INSECTICIDES AND FUNGICIDES 1017 



Fumes of formalin produced either by heat or by the use of perman- 

 ganate of potash have been recommended as a remedy for potato scab, 

 but the writer's experience with the fumes has not been such as to warrant 

 him in recommending them for this or for other purposes. 



Bichloride of Mercury. — A very poisonous chemical, valuable in dilute 

 solutions (1 part in 1000) as a disinfectant, and particularly good as a 

 remedy for potato scab. The whitish, crystalline, very heavy material is 

 very dangerous to have about, since it may attract the attention of children 

 or animals. It should of course always be kept labeled as a poison. It 

 dissolves slowly in cold water, and it is best, therefore, to make use of heat, 

 afterward turning the dissolved poison into the larger quantity of water 

 required, best kept in a barrel. Good results have been obtained in check- 

 ing potato scab with this disinfectant, using 4 ounces in 30 gallons of 

 water and soaking the seed potatoes one hour. They were placed in the 

 fluid in gunny sacks and afterward spread out on a barn floor to dry. 



It is very essential that poisoned potatoes be not left where stock will 

 eat them, and the poisonous fluid must be disposed of after treating the 

 seed, so that it will do no harm. 



Lime-Sulphur Wash. — This preparation of sulphur and lime has 

 already been mentioned under insecticides. It has undoubted fungicide 

 value both in concentrated and dilute preparations. For foliage the latter 

 must always be used. Even the sulphur alone thickly strewn over leaves 

 is a fairly good remedy for mildew. A very small quantity of the sulphur 

 dissolved in the presence of lime renders it more effective both as an insect- 

 icide and as a fungicide. 



COMBINED INSECTICIDES AND FUNGICIDES 



The cost of treatment for pests is greatly increased by the necessity 

 for frequent spraying when insecticides and fungicides are used separately. 

 They have been combined in some cases with no loss in the effectiveness of 

 either, and one of the important problems of both entomologists and plant 

 pathologists at the present time is the finding of ways and means of reducing 

 the number of sprayings still further. 



Some work in determining the compatibility of different mixtures has 

 already been done, and it may be said that the following mix without less 

 and in some cases with a gain in effectiveness: 



Arsenate of lead (acid) and Bordeaux mixture. 



Arsenate of lead and tobacco. 



Arsenate of lead and acids. 



Arsenate of lead (neutral) and Bordeaux mixture. 



Arsenate of lead (neutral) and lime-sulphur. 



Arsenate of lead (neutral) and tobacco. 



Paris green and Bordeaux mixture. 



Arsenite of lime and Bordeaux mixture. 



Arsenite of lime and tobacco. 



Lime-sulphur and tobacco. 



Soaps and Bordeaux mixture, 



