动态第760页 - 绿手指 - 养花技巧、花生病了怎么办、花园打理和设计

2017年09月15日

Distorted, yellowing or slowed growth on plants can often be a sign of scale insects. These look like tiny brown or orange blobs and can often be found on the undersides of the leaves near the veins, on the stems or in the leaf joints. They produce sticky honeydew as they feed which can cause the foliage on infested plants to become sticky and covered with dark sooty mould.[图片]Plants affected Scales are usually pests of ornamental plants and can be especially troublesome in greenhouses. Over 300 species of ornamental plants are known hosts. About Scale insects Scale insects are small sap-sucking insects, so called because they produce an umbrella-like waxy coating or 'scale' over their soft bodies. They're often difficult to detect on plants, although leaf yellowing or sticky honeydew deposits can be the first signs of infestation. Scale insects may appear as small, flattened white, yellow or brown 'discs' or 'blobs', on stems or on the underside of leaves near the veins. Scale insects are divided into two families - soft scale (Coccidae) and hard scale (Diaspididae).[图片]Soft scales can breed all year round on protected crops and produce large amounts of sugary honeydew when they feed on the plant's sap. This honeydew attracts sooty moulds that grow on the leaves. Hard scales lay eggs under their scales which hatch into nymphs or 'crawlers' after the female dies in early summer. The nymphs can move short distances on a plant, but disperse long distances on the wind or on animals. Hard scale don't produce large amounts of honeydew. Female scale insect nymphs become immobile once they find a suitable feeding site and become adults. Males are rarely seen but are often winged and midge-like in appearance. The 'scale' produced by these insects can remain on a plant for a long time after they're dead.[图片]Treatment Chemical Products containing the following chemical ingredients are all effective on Scale insects Pyrethrum Natural fatty acids Rape seed oil Tar oil wash (for use on deciduous trees and roses in December) Thiacloprid (for use with outdoor fruit crops) Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments.[图片]Organic Check bought plants thoroughly. If an infestation is in the early stages, the scales can be cleaned off using a brush and water, or just a thumbnail. Biological control is available in the form of a tiny wasp which parasitises soft scales, Metaphycus helvolus. This can be purchased for release into the greenhouse but requires good light and temperatures of at least 22°C (72°F) to be effective. The small predatory ladybird Chilocorus nigritus can also be purchased, that feeds on hard scale species. Lacewing larvae also control scale.[图片]Prevention Check plants regularly for signs of scale infestation and deal with them as soon as they appear. Keep the environment clear of weeds because these often harbour the pest. Monitor plants for signs of scale, such as leaf drop, honeydew or sooty mould. Look out for ants running up and down the plants, 'milking' the honeydew. Avoid using broad spectrum insecticides which will kill beneficial insects as well as scale. Destroy any leaves that have been removed from an infested plant because these can harbour many mobile juvenile scales.

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2017年09月15日

Stunted and deformed foliage, collapsed plants, swollen and distorted roots. The foliage may develop a purple tinge and wilt easily on hot dry days.[图片]Plants affected Members of the brassica family, including cabbages, Brussels sprouts, broccoli, cauliflower, swede, wallflowers, and related weeds. About Clubroot exists as spores in the soil and can survive for at least 20 years, waiting for a suitable plant to infect. The spores enter plants through the roots. Once inside the roots, more spores are produced which end up back in the soil when the infected plant ultimately rots away. The disease can be easily transported to new sites in soil or on muddy boots or plant material.[图片]Treatment Preventing the disease from entering your garden is by far the most important consideration when dealing with clubroot. Take care when buying brassica plants, especially when you’re not sure where they come from. For example those sold at car boot sales and small plant fairs. Aim to grow all new brassicas from seed. Clean tools, pots and boots carefully after use on contaminated ground. Affected plants should be removed entirely once harvested, dried and then burned.[图片]Some control of the symptoms is possible by liming the soil to raise the pH to around 7. Keep your garden clear of related weeds which can harbour the disease. These include wild radish and shepherd’s purse. Some varieties are more resistant to clubroot than others. Good choices include: Cabbage ‘Kilaxy’, Cauliflower ‘Clapton’, Brussels sprout ‘Crispus’ and Swede ‘Gowrie’

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2017年09月15日

Shoots, buds and leaves that are wilting and quickly dying back towards the roots, turning black as the plant dies. In some cases discoloured lesions can appear on stems.[图片]Plants affected Clematis, especially varieties and cultivars that produce large blooms. About Clematis wilt is a very common although little understood problem. The disease is caused by a fungus known as Phoma clematidina. The fungus causes lesions on the plant’s stems which in contact with water, release their spores that spread the infection. The disease is thought to also be affected by water-logging, wind and failed grafts. Sometimes clematis wilt is caused or aggravated by root damage and damage caused by slugs and insects, possibly transporting the spores. The disease is rarely fatal to the plant and new shoots normally reappear in the next season.[图片]Clematis wilt is often misdiagnosed because damage to the stems and lack of moisture at the roots causes wilting anyway. Critical points that define Clematis Wilt are: Leaves going black not brown; blackening from the top down; rapid onset. Treatment Chemical Products containing the following chemical ingredients are all effective on Clematis wilt Myclobutanil Penconazole. Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments.[图片]Organic Cut back affected stems to ground level Avoid plant stress by keeping the soil well fed and mulched. Plant more resistant varieties of clematis such as c. montana, C. viticella or C. tangutica. Plant Clematis deeply, around 6 inches lower than other plants. This encourages more bud development, so the plant can recover more easily if all the stems above ground need to be cut back.[图片]Put a shield around the base of the plants to stop infected water splashing up onto the base of the stems. The top of a fizzy drinks bottle is good for this.

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2017年09月15日

Yellow/ brown patches on lawns. Wilting plants and damaged leaves on garden shrubs, vegetables and immature trees.[图片]Plants affected Chafer larvae attack the roots of lawns and some ornamental plants, fruit and vegetables, while adult chafers feed on the leaves of a range of different shrubs, plants and immature deciduous trees. However the adults rarely cause much damage. About Chafer grubs Adult chafers range in size, the biggest at 30mm in length being the Cockchafer, and the smallest the Welsh chafer at 11mm. The adult chafers are mainly reddish brown in colour with distinctive large antennae.[图片]Chafers have strong, hard cases that protect their delicate wings, when in flight these cases make a distinctive whirring sound. The creamy, white larvae or grubs are often found curled up just below the soil surface, feeding especially on roots, mainly in August and September. Larvae have distinctive grey ends to their abdomens, and brown heads. Some species remain as larvae for up to three years. Plant damage is mostly caused by the larvae although the adults can also seriously damage the upper parts of the plants. Chafers overwinter below ground as pupae and the adults emerge in spring. Adults often return to the same location to lay their eggs over a two week period during early summer. Chafer predators such as foxes, badgers, rooks, crows, jays and magpies often damage lawns and community greens searching for grubs.[图片]Treatment Organic Try natural pest controls, such as the parasitic nematode, Heterorhabditis megidis. Where possible eradicate the larval stages by lifting sections of turf and disposing of the larvae. Encourage birds that prey on the beetles and their larvae. Use barrier methods such as fleece, to keep adults away from plants at risk.[图片]Prevention Check regularly for signs of chafer infestation and quickly deal with them. Scarify and aerate lawns in autumn. Where lawns have a history of infestation try to compress the turf by rolling it heavily during spring.

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2017年09月15日

Carrot flies, also known as carrot root flies, infect their host plant's roots causing widespread damage to crops. The damage is caused as the fly larvae feed. Signs to check for are leaf discolouration, and holes or tunnels in the carrot. The holes often turn a rusty colour due to a fungal disease called carrot or parsnip canker which commonly infects the damaged area.[图片]Plants affected Carrot flies are a major pest of the whole carrot family. The main host plant is carrots but they also attack celery, celeriac, parsnips and parsley. About Carrot fly Adult carrot flies are part of a group known as stilt-legged-flies. They have long orange legs, a black body and a red/brown head. They're about 4-5mm long and poor fliers.[图片]The larvae of the carrot fly are the major cause of plant damage. They are maggot-like in appearance, growing to about 10mm in length and are creamy yellow in colour. Carrot fly pupae are brownish yellow in colour and are found in the soil. Carrot fly larvae often cause widespread damage since they move through the soil feeding on different roots. Adult carrot flies overwinter below ground and emerge in the spring to mate. The first generation of eggs are laid into the soil surrounding the host plants. A second generation emerges in July and August. It's this generation that overwinters in the soil. Occasionally there can be three generations a year if environmental conditions are favourable. If carrot or parsnip canker spores are present within the soil, they can often infect the areas where carrot root fly larvae have been feeding. This causes a rust colouration of the affected areas.[图片]Treatment Chemical Products containing the following chemical ingredients are all effective on Carrot fly There are no approved insecticides currently available to amateur gardeners. Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Regular checks for damage or infestation. Crop containment, for example, covering plants with a fleece barrier. Choose growing sites that are fairly open and exposed.[图片]Remove damaged plants to reduce the smell of carrot which attracts the flies. Companion plant with strong smelling plants to mask the carrot smell, such as onions. Avoid sowing susceptible plant seed during the early spring and late summer when carrot flies will be laying eggs. Thin seedlings in the evening when adult flies are less active and then destroy all thinned plants. Firm the soil around the plants after thinning as this deters the flies from laying eggs.[图片]Prevention Check the crop regularly for signs of infestation and promptly remove any affected plants. Grow less susceptible varieties, such as 'Fly Away' and 'Resistafly', which are low in phenolic acid. During the winter, thoroughly fork through the soil where susceptible plants will be grown. This should expose overwintering carrot flies to frosts and predators.

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2017年09月15日

Distorted and misshapen leaves, flowers, buds and fruit growth. The leaf tissue around affected areas may become brown and eventually die.[图片]Plants affected Many different garden plants are affected including fruits, vegetables, ornamentals, trees and weeds. About Capsid bugs Capsid bugs feed on plant sap and in doing so cause deformation of plant material. There are many different species of capsid bugs in the UK. Capsids are also known as mirid bugs. Some species of capsid also feed on other small insects. Adults vary in colour from green to red/ brown, around 6mm in length, and have a long, slender feeding tube. Young are similar in shape and colour, but smaller and wingless. When disturbed they fall down onto the soil as a defence.[图片]When feeding they inject saliva which is toxic to plants. There can be one or two generations per year depending on the species. Eggs are laid into cracks in tree bark, woody stems, and at the base of hedges. They hatch in late spring. Depending on species, over-wintering takes place as eggs or as adults in plant debris. Treatment Chemical Products containing the following chemical ingredients are all effective on Capsid bugs Pyrethrins Pyrethroids Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments.[图片]Organic Regularly inspect plants in spring. Remove and destroy adults by hand. Winter wash trees to destroy eggs. Prevention Keep areas around plants free from plant debris. Remove weeds around plants.

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2017年09月15日

Large holes in the leaves of brassica crops and nasturtiums are usually the work of cabbage white caterpillars. Before an attack you may notice large numbers of white buttlerflies around your plants, as they lay eggs. These hatch into larvae which make small holes in the leaves as they start to feed on them, becoming much larger as the caterpillars start to feed more vigorously. Caterpillars also produce small brown or dark green granular deposits as they feed.[图片]Plants affected All types of brassica are affected by cabbage white caterpillars, including cabbages, cauliflower, Brussels sprouts, swede and turnips. About Cabbage white butterflies The caterpillars of a few species of butterflies can cause extensive damage to cabbages and other brassicas, eating holes in leaves and tunnelling into the hearts. Plants begin to rot and become spoiled with excrement.[图片]Two species are particularly important pests: the large white butterfly, Pieris brassicae, and the Small White butterfly Pieris rapae. Both species are commonly seen flying within our gardens and are affectionately called summer snowflakes. While the small white is a native species, the large white has usually migrated from southern Europe becasue they don't often survive a north European winter. Large white butterflies have often been seen crossing the English channel in swarms of many hundred individuals. Cabbage white butterflies overwinter as pupae. Those that survive the cold months will hatch into butterflies during the spring.[图片]The butterflies mate then each female lays a few hundred eggs, on the leaves of cabbages, other related plants and nasturtiums. The large white's eggs are often laid in batches of ten to 20,which hatch into yellow and black slightly hairy caterpillars in about two weeks. Large white caterpillars feed for a month or more and can reach 50mm in length before they turn into pupae. The small white's eggs are laid singly and hatch into bright velvety-green caterpillars. Unlike the large white, these caterpillars often burrow into the hearts of cabbages to feed. Cabbage white caterpillars leave their food plants when ready to pupate and usually attach themselves to a vertical surface such as a fence or wall with a silk girdle before their final skin shed.[图片]During the summer months, the pupae soon hatch into the next generation of butterflies and the cycle continues. The severity of cabbage white problems can vary considerably from year to year due to weather, immigration and diseases. Treatment Chemical Products containing the following chemical ingredients are all effective on Cabbage white butterflies Pyrethrum Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Inspect the undersides of leaves and remove any egg clusters.[图片]Remove caterpillars by hand, particularly before cabbages begin to develop hearts. Encourage insectivorous birds within the garden by using bird-feeders in winter and nest boxes in spring. Don't remove dead older caterpillars that have become parasitised because these will produce many more parasites that will attack and kill further generations of caterpillars. A naturally occurring bacterium, Bacillus thuringiensis, kills only caterpillars and not the predatory insects, and is very effective when sprayed thoroughly above and below leaves. Prevention Inspect susceptible plants on a daily basis during the growing season and remove any eggs or caterpillars that are found. The appearance of white butterflies hovering around susceptible plants almost certainly means that eggs have been laid.[图片]Cover plants with insect-proof mesh or fleece, although this can lead to overheating during the warmer summer days. Transfer any parasitised caterpillars to plants where new caterpillar infestations are expected. Avoid planting colourful, high nectar plants near the cabbage patch as these will encourage adult butterflies into the garden.

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2017年09月15日

Mature plants can exhibit wilting, discoloured leaves. Younger and newly transplanted plants can show slower growth, and may eventually be killed.[图片]Plants affected Virtually all Brassica plants are attacked as well as some ornamentals. About Adults are similar in appearance and size to common house flies. Larvae are white, legless grubs up to 1cm long, and can be found in the soil around plant roots. Pupae are reddish brown, and are also found in the soil. After over-wintering, adults emerge from pupal cases in late April / May to mate, and lay small white eggs in the soil at the base of plants. Eggs will hatch in about a week and the tiny white larvae will begin feeding on the roots of susceptible plants. After around a month of feeding, the larvae will pupate below the soil surface.[图片]A second generation of adults will emerge in June / July, and a third later in the autumn. Damage to older plants from larval feeding rarely results in death, although yields may be reduced. Treatment Organic Regularly cultivate soil to expose larvae and pupae to predators. Chickens are particularly good for this, if you have access to them. Allow them onto the land during the winter, when they will happily consume the larvae. Encourage insectivorous birds by hanging boxes and feeders. Encourage predatory ground beetles by providing suitable winter shelters.[图片]Prevention Fleeces and netting can be used around bedding plants to prevent flies laying eggs. Alternatively, lay 15cm discs of carpet, plastic or cardboard around the base of plants. Use sticky traps around plants to trap adults, and to monitor the first signs of pest presence.[图片]A four year crop rotation will help stop larvae populations from building up in the soil. In simple terms, after growing brassicas, do not grow more brassicas in the same place for at least four years.

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2017年09月15日

Waxy residues and small white skin sheds on leaves and heads of many brassicas and cabbage family plants. There may be a covering of a sticky, sugary substance on the leaves which could become infected with sooty mould. Leaves may become yellow with high infestations. Dense colonies of aphids may be found on the undersides of older leaves.[图片]Plants affected Cabbages, cauliflowers, kale, rape, spinach, Brussels sprouts, turnips, broccoli, mustard, other cabbage family crops, radishes, swedes and some weeds. About Mealy cabbage aphid Aphids are usually found on the youngest leaves and shoots, or on the heads of cabbages. The undersides of more mature leaves will also be affected when infestations are large. Adult aphids are up to 2mm long and elliptical in shape. They are mainly green in colour although their waxy coating gives them a powdery grey appearance.[图片]During the warmer months aphids give birth to as many as five live young a day so rapidly produce large colonies. When the colonies become over populated, they move to different locations by producing winged aphids. During the autumn, aphids mate and produce eggs which overwinter. Mealy cabbage aphids can damage plants in two ways, either directly by piercing the leaf with their feeding tubes and sucking the sap, or indirectly by infecting the plant with a virus. Aphid-transmitted viruses can often result in deformed and stunted plants. Aphids feed on plant sap, and excrete plant sugars as honeydew Honeydew often covers the leaves of a plant and then becomes infected with unsightly black sooty moulds.[图片]Treatment Chemical Products containing the following chemical ingredients are all effective on Mealy cabbage aphid Pyrethroids and Pyrethrin Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Regular and thorough observation of plants. Spray infested areas with a firm jet of water. Spray with natural fatty acids, for example insecticidal soap. Netting and fleece can be used to stop the aphids spreading. For outdoor plants, aphid predators such as ladybirds, hoverflies, lacewing larvae and parasitic midges called aphidoletes, can be released onto affected plants.[图片]For greenhouse plants in a contained environment, parasitic wasps such as Aphidius colemani and Aphidius ervi can be used. Prevention Regularly check plants for signs of aphid infestation and deal with them as soon as they appear. Encourage natural enemies like ladybirds, hoverflies and lacewings to become established in the garden by planting daisy-like flowers, yellow flowers and in particular, the poached egg plant Limnanthes douglasii.[图片]Avoid using broad spectrum insecticides which will kill beneficial insects as well as aphids. Encourage insect-eating birds such as blue tits, by hanging feeders during the winter months and nest boxes in the spring. Maintain a weed-free environment around the brassica plants and collect and destroy all shed leaves.

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2017年09月15日

Botrytis infects plant material above ground which is usually dead or dying. Depending on the species of the plant and the fungus there may be different symptoms at different times of year. A common sign of botrytis is a grey mould on leaves, stems, fruits, flowers and buds. Before the mould appears symptoms include dead brown patches on leaves, stems and buds, white or pale brown spots on petals and fruit, and rotting on unplanted bulbs.[图片]Plants affected Most fruit and vegetables, some houseplants, ornamentals, shrubs and trees. About Grey mould There are many species of botrytis with different infection methods. They cause a range of symptoms before the fuzzy grey mould appears including dead brown patches on leaves, stems and buds, white or pale brown spots on petals and fruit, and rotting on unplanted bulbs. The spores will attack weak or dying plants in preference to healthy ones.[图片]Conditions must be cool and humid for plants to be infected. The fungal phase can only survive a narrow range of temperatures. Botrytis overwinters as small, dark, hard structures, called sclerotia, on plant debris and other surfaces. When spring weather conditions are favourable they produce spores. These are dispersed by wind, air movement, water splash and pesticide sprays. Once a plant is infected, botrytis may spread to all parts depending on its species and variety.[图片]Treatment Chemical Products containing the following chemical ingredients are all effective on Grey mould Myclobutanil Penconazole Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Regular observation is essential to prevent infections establishing. Remove all dead and injured plant material before it can become infected. Remove infected leaves, fruits and buds by cutting right back into healthy growth. Bin or burn the infected material to help reduce the spread of infection.[图片]Isolate infected plants to reduce infection spread. Place fleece between plants to reduce the movement of spores. Prevention Regularly check plants for signs of infection and deal with them as soon as they appear. Ensure greenhouses are always well ventilated.[图片]Space plants out to reduce the humidity around them and prevent infections establishing. Reduce the humidity in greenhouses and around houseplants to prevent infections establishing.

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