HtEVENTION AND DESTRUCTION OF INSECT PESTS. 495 



remedy is the employment of bisulphide of carbon put in small 

 phials in holes just under the ground, or, better still, forced 

 in by an ejector. Wireworm are also killed by these poisonous 

 fumes, which, being heavier than air, descend into the soil and 

 permeate through it. I have used this method with marked 

 success in the maggot attack in carnations, and in flower-beds 

 suffering from the devastations of wireworm and surface grubs. 

 It also readily destroys snake millepedes. Fumigation with 

 hydrocyanic acid gas may also be of some value under glass, 

 especially in peach-houses and vineiies, where scale, mealy bug, 

 &c., are prevalent. This gas is formed by putting lumps of 

 cyanide of potassium (90 per cent grade) in a saucer of M'ater, 

 and then pouring sulphuric acid on to the cyanide. For a green- 

 house forty feet long 8 ounces of cyanide, 8 ounces of sulphuiio 

 acid, and 18 ounces of water are required. The fumes should not 

 be allowed to ascend for more than twenty minutes, and fumigation 

 should only take place at night, as sunlight helps to scorch the 

 leaves. The slower the gas generates the better ; the larger the 

 lumps of cyanide and the greater the quantity of water used the 

 slower the gas comes oft', and the more effectually is the scale 

 destroyed. Hardy plants might also be similarly fumigated, but 

 delicate plants should not be treated with it. Both fumes and 

 ingredients are deadly poisons. A full and interesting account of 

 the emploj'meut of these fumes as a means of destroying scales on 

 fruit-trees is given by Mr Lounsbury in liis last year's (1897) re- 

 port to the Cape of Good Hope Government. 



The effect of artificial manures on insect pests is often most marked. 

 Nitrate of soda and kainit are frequently of much service in destroy- 

 ing surface grubs, whilst on the other hand superphosphates have no 

 effect. Bone-meal and guanos encourage many insect posts. So(jt 

 forms an excellent deterrent to many leaf-eating beetles and onion 

 fly ; dusting over the seed lea\'es and broadcasting o\'er beds of 

 pickling onions is nearly always followed by cessation of attack 

 in such insects as the turnip flea and onion fly, especially if it is 

 broadcasted when there is dew on the leaves : at the same time it 

 stimidates the plant to growth, and makes good the damage caused 

 by the insects. 



Infestation is often carried to r/ardens in dung and leaf-mould: 

 these should be examined, and if found to be very foul, should be 

 mixed with lime— gas-lime if possible— and not used until the lime 

 has done its work, and so purifiied the manm-e. I have seen many 



