48 



their protection from the beetles. The reputation of the division was 

 thus at stake, and it was resolved not only to endeavor to i)reve!it 

 serious damage but to prevent all injury at whatever cost. 



If the results of remedial treatment reported as thoroughly success- 

 ful for the more northern range of this insect could have been dupli- 

 cated here the problem would have been of simple and easy solution. 

 A single spraying, or at most two, for the larv;e, would have accom- 

 plished the desired i)rotection. The experience of other years, however, 

 has demonstrated that little if any practical protection is secured by 

 such treatment, largely from the fact of the presence of the pest 

 throughout the growing season instead of for a few weeks only, and, in 

 the case of the Department elms, from the constant renewal of the 

 insects from adjoining groves. 



A chronological statement of the work on the elms in the Dei^artment 

 grounds during the present summer will give a fair idea of the difficulty 

 of controlling this insect under the conditions outlined, and I doubt if 

 any very great diminution of this labor will prove successful anywhere 

 in the southern range of the insect. 



The beetles begin to ai^pear by the loth of Ax)ril and toward the end 

 of the month are out in force, before many of the elm trees have put 

 out their folmge. The European elms of the Department grounds are 

 somewhat in advance of the native species in leafing, and thus act as 

 lures or decoys for the beetles, which collect on them in great numbers, 

 sitting about on the buds, waiting with imi^atience for the leaves to 

 unfold. If undisturbed the insects will attack and riddle the young 

 and tender leaves as fast as they develop. Spraying, therefore, is neces- 

 sitated as soon as leafing begins. The first treatment was therefore 

 made April 25, when many of the trees showed scarcely a leaf. Arsenate 

 of lead in very strong solution, 1 pound to 17 gallons of water, was 

 used. The beetles are not easily killed, and even at this strength from 

 10 to 25 i)er cent failed to succumb. This poison has the advantage 

 that it can be applied at any strength, and, as the protection of the trees 

 was imi^erative, on the 2d day of May they were again sprayed with a 

 mixture twice as strong as in the first instance. Many of the trees 

 were still white from the first application, and the effects of these two 

 sprayings remained visible on much of the foliage throughout July. 

 The second spraying resulted in the killing of practically all the beetles, 

 those appearing on the trees after that being undoubtedly recent comers, 

 the renewal, however, becoming much less abundant as the season 

 advanced. Few eggs were deposited during May, which, however, was 

 a very cold, wet month and kept the insects throughout the city in 

 check to a considerable extent. Larvie beginning to appear about the 

 1st of June, the trees were again treated, the spraying this time being 

 with Paris green, at the rate of 1 pound to 100 gallons of water. The 

 larvae were never very numerous, not sufficiently so to do any particular 

 d amage. The spraying was successful enough, but belated beetles were 

 continually coming in from outside, and toward the end of June new 



