Garden Insecticides and Fungicides – Letting Science Help in the Garden


Nearly all insect pests in the garden are either suckers or chewers, they suck sap from or chew leaves. Among the former type, the suckers, are aphids such as greenfly and blackfly and among the latter are caterpillars. It is not sufficient then, if we wish to rid ourselves of both types with one spray, merely to spread a poison on the leaf surface, for the sap is not affected. There are several types of systemic insecticide available to us which will kill all kinds of insects. These not only spread a poison on leaf surfaces; they are actually absorbed into the system of the plant so that the sap contained is also contaminated.

I cannot too strongly emphasise that an insecticide of this type is lethal and it must therefore be used with the utmost care and as seldom as possible. Never allow it on your hands and do not let any spray blow into your face or onto your clothes. If your skin is contaminated wash at once. Never allow these insecticides near children, never spray open flowers during the day or beneficial insects will also be killed. Spray only when you are sure that pests are present. Read the label on the bottle, can or packet with great care and follow instructions implicitly.

Fungicides, on the other hand, are more successful when used as a preventive rather than a cure. They are much less effective in curing black spot and mildew on roses than in preventing these diseases. And as they are not toxic to birds and animals in the same way as an insecticide they can be applied before the disease becomes apparent and applied in regular doses to prevent the disease from appearing and spreading.

These, then, are the basic chemical aids in killing or preventing insect and disease attack. Occasional war must be waged against other pests such as slugs, ants and wasps, but clean and thorough gardening can help keep all these pests and diseases to a minimum.

Good gardening obviously depends mainly on the soil and soil improvement is really important. This can be done with the use of garden compost or John Innes No 1.

garden compost

Garden compost is composed of rotted vegetable matter. The best available natural soil is leafmould and this is composed of leaves, twigs and other vegetable matter that has naturally fallen to the ground and rotted. We can make our own good soil on the same principle and this soil will be better in many ways than anything we can buy. For this reason the bonfire should be used only for tap-rooted weeds and for woody material which will take too long to decompose. Everything else from the garden should go on to the compost heap. This will include waste vegetable matter from the kitchen, grass cuttings, hedge trimmings, fallen leaves and even the contents of the vacuum cleaner bag.

The garden compost heap is made of an open topped “box” with sides sufficiently open to allow some air through. (You can buy ready made bins. You can also use metal netting). If one side is removable it is so much more convenient, but this is not necessary. Dimensions depend on the size of the garden and hence the quantity of the material at hand, but generally it should be at least three feet square. At the base, lay at least six inches of fairly heavy twiggy material so that some air is allowed to percolate under the heap and so that moisture can get away easily.

Then on this base the compost heap proper can be started. All green vegetable matter should be thrown into the bin or box and when there is a layer some six to nine inches deep it should be covered with a couple of inches of soil. Layers of this sort should be continued until the heap reaches the top. In practice it will seldom be found that the top is reached, for the material will rot quite quickly and settle downwards. Special compost accelerators can be bought which will speed the rotting process, but these are not essential and even without them it will be found that roughly two loads of garden compost a year can be removed and used on the garden.

The compost heap should not be allowed to get too dry and in periods of drought it will be helpful to give it a good watering occasionally. On the other hand it must not be allowed to get waterlogged, so in bad weather it is helpful to cover it.

It will be found that the centre of the heap usually rots down into good soil more quickly than the outsides, so it helps to turn the outside to the centre and vice-versa when it is apparent that this is necessary.

Garden compost is both a fertilizer and a provider of much needed humus, so the more that can be made the better for your garden soil. Use it lavishly as a mulch, or, alternatively, dug into the top few inches of soil and keep the compost heap always going to provide a continuity of supplies.

Mention has been made in certain sections of this site of John Innes composts or soil mixtures. These are not a proprietary product, but were devised by scientists at the John Innes Research Institute. They are, in fact, merely a special soil prepared to a standard recipe and can generally be bought from all nurseries, garden centres and indeed from many chain stores. They have certain distinct advantages, which is why they are recommended. In the first place, there are several types, for sowing seeds, for potting plants, for taking cuttings. Secondly, if they are correctly made, they are standard and will not vary in strength. Thirdly, the soil content has been sterilised, which means that all weed seeds in them have been heat-killed. So if you sow some seed in a John Innes (frequently shortened to JI) seed mixture you will know that the tiny green leaves appearing are those of the germinated seed you have sown rather than some unknown weed. JI mixtures are available ready bagged in small or large quantities. It is possible to make your own from the standard recipes, but as this involves the purchase of a soil steriliser the expense is not generally justified.

In the past few years a number of other soil composts have appeared on the market, most of them doing without soil because of the problem of sterilisation and consequently known as “no-soil” composts or mixtures. Some of these appear to present problems, but more recently a new type has appeared which seems likely to surpass even the old standby of JI soils. This is known as Levington compost and it comes in two types only, for seeds and for potting. This is a peat-based mixture which like JI contains its own balanced fertilizer. It absorbs many times its own weight in water, for it is very light in weight. Consequently it is even more convenient.

But obviously the extent to which you use the latest scientific aids in your garden must necessarily depend on the amount you wish to spend and the size of your garden. It is perfectly possible to have a most beautiful garden without the use of any of them. Perhaps the best advice I can give to gardeners is that they should obtain a good and comprehensive catalogue of garden sundries. From this it can be seen at a glance what products exist and the price can then be balanced against the value of the product in your own garden.

26. September 2010 by Dave Pinkney
Categories: Garden Management, Pests and Diseases | Tags: , , | Comments Off on Garden Insecticides and Fungicides – Letting Science Help in the Garden


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