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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Oriental chestnut gall wasp (OCGW) was discovered for the first time in the UK in a woodland in Kent, England, in June 2015. A second site was later confirmed with OCGW present in a small number of trees in a single street in St Albans, Hertfordshire.
Working with site owners and our partners in government, we took swift and appropriate action to reduce the population, and the risk of spread, as much as possible. We conducted surveys around the country for evidence of any other outbreaks, but found none. Then follow-up surveying in summer 2016 found OCGW at several places in London and South-East England. The survey was mounted to find out whether OCGW was present at other locations than those found in 2015, and in compliance with our Protected Zone status for the species. (See 'Regulations and Powers' below.)
dentification and symptoms OCGW is an insect of Asian origin which affects sweet chestnut trees in the Castanea family of trees. The only species of the Castanea family grown in significant numbers in Britain is the European sweet chestnut (Castanea sativa). It is a pest of sweet chestnut trees because activity by its larvae (the 'grubs', or immature life stage) causes abnormal growths, called galls, to form on the buds, leaves, and petioles (leaf stalks). The presence of these galls is the most obvious symptom of OCGW infestation. The galls can be either green, rose-coloured, or red. They gradually dry out and turn brown and woody over the summer, when the adult wasps emerge from them, and they can cause the leaves to drop early. Most galls fall off the tree when the leaves fall, although galls attached to the bases of petioles (leaf stalks) can stay on the tree for some years.
Galls can grow up to 4cm (1.75in) in diameter, although most of those seen in England have been between 1cm and 2cm. They can occur at any height on the tree, and on any age of tree with buds. No other organism is knoRose-coloured call caused by oriental chestnut gall wasp (Dryocosmus kuriphilus) on sweet chestnut (Castanea sativa) leaf stalkwn to cause galls on sweet chestnut trees, so their presence is a reliable indicator of OCGW infestation. The adult wasp is tiny, being only 2.5-3mm long, with a black body, translucent wings and orange legs. It emerges in June and July, but its small size mean it is unlikely to be seen by most visitors to affected sites.
Treatment Control options include insecticide treatment. However, insecticide treatment of widespread outbreaks in the wider environment is unlikely to be effective because the galls encase the larvae, protecting them from chemical treatments. An option in localised outbreaks is to conventionally harvest affected trees by felling or coppicing them and burning, deeply burying or mulching the lop and top (branches and tree-top material). Mulching (grinding the material into small fragments to destroy the pest) was used at Farningham Woods. The timber from the trunks can then be used in a bio-secure manner, e.g. for fencing. Lifecycle The female wasp lays eggs in the trees’ growth buds during the summer, and the eggs hatch within 30 to 40 days. The early stages of the larvae then lie dormant in the bud over the winter.
Oriental chestnut - gall wasp damageLarval activity resumes the following spring, and this activity causes the formation of galls, inside which the larvae develop, in early summer. The galls are formed on young twigs, on leaf petioles (stalks) or on the midrib of leaves. These green, red or rose-coloured galls start at approximately 5–20 mm in diameter, and can develop up to 4cm in diameter as the leaf tries to form. Adult wasps emerge during June and July, leaving exit holes in the galls. The galls turn brown and woody over time, and can remain on the tree for two years or more.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Identification OPM caterpillars are most easily recognised by their distinctive habit of moving about in late spring and early summer in nose-to-tail processions, from which they derive their name, and the fact that they live and feed almost exclusively on oak trees. They can sometimes be seen processing across the ground between oak trees, and clustering together as they feed on oak leaves.
In early summer they also build distinctive white, silken webbing nests on the trunks and branches of oak trees (almost never along the leaves), and leave white, silken trails on the trunks and branches. These nests and trails become discoloured after a short time, and more difficult to see as a result. NOTE: OPM nests are almost never made among the leaves of oak trees or any other tree or shrub, or on any structure. Such nests are usually made by harmless species, and need not be reported.
The nests can occur in a range of shapes, including hemispherical (half a ball), tear-drop shaped, bag-like, and like a blanket stretched around part of a trunk or branch. Sizes range from as small as the width of a 50p coin to stretching several feet up the oak tree trunk in some cases. They can occur anywhere from ground level to high in the oak tree, and can fall out of oak trees and be found on the ground. The caterpillars rest up in these nests during the day between feeding periods, and later in the summer they retreat into the nests to pupate into adult moths. The adult moths emerge from pupation and are active from mid to late summer, and lay their eggs on the small twigs and branches in oak trees. They are an undistinctive, brown moth very similar in appearance to other, harmless species, and because of the difficulty in accurately identifying them, we do not require reports of moth sightings.
Health precautions People in the affected areas can take these simple precautions to minimise the health risks to themselves and their pets and livestock: DO NOT: touch or approach nests or caterpillars; let children touch or approach nests or caterpillars; let animals touch or approach nests or caterpillars; or try removing nests or caterpillars yourself. DO: teach children not to touch or approach the nests or caterpillars; train or restrain pets from touching or approaching them; keep horses and livestock a safe distance from infested oak trees. Covering or stabling livestock can help; see a pharmacist for relief from skin or eye irritations after suspected OPM contact; call NHS111 or see a doctor if you think you or someone in your care has had a serious allergic reaction; consult a vet if you think your pet or livestock has been seriously affected; call in a pest control expert to remove infestations in your own trees;
Treatment and management To be most effective the job should be carefully timed and carried out by professionals with appropriate training and equipment. Do not try to remove OPM caterpillars or nests yourself, because of the health risks. Report the presence of the pest and, if your trees are in the OPM Core Zone, get a professional pest control operator to remove the infestations. Your local council or our Plant Health Service can provide details of suitable pest control operators working in the area. Larger land-managing organisations with professional grounds or tree-care staff might acquire their own equipment and train their own staff to do the job. Even if OPM is not known to be present, tree surgeons and others working on or close to oak trees in affected areas are strongly advised to wear protective clothing. Life cycle Adult moths emerge from the pupae in mid to late summer. They live for an average of three days, during which time they mate and lay their eggs in healthy oak trees, usually high in the canopy.
The eggs spend the winter on the trees, and the larvae (caterpillars) emerge the following spring. Larval emergence begins about mid to late April in an average spring, but can be as early as March. As they grow, the caterpillars descend lower in the trees to feed and build nests, and this is when they are most likely to be seen by the public. This is also when they develop the irritating hairs which pose the health problems. They spend their days in the nests, emerging mostly at dawn and dusk to feed, although this pattern can vary. They can sometimes be seen processing across the ground between oak trees.
In July the caterpillars congregate in the nest to pupate into adult moths, which can take up to four weeks. Spent nests found after adult moth emergence will invariably contain pupae cases and cast-off hairs, and should not be handled without personal protecive clothing.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Concerns about the presence of the Oak Pinhole Borer (Platypus cylindrus) in oak logs imported from the continent have been raised with the Plant Health Service.
This beetle used to be regarded as rare in this country but populations grew in the south and south-east as a result of the gales in 1987 when it took advantage of the sudden glut of suitable breeding material. A similar situation now exists on the continent following the severe gales in the winter of 1999 and buyers are reporting damage to oak logs bought in from mainland Europe. Adults emerge from June to September from larvae that may have been present for up to two years.
The beetle is the only borer which, in the absence of fungal decay, will bore into the heartwood of oak thus reducing its value. However, it is not on the quarantine list as it is already present in this country and is not a pest of standing healthy trees. There are, therefore, no quarantine controls against it and there are no treatments available that will provide protection.
We strongly recommend that anyone intending to purchase oak logs from areas where the beetle is known to occur specifies wood that is free from signs of wood borer damage.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Horse chestnut leaf miner (Cameraria ohridella) is an exotic insect pest which lives in horse chestnut trees. It was first reported in the UK in 2002, in the London Borough of Wimbledon, and has since spread north, south and west to most of England and parts of Wales, and there has been one confirmed sighting in Scotland.
Its larvae (caterpillars) mine within the leaves, and at high population densities they can destroy most of the leaf tissues. Although it can cause severe damage to horse chestnut leaves on an annual basis, and discolouration and defoliation before normal autumn leaf-fall, on its own the pest does not significantly impair trees' health, and they will usually flush normally the following spring.
However, it is possible that differences in climate, or interactions with other pests and diseases, might lead to greater impact in the UK. Consequently, the effects of the moth and its interaction with other pests and diseases, especially bleeding canker of horse chestnut, is being studied through the long-term monitoring of more than 300 chestnut trees at several sites in southern England. These trees are assessed twice each year for infestation, disease crown condition, growth and signs of dieback.
Origins Horse chestnut leaf miner was first observed in Macedonia, in northern Greece, in 1985, and was described as a new species in 1986. In 1989, it appeared unexpectedly in Austria, and since then it has spread throughout central and eastern Europe. It was first found in Great Britain in 2002 in the London Borough of Wimbledon. Spread Dispersal of the moth from infested areas occurs on a broad front through adult flight, assisted by the wind, and through the passive transport of adult moths or infested leaves in or on vehicles. Transportation by vehicles appears to be responsible for the sudden appearance of the moth in towns and cities a long way from known areas of infestation.
Distribution The map shows areas where confirmed sightings of horse chestnut leaf miner had been reported up to 2014. Forest Research scientists are conducting a long-term study to determine whether there are any interactions of Horse chestnut leaf miner and the bacterum P. syringae pv. aesculi , which causes bleeding canker of horse chestnut, including whether one influences the extent of the other, and how they affect the health of affected trees. A paper reporting the results of the first 10 years of the study was published in the journal Agricultural and Forest Entomology.
Treatment Damage can be reduced by removing fallen leaves during the autumn and winter and either composting them thoroughly, to destroy the over-wintering pupae, or if the leaves are collected into smaller heaps, by covering them with a layer of soil or other plant material to prevent adult emergence the following spring.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
The great spruce bark beetle (Dendroctonus micans) is found in forests throughout mainland Europe. It damages spruce trees by tunnelling into the bark of the living trees to lay its eggs under the bark, and the developing larvae feed on the inner woody layers. This weakens, and in some cases can kill, the tree.
Outbreak stage The beetle was first discovered in Great Britain in 1982 after it was accidentally introduced, most likely via a consignment of imported timber. It has become an established pest in Wales and western England, and has more recently expanded its range to southern Scotland.
Impact The rate and extent of damage to individual trees and forests is variable. Neither the beetle nor its larvae burrow into the wood itself and, consequently, provided the wood is salvaged before the tree is completely dead, the timber is not spoiled in any way. Trees are killed by being completely girdled, at one or more points along the stem, although this may take several years of sustained attack. However, large breeding populations can be building up long before individual trees are killed, creating a risk of spread to adjacent and nearby trees.
Susceptible species The beetle attacks and breeds in all species of spruce grown in Britain. Symptoms Look out for signs of poor tree health. Check especially for isolated or small groups of dead or dying trees characterised by browning foliage over some or all of the crown. The entry of female beetles into the bark of trees gives rise to characteristic ‘resin tubes’ on the trunk. Resin tubes and granular resin at the base of the tree are reliable signs of stem or root attack. Resin tubes vary in colour from white and cream, to shades of purple and brown. They may be accompanied by copious resin bleeds. Loose bark with exposed beetle galleries usually indicates older infestations that have been attacked by woodpeckers.
Inspect the bark around resin tubes, particularly those that are purple to brown. A hollow sound when the bark is tapped often indicates successful attack. Remove the bark carefully and inspect for signs of the beetle. The most characteristic indicator is the presence of a mixture of insect faeces (frass) and bark packed into ‘islands’ creating a quilted appearance. All beetle stages, from egg to adult, might be present. The beetle has a long life cycle, ranging from 12–18 months under British conditions. This results in extensive overlap of generations so that it is possible to find any stage at any time of year. However, there are periods, particularly in the winter, where most can be at the same stage. Adult beetles are 6–8 mm long and 2.5–3 mm wide.They are black when mature, with a covering of orange hairs. The large size of the beetle enables the females to withstand the resin flow produced when they bore into the bark of trees.
Eggs are laid within a small egg chamber in the cambium of the tree. Each female can produce up to 300 eggs, laid in groups of 50–80, in interconnecting chambers. Eggs are usually laid on one side of the chamber. Larvae - The beetle has five larval stages (instars), which each become progressively larger. All larval stages feed under the bark in a similar manner: larvae feed side-by-side, packing powdery wood debris (or ‘frass’) and diseased or dead larvae behind them into islands away from the main feeding site. The mixture of resin and frass forms a distinctive quilted pattern. Pupae are the immobile, resting stage of beetle development before the larvae moult to the adult stage. Pupae are found in pupal cells among the larval frass. They are often found in close proximity and give rise, upon emergence, to aggregations of adults under the bark. These stages can be prolonged over several weeks or months, depending on temperature.
The newly emerged adults are light brown. As they mature the colour darkens to brown and black. Adult beetles move within and between trees mainly by crawling (at temperatures of 12°C or greater), but they occasionally fly (at temperatures of 22.5°C or greater). Treatment Information on treating infected trees can be found in the guidance document Minimising the impact of the great spruce bark beetle Action Statutory controls against the spread of D. micans were first put in place in Great Britain in 1982. Following the discovery of three new outbreaks outside the main infested area, the Forestry Commission reviewed the controls and consulted the forestry industry on two options: extension of the designation of the infested area and continuing the policy of movement restrictions into Scotland and north-east England, or revocation of our EU protected-zone status. The second of these options was agreed, and from 15 May 2005 the movement within Great Britain of conifer wood and conifer bark was no longer subject to any treatment requirements.
Part of the west of Scotland is designated as a ‘pest-free area’ out of which wood and bark can be moved without treatment under the EU plant passport regime.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Asian longhorn beetle (ALB), Anoplophora glabripennis, is a native of China and the Korean peninsula, and poses a serious threat to a wide range of broadleaved trees. It has caused extensive damage to trees in the USA and Italy since being accidentally introduced there in recent years, and there have been outbreaks in several other European Union countries.
The beetles tend to stay close to the site of original infestation in the early stages of an outbreak. However, they can fly more than 2km. Analysis of climate data suggests that most of England and Wales and some warmer coastal areas of Scotland are suitable for beetle establishment, but south-east England and the south coast are at greatest risk. The lifecycle from egg to beetle is one to two years in parts of Asia, and possibly as long as four years in the UK. Beetles emerge during the summer and will mate and lay eggs, after which they die. Because it is often the resulting emergence holes that are the earliest evidence of an outbreak, it is important to survey and monitor the surrounding area to ensure the adults have not already spread to neighbouring host trees.
Outbreak stage Individual specimens of Asian longhorn beetle have occasionally been found from time to time in the UK, but in March 2012 a breeding population was confirmed by Forest Research scientists in the Paddock Wood area near Maidstone in Kent. We and the Food & Environment Research Agency (Fera: now the Animal & Plant Health Agency (APHA)) rapidly implemented measures to eradicate the outbreak and prevent it spreading further afield. More than 4700 potential host trees were surveyed, and 2166 host trees were removed. A total of 66 infested trees were detected, of which only 24 were found by visual inspection, the remaining 42 only being detected after they were felled.
Fortunately this outbreak was detected before the 2012 adult beetle emergence period, which provided time to inspect and deal with infested trees. Origins It is suspected that the original beetles might have emerged from wood packaging material which had been used to import slate from China to a site next to where the outbreak was located. Untreated wood packaging is a known pathway for Asian longhorn beetles, and all wood packaging material imported into the EU should be marked to show that it has been treated to reduce the risk of carrying quarantine pests. It is illegal to import wood into the UK which shows signs of the beetle.
Susceptible species Known hosts (tree species which it can infest) include: Acer (maples and sycamores) Aesculus (horse chestnut) Albizia (Mimosa, silk tree) Alnus (alder) Betula (birch) Carpinus (hornbeam); Cercidiphyllum japonicum (Katsura tree) Corylus (hazel) Fagus (beech) Fraxinus (ash) Koelreuteria paniculata; Platanus (plane) Populus (poplar) Prunus (cherry, plum) Robinia pseudoacacia (false acacia/black locust) Salix (willow, sallow) Sophora (Pagoda tree) Sorbus (mountain ash, whitebeam etc) Quercus palustris (American pin oak) Quercus rubra (North American red oak) Ulmus (elm) Apple and pear trees can also be attacked.
Lifecycle The lifecycle from egg through larvae to beetle is one to two years in Asia, and possibly longer in the UK. Beetles emerge from spring onwards and will mate and lay eggs, after which they die. In North America and central and southern parts of Europe, ALB completes its life-cycle in 1-2 years, but in cooler regions the life-cycle can take up to three or four years. It is likely that in southern Britain most individuals will complete their development in two years, and climatic mapping work suggests that conditions along the south coast and south east England would be suitable for a two-year life cycle. Further north, the beetle is less likely to be able to complete its lifecycle in two years. However, there is always an element of uncertainty about these predictions, which results from very local variations in climate, our changing climate, and uncertainties about the origin of the invasive beetles.
Action Residents and landowners within a 2km buffer zone around the infestation were asked to hold back from any felling/tree surgery or pruning of woody shrubs in gardens. This was because the beetle's larvae live in trunks and branches, so it was important to make sure these were properly disposed of. Residents in this zone who needed to prune or fell trees or woody shrubs were asked to ensure that all woody material was taken to an appropriate Kent County Council waste transfer station or recycling site. The buffer zone area was extended in 2012 to include an infested tree found on the northernmost edge. We urged everyone within the 2km buffer zone to keep a look out for, and report, the beetle or evidence of its presence to ensure the best prospects for eradicating this outbreak. We repeated this advice again in summer 2013.
We have re-surveyed the area every year to check for signs of any contnuing presence of the pest. No further evidence of its presence has been found, but will continue the surveys until 2018 before we can declare the pest eradicated from the area. The only insecticides that could be considered are not completely effective, so there is no real substitute for tree removal as a means of eradicating Asian longhorn beetle. ALB does not attack wood in houses. The adults only lay their eggs on living trees, and although the larvae can continue to develop in felled wood, the early-stage larvae require the conditions and nutrition found in living wood.
Movement controls and treatment This pest is regulated, so movement of plants, logs and wood from infested areas is subject to statutory controls. Movement restrictions on host plants and woody material for two commercial retailers in the affected areas were implemented by plant health notices. We advised local people not to undertake any tree surgery or felling until we had completed our survey, unless it was necessary for safety reasons, or to move any logs or branches which had been recently felled. Movement of infested material could carry the beetle to new locations. Also, the larvae can complete their development in felled trees or branches if left untreated, especially in the summer months, so this material would present an ongoing hazard.
Notices were served on plant retailers in the affected area to prevent the movement of any potentially infested host plants or host plant material (with stems more than 2cm in diameter). Larvae within wood will not survive if the wood is chipped to lengths no longer than 25mm. Once the wood has been chipped in this way it is deemed safe and can be disposed of. There is no reason to restrict people’s movements in infested areas or buffer zones. The only possible restrictions would have been brief local exclusions for safety reasons during any tree felling which became necessary.
Identification Some common native beetles can be mistaken for Asian longhorn beetles. The adult beetles are large, about 20-40 mm long, and shiny black with variable white markings. Particularly distinctive are their antennae, which are up to twice the body length and black with white or light blue bands. They are almost identical in appearance to citrus longhorn beetle (Anoplophora chinensis), another non-indigenous longhorn beetle that threatens trees in Britain. The most obvious symptoms of Asian longhorn beetle damage are the circular exit holes made by the emerging adult beetles in the trunks and branches, which are about 10 mm in diameter and are usually found in the main trunk and above.
Other signs which might be present, but less obvious, include piles of sawdust-like droppings at the base of infested trees, scraped bark, possibly sap bleeding from sites where eggs have been laid, and feeding damage on the bark of smaller branches and shoots.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Wilting plant leaves, sagging stems, and aborting flowers and fruits. Dry soil, especially where new plants have not had a chance to put down deep roots. Dry compost in pots and hanging baskets, and pots blowing over.
Plants affected All plants are affected. About Wilting through lack of water Plants have a vascular system which enables water and nutrients to be taken from the environment through a complex root system. The continual flow of water and nutrients ensures that the vascular system remains firm, and that the plant continues to grow in a healthy way. Lack of water results in a loss of firmness which causes the symptoms of wilting. Plants respond to lack of water by closing down areas of the vascular system, which consequently results in leaf, flower and fruit loss. Plants can usually recover from short periods of lack of water, but sustained periods of drought often result in death.
Treatment Chemical Products containing the following chemical ingredients are all effective on Wilting through lack of water There is no chemical control available for this problem. Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Water wilted plants as soon as possible. Plunge pots with very wilted plants into a bucket of water for an hour or so. After plunging or watering, place pots with wilted plants in the shade to recover, and consider moving them to a shady spot permanently. Move wilted plants out of windy spots, and avoid putting them back in the same place.
If the problem is affecting plants in the greenhouse, after watering them, damp down the floor with a hose or watering can. Prevention Regularly monitor plants for wilting symptoms. Design a watering schedule for plants based on their individual needs. As a general guide, pots need watering once a day, hanging baskets twice a day, new plants in the border need careful monitoring in their first year and will probably need watering two or three times a week. Established border plants will have deeper roots and will benefit most from one long drink each week rather than a daily dose. For potted and hanging basket plants, water-retaining gel granules can be used in the compost.
The base of the pot or basket can also be lined with a plastic bag to help retain water. If lining a pot, make a few small holes in the bag with a kitchen fork so the compost does not get waterlogged. Avoid planting delicate plants in locations of intense sunlight, or strong winds.
During summer use shading to protect greenhouse crops. Incorporating mulch and organic material into the soil improves its water retention.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Viruses affect almost all types of plant from time to time and the symptoms are varied. Leaves may be yellowed or mottled. Spots, mosaics and other marks may also appear. Leaves can become deformed and twisted. Flowers may become streaked or develop a green colour.
Plants affected Almost all plants can be affected by viruses and virus-like organisms with the notable exception of conifers. About Viruses are the simplest form of microscopic life. In fact some experts do not consider them true forms of life at all. They cannot metabolise themselves, requiring a host to carry out any of their functions. They can only reproduce inside a plant or animal host.
Viruses are usually carried from plant to plant by animals known as vectors. In plants, aphids are one of the most common vectors. The same virus can cause very different symptoms in different plants. Treatment Prevention is the best place to start when dealing with viruses. Try to use certified virus-free seed potatoes and fruit trees. Any plants showing signs of virus should be removed to prevent spread onto other plants.
Control of the organisms which transmit the virus is important to prevent its spread. Aphid control is particularly important. Regular weeding will help by reducing other potential host plants in the area. Where there are weeds nearby which are in the same family as the plants at risk, this is especially important. Keep the garden tidy and remove dead or dying plants promptly.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Small silver patches and black dots on the leaves. Feeding thrips can also turn petals on flowers brown. New growth can be distorted, browning and curled.
Plants affected Virtually all garden plants can be affected, from ornamental species, to fruit, vegetable, and cereal crops. Flowers and leaves of plants are most affected. About Thrips Thrips are sometimes known as thunderflies or thunderbugs. There are over 3000 recorded species worldwide, with over 150 in the UK. They are typically small, slender, dark-coloured insects about 2mm long or less and usually have two pairs of feather-like wings. Thrips rasp through upper leaf cells to feed on plant sap, causing a silvering appearance. Thrip droppings are minute black specks on the leaves.
Thrips have six lifecycle stages including egg, larvae, pupa and adult. Larvae and pupae can be a lighter colour than adults. Females have a serrated tube for laying eggs into plant tissue. They are predominantly a summer pest, favouring warm temperatures and dry conditions. Thundery conditions trigger swarming. Some species can transmit viruses such as tomato spotted wilt virus. Treatment Chemical Products containing the following chemical ingredients are all effective on Thrips
Pyrethrins Methiocarb Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Release the predatory mite Amblyseius cucumeris, and predatory bug Orius laevigatus. Spray organic plant oils approved for use on plants. Remove and destroy infested leaves, particularly silvery areas where eggs are present.
Prevention Thoroughly clean greenhouses at the end of the season to remove any over-wintering thrips. Use sticky traps to monitor the first appearance of thrips. Blue coloured traps are thought to be more effective than other colours. Netting and fleeces can be used as a barrier between plants.
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Dummer. ゛☀
2017年09月15日
Dummer. ゛☀
Leaves that become skeletonised or transparent with just their veins remaining tend to be the work of sawflies, which eat through the tissue of the leaf until it has almost completely disappeared. The larvae can often be seen around the edges of the leaves and most curl up into an S-shape when disturbed. Larvae will also bore into developing fruits causing them to become scarred and exude sticky liquid.
Plants affected Sawflies affect a number of different plants but different types tend to affect different crops. Some of the most common are the apple sawfly (hoplocampa testudinae), the common gooseberry sawfly (Nematus ribesii), the turnip sawfly (Athalia rosae) the pear and cherry 'slugworm' (Caliroa cerasi), the rose slug sawfly (Endelomyia aethiops), also known as the rose 'skeletoniser'.
About Sawflies Adult sawflies are usually inconspicuous flying insects with two pairs of wings and often dark coloured bodies and legs. They resemble flying ants but have no 'waist' between thorax and abdomen. They're often seen flying on warm sunny days in spring at blossom time when they usually feed on pollen and nectar. The adults live for about two weeks, during which time they mate before the females start laying eggs into plant tissue. Eggs are inserted into cuts on the leaf surfaces that the female makes with her saw-like ovipositor. Eggs hatch into larvae that resemble moth caterpillars, although they have more pairs of 'pro-legs' on their abdominal segments. The larvae usually feed in groups on leaves and fruit of plants.
When disturbed, the larvae of most sawfly species adopt an S-shaped pose, often raising their rear ends and waving them about. At least 400 different species of sawfly have been recorded on plants in Britain. Larvae usually feed for about four to five weeks before pupating in the soil. Infestations of sawfly larvae often defoliate plants although infestations are usually localised and rarely devastating. Two or three adult generations may develop during the growing season with the third generation overwintering as pupae that emerge in the spring Treatment Chemical Products containing the following chemical ingredients are all effective on Sawflies
Pyrethrum Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments. Organic Inspect bushes every week from April/May onwards for the signs of sawfly infestation then search for the larvae and remove by hand. Tell-tale signs include transparent patches on leaves where young larvae are feeding; seeping sap, where the insects have damaged plant tissue as they lay eggs; areas of defoliation or skeletonised leaves.
Position susceptible plants in an open position where birds can easily feed on the larvae. Prevention Select varieties that are reported as less susceptible to attack, particularly roses and apples.
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