Insect Pests and Fungoid Diseases. 403 



it is constantly agitated or stirred. With knapsack machines this can be 

 done by the man carrying it giving it an occasional shaking, but larger 

 machines should be fitted with some efficient means of agitating the liquid, 

 and in purchasing it is important that this point is not overlooked. 



MATERIALS. There is some difference of opinion as to whether it is 

 better for the gardener to mix his own washes or to buy them ready-made 

 in a concentrated form from horticultural chemists. For the large grower, 

 especially if he has had some practice in exact weighing and measuring, 

 and has some knowledge of elementary chemistry, there are many advan- 

 tages in buying the separate ingredients and mixing the washes at home. 

 The quantities he will use and the better physical condition of some washes 

 wh&i newly-made make it worth his while to take the trouble to become 

 efficient in the mixing of them. The case of the small grower is different ; 

 he uses relatively small quantities, and the extra convenience of concen- 

 trated washes generally outweighs any disadvantages they may have. 



The following are the washes most generally useful to the vegetable 

 grower : 



INSECTICIDES. 



ARSENATE OF LEAD. This is the best form in which to use arsenic 

 for insecticidal purposes. Paris green and London purple also contain 

 arsenic, but are much more likely to damage the foliage and are certainly 

 no more effective than arsenate of lead. Of the latter there are many 

 good brands now on the market, and it is unwise for the grower to attempt 

 to make .his own. Directions for use are given with the purchased chemical. 

 The amount to use will be from 3 to 12 ozs. in 10 gallons of water, varying 

 with the particular insect to be dealt with. This compound is very 

 poisonous and should be kept under lock and key when not in use; it 

 should not be used on crops within six weeks of harvesting. 



CARBON BI-SULPHIDE. This is ueful to destroy soil insects on small 

 areas, but for extensive use its cost is prohibitive. It is a very inflammable 

 and volatile liquid and requires careful handling. It has a strong and dis- 

 agreeable odour. A " Vermorel " injector, which has a long nozzle and a 

 sharp point, is a very suitable instrument with which to apply it. The 

 nozzle is thrust about Gin. below the surface of the soil, the liquid injected, 

 and the soil pressed back over the hole left by the nozzle. Use 2ozs. to the 

 square yard. 



HELLEBORE POWDER. This is a yellowish-brown powder, made from 

 the root of Veratrum album and V. viride. It is poisonous, but less so 

 than arsenate of lead. For effective use it must be freshly ground, as it 

 soon loses its poisonous properties on exposure to the atmosphere ; hence it 

 is particularly adapted for use on crops which are badly attacked by cater- 

 pillars within a few weeks of ripening. Two applications should be given 

 with a short interval between. It may be used dry, either alone or with 



