HOME GARDENS

Bay of Plenty Beacon, Volume 14, Issue 42, 23 September 1949, Page 7

HOME GARDENS

(By J. S. Yeates, Massey Agriculd tural College)

VIRUS DISEASES

The most insidious plant diseases are those produced by different types of virus. Not only do they affect a very large proportion of cultivated plants, but also, they are very difficult to detect except when they have reached an advanced stage. The virus which causes these diseases cannot be seen with a microscope and can be detected only by the disease symptoms it causes. Finally, the most important to gardeners, once a plant has the disease it cannpt be cured; it should be burned before it spreads, the trouble to others.

Some of the common plants liable to serious harm from virus diseases are: tomato, tobacco, dahlia, -carnation, tulip, lilies, freesias, daphne, nasturtium, raspberry, and strawberry.

Spread of the virus is by the transference of sap from a diseased plant to a healthy one. This can be done in various ways—even by brushing against first one and then the other plant. The smoker who handles tobacco made from diseased plants and then handles his tomato plants may easily spread the disease. But the virus is carried in most cases by the juice-sucking insects —especially aphids or green flies. To prevent the spread of these diseases, the methods are to destroy all plants which show infection, and to destroy also the insects responsible for their spread. For the latter purpose nicotine sulphate (black leaf 40) is about the most generally used spray today. Nicotine sulphate is the general spray used against these aphids and also against red spider, thrips, (those tiny black, slow moving insects common inside many flowers) and in fact against any of those sucking insects which are not fixed in one spot on the plant. D.D.T. Spray ftfr Aphids, etc. Instead of nicotine sulphate, a suitable form of D.D.T. can now be used for spraying against these insects. The newer material gammexane is also very useful for such purposes, and before long there should be available mixtures of D.D.T. and gammexane which will cover a wide range of uses in the garden and orchard. The D.D.T. now readily available in shops is a dispersable powder containing 25 per cent of D.D.T’. One teaspoonful is enough for an ordinary knapsack pump full of water (3 gallons), or about half a teaspoonful is ample for the ordinary hand atomiser. Do not on any account use domestic D.D.T. on plants, because it is dissolved in kerosene or the like which will wreck most plants. I have used D.D.T. myself on lilies against aphids, and on rhododendrons and camellias against thrips. The advantage of D.D.T. is that it stays on the leaf until washed off, and in the meantime any of the insects concerned has only to walk over a spot of the spray to be killed. I have found aphids on my lilies quite active within a day or two of very thorough spraying with nicotine sulphate. Flower Garden

Gladioli can be planted this month or in October for the main summer display, so it is time to think about preparing the ground and maybe procuring some corms if you intend to grow them this summer, Gladioli have become extremely popular in recent years,, partly because of new Varieties coming on the market, partly because they increase in number so rapidly, but also because they give a really brilliant display With a minimum of attention. They are very suitable and popular as cut flowers; for which purpose they are best brown somewhere in the vegetable garden. Like most plants they grow better in soil that has been deeply dug and manured, preferably with some well-rotted animal manure or rich compost. They like a well drained soil on the light side rather than a heavy soil, and in windy situations are all the better for staking when flowering commences. They, can be planted at intervals over a period of about three months in the spring in order to give a succession of bloom. The corms should have any loose material peeled off and should then be inspected for any signs of rot or scab. The answer to such diseases lies in the use of a chemical “Aretan” which can be bought readily, complete with instructions. Gladioli should be planted about eight inches apart and with about three inches of soil above them; or two inches of soil and two of sawdust if you use that method of saving the work of weeding.