Identifying and Treating Infestations

With ever-increasing threats from pests and diseases, it's important for gardeners to be alert and try to prevent problems taking hold. Keeping your plants healthy by good cultivation and sanitation is the best way to prevent pest and disease problems

To keep your trees healthy and disease free

  • First you need to be able to recognise/identify the infestation or disease affecting your trees and then know how to treat or at worst dispose of it To make matters worse the predicted change in our climate is likely to inflict particular stresses on trees and other plants and this may increase their susceptibility to certain pests and diseases. This review highlights the various ways in which climate change may affect the health of urban trees. In summary, climate change may alter the development and survival of the pests and pathogens, and their natural enemies and competitors. This may alter the impact of native pests and diseases and increase the populations of some species not currently recognized as pests to epidemic proportions. The global trade in bonsai trees is a recognized pathway for the accidental introduction of pests and pathogens even though plant health legislation exists to minimize such accidental introductions.
  • Like any other living plant, bonsai trees can be infected by any kind of pest or disease. However, when your plants are healthy and cared for properly, the risk of infection is reduced to a minimum.
  • Make sure your trees are potted using the right soil mixture, you understand how and how often to water, you don’t over or under fertilize and your bonsai is positioned correctly. Although chances of infection of healthy trees are low, of course they can still get infected.
  • It is often hard to identify the problem correctly you might want to take pictures and ask for help with identification

After you have identified the insect or disease buy the appropriate insecticide (chemical or organic) to treat the trees with; be careful to follow the instructions and you might want to start using a half doses first; if necessary you can increase the doses later on. If it is a disease you are dealing with, you need to assess if there is legislation regarding its treatment. Please seriously remember - disposing of a dead or infected tree means just one thing - BURN IT. A dead tree on the compost heap or taken away with ‘garden waste’ is still very infectious and can pass that disease on to other trees, not just your collection.

For detailed information on pesticides at present available and permitted by’ European law’ see article available from The Royal Horticultural Society at RHS website gardening Pesticides for gardeners a PDF document

Identifying Infestations - A Tree With Plant Problem Symptoms Is Easy To Spot

  • A tree, shrub, or plant may wilt or become discoloured.
  • It may fail to come into leaf or to bloom at all.
  • Insects, which may be the cause of the plant's poor health, may be seen on part or all of the plant.
  • Sometimes an infestation or disease in the roots may noticed first through symptoms in the leaves.

These will give clear indication of the existence of problems, now we must study how to prevent and control the pests, diseases, and physiological disorders that can cause the problems.

What is a Pest?

  • Pests are creatures that cause damage to cultivated plants.
  • Some, such as slugs, snails, rabbits and squirrels, are well known; However most, are small invertebrates such as mites, eelworms, woodlice, and millipedes, which are less evidently plant pests.
  • The largest group by far in this category are the insects. Pests may damage or destroy any part of a plant or, some cases, even the whole plant.
  • They feed in various ways - by sap sucking, leaf mining, defoliating, or tunnelling through stems, and producing abnormal growths known as galls.
  • Some pests also indirectly damage plants by spreading viral or fungal diseases, while others coat plants with a sugary excrement that encourages the growth of sooty moulds.

What is a Disease?

  • A plant disease is any pathological condition caused other organisms, such as bacteria, fungi, or viruses.
  • Fungal diseases are commonest; bacterial diseases are relatively rare.
  • The symptoms that these organisms produce vary considerably in appearance and severity, but the growth or health of the plant is almost always affected and, in severe attacks, the plant may even be killed.
  • The rate of infection is affected by factors such as weather and growing conditions.
  • In some cases, the disease-causing organism (pathogen) is spread by a carrier, such as aphids. The pathogen is sometimes visible as a discoloration on the plant, as with rusts. Symptoms such a discolouration, distortion, or wilting are typical signs of disease infection.
  • What is a Disorder?

  • Plant disorders usually result from nutritional deficiencies or from unsuitable growing or storage conditions.
  • An inappropriate temperature range, inadequate or erratic water or food supply, poor light, or unsatisfactory atmospheric conditions may all lead to physiological disorders
  • Problems may also be caused by deficiencies of the mineral salts that are essential for healthy plant growth.
  • Weather, cultural, or soil conditions may lead to a range of plants being affected. The problems become apparent through symptoms such as discoloured leaves or stem wilt.
  • A plant that lacks water, food, or the appropriate environmental conditions will not only appear unhealthy but will also be far less able to resist attack from either insect pests or diseases caused by fungi, viruses, or bacteria.
  • Unless problems are correctly diagnosed and treated, affected plants may die.

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