Don't panic, the ladybirds are on it
A recent spell of warm weather has brought about an explosion of plant pests. Horticultural lecturer and author of The Plant Listener, Julie Kilpatrick, has found herself having to answer more than her usual amount of questions from plant owners who are horrified at the numbers of black, green or brown insects infesting their plants.
“Although we often call them greenfly,’ says Julie. ‘Aphids come in a range of colours and most of them don’t fly. Only when colonies get very large do some of the females develop wings so they can fly off and start new colonies elsewhere. In spring, there’s a lot of fresh green growth on the plants and this is perfect food for aphids. Aphids are always around during the growing season but, in warm weather, they breed rapidly and this is when we start to notice them.”
Along with scale insects, thrips, whitefly and others, aphids are sap-sucking pests. They are rarely responsible for directly killing plants but they can weaken them and spread viruses. Ornamental plants can be rendered extremely unsightly, especially when all the conditions are right for a spate of exponential growth in pests.
However, Julie is urging gardeners not to reach for the sprays. “Exponential growth happens because the larger a population gets, the faster it grows. Yes, the aphid numbers are rising but this means food for ladybirds and other beneficial insects and their populations are rising as a result. This is a natural phenomenon – pests increase in numbers but, following closely behind are the predators until, eventually, you reach a point where, all things being equal, the populations settle back down again. I’ve seen a lot of ladybirds mating recently and this means they’re responding to the availability of food.”
One female ladybird can lay up to 1000 eggs in a season and ladybird larvae are ferocious consumers of aphids and other sap-sucking pests but Julie believes ladybird larvae get a raw deal.
“Ladybird larvae are quite small and they look like tiny little crocodiles so many gardeners don’t recognize them as friendly visitors. As a result, they often fall victim to insecticides. Insecticide sprays, including many of those labelled organic, kill most beneficial insects too and ladybird larvae are especially vulnerable. Not just ladybirds are at risk from the indiscriminate application of insecticides. Hoverflies, lacewings, parasitic wasps and a whole host of other predators are on the case, producing young as fast as they can to deal with the pest explosion on our behalf but they can’t do that if we take them out before they’ve had a chance to prove their worth.”
For commercial growers, aphids can be a real problem pest sine no one will purchase plants unless they are in pristine condition but, in her own garden, Julie is happy to let the ladybirds and others do their work.
“I totally understand the need to apply insecticides in some situations, especially if your livelihood depends on it but I believe ordinary gardeners like me should be prepared to take a few losses for the sake of the bigger picture. I’m a great believer in the principles of organic horticulture and that means working with nature, rather than against it. If we have a little patience and don’t resort to chemicals, a short spell of cold weather should knock down the numbers of pests and all that ladybird sex I’ve been witnessing, will result in eggs hatching pretty soon. So don’t panic, the ladybirds have got it covered and, this year, I’ve a feeling we’ll be seeing a lot more ladybirds than we’re used to.”
Julie is author of The Plant Listener, ISBN no: 978 1 9997243 0 6. She blogs at www.theplantlistener.com.
Contact Julie: julie.kilpatrick@gardenzine.co.uk Tel: 07807142661