By encouraging natural predators, following good garden practice, and making regular checks on your plants, you can keep many pests at bay. Aim to create conditions that support a healthy balance of predators and their prey, and you will limit the damage and need fewer chemical controls.
Pest patrol should begin when you buy new plants or accept leafy gifts. Unwelcome visitors also fly or crawl in from neighboring gardens, so keep your eyes peeled and take prompt action.
To prevent a plague of pests, avoid growing large areas of one type of plant. It is more difficult for pests to home in on their target when confronted by a variety of different plants, such as perennials, annuals, and shrubs, as well as herbs, vegetables, and fruit. The abundant nectar also draws in beneficial insects. Don’t overfeed plants because aphids love the resulting soft growth.
Use a hand lens to scan flower buds, shoot tips, and the undersides of leaves for mites, aphids, and whitefly. Also look for grubs or nibbled roots when you take plants out of their pots, and search for caterpillars on rolled or skeletonized leaves. A night-time foray with a flashlight
will reveal nocturnal pests, such as slugs and snails; seek them out during the day by checking under pots. Weed regularly, and look out for pest hideouts.
Neaten potential slug and snail roosting sites (image 1).
Check buds and shoot tips for aphids (image 2).
Pick off larger pests, such as lily beetle, by hand (image 3).
There’s often a frustrating lag between the appearance of pests, like aphids, and their natural predators, such as ladybirds, lacewings and hoverfly larvae. So, don’t be too quick to reach for insecticides, as killing off natural predators’ food sources may drive them away. Chemical pesticides also kill friendly bugs, as well as unwanted insects. Simple, open nectar-rich flowers, such as blanket flower (Gaillardia), are a magnet to bees and hoverflies, which appreciate an easy meal.
It is important to recognize the chief insect predators; they are often the larvae of more familiar adults, like ladybugs and hoverflies, but some are quite different in appearance. By knowing what these larvae look like, you will be less likely to confuse them with pests, and may be able to move them to badly infested plants. Some predators hide under leaf litter and bark mulch, and are invisible during the day, actively feeding at night. One example is ground beetles, which attack slugs. Visit internet websites to identify mystery bugs or try ask the experts at your garden center.
Lure beneficial insects into your garden by providing hibernation sites, such as a log pile, and simple flowers, which attract nectar-feeding types. Grow leafy ground cover to shelter slug-munching frogs and toads, and add a small pond with grassy margins. Delay cutting herbaceous plants till spring for winter cover, and provide food, water, and nesting sites for birds.
Ladybugs and their larvae both gorge on aphids. Encourage them to visit in spring by avoiding insecticides, and provide cover, such as evergreen shrubs on a south wall, a hedge base, bark crevices, or leaf litter, for overwintering adults.
Frogs and toads eat slugs and flies, and even without a pond, will colonize a garden if there is shady ground cover, and a log or rock pile.
Garden spiders, especially web-building species, trap and eat large numbers of flying insect pests, including aphids and crane flies.
Hoverflies vary enormously. Larger species are sometimes confused with wasps, despite their hovering flight. Adults pollinate flowers and crops, and most larvae have a good appetite for aphids and other pests. Adults prefer yellow, orange, and white blooms.
Lacewing adults are most often seen seeking shelter indoors in autumn. Provide cover as for ladybugs. Green lacewing larvae, called aphid lions, also have a voracious appetite for other pests.
Thrushes are one of the few birds that eat snails. Most birds, including seedeaters, feed nestlings on insects and caterpillars. Encourage them with a year-round water supply, supplementary food, and roosting and nesting sites.
Excerpted from How to Grow Practically Everything
© 2010 Dorling Kindersley Limited