动态第761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

The main symptoms of this prevalent disorder are large, black/brown, leathery sunken pits on the base of fruits. This is especially common on tomatoes and peppers.[图片]Plants affected Peppers, tomatoes, squashes, aubergines and watermelons. Plants with soft, succulent fruits suffer the worst from this condition. About Blossom-end rot Blossom-end rot is not a disease but is the result of a number of environmental and physiological factors. It's most common for the disorder to arise as the fruits are half way through their development. The disorder develops if the plant's water intake is not sufficient for example in drought, and consequently the plant cannot extract enough calcium from the soil.[图片]Plants grown in acid soil are at a higher risk of developing these symptoms. Over-watering can also cause the disorder. Blossom-end rot can cause considerable fruit/crop damage, sometimes with large areas of the fruit affected. The rot is not transmittable from plant to plant or fruit to fruit. Treatment Chemical Products containing the following chemical ingredients are all effective on Blossom-end rot[图片]Calcium carbonate Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Use Organic fertilisers with added plant nutrients, especially those containing calcium. Try to maintain a constant soil pH around 6.5. Prevention Thorough checks of crops during the fruiting season will reveal the presence of this disorder and enable the growing conditions to be corrected.

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2017年09月15日

Dark brown or black patches surrounded by paler areas on wilted and curled leaves. As the plant weakens, stems can also be affected showing brown discolouration and decomposition of the whole plant soon follows. Underground potato tubers suffer from an all over reddish brown rot that destroys the vegetable and has a foul odour. The fruits on a tomato will soon start rotting after the leaves become infected.[图片]Plants affected Potatoes, tomatoes and other members of the Solanaceae family. About Potato blight and tomato blight are both caused by the same fungal disease. Once the fungus takes hold it rapidly spreads rapidly by wind-borne spores. Tomatoes grown under glass will be less likely to succumb as the blight spores do not easily get inside greenhouses. The fungus spreads easiest when weather conditions are above 10 degrees centigrade and when there is high humidity in the air. Tubers carrying the disease which are not incinerated can become ‘Primary Infectors’ if they are replanted and conditions are ideal for the fungus. Periods of hot dry weather can subdue and delay potato blight symptoms.[图片]Blight cannot survive in soil or fully composted plant material. It over-winters in living plant material and is spread on the wind the following year. The most common way to allow blight to remain in your garden is through ‘volunteer potatoes’. These are tiny potato tubers which survive over the winter in the soil or the compost heap and shoot up again in the following spring. Treatment Chemical There are a number of copper based fungicides, including Bordeaux mixture which will have some effect. They mainly work in a preventative way so waiting until the first symptoms appear may be too late. 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 observe crops to check for damage and remove all affected plants immediately and incinerate. Keep weeds under control that could be alternative host plants e.g. Deadly Night Shade. Avoid growing at times of year when weather conditions are favourable for the fungus. At the first sign of infection, cut down all the tops of potato plants (known as the haulms) and burn or fully compost them. Then leave the tubers in the ground for a few days before lifting them to allow any blight spores on the soil surface to die off. Do not compost infected or unused tubers.[图片]Tomatoes should be harvested as soon as blight becomes apparent even if they’re still green (make chutney!) Preventing Further Infection Grow resistant varieties such as: Potatoes ‘Axona’ or ‘Mira’ and Tomato ‘Ferline’.

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2017年09月15日

Large black or dark purple spots on the surface of the leaves or stems are the main signs of black spot. As the problem gets worse the foliage gradually turns yellow and drops prematurely, weakening the plant.[图片]Plants affected Rose black spot is an extremely common and widespread fungal disease of both cultivated and wild rose varieties. About Rose black spot Rose black spot is specific to roses and all types are susceptible. The disease causes dark spots or irregular brown or black blotches on both leaf surfaces. Leaves then turn yellow and drop prematurely, resulting in weakened plants. The disease is worse in warm, wet weather. The black spot fungus produces spores which are released under wet conditions and usually spread by rain-splash. The disease can also be passed from plant to plant on hands, clothing or tools.[图片]Spores overwinter mostly on the shoots, but can survive on fallen leaves and within the soil. Recently, rose black spot has become more common in town and city gardens due to less sulphur dioxide within atmospheric pollution. Sulphur is known to reduce fungal problems. Treatment Chemical Products containing the following chemical ingredients are all effective on Rose black spot Penconazole Myclobutanil - alternating any of these with the protectant Mancozeb to prevent the fungus developing resistance to the fungicides. Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Remove infected, fallen leaves promptly and burn. Hard prune shoots in spring and burn the prunings. Treat infections with powdered sulphur, which is deemed organically acceptable.[图片]Some cultivars are partially resistant to black spot but in a bad year all varieties may succumb. Generally, many of the older cultivars and more yellow than red or pink cultivars are susceptible to the disease. So checking catalogues and choosing resistant varieties, such as 'Bonita', 'Royal William' or 'New Dawn', and growing a mixed planting should help. Rose varieties less than five years old should be relatively disease resistant. Prevention Prevention of rose black spot is very difficult and many strains of the fungi are resistant. However, regular raking around the plant with a hoe and pruning and burning of infected material will certainly help along with the advised treatments. Choosing resistant varieties also helps, but don't rely too heavily on resistance because there are many species of fungus and even new varieties can quickly succumb.[图片]Adopt a regular, fortnightly spraying regime to protect your plants before the problem begins. It's a good idea to alternate the chemical that you use to prevent resistance occurring. Dig in plenty of organic matter at planting time and keep plants well fed throughout the growing season. Strong healthy plants will generally resist attack better those that are weak.[图片]Surround plants with a fresh layer of mulch each spring. This will smother any spores that have fallen around your plants and stop them from being splashed on to roses by rain.

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2017年09月15日

Colonies can usually be found on the undersides of leaves as well as on soft new shoot tips or buds. Black bean aphids cluster together and are noticeable because of their dark colouring. As they feed, they secrete a sticky, honeydew substance which drips onto lower foliage and often becomes covered in a sticky black mould.[图片]Plants affected Black bean aphids affect a wide range of garden plants, trees shrubs and certain vegetables (mainly beans and peas). About Black bean aphid The black bean aphid is more commonly known as 'Black fly'. Adult aphids are up to 2mm long and elliptical in shape. They are black in colour, although they can also appear dark green or purple. Black bean aphid infestations are commonly managed by black garden ants which 'farm' the aphids and 'milk' the sticky honeydew that they produce. Ants will often carry young aphids onto new plants to establish new colonies.[图片]Large colonies can cover areas on the youngest sections of stems, and the undersides of leaves and sometimes on flowerbuds. During the warmer months aphids give birth to as many as five live young a day, so large colonies can develop very quickly. When the colonies become over-populated, they move to different locations by producing winged aphids. During the cooler months, aphids mate and produce eggs which overwinter. Aphids feed on plant sap and excrete plant sugars as honeydew. Honeydew often covers the leaves of a plant and then becomes infested with black sooty moulds. However, this is less common with black bean aphids where ants are collecting the honeydew.[图片]Treatment Chemical Products containing the following chemical ingredients are all effective on Black bean aphid Pyrethrum Natural fatty acids Surfactant based products Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Inspect plants regularly and deal with early symptoms immediately. Remove as many aphids as you can by hand or, if possible, cut off infested shoots and stems on susceptible shrubs. Spray the infested areas of a plant with a strong jet of water to keep aphid numbers down. Use nettings and fleeces to stop aphids spreading to susceptible plants.[图片]Encourage natural aphid predators such as ladybirds, Aphidoletes, hoverfly and lacewing larvae. These can be obtained from commercial suppliers and released on to affected plants outdoors. For greenhouse plants use parasitic wasps of aphids such as Aphidius matricariae and Aphidius ervi which can be purchased for release in a contained space. Prevention Regularly check plants for signs of aphid infestation and deal with them as soon as they appear. Encourage natural enemies. Avoid using broad spectrum insecticides which will kill beneficial insects as well as aphids.[图片]Encourage insectivorous birds by hanging feeders during the winter months and provide nesting boxes in the spring.

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2017年09月15日

Dark spots or pits on the skin of the fruits and small brown blotches spread through the flesh.[图片]Plants affected Apples. About Bitter pit is caused by calcium deficiency. In most cases, the soil has enough calcium, however it is not always available to be taken up by plants. Levels of other nutrients such as potassium and magnesium can affect calcium availability. Other factors which play a part include, soil acidity and moisture levels.[图片]Treatment On acid soils, steps can be used to raise the pH to an ideal level of around 6.5. pH testing kits are widely available and the level can be raised by adding lime to the soil. This can be a long process and the benefits of liming can be slow to appear. Avoid using high potash (potassium) feeds. Although these are known to encourage flowering and fruiting, they can also reduce the availability of calcium in the soil.[图片]Mulch with bulky materials which improve soil structure, such as home made compost or leaf mould. Sprays containing calcium chloride or calcium carbonate can be applied directly to the fruits. These are often marketed as treatments for blossom end rot.

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2017年09月15日

Bright red, cream and dark blue coloured beetles, oval shaped and about 1cm long. They will be feeding or laying eggs on asparagus spears and fronds. Larvae are grey coloured hump-backed grubs with black heads and three pairs of short legs. They will usually be found feeding on the fronds. The tiny dark coloured eggs are laid pointing away from the plant tissue.[图片]Plants affected Asparagus About Asparagus beetle Adult asparagus beetles are up to 8mm long. Adults appear in mid to late spring as asparagus spears are emerging through the soil. They will mate and lay their dark coloured eggs in small rows on the spears. When the eggs hatch the larvae will initially feed on the tips of spears, but later will migrate to the fronds. They will feed for a few weeks before pupating in cocoons in the soil around the base of the plant or in nearby mulch. There may be two or three generations per year depending on temperature and availability of food.[图片]Adults will overwinter in the soil, leaf litter, or in hollow stems of asparagus plants. Feeding by adults and larvae will cause yellow-brown discolouration of the leaves and stems. Large infestations can completely defoliate and eventually kill plants. Treatment Chemical Products containing the following chemical ingredients are all effective on Asparagus beetle Pyrethrum Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Regularly inspect plants and hand pick adults and larvae from the spears and fronds. Remove old dead stems and dispose of them to prevent adults over-wintering.[图片]Prevention Inspect spears as soon as they emerge for adults mating and laying eggs. Wipe away any eggs from the spears. Remove any old plant debris around the base of plants to prevent larvae pupating.

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2017年09月15日

Leaves will become a dark brown colour and drop. Blossoms will die back. Fruits will become discoloured and wrinkled. A white slimy substance may excrete from infected areas. Often, the first time this disease becomes apparent is when new leaves do not appear in spring on deciduous trees and shrubs. Alternatively, woody plants may suddenly defoliate and die-back along their stems. Determining the cause as honey fungus can be tricky though. A clear indicator is the presence of strands of the fungus in the soil around affected plants. These look like thick black bootlaces. Pale brown or yellowish toadstools may appear in autumn and a gooey resin may be found oozing from the base of stems.[图片]Plants affected The most susceptible include: apples, crab apples, walnut, willow, wisteria, cotoneaster, rhododendron, roses and many conifers, including pine, cypress and thuja. In addition almost all garden trees and shrubs and some herbaceous plants can also succumb.[图片]About Honey fungus Honey fungus lives in dead tree stumps and spreads from there to healthy plants nearby. There are a group of closely related fungi which are collectively known as honey fungus. Honey fungus is notoriously difficult to diagnose as the symptoms are easily confused with other problems. Honey fungus remains in the soil for years if allowed to establish.[图片]Treatment Chemical There is currently no chemical control commercially available for honey fungus. Organic Remove diseased plants and dig out the roots as far as possible. Do not replant with trees or shrubs for at least a year. Remove and replace the infected soil from around the affected plant. Where possible, have any large stumps removed from the garden. When replanting, stick to resistant plants such as oak, ash, beech, yew, clematis, laurel or mahonia.[图片]Prevention Sterilise any tools used for removing infected material with a household bleach solution after every use

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2017年09月15日

Yellowing and often disfigured leaves, which are caused by whitefly feeding on the plant cells. Whitefly secrete sticky honeydew deposits as they feed which fall on to the surrounding foliage. This causes dark sooty mould to develop on the leaves.[图片]Plants affected Whitefly colonies affect a wide range of vegetables, ornamental plants and trees. About whiteflies Whitefly adults are tiny, moth-like insects that feed on plant sap. They have two pairs of white wings that fold back over their abdomen when at rest. Over 1400 species of whitefly have been recorded worldwide and 56 of these have been found in Europe. Development of egg to adult takes around three to four weeks, depending on the temperature Females usually lay up to 200 eggs on the underside of leaves, often in neat circles. Eggs hatch into larvae that initially crawl over the leaf surface for a few hours then settle to feed on plant sap.[图片]The larvae are small and scale-like in appearance. After the first skin-shed, the larvae become fixed to the leaf by their feeding tubes until they turn into pupae from which the adults emerge. Glasshouse whitefly, Trialeurodes vaporariorum, as their name suggests, usually infest plants grown indoors and under glass such as tomato, cucumber, pepper and many ornamentals. Cabbage whitefly, Aleyrodes proletella, is a common pest in southern England even in the colder winter months. It's similar to glasshouse whitefly, but has grey spots in the centre of each wing, and attacks only cabbages and other brassicas. Tobacco whitefly, Bemisia tabaci, is a notifiable pest that has to be reported to DEFRA Plant Health if found. It occasionally appears in the UK on imported ornamentals and cut flowers. In southern Europe, the tobacco whitefly causes serious damage to horticultural crops by transmitting plant viruses. It's similar in appearance to the glasshouse whitefly, although smaller and less triangular in shape when at rest.[图片]Treatment Chemical Products containing the following chemical ingredients are all effective on whiteflies Pyrethrum Natural Fatty Acids Surfactant based products Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Inspect your plants every day and thoroughly. Adult whiteflies feed and lay eggs on the new growth of plants, so these areas need to be inspected first. If adults are present, then an organic ,approved natural fatty acid or natural soap product will control them.[图片]If you spot adult whiteflies, particularly on older plants, then they're likely to have emerged from an infestation of larvae and pupae on the lower leaves. Carefully inspect the lower leaves and remove and destroy any that are infested with whitefly larval scales. Nettings and fleeces can be used to cover greenhouse vents and stop whiteflies spreading on to susceptible plants. Use natural enemies such as spiders, which catch large numbers of adult whiteflies in their webs. Ladybirds, hoverfly and lacewing larvae will also eat whitefly. For greenhouse plants use the parasitic wasp Encarsia formosa which is commercially available. This will attack and kill the larvae of glasshouse whitefly. Yellow sticky traps should be placed within a greenhouse to catch adult whitefly. Prevention Check plants every day for signs of whitefly infestation and deal with them as soon as they appear.[图片]Monitor whitefly activity by hanging yellow sticky traps among greenhouse and conservatory plants. Be wary of weeds that can often host whitefly within or near cultivated plants. Encourage natural enemies into the garden. Don't use broad spectrum insecticides that kill beneficial insects as well as whiteflies. Destroy leaves that have large infestations of whitefly larvae since many whitefly adults will still develop and hatch from detached and discarded leaves. Encourage insectivorous birds by hanging feeders during the winter months and provide nesting boxes in the spring.

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2017年09月15日

Long white, or occasionally blue-grey, waxy residues which look like cotton wool appear on the bark and branches especially around old pruning wounds. There may also be droplets of sticky, sugary honeydew on the bark which may become infected with black sooty mould. Cankers may also be present on aphid infested areas.[图片]Plants affected Apple, pear, prunus, crab apple, pyracantha, cotoneaster, elm, hawthorn and mountain ash trees. About Apple woolly aphid Adult aphids are up to 2mm long and elliptical in shape. They are pinkish-brown but their waxy coating gives them a white, woolly appearance. This species does not overwinter as eggs but as young, under loose bark, or in cracks in bark or surface roots. Young emerge in spring to re-establish the colony. Aphids can give birth to as many as five live young a day so rapidly produce large colonies. After a few generations, winged adults develop and move to new trees.[图片]Colonies will develop around cracks and wounds in trees, as well as new shoots. Feeding by apple woolly aphids will cause knobbly galls to form making the tree more susceptible to canker and other infections. Aphids feed on plant sap and excrete plant sugars as honeydew. Honeydew often covers the leaves of a plant and then becomes infested with unsightly black sooty moulds. Treatment Chemical Products containing the following chemical ingredients are all effective on Apple woolly 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.[图片]Organic Check tree shoots and bark regularly for signs of woolly aphid. Scrub areas within easy reach with a brush and a bucket of soapy water. Spray infested areas with a firm jet of water to help reduce aphid numbers. Spray with natural fatty acids such as an insecticidal soap. The parasitic wasp Aphelinus mali will attack aphids above ground level. Aphid predators such as ladybirds, aphidoletes, hoverflies, and lacewing larvae can be encouraged by providing suitable overwintering sites and by growing flowers which attract them.[图片]Prevention Regularly check plants for signs of 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. 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 in winter and nest boxes in spring.[图片]If planting new apple trees, use rootstocks which are resistant to apple woolly aphid. Paint pruning wounds with a tree coating composition to help prevent infestations establishing.

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2017年09月15日

Cankers are deformed and diseased areas of tree bark. The directly infected area is usually sunken down, with the surrounding bark cracked and distorted. Initial signs of infection may include new shoots dying and wilting or discoloured leaves. Fruits can also be affected and may rot. Cankers usually have white or red coloured pustules depending on the time of year.[图片]Plants affected Apple canker infects apple, pear, mountain ash, beech, hawthorn, poplar and willow. Some varieties are more susceptible than others. About Apple canker Apple cankers occur when the fungus Nectria galligena finds its way into cracks and wounds in tree bark. The infection will kill the tissue beneath the bark first. The bark around the canker will eventually die back revealing the tissue. Damage from pruning can also become infected. Fungal spores appear creamy white in the spring and a darker red colour later in the year. Spores can move between wounds by wind, water splash, or insect. Wet soil exacerbates the infection.[图片]Mild infections still allow some fruit to set. Severe infections can rarely be cured and the tree may die. The more infected and exposed areas a tree has, the more susceptible it is to further damage and infections. Treatment Chemical Products containing the following chemical ingredients are all effective on Apple canker Myclobutanil Mancozeb Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Remove infected branches and twigs, making clean, neat cuts. Larger cankers on trunks and thick branches can be cut out, although care must be taken to ensure that all bark showing symptoms of disease is removed. Burn all removed infected material to ensure the spores are destroyed.[图片]Prevention Disinfect blades before and after pruning. After pruning, apply canker paint to exposed healthy tissue. Try to prune only in dry weather. When planting new trees, pick varieties with a higher level of resistance to canker. Include a spade of lime with the soil when planting a new tree. Pruning back leaves and branches to improve the air circulation of older trees will help to stop the disease establishing.

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