Spray Control Of Weeds, Pests, Fungus Diseases

Press, Volume CVIII, Issue 31771, 30 August 1968, Page 6

Spray Control Of Weeds, Pests, Fungus Diseases

In spring pests and diseases start to become prevalent again, and thoughts turn to how best to destroy them before they damage the host plant. Unfortunately the use of chemicals for this purpose still seems to be largely a mystery, and lack of knowledge and indiscriminate use are all too often shown. Perhaps the greatest confusion lies in the fact that most preparations are sold under an assortment of proprietary names, although sales by chemical formulation would not be possible in many cases, because of the length of tongue-twisting names. However, by law all materials sold must carry a full description of the contents and usually reasonably comprehensive instructions on their use is given as well. Chemicals are available for three main purposes:

(1) Insecticides, which are designed for control and extermination of insect pests only.

(2) Fungicides, which are for the prevention and control primarily of fungus diseases, but in some cases can be used against bacteria as well. (3) Weedicldes or weedpurpose of checking or destroying unwanted plant growth. An insecticide is ineffectual against diseases and by the same token virtually no fungicide has dual properties. Weedkillers mean just that and should never be applied as a substitute for, or in combination with, either of the previously mentioned groups. Compatibility

Many fungicides and insecticides are compatible with one another and can be safely mixed and applied together. Some display incompatibility of varying degrees and should not be mixed otherwise—such eventualities as loss of residual effect or plant damage can occur.

Some materials are relatively safe to use, can be handled with normal care and treated crops could be harvested the following day. Others may necessitate more careful handling and may have prolonged waiting periods before sprayed plants can be used.

For Instance, a vegetable treated with carbaryl on one day could be eaten on the following day, but lindane oredudes use for three weeks. Yet again the use of D.D.T. necessitates varying waiting periods depending on the crop that it is used on. It should be noted that certain materials of a very poisonous nature are available only to commercial growers, purchase of some is restricted In quantity and it is necessary to sign * so-called poisons book in order to buy others. Follow Directions

Instructions should be read carefully for they have been printed for the purpose of im-

parting information. If the directions state that one ounce of material should be added to 3 gallons of water it means just that Do not use double the strength in the hope that it will be more effectual, for damage to plant may result. On the other hand, a weaker solution should not be used toj’make it go further.” The active ingredient of some materials may vary and for this reason different amounts may have to be added to the same quantity of water. This is another reason why it pays to become familiar with the instructions given with each individual material to ensure efficiency of preparation.

Many materials deteriorate when exposed to the atmosphere and therefore are not as effective after some time. They are also likely to absorb moisture and become lumpy and in consequence do not dissolve as readily. To keep them in a fresh state, and also in safety, use well-marked containers. However as some substances, notably copper sulphate, are corrosive to metal, polythene bag liners could well be used.

When purchasing your spray materials work out what controls you are likely to need beforehand and buy just those. Do not buy a host of different ones for the sAme purpose but stick to the same few for specific purposes and do not change them unless you are quite certain that the desired results are not being achieved. Timing Important

To be effective materials must be applied at the right time. Timing is all important. A spray schedule is designed to provide protection, not a cure or even a control. Prevailing conditions such as prolonged periods of wet and humid weather may require more frequent follow-up treatment

Applications should be made to dry surfaces, preferably on a windless day. Fungicides and insecticides are best applied before the day has become too warm and the latter should never be used on plants in full flower as this constitutes a hazard to bees. Weedkillers generally become even more effective on warmer days.

Thorough application is necessary to achieve good results. Over-all coverage can be assured by a systematic approach to application such as for instance working from left to right or up and down, but not up and about as

though waving a fairy wand In particular, when spraying trees, don’t miss the terminal growths.

Sometimes the addition of a wetting agent is recommend ed when applying a particular spray or when applying tc a particular crop or plant Again, the amount usee should be strictly in accord ance with the instructions Too much can lead to exces sive run off or plant injury Measure out material: accurately, do not guess them Egg scales are ideal for weigh ing small quantities of powde and plastic measuring jug are most suitable for fluids Have separate, clearly mark ed, measures for weedkiller and fungicides and insect: cides. Handle all material with care and check dis pensers thoroughly before an after use. Always wash ther out afterwards. ' I