ForumRunner_20120807_105317.png 476.7K
78 downloads
ForumRunner_20120807_104930.png 475.52K
85 downloads
ForumRunner_20120807_104955.png 414.79K
81 downloads
ForumRunner_20120807_105013.png 478.55K
69 downloads
ForumRunner_20120807_105317.png 476.7K
78 downloads
ForumRunner_20120807_104930.png 475.52K
85 downloads
ForumRunner_20120807_104955.png 414.79K
81 downloads
ForumRunner_20120807_105013.png 478.55K
69 downloads
Guest_xxxxxxxxxxxx_*
Aphids are one of the most easily recognised and common garden and glasshouse pests. All aphids species are sap-sucking; some have a wide host range while others are restricted to specific plants or plant types.
One reason that aphids are so successful as plant pests is the rate of reproduction. In most aphid species as well as laying eggs the females can produce live young without mating, which condenses their life cycle. Live young are born fully active and can mature into adults in as little as 7days. There are a variety of ways that aphids can inflict plant damage – distorting and reducing plant growth, transmitting viruses and producing honeydew which attracts other plant pests and moulds.
Aphids feed by probing plant cells with their filamentous mouthparts, sucking up sugar-rich sap. Because they have to ingest large amounts of sap to obtain enough nitrogen the excess sugar is excreted as honeydew which provides the ideal environment for sooty moulds.
Some aphids strains are resistant to insecticides. In protected situations biological control is the main way of control, due in part to the range of natural enemies commercially available now. Identification of the correct aphid species is important because some biological control agents are species specific. Programmes depend largely on Aphidius and Aphidoletes. These are recommended to be used preventatively.
How to recognise them
There are hundreds of species of aphid but five are commonly found infesting glasshouse crops.
* Glasshouse-potato (Aulacorthum solani) – shiny bodied, yellow-green with dark area around the base of the body.
* Peach-potato (Myzus perscae) – one of the commonest aphid pests because of its varied host range. It ranges in colour from pale yellow to green to pink. This pest is an important vector of viruses.
* Melon-cotton (Aphis gossypii) – light to dark green, sometimes yellow.
* Mottled arum (Aulacorthum circumflexum) – shiny bodies, yellow or green sometimes with dark patches.
* Potato (Macrosiphum euphorbiae) – larger and longer-legged than most aphid species, green or pink in colour.
================================================== ================================================== ==================
Leaf miner is a term used to describe the larvae of many different species of insect which live in and eat the leaf tissue of plants. The vast majority of leaf-mining insects are moths (Lepidoptera) and flies (Diptera), though some beetles and wasps also exhibit this behavior.
Like Woodboring beetles, leaf miners are protected from many predators and plant defenses by feeding within the tissues of the leaves themselves, selectively eating only the layers that have the least amount of cellulose. In attacking Quercus robur (English oak) they also selectively feed on tissues containing lower levels of tannin, a deterrent chemical produced in great abundance by the tree.
The precise pattern formed by the feeding tunnel is very often diagnostic for which kind of insect is responsible, sometimes even to genus level. The mine often contains frass, or droppings, and the pattern of frass deposition, mine shape and host plant identity are useful to determine the species of leaf miner. A few mining insects utilise other parts of a plant, such as the surface of a fruit.
Some patterns of leaf variegation are part of a defense strategy employed by plants to deceive adult leaf miners into thinking that the leaf has already been predated.
================================================== ================================================== ==================
Mealybug is the common name of insects in Pseudococcidae, a family of unarmored scale insects found in moist, warm climates. They are considered pests as they feed on plant juices of greenhouse plants, house plants and subtropical trees.
Mealybugs are sexually dimorphic, meaning that the sexes have distinct morphological differences. Females are nymphal, exhibit reduced morphology, and are wingless, though unlike many female scale insects, they often retain legs and can move. The females do not change completely and are likely to be neotenic (exhibiting nymphal characteristics). Males are winged and do change completely during their lives. Since mealybugs (as well as all other Hemiptera) are hemimetabolous insects, they do not undergo complete metamorphosis in the true sense of the word, i.e. there are no clear larval, pupal and adult stages, and the wings do not develop internally. However, male mealybugs do exhibit a radical change during their life cycle, changing from wingless, ovoid nymphs to "wasp-like" flying adults.
Mealybug females feed on plant sap, normally in roots or other crevices. They attach themselves to the plant and secrete a powdery wax layer (therefore the name mealybug) used for protection while they suck the plant juices. The males on the other hand, are short-lived as they do not feed at all as adults and only live to fertilize the females. Male citrus mealy bugs fly to the females and resemble fluffy gnats.
Some species of mealybug lay their eggs in the same waxy layer used for protection in quantities of 50–100; other species are born directly from the female.
================================================== ================================================== ==================
Sciarid Fly To the naked eye, Sciarid and Shore flies are dark midge-like flies found on and around the growing media of glasshouse crops and plants in interior landscapes. It is important to distinguish between the two flies. Shore flies are mainly just a nuisance, although their back frass can reduce plant quality. Sciarid fly on the other hand is a damaging pest. Their larvae feed on plant roots, checking growth and sometimes leading to the plant’s death. The adult flies are capable of transmitting plant diseases.
Sciarid flies, which are also known as fungus gnats, are attracted to organic matter in the growing media and decaying plant tissue. It has bee suggested that they are particularly attracted to media containing composted material. They are especially troublesome in some pot-plant crops such as poinsettias, and in the warm, humid environment of the propagation house where life cycles are quick to complete.
Some of the newer chemical controls are granule formulations targeting fly larvae, which must be evenly mixed into the growing media for best results. Trials by the HDC have included an evaluation of the effect of insecticide granules in the plant plugs when control is difficult to achieve.
There is a reasonable choice of biological controls for Sciarid fly but creating the environmental conditions that discourage flies goes a long way towards keeping them at manageable levels. In interior landscapes such as offices, that includes finding somewhere else for staff to empty the dregs from tea and coffee cups as such action can foster ideal breeding conditions for this pest.
How to recognise them
Adult Sciarid flies Lycoriella auipila are 3mm to 5mm long, black with long, tapering antennae. They run or hop more than they fly over the compost surface. They are most often encountered in heated glasshouses but the can be found outdoors too.
Larvae are legless and translucent 6mm to 10mm in length with dark, shiny heads. They mainly inhabit the surface layer of the growing medium so are difficult to find although you may see them underneath leaves flush to the media surface.
Shore flies Scatella stagnalis are slightly longer and broader. They have stunted antennae and white spots on their wings. The larvae feed solely on algae.
================================================== ================================================== ==================
Red Spider Mite Despite its name, the glasshouse red spider mite, also known as two-spotted mite, is a troublesome pest of both protected and outdoor plants. On outdoor crops, it is joined by the fruit tree red spider mite, for example on trees such as Sorbus and flowering cherries. The key to controlling both is vigilant crop inspection, enabling early application of control measures – spider mites can multiply rapidly under the right conditions and infestations can easily get out of hand. The worst infestations occur from June to September both outside and under glass.
In protected crops, control can be complicated further by hybridisation between the two species of glasshouse red spider mite Tetranychus urticae and Tetranychus cinnabarinus. Strains resistant to some pesticides are also known. On outdoor crops, target inspections and control programmes from May to June before the pest becomes established.
Many advisers suggest heavy infestations on protected crops are best controlled by sprays of non-persistent acaricides – pesticides designed specifically to target spider mites and their relatives – before introducing biological control predators in an integrated pest management approach; however this can be expensive and inappropriate for the home gardener.
Both glasshouse and fruit tree red spider mite populations build up most rapidly in hot, dry seasons, which means growers need to be particularly vigilant in these high risk conditions.
How to recognise them
olonies of adults, nymphs and eggs are normally found on the lower surfaces of leaves, adjacent to veins, and are best identified with a hand lens. Adutls are around one millimetre long with four pairs of legs characteristic of the spider family, compared with the three pairs of legs of an insect pest. Despite the name, they tend to be light to dark green in colour but are sometimes orange to carmine red (Tetranychus cinnabarinus).
Glasshouse red spider mite/two spotted mite have two dark spots on its back. The over-wintering females are orange-red in colour.
================================================== ================================================== ==================
Whitefly Like the aphid, which it is related to, the glasshouse whitefly (Trialeurodes vaporariorum) is an all too familiar pest of protected ornamental crops, sucking sap from plants and excreting sticky honeydew.
Monitoring populations is all the more important, however, because of the closely related tobacco whitefly (Bemisia tabaci), which is a notifiable pest. Tobacco whitefly has become one of the most serious horticultural pests around the world. It poses a threat to many valuable glasshouse salad crops because of its propensity to carry damaging viruses and the difficulty of eradicating the pest, which has become resistant to a range of insecticides. Its main route into the UK is on ornamental plants, particularly on poinsettia but also other plant materials such as Verbena. Once type of the pest, known as the poinsettia strain, is of particular concern because it can develop faster and reproduce more quickly.
ADAS reported the incidence on glasshouse ornamentals of two other whitefly species last year, Lonicera whitefly (Aleyrodes loncerae) and Brassica whitefly (Aleyrodes proletella). Both were noted flying through vents and causing confusion for growers monitoring their crops with sticky traps. Cabbage whitefly, which can survive the winter outside, can be distinguished by grey patches on its wings.
Other species which may need to be treated on nursery stock include Rhododendron, azalea, and Viburnum whitefly.
Compared to the control of other pests of ornamentals, there is a wide choice of insecticides against whitefly particularly since several have become available through the SOLA route. The main drawback is that they are active against adults and newly hatched larvae so applications have to be repeated to secure control.
How to recognise them
Whitefly adults are small, white winged plant bugs which look like small flies. The main differentiating characteristic between glasshouse and tobacco whiteflies is the way the adults carry their wings; the tobacco whitefly keeps its wings alongside its yellow body, while the glasshouse whitefly folds its wings over the top of its body in the shape of an old-fashioned tent.
Another difference is that the glasshouse whiteflies tend to occupy young leaves and growing points whereas tobacco whiteflies will colonise older foliage too.
Eggs are laid on the undersides of leaves. Glasshouse whiteflies lay eggs in semi-circular groups; tobacco whiteflies more randomly except on smooth-leaved plants where they are laid in a similar pattern to glasshouse whitefly. Newly laid eggs are white but darken before hatching.
Hope this post helps people - on the lil pests who munch our green
Edited by xxxxxxxxxxxx, 09 August 2012 - 01:22 PM.
Guest_xxxxxxxxxxxx_*
0 members, 0 guests, 0 anonymous users