British Cactus and Succulent Society

Highlands & Islands Branch

Appendix

 
 

This section is a collection of detailed explanations of relevant subjects gleaned from various sources as shown at the foot of each one. It is hoped this will make them more accessible and not clutter up other parts of the site.

 
 
  • Abbreviations
  • Augmentation(such as parasitoids)
  • Classical Biological Control
  • Conservation
  • Diatomaceous Earth
  • ICBN
  • Insecticidal Soap
  • Meristem Culture
  • Organisations
  • Wasps
  • What is pH
  • Anaphylactic Shock
  • Acknowledgements
  •  

     


    Augmentation
    This third type of biological control involves the supplemental release of natural enemies. Relatively few natural enemies may be released at a critical time of the season (inoculative release) or literally millions may be released (inundative release). Additionally, the cropping system may be modified to favor or augment the natural enemies. This latter practice is frequently referred to as habitat manipulation. An example of inoculative release occurs in greenhouse production of several crops. Periodic releases of the parasitoid, Encarsia formosa, are used to control greenhouse whitefly, and the predaceous mite, Phytoseiulus persimilis, is used for control of the two-spotted spider mite.

    Lady beetles, lacewings, or parasitoids such as Trichogramma are frequently released in large numbers (inundative release). Recommended release rates for Trichogramma in vegetable or field crops range from 5,000 to 200,000 per acre per week depending on level of pest infestation. Similarly, entomopathogenic nematodes are released at rates of millions and even billions per acre for control of certain soil-dwelling insect pests. Habitat or environmental manipulation is another form of augmentation. This tactic involves altering the cropping system to augment or enhance the effectiveness of a natural enemy. Many adult parasitoids and predators benefit from sources of nectar and the protection provided by refuges such as hedgerows, cover crops, and weedy borders. (Extracted from Cornell University web-site - see below)

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    Classical Biological Control
    In many instances the complex of natural enemies associated with an insect pest may be inadequate. This is especially evident when an insect pest is accidentally introduced into a new geographic area without its associated natural enemies. These introduced pests are referred to as exotics and comprise about 40% of the insect pests in the United States. Examples of introduced vegetable pests include the European corn borer, one of the most destructive insects in North America.

    To obtain the needed natural enemies, we turn to classical biological control. This is the practice of importing, and releasing for establishment, natural enemies to control an introduced (exotic) pest, although it is also practiced against native insect pests. The first step in the process is to determine the origin of the introduced pest and then collect appropriate natural enemies (from that location or similar locations) associated with the pest or closely related species. The natural enemy is then passed through a rigorous quarantine process, to ensure that no unwanted organisms (such as hyperparasitoids) are introduced, then reared, ideally in large numbers, and released. Follow-up studies are conducted to determine if the natural enemy successfully established at the site of release, and to assess the long-term benefit of its presence.

    There are many examples of successful classical biological control programs. One of the earliest successes was with the cottony cushion scale, a pest that was devastating the California citrus industry in the late 1800s. A predatory insect, the vedalia beetle, and a parasitoid fly were introduced from Australia. Within a few years the cottony cushion scale was completely controlled by these introduced natural enemies. Damage from the alfalfa weevil, a serious introduced pest of forage, was substantially reduced by the introduction of several natural enemies. About 20 years after their introduction, the alfalfa acreage treated for alfalfa weevil in the northeastern United States was reduced by 75 percent. A small wasp, Trichogramma ostriniae, introduced from China to help control the European corn borer, is a recent example of a long history of classical biological control efforts for this major pest.

    Many classical biological control programs for insect pests and weeds are under way across the United States and Canada. Classical biological control is long lasting and inexpensive. Other than the initial costs of collection, importation, and rearing, little expense is incurred. When a natural enemy is successfully established it rarely requires additional input and it continues to kill the pest with no direct help from humans and at no cost.

    Unfortunately, classical biological control does not always work. It is usually most effective against exotic pests and less so against native insect pests. The reasons for failure are often not known, but may include the release of too few individuals, poor adaptation of the natural enemy to environmental conditions at the release location, and lack of synchrony between the life cycle of the natural enemy and host pest.

    Conservation The conservation of natural enemies is probably the most important and readily available biological control practice available to growers. Natural enemies occur in all production systems, from the backyard garden to the commercial field. They are adapted to the local environment and to the target pest, and their conservation is generally simple and cost-effective. With relatively little effort the activity of these natural enemies can be observed. Lacewings, lady beetles, hover fly larvae, and parasitized aphid mummies are almost always present in aphid colonies. Fungus-infected adult flies are often common following periods of high humidity. These natural controls are important and need to be conserved and considered when making pest management decisions. In many instances the importance of natural enemies has not been adequately studied or does not become apparent until insecticide use is stopped or reduced. Often the best we can do is to recognize that these factors are present and minimize negative impacts on them. If an insecticide is needed, every effort should be made to use a selective material in a selective manner.
    (Extracted from Cornell University web-site - see below)


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    Conservation
    The conservation of natural enemies is probably the most important and readily available biological control practice available to growers. Natural enemies occur in all production systems, from the backyard garden to the commercial field. They are adapted to the local environment and to the target pest, and their conservation is generally simple and cost-effective. With relatively little effort the activity of these natural enemies can be observed. Lacewings, lady beetles, hover fly larvae, and parasitized aphid mummies are almost always present in aphid colonies. Fungus-infected adult flies are often common following periods of high humidity. These natural controls are important and need to be conserved and considered when making pest management decisions. In many instances the importance of natural enemies has not been adequately studied or does not become apparent until insecticide use is stopped or reduced. Often the best we can do is to recognize that these factors are present and minimize negative impacts on them. If an insecticide is needed, every effort should be made to use a selective material in a selective manner.
    (Extracted from Cornell University web-site - see below)


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    Diatomaceous Earth
    Diatomaceous Earth is a desiccant and based on the fossil remains of diatoms, in the form of a dust. It apparently works on ants, earwigs, woodlice, and the like. These insects pick up the dust by electrostatic attraction after it has been sprayed in their vicinity. The dust causes the insects cuticle to crack so that the insect looses moisture and then dies within a few days.

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    International Code of Botanical Nomenclature
    When I first started to write this section on 'Classification' I had followed Britton & Rose and Backeberg as far as cactus names were concerned. This was because that was more stable than the constant changing of names that seemed to happen. Many nurseries, and even some academics did the same. But we have to change because the International Code is becoming the standard. Unfortunately, the 'change of names' previously alluded to is set to continue because many plants have been wrongly named in the past, and are now rather publicly changed at plenary sessions of a Congress. The old name, and the person who got it wrong is recorded, together with the new name, and published.

    All plant names should now be based on the International Code of Botanical Nomenclature (ICBN) which first declares that botanical nomenclature is independent of zoological and bacteriological nomenclature which each have a similar 'International Code' structure of their own.

    The purpose of ICBN is to promote standardisation of botanical names in given plants. In addition, the intention is that each taxonomic group has only one correct name. The term 'taxon', with the plural 'taxa', applies throughout. The Code (ICBN) can only be changed by a plenary session of an International Botanical Congress and the 'Vienna Code (2006)' is the current online one. The 'Vienna Code (2006)' will supersede that when it is published.

    A formal starting date for plant nomenclature has been proposed by ICBN as 1st May 1753 when Linnaeus published his 'Species Plantarum'. Not as Linnaeus's book 'Fundamenta Botanica' of 1736 in which he reformed all the practices that had preceded 1736. In that book he established the principle of 'genus' and 'species' as a descriptive binomen for not only plants but all other living things.

    To quote from the web-site-

    "Every plant is treated as belonging to an indefinite number of taxa of consecutively subordinate rank, among which species (species) is basic." It goes on to say that the principal ranks of taxa in descending sequence are:
    kingdom (regnum), division or phylum, class, order, family, genus, and species (species). Thus each species is assignable to a genus, each genus to a family etc. When a collector discovers a new plant, he deposits plant material in a herbarium where it is named and becomes a 'type' or taxon with that name.
    The ICBN is accessable at http://www.bgbm.fu-berlin.de or key in 'ICBN'

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    Insecticidal Soap
    Another alternative, on a similar spraying regime, is an insecticidal soap based on fatty acids. These are not ordinary soaps as they contain unsaturated, long-chain fatty acids (potassium or alkanolamine salts) such as oleic acid which comes from animal fats, and also some plant fats. These soaps work on contact and are only effective when wet. They dissolve the cuticle of insects yet do not affect the cuticle of most plants. They are biodegradable and can be used on aphids, mealy bugs, scale, spider mites, white fly, and many other large and small insects, both indoors and out. Available on-line and also at some garden centres.

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    Meristem Culture
    The method takes the apical meristem, which is that translucent tip of the root of a plant, and divides it, under a microscope, into the smallest pieces. Actually, the apical dome of the root tip is used, and that is only about 0.1mm in size.

    The pieces are put into a nutrient culture medium and grown on. This they do quite rapidly until they have grown to a size which can be divided again. This process is repeated until the required number is reached. Eventually, these meristemic sections are allowed to grow on in a culture until first leaves and roots show, at which point they are treated, more or less, as seedlings.

    The prime advantage to commerce and industry is that meristem culture produces plants which are virus and bacteria free. Another enormous advantage is that it produces exact clones of the original plant. A exceptional plant, which has received high awards at the RHS for example, can be mass-produced, and in far greater quantities, than conventional methods would allow. Exact copies are produced in terms of flower type, colour, and all the other characteristics of the original plant. It is what has given the world cheap, high quality orchids and other plants.

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    John Innes Composts
    The composts are based on - (parts by volume)
    a) good quality sterilised loam = 7
    b) peat substitute (or peat) = 3
    c) sand = 1

    To each cubic metre is added:
    d) 594g of limestone
    or 1.2Kg of hoof & ho
    rn 1.2Kg of superphosphate of lime
    e) and 594g of potassium sulphate

    All this is based on the original formula which was
    f) 1lb of groung limestone
    g) 1lb of potassium sulphate
    h) 2lb of hoof & horn
    i) 2lb of superphosphate of lime.

    per cubic yard.

    It is said that the original formula was JI-1 and
    that JI-2 has twice as much fertiliser, and
    that JI-3 has three times as much.

    JI Seed Compost
    j) 2 parts (by volume) of sterilised loam
    k) 1 part of peat
    l) 1 part of sand

    To each cubic metre is added -
    m) 1.2Kg (2lb) of superphosphate of lime
    n) 594g (1lb) of ground limestone

    The whole mixture has to be quite fine so that seed can make good contact.

    Cutting Compost
    First requirement is that it be free-draining and able to function in high humidity
    without causing damping-off. It may be suitable for some succulents, but not cacti,
    These composts typically comprise -
    50% of sand
    50% peat

    To each cubic metre is added
    4.4Kg of dolomitic lime
    1.5Kg of hoof & horn or dried blood, superphosphate of lime, calcium carbonate
    148g (4oz) each of potassium nitrate and potassium sulphate.

    They say that because cutting composts are low in nutrients, cuttings need to be fed
    once rooted.

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    Organisations
    CITES - Convention on International Trade in Endangered Species of Wild Flora and Fauna
    IAPT - International Association for Plant Taxonomy
    ICBN - International Code of Botanical Nomenclature
    IOS - International Organisation for Succulent Plant Study
    IPNI - International Plant Names Index
    IUCN - International Union for the Conservation of Nature and Natural Resources
    RBGE - Royal Botanic Gardens Edinburgh
    WCMC - World Conservation Monitoring Centre
    WTMU - Wildlife Trade Monitoring Unit

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    What is pH
    An over-simplified explanation is that pH is 'potential Hydrogen ions'. More precisely, it is a measure of the range between high acidity and high alkalinity in soils. This measure ranges from unity (=1) to 14, with 7 regarded as neutral. This can be explained as follows.

    When hydrogen(H+) and hydroxyl(OH-) ions are in equal numbers they neutralise each other. This occurs at 0.000,0001 g/litre, or 10-7gH+ from which the figure of 7 comes. By the same reasoning a pH of 1, or 0.1gH+ is very acid. Conversely, a strongly alkaline solution at pH=14 is equivalent to 0.000,000.000.0001gH+ or 10-14gH+. It can therefore be seen that an apparently small change in acidity/alkalinity numerically represents quite a large chemical change.

    Physiologically, pH is important because it affects the availability of essential elements in the soil, and is critical in the metabolism of plants on either side of pH7. It (pH) affects how a plant takes up two of the most important primary nutrients, nitrogen, and phosphorus. Soil pH does not actually control 'nitrogen' (N), rather it affects the activity level of the microbes which do the work. High pH causes nitrogen loss in other ways. The position with phosphorus is more serious. The availability of P is at a maximum between pH5.5 and 7.5 At pH5.5 and below P gets 'locked up' and is no longer available. At pH above 7.5 an excess of calcium (lime) can decrease the availability of P. Below pH6.5 manganese can reach a toxic level for some sensitive plants. Micronutrients are directly influenced by pH. In some cases availability increases, in others it decreases.

    Testing pH
    There is an easy way of testing this outside a plant physiology facility. A kit seems to be a suitable solution. They are very easy to use. Take a sample of compost - add some water - add a powder - shake well - then watch the colour develop. Compare that to a chart and there you have it. They even tell you how to adjust your pH. Such a test will not give you laboratory accuracy, which would be to one-tenth of a pH, but it tells you enough. See illustrations of kits.

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    Wasps
    There are about seven different types of social wasp in Britain, as well as a large number of solitary ones. In addition there are the Chalcid wasps which we employ in the parasitoid mode in Biological Control.

    The seven social wasps in Britain are the Common Wasp (Vespula vulgaris), the German Wasp, (Vespula germanica), the Norwegian Wasp (Vespula norvegica), the Tree Wasp, ( Vespula sylvestris), the Red Wasp (Vespula rubra), the Cuckoo Wasp (Vespula austriaca), and the Hornet (Vespa crabra). All of them may hunt in your garden but telling which is which is difficult because identification is mainly based on facial patterns. The Hornet is recognisable as bigger and is a brownish colour.

    The one we see most often is the Common Wasp which is reputed to build nests in holes in the ground, as also does the German Wasp and the Red Wasp. They use rabbit burrows, mouse holes, or any convenient cavity. In my experience, nests in the ground are not common because it is usually too wet. Most 'bikes', as nests are called, are located in buildings, and most commonly in the eaves of houses. Residents then have to get the authorities to remove them. The Tree Wasp and the Norwegian Wasp, both of which may hunt in your garden, build a nest in trees and bushes, and they can be seen hanging from branches. The Cuckoo Wasp is different in a number of ways. Firstly, although a social wasp in a sense, it has no workers, and lays its eggs in the nest of Red Wasps. The Hornet builds in a hole in a tree.

    A young, fertilised Common Wasp queen, who has over-wintered, starts the nest as a small umbrella-like structure. She lays some 10 to 20 eggs from which worker larvae hatch. She feeds them until they pupate, after which they do the bulk of the work of building the colony and feeding future broods. On one occasion the author found such a structure suspended from the roof of a shed. This he removed when the wasp was away collecting more wood shavings, and it was quite comical to see the way the wasp reacted when it could not find the umbrella. Anyway, it did not come back to try again.

    Wasp nests usually comprise seven horizontal layers like a block of flats. They are made of wood shavings held together by saliva as wasps cannot produce wax (and therefore combs) as bees do. Another difference between bees and wasps is that bees feed their larvae on nectar and pollen, whereas wasps feed their larvae on protein (other insects, meat, even carrion). Yet another difference between bees and wasps is that bees are hairy, from whence their colour comes, and wasps are not.

    The other major group of wasps, just as useful to gardeners, are the solitary wasps. There are two major kinds - the 'digger' wasps, and the 'potter' wasps. The difference is that diggers dig a hole in a dry sandy place, place one or two paralysed caterpillars in it, lay an egg, then seal up the hole. The larva hatches, feeds, pupates, and eventually digs its way out.

    The 'potters' build a small pot, like a Grecian urn, attached to a plant, shrub, and the like. Otherwise, it does the same as the 'digger', even sealing up the pot.

    There is yet another type of solitary wasp which superficially looks like a social one. but is actually a spider hunter. It can be recognised because it folds its wings flat, whereas the other wasps fold their wings along the length of their bodies.

    Chalcid Wasps (some 1,500 known species) are mostly tiny, and less tham 3mm in length. This group includes the parasitoids we employ in Biological Control.

    The author cannot resist including another useful insect, also in the Order Hymenoptera, the Ichneumon Fly; they, too, are parasitoid. They deposit an egg via an ovipositor, but at least one of them can do this through wood, after it detects a caterpillar. Others can do the same thing through the stem of a plant without actually seeing their prey. They must detect them by the noise they make.

    Anaphylactic Shock
    Although wasps are generally not aggressive, unless under threat individually or collectively, there is always the possibility of being stung. This is especially so in the autumn. Unfortunately, some people may be allergic to the proteins which enter the bloodstream on such occasions. As Paisley University point out in their web-site, this can cause anaphylactic shock which can be severe and even fatal. They go on to recommend immediate medical treatment on such occasions.

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    Acknowledgements
    1 - All American pictures came from http://pdphoto.org and are public domain - an excellent site worth looking at.

    2 - Ladybird on 'Biological Control' courtesy of Henry Doubleday Research Association http://www.gardenorganic.org.uk

    3 - Cryptolaemus larva and Lacewing pictures from Wiki-pedia.org

    4 - Augmentation, Classical Biological Control, and Conservation paragraphs from Biological Control - Cornell University, Weeden, Shelton, Li, Hoffman (editors) http://nysaes.cornell.edu/ent

    NOTE: the webmaster has acknowledged as best he could and consulted where possible. If anything is unsatisfactory it will be put right - let us know via the email link on the Contacts page.
       
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