librarian2003 (librarian2003) wrote in weagardening, @ 2009-11-30 19:49:00 |
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Current mood: | thirsty |
Week 8 - Garden Wildlife
Our main topic for this week is Garden Wildlife, concentrating on invertebrates - the Good, the Bad, and the Bugly.
Here are the images:
Garden Wildlife
And here's the handout:
GARDENING FOR PLEASURE
Garden Wildlife – Friend or Foe?
A healthy garden with a wide range of plants will attract many forms of wildlife including natural predators such as birds, ladybirds, frogs and toads. Their presence will help maintain a naturally balanced environment and the need for artificial pest control will be kept to the minimum. Regular hoeing between plants will not only control annual weeds, but bring many pests to the surface where birds can deal with them.
Some insects are useful, some are unwelcome pests, and some just get on with their lives and we hardly notice them at all, until we step on them.
Pests
Spring pests
Cabbage root flies – These pests will also attack stocks and wallflowers. The tiny white maggots eat the roots, causing leaves to wilt and turn a bluish colour.
Chafer grubs – Bulbs, tubers and fleshy roots are attacked by these 1½ in long, brown-headed, white grubs.
Craneflies – the larvae, called leather jackets, of the crane fly, popularly named daddy-long-legs, eat roots and the base of stems of many plants. They are 2in long, grey-brown, plump and tough-skinned.
Flea beetles – When the leaves of plants such as wallflowers, stocks and alyssum become pitted with small holes, these small striped beetles, are the likely culprits.
Froghoppers – The white froth commonly known as cuckoo spit covers the immature froghoppers while they feed on young growth.
Leaf miners – The grubs of this pest will tunnel inside the leaves of chrysanthemums, rhododendrons and lilacs, leaving unsightly white tracks.
Slugs and snails – Perhaps the most common of garden pests, these gastrapods cause great damage to flowers and foliage.
Wireworms – These damage the roots of most flowering plants, particularly carnations and chrysanthemums.
Woodlice – These grey, flat, oval-bodied creatures may feed on stems, leaves and roots, but rarely do real damage.
Woolly aphids – Cotoneaster, pyracantha and ornamental crab apples are among the shrubs and trees at risk from these aphids, easily recognised by their white woolly tufts. They puncture stems and suck the sap, and also damage the bark which splits and later becomes infected with diseases such as canker.
Summer pests
Ants – Ants build nests in garden soil and around plant roots.
Cabbage white caterpillars – The leaves of nasturtiums, wallflowers, stocks and ornamental brassicas are eaten by this caterpillar, as well as kitchen brassicas.
Capsid bugs – These tiny creatures are ¼ in long and may be green, brown or yellow. They attack herbaceous plants, leaving ragged holes and distorted tissue in young growth, and punctured buds, so that when the flowers open they are malformed.
Cutworms – Plants that topple over because the stems have been eaten at soil level may have been attacked by cutworms. They are flat, soft, greeny-brown caterpillars with dark marks on each side of their 2in long bodies.
Earwigs – These familiar insects, with their glossy brown bodies and pincers at the tail, may damage young leaves and flowers.
Leafhoppers – There are two species of this sap-sucking insect to watch out for, the pale yellow rose leafhopper and the green, red-striped rhododendron leafhopper. The insects feed on the undersurfaces of leaves, causing white flecks or mottling on the surface.
Lupin aphids – These pests that appear on lupin stems are like large greenfly, but are covered with a wax coat which makes control difficult.
Red spider mites – You may need a hand lens to detect these tiny creatures on the underside of foliage, but their presence is indicated by the discoloration of leaves, which drop off prematurely.
Rose sawflies – When rose leaves roll up tightly, this is a sign that the larvae of the sawfly are feeding in them.
Thrips –The larvae of these minute insects, sometimes called thunder flies, attack gladioli, roses and carnations and cause silver streaking on leaves and flowers.
Whiteflies – The adult whitefly is a tiny, moth-like insect commonly found in greenhouses, but also known to infest outdoor plants such as rhododendrons, honeysuckles and viburnums. The young insects feed on sap and foul the leaves with a sticky excretion called honeydew, which encourages sooty mould.
Autumn pests
Swift moth caterpillars – These 1-2in long caterpillars live underground and feed on fleshy roots and bulbs. They are often found when herbaceous borders are dug in the autumn.
Winter pests
Mice – Young shoots, seeds and seedlings in a cold frame or greenhouse, and bulbs in the garden, are a favourite diet of mice.
Beneficial insects and other animals
Centipedes - Ground-living predators sometimes shelter beneath ground cover during the day, but at night prey upon slugs, slug eggs and soil dwelling insects. Distinguish from vegetarian millipedes – centipedes have only one pair of legs per segment and move much more quickly. Centipedes are found in a variety of habitats, but prefer dark, moist, protected areas such as under stones, rotted logs, leaves and bark. They overwinter as adults and lay eggs in the soil during the spring and summer. A few species give birth to living young. Centipedes are relatively long-lived; some species have been known to live up to 6 years.
Predatory bugs - Many bugs from several families, notably capsids and anthrocorids, are predators of other plant-feeding bugs. Anthocoris bugs are 1/6 in long and black-brown. They often gather on willow catkins, and eat scale insects, capsid bugs, caterpillars and midges.
Lacewings - The larvae are ferocious predators of aphids and similar insects, eating around 300 during their development. Encourage overwintering of populations by putting up lacewing boxes. They can be bought as biological controls. Lacewing larvae can be difficult to spot, since they have the endearing habit of covering themselves with the dead remains of their prey. In addition to aphids, lacewing larvae feed on mites, thrips, soft scales, butterfly and moth eggs and other soft-bodied prey.
Hoverflies - Hoverflies are two-winged flies that as adults generally feed on the nectar or pollen of flowers. They prefer sunny and still conditions and have remarkable powers of flight including their renowned hovering close to food plants or patrolling their territories in shafts of sunlight. Larvae of many common species are predatory, especially on aphids. Their colour varies, but is usually bright and is often green. They resemble small flattened fishing maggots. Adults can be encouraged by planting open-flowered plants. Many species mimic wasps, with black and yellow markings. The smallest are tiny black flies of less than 5 mm in length whilst the largest compete for size with bumble bees. None are able to bite or sting and the adults are useful pollinators.
Predatory midges - A number of species of tiny midges have wandering, predatory larvae that feed only on aphids. Some can be bought as biological controls.
Tachinid flies - Adult females of these flies, which resemble very bristly houseflies, lay eggs on or near other insect hosts, especially butterfly or moth caterpillars, and the larvae, or maggots, develop as parasites within the host. Adults are encouraged by open-flowered plants.
Wasps - The adult females of solitary species such as mason wasps collect insect pests to provide food for their grubs. A pile of rotting logs makes a good nesting site. Social wasps are also useful predators in spring/early summer, when adult females collect insect pests to feed the grubs. However, they become pests of ripening fruit in late summer and autumn.
Parasitic wasps - Adult females lay eggs in other insects and the larvae develop as parasites, killing the host. Most insect species have specific wasps parasitising their larvae. One wasp, for example is a significant predator of cabbage white butterfly larvae. A number of them can be purchased as biological controls.
Beetles - Many species of ground beetle are predatory, both as adults and larvae, feeding on juvenile and egg stages of slugs and snails as well as other ground-based insects. Rove beetles are similar to ground beetles; many species are good fliers, feeding on a range of plant-feeding pests. Encourage beetles by minimising soil disturbance and with use of mulches. Ground beetles like damp, sheltered conditions during the day, but emerge at night to hunt out eelworms, leather-jackets, larvae and insect eggs.
Ladybirds - Both larvae and adults feed on aphids, the former devouring hundreds during development and the latter consuming thousands. Also favoured are thrips, spider mites, mealybugs, soft scales, whitefly and a wide variety of other soft-bodied, plant-eating insects. By summer's end they may eat pollen. To attract ladybirds, provide pollen- and nectar-rich flowers and leave the wild blooms of dandelions, wild carrot and yarrow. Ladybirds can be bought as biological controls. Eggs are laid in the spring among prey populations, such as aphids, and are white or yellow, oval shaped and often deposited in clusters. They hatch in three to five days. After two to three weeks of feeding, the larvae pupate inside the last larval skin. Adults appear in seven to 10 days. In the autumn, adults lay eggs and die or hibernate. There can be several generations. Some of the smaller yellow and black ladybirds eat mildew and other moulds.
Mites - Many predatory mites feed mainly on plant-feeding mites, such as red spider mite. A number can be bought as biological controls.
Harvestmen - These are roving, spindly-legged ground-living predators related to spiders. They have a round, one-part body. Female harvestmen lay their eggs on the ground or in rotten wood in autumn. In the spring, the tiny arachnids hatch, white and tiny copies of the adults. The young harvestmen soon darken, and as they grow through the summer, moult seven times until they reach full size. The adults then mate and lay eggs for the next year’s generation. Most species live for only one year. Harvestmen are most commonly found in late summer when they have reached adult size. They are usually found in cool sheltered areas, such as near trees or structures. They need lots of moisture to survive, drinking from puddles and other water sources.
Harvestmen are generally nocturnal and solitary, although occasionally they may be found in groups with legs entwined in protected areas such as holes in trees. Harvestmen generally feed on dead insects, although they will kill very small insects and mites when possible. Prey includes leafhoppers, aphids, snails, earthworms, flies, true spiders, other daddy-longlegs and insect eggs. They do not spin webs to catch prey. They also suck juices from soft berries and fruits, and will occasionally eat plant matter and fungi.
Spiders - All spiders are predatory on insects and other arthropods, although catching systems vary and not all spiders use webs.
Nematodes - Parasitic, microscopic roundworms. These are available as biological control agents for the control of slugs and vine weevil. These parasites are host-specific and are completely harmless to other organisms.
Frogs, toads and newts - The adults of all these creatures feed on many pest species; the young are aquatic, so a pond is required nearby. Frogs and toads will keep the slug population at bay, and also eat woodlice.
Common shrews - Common shrews have silky dark brown fur, with a pale underside and light brown flanks. Shrews have pointed, mobile snouts and small eyes. They are abundant in woodland, grassland and hedgerows. Common shrews are insectivorous and carnivorous, feeding on insects, spiders, worms and carrion. They need to eat 80-90% of their own body weight in food daily. Except for when rearing young, shrews are solitary and are extremely aggressive towards each other. They have home ranges, which vary in size from 370-630 square metres. They are active both day and night (but mostly at night). They build nests below the ground or under dense vegetation. Shrews have a good sense of smell and hearing, but their eyesight is poor. They locate prey hidden up to 12 cm deep in soil, by probing and sniffing with their snout.
Birds - may reduce your crop of autumn berries, but will help control grubs, snails, slugs, caterpillars and aphids.
Hedgehogs - will leave their shelter beneath hedges or a pile of logs at night to forage for slugs, cutworms, wireworms, woodlice and millipedes.
Good bug or bad bug?
Earwigs - Earwigs are predators, feeding on aphids and but they will also feed on living plants, becoming pests in greenhouses and on certain crops such as vegetables, fruits, ornamentals, forages and field plants. Female earwigs feed the litter of young on insects. Earwigs develop from egg to adult through gradual metamorphosis with four to five nymphal instars or stages. During the spring or autumn, females lay 20 to 50 smooth, oval, pearly-white or cream-coloured eggs in a below-ground chamber (upper two to three inches of soil). The female moves, cleans, and provides maternal care by protecting the eggs and new young until the first moult. Young then leave the nest, fend for themselves and mature in one season. Both eggs and adults overwinter. Earwigs may dig as deep as six feet below ground to escape the cold temperatures. They are active at night and are often found around lights. During the day, they hide in moist, shady places beneath stones, boards, and debris.
Woodlice - Woodlice cause very little damage, but they are often regarded as a nuisance. They mainly live on vegetable matter. In gardens they can cause damage to seedlings and young plants. On the other hand in compost they are very useful. They have a similar function to earthworms. Also, woodlice have been seen eating slug eggs. The woodlouse can only survive in high humidity, because they breathe through specialised dry gills. Woodlice have a very individual method of breeding. The females carry the fertilised eggs and eventually the freshly hatched young lice with them, in a breeding area on their stomach that is filled with fluid. The young insects are white at first, and then shed their skin several times. After about three months they are fully grown and will live for several years. In the past, woodlice were often carried in a small pouch attached to a cord around the neck. These were swallowed as a cure for stomach aches and other minor ailments. It is possible that the calcium carbonate in their exoskeletons is able to neutralise stomach acids.
The beneficial effects of woodlice far outweigh any damage that they do. However, woodlice have an ill-deserved reputation as pests, mainly because they wander into houses at night, usually to escape supersaturation with water during wet weather. Woodlice may travel considerable distances during these nocturnal rambles. In the garden, woodlice rarely attack living plants, preferring to eat vegetation that has begun to decompose. In glasshouses, woodlice may nibble seedlings but they rarely do any significant economic damage. In the litter layer of deciduous woods, and on compost heaps, woodlice perform a vital role. They chew dead plants into small fragments and deposit these as faecal pellets that decompose rapidly. Woodlice may also graze fungal hyphae from leaves. Deposition of faecal pellets containing fungal spores in deep moist leaf litter by woodlice may be important in stimulating decomposition in woodlands. Thus, the feeding activities of woodlice speed up the decomposition process and help to return essential nutrients to the soil.
Woodlice are members of the class Crustacea, which also includes crabs, shrimps and lobsters.
Biological control agents
Biological controls are available for:
Glasshouse whitefly
Red spider mite
Mealybug
Aphids
Vine weevil
Soft scale insect
Slugs
Thrips
Leatherjackets
Chafer grubs
Biological controls are usually bought by mail order – they would not survive on the shelves of the garden centre. You can send for them direct from advertisements, or buy the empty box from the garden centre, with instructions on how to get your insects sent to you.
Images
http://www.cgm-gardenlife.co.uk/toc.htm
http://www.arkive.org/
Jo Hanslip
November 2009
Don't forget to check out that wonderful site ARKIVE, which is such a fabulous source of wildlife images. The address is at the bottom of the handout.
Jo