30 ANNUAL REPORTS OF DEPARTMENT OP AGRICULTURE. 



An important development in this practical entomological work 

 of recent years has been the establishment of a number of more or 

 less temporary field laboratories, scattered over the country. Thus 

 the expert workers are taken into the centers of activity of the inju- 

 rious species. Great stress is being laid on what may be termed 

 the cultural method of insect control. The intimate life round of the 

 insect pest is studied in close connection with farming methods 

 in order to ascertain whether by variation of cultural practice the 

 insect damage can not be considerably reduced. Remedial work of 

 this sort is extremely practical. Investigations have shown that in 

 many instances partial or nearly complete control can be gained by 

 some change in farm management. This naturally is the best remedy, 

 except possibly in the case of introduced pests, where control can be 

 secured by the employment of parasites or other natural enemies. 



Technical methods of control, mechanical and chemical, includ- 

 ing sprays and spraying machinery, fumigation for citrus orchards, 

 nursery stock, mills and warehouses, or trapping methods and other 

 means of mechanical destruction also have been studied and devel- 

 oped. In the large problems it frequently has happened that cul- 

 tural, biological, and technical measures are used at the same time. 



When the enormous annual losses from injurious insects are con- 

 sidered it is clear that the value of the department's work in applied 

 entomology is very great. 



PLANT QUARANTINES. 



Important service is rendered to the farm and fruit interests of 

 the country, under the Plant Quarantine Act, by preventing the in- 

 troduction of new and dangerous insect pests and plant diseases. 

 There are now in force nine foreign quarantines forbidding the entry, 

 or permitting the entry only under restrictions, of various farm, 

 orchard, and forest products which may harbor injurious insects or 

 diseases. The more important quarantines relate to the Mediter- 

 ranean fruit fly, perhaps the worst fruit pest of the tropical and 

 subtropical countries; the pink boll worm, an insect which threatens 

 to become the most serious enemy known to cotton ; the potato wart, 

 a disease which not only destroys the tuber but infects the soil; and 

 the white-pine blister rust and the citrus canker, two diseases 

 which became established in the United States prior to the passage 

 of the act. 



