INSECTICIDES AND FUNGICIDES 275 



destroys the outer skin. It cannot, therefore, be employed except when 

 greatly diluted. But since it retains its active fungicide and bactericidal 

 properties even when very greatly diluted, and is not so dangerous a poison 

 in this condition as are corrosive sublimate and other antiseptic agents, it 

 becomes very useful in the hands of those who wish to disinfect quarters in 

 which have been lodged people, or animals, affected with communicable 

 diseases. The wash or spray of the dilute formalin has always seemed to 

 the writer much better for such uses than the fumes of formalin as generally 

 produced. 



On plants the action of even dilute sprays is very quickly destructive, 

 and I doubt if it has a value for their treatment. But for seed wheat, 

 likely to produce smutted heads and for potato scab it has proved very 

 convenient and useful. A pint of the 40 per cent formalin may be poured 

 into a barrel containing 30 gallons of water, stirred thoroughly, and the 

 potatoes in a sack can be set in the barrel for disinfection. They should be 

 left hi the fluid for two hours and may then be removed and spread out on 

 grass or on a clean plank floor to dry, when another sack may be placed 

 in the barrel. The treated potatoes must not be put in barrels or sacks 

 that have not been treated with the formalin. By having a number of 

 barrels at hand, the work proceeds rapidly. 



Oats and wheat liable to smut may be treated by sprinkling the seed 

 with dilute formalin (1 pint in a barrel of water) until every seed is moist, 

 not wet, then leaving for several hours hi a heap, finally spreading out 

 to dry. 



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 dilate 

 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 



