methodically work their way from the leaf tips towards the stem.
“Adults are occasionally found on other plants, including Solomon’s seal and lily-of-the-valley, but these plants do not seem to be eaten by the larvae.
“After mating, the female lays 200-300 orange eggs on suitable plants. About a week later, these hatch into reddish-brown larvae that cover themselves with their own black, slimy excrement. When the grubs are mature, they burrow into the soil to pupate, emerging as adults in mid- to late-summer.”
If you grow only a few lilies, it’s easier to control lily beetles by inspecting them regularly. To remove them, pick off and squash the adults, grubs and eggs; the earlier you start looking, the more likely you are to break the pest’s life cycle.
Keep the beetles under control, at least until the plants finish flowering, to allow the bulbs to build up enough to form next year’s flowers. Where plants have been badly damaged, feed the remaining leaves with liquid feed sprayed onto the leaves.
If you have lots of lilies and wish to spray them, use the insecticide Westland Resolva. If plants are flowering, spray at dusk to avoid harming bees. Grubs are more susceptible than adults, who are protected by their hard coats.