112 INJURIOUS INSECTS OF 1903. 



their greenhouses four or five times a year, and are able 

 to keep down all injurious pests except the red spider. 



When fumigating mills and other buildings for pests, 

 be sure that there is some method for ventilating the 

 room or rooms from the outside. After fumigation the 

 room must be thoroughly ventilated at least half an hour 

 before ventin'ing therein. Give 20 to 24 hours" exposure. 



29. Iron Sulphate and Sulphuric Acid — 



Formula : 



Hot water. 100 parts ; 



Iron sulphate, as much as will dissolve (about 100 



pounds) ; 

 Commercial sulphuric acid, i part. 

 Add the acid to the crystals and then pour on the 

 water. This is a good fungicide for dormant grape vines 

 attacked with anthracnose. (Mass. Bui. 80, 1902.) Apply 

 with sponge or brush. , 



30. Kerosene — 



This insecticide is used pure, and also diluted with 

 water, for scale insects, plant lice, etc. When diluted a 

 mechanical emulsion, made by a kerowater spray pump, 

 or a regular emulsion is employed. (See Ker. Emul.) 

 Experiments seem to indicate that, like crude petroleum, 

 the safest time to apply is on a bright, windy day in early 

 spring, just before the buds begin to swell, in the form of 

 a very fine spray. 



One part of kerosene to six parts of water can be used 

 on trees in foliage without injury, while plant lice are 

 killed in a mixture as weak as i part of kerosene to 15 or 

 20 parts of water. (Col. Bui. 71, 1902.) For plant lice, 

 therefore, i part of kerosene to 10 of water is probably the 

 best proportion to use. This proportion will also kill 

 young scales. 



Pure kerosene if properly applied may be used on 

 apple trees in winter without great danger to the trees, 

 but 40 per cent and 60 per cent is almost as destructive to 

 insects, and may be used on apple and pear trees in winter 



