REMEDIES AGAINST FOREST INSECTS. 33 



thirteen quarts capacity, aud having a cross-septum of fine wire gauze, such as is used 

 for sieves, also having vertical sides, and a rim to keep it from rocking on the barrel, 

 was used. About three quarts of cheap flour were placed iu the funnel and washed 

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

 divided, and will dift'use in the water without appearing iu lumps. The flour is a suit- 

 able 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 mixing in this 

 way less flour will suffice. Three-eighths of a jiound of London purple to one barrel of 

 water maybe taken as a suitable percentage. 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 be the min- 

 imum 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 attained, and this should be applied only 

 as an extremely fine mist, without drenching the foliage. 



Effects of the Mixture. — The flour seems to keep the poison from taking eftect 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 per- 

 manent. On the leaves, especially on the under surfaces, the London purple and 

 flour 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 administer the poison before the insect has 

 worked, and, above all, to diffuse the spray finely, but not in large drops, no harm 

 worth mentioning will accrue to the plant from the proportion of poison recom- 

 mended. The new growth, that developed after the first poisoning, was protected 

 by one-fourth of a pound to the barrel in 188'2. From midsummer until autumn the 

 uupoisoned half of the grove remained denuded of foliage, while the poisoned half 

 retained its verdure. The little damage then appearing in the protected part was 

 mostly done before the first treatment. Eggs were laid abundantly throughout the 

 season. Many of these seemed unhealthy and failed to develop, probably because 

 they were poisoned. Many hatched, but the young larvae soon died. The eggs were 

 seldom deposited on the young leaves that were appearing after the poison was ap- 

 plied, but were attached to the developed leaves, and here the larvje generally got 

 the poison to prevent their attack upon the aftergrowth. Still the young leaves be- 

 came perforated to some extent. The adults, which fly from tree to tree, ai)peared 

 plentifully without much interruption throughout the season, and often several 

 could be seen feeding on each tree. Possibly many of these may have become poi- 

 soned before depositing the eggs. 



The efficiency of London purple being established, it will generally be preferred to 

 other arsenicals, because of its cheapness, better difiusibility, visibility on the foli- 

 age, etc. As the effects of the poisons commonly do not appear decidedly for two or 

 three days after their administration, the importance of the preventive method of 

 poisoning in advance can not be too strongly urged. As the effect is slow in appear- 

 ing, impatient parties will be apt to repoison on the second or third day, and thus 

 put on enough to hurt the plant when the effect does come. Much depends on dry- 

 ness or wetness of the weather ; but good effects may be expected by the third or 

 fourth day. 



London purple seems to injure the plant less than Paris green. 



Treatment with Paris green. — In 1883 the Paris green was first applied on the 29th of 

 May, at which date the eggs were extremely abundant and hatching rapidly on the 

 leaves. Paris green, flour, and water were mixed by the means previously employed 

 with London purple and already described. The mixture was applied to the north 

 part of the same grove of elms. Thus far experience shows that the Paris green is 

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