THE IMPORTED ELM LEAF-BEETLE. 17 



kinds of injury ; first, that directly from the eating by the insect ; 

 ond, that which follows indirectly from the deleterious effects of the 

 poison on the plant, for its caustic effect is much greater where the 

 leaves have been so gnawed that the poison comes in contact wirli the 

 sap. 



Treatment with London purple. — Already early in June the insect ap- 

 pears plentiful. On June 7, 1882, it was at work on all the trees, and 

 its clusters of eggs were numerous beneath the leaves. Some of the 

 trees had half of the leaves considerably gnawed and perforated by 

 larv, r e of all sizes, and by the adults. At this date fifteen trees, consti- 

 tuting the south part of the grove, were treated. 



Preparation of the Poison. — London purple (one-half pound), flour (3 

 quarts), and water (barrel, 40 gallons) were mixed, as follows : A large 

 galvanized iron funnel of thirteen quarts capacity, and having a cross- 

 septum of fine wire gauze, such as is used for sieves, also having verti- 

 cal sides, and a rim to keep it from rocking on the barrel, was used. 

 About three quarts of cheap flour were placed in the funnel and washed 

 through the wire gauze by water poured in. The flour in passing through 

 is finely divided, and will diffuse in the water without appearing in 

 lumps. The flour is a suitable medium to make the poison adhesive. 

 The London purple is then placed upon the gauze and washed in by the 

 remainder of the water until the barrel is filled. In other tests the 

 flour was mixed dry with the poison powder, and both were afterward 

 washed through together with good results. It is thought that by mix- 

 ing in this way less flour will suffice. Three-eighths of a pound of Lou- 

 don purple to one barrel of water may be taken as a suitable percent- 

 age. Three-eighths of an ounce may be used as an equivalent in one 

 bucketful of water. The amount of this poison was reduced to one- 

 fourth of a pound to the barrel with good effect, but this seems to he the 

 minimum quantity, and to be of value it must be applied in favorable 

 weather and with unusual thoroughness. With one-half or three fourths 

 of a pound to the barrel, about the maximum strength allowable is at- 

 tained, and this should be applied only as an extremely fine mist, with- 

 out drenching the foliage. 



Effects of the Mixture. — The flour seems to keen the poison from tak- 

 ing effect on the leaf, preventing to some extent the corrosive injury 

 which otherwise obtains when the poison is coarsely sprinkled or too 

 strong. It also renders the poison more permanent. On the leaves, 

 especially on the under surfaces, the London purple and dour can be 

 seen for several weeks after it has been applied, and the insect is not 

 only destroyed, but is prevented from reappearing, at least for a long- 

 period. By poisoning again, a few weeks later, the insect is deterred 

 with greater certainty for the entire season. By being careful to ad- 

 minister the poison before the insect has worked, and. above all, to 

 diffuse the spray finely but not in large 1 drops.no harm worth mention- 

 21061— -Boll Id 2 



