20 BULLETIN 204, U. S. DEPARTMENT OF AGRICULTURE. 



RESULTS OF EXPERIMENTAL WORK. 



Many of the experimental projects which have been undertaken are 

 nearing completion and detailed reports will be published later. 



The information on food plants will now form a definite basis for 

 practical work, and as has been brought out by the observations in 

 Europe on both parasites and food-plant conditions, it will be neces- 

 sary to bring about in our forests a great reduction of the favored food 

 plants of the gipsy moth before natural enemies can be expected to 

 keep this insect within reasonable bounds. 



The parasites and wilt disease, as has already been shown, are doing 

 effective work, but the results would be greatly amplified by eliminat- 

 ing favored food plants. 



The study of the increase of the moth in the field furnishes valuable 

 data on all phases of the forest control problem, while the work on 

 dispersion is of special value in connection with the field control work 

 which is being carried on. 



Secondary insects are important inasmuch as they may prevent the 

 recovery of'many trees which have been defoliated and which would, 

 under normal conditions, gradually recover. 



SILVICULTURAL WORK. 



During the time the gipsy moth has been known to exist in this 

 country it has done an immense amount of damage to tree growth of 

 the infested region. The injury has caused the death of many of the 

 trees attacked or the retardation of their growth and development, 

 and has produced conditions favorable to the increase of secondary 

 enemies. The tree growth affected may be divided into three classes, 

 (1) fruit trees, (2) shade or ornamental trees, and (3) forest trees. 

 All have suffered severely, but owing to their greater value and 

 relatively smaller numbers it has been possible to prevent a large 

 amount of the injury by applying hand methods of suppression to 

 fruit and shade trees. Gipsy-moth damage to forest trees, however, 

 can not be controlled in the same way owing to the great expense 

 involved, hence the problem of preventing damage in woodlands is a 

 serious one. In some European countries this has been solved to a 

 considerable extent by growing species which are not so susceptible 

 to gipsy-moth attack. The investigations on the food plants and 

 feeding habits of the gipsy moth indicate that the work of eliminating 

 the most susceptible and encouraging the growth of those that are 

 not favored as food by this insect is likely to give good results. As 

 this work involves, to a considerable extent, the practice of silvicul- 

 ture, the Bureau of Entomology requested and received the coopera- 

 tive assistance of the Forest Service, and these two branches of the 

 Department of Agriculture are now working together on this problem. 

 Mr. George E. Clement, who was formerty an assistant in the Forest 



