TERMITES IN THE UNITED STATES. 31 



a treatment to render timber more resistant to attack by insects. 

 Wood soaked in a 2 per cent solution is under test. 



STORED MATERIAL. 



Injury to books, paper, documents, and other stored material or 

 products is usually indirect, the insects as a rule burrowing through 

 such material only where it is in contact with infested wood. Hence, 

 since the source of infestation is decaying wood, if the insects can 

 be kept out of wooden structures this damage can be prevented. 

 "When once the source (white ants coming up through the earth where 

 there is moisture) is shut off, the insects infesting stored material 

 soon die out or can be killed by spreading out infested books, docu- 

 ments, and other stored material or products to dry in the sun or in 

 an oven. Later they can be restored to the repaired building or a 

 safer place. Most damage of this sort can be prevented by the sub- 

 stitution of concrete foundations to buildings or by using timber 

 impregnated with coal-tar creosote. 



FUMIGATION. 



Where the injury is confined to books and paper's, other stored 

 material, or exposed woodwork and furniture, hydrocyanic-acid gas 

 fumigation can be attempted, exposing if possible also, by opening 

 up floors, the infested joists beneath and spreading out the books 

 and opening cases and wardrobes. As Irydrocyanic-acid gas is poison- 

 ous and dangerous, fumigation should be attempted only by those 

 with experience. 1 



LIVING TREES. 



Owing to the subterranean habit of termites, it is extremely diffi- 

 cult to prevent or remedy injury to living forest, fruit, or shade 

 trees. Care should be taken that the trees do not become scarred near 

 the base, in order to prevent heart rot and subsequent infestation. 

 Proper clean forest, orchard, and horticultural management is to be 

 recommended. Properly executed tree surgery 2 sometimes may be 

 effective in repairing damage to valuable old trees. Dead and dying 

 infested trees should be removed and burned. Primings should not 

 be left lying on the ground, but should be burned. 



NURSERY STOCK, FIELD CROPS, AND VINEYARDS. 



Injury to nursery stock will be most serious on recently cleared 

 land where there is abundant decaying wood. Such debris, in which 

 the insects breed, should be removed. In general, the use of recently 



1 For a description of the use of hydrocyanic-acid gas see Howard, L. O., and Popenoe, 

 C. H., Hydrocyanic-acid Gas Against Household Insects, U. S. Dept. Agr., Farmers' 

 Bui. 699. 



2 Collins, J. F. Practical Tree Surgery. In U. S. Dept. Agr. Yearbook for 1913, p. 

 163-190, pi. 16-22, 1913. 



