336 DAVENPORT ACADEMY OF NATURAL SCIENCES. 



EFFECT ON THE TREES. 



As may be easily imagined the effect of so extensive a diversion of 

 the sap from its legitimate functions, soon shows its ill effects upon the 

 tree. In the case of the soft maple, the green of the leaves begins to fade 

 away until they turn yellow and prematurely fall off, then the smaller 

 outer extremities of the twigs die, and if the devastation is very exces- 

 sive or prolonged the larger branches follow until finally the entire tree 

 dies. But this last event is not very common, for which we must prob- 

 ably thank the enemies and p irasites. Badly affected trees become 

 more stunted in their growth, their leaves smaller and weaker, the ordi- 

 nary pale grayish bark becomes very dark, almost blackish, thus render- 

 ing it very easy to recognize an infested tree from a distance. They 

 also put forth their leaves later and shed them earlier than healthy trees. 



My observations have been mostly made on the soft maple, but the 

 effect upon other trees is probably not essentially different. I have not 

 the exact data, but I think I am safe in saying that less than five per 

 cent, of the trees infested with this insect during the past thirteen years 

 iiave died therefrom. This would probably be less than one per cent, of 

 the trees liable to their attacks in this city. But this is a mere estimate 

 and simply conveys the impression made upon me. 



REMEDIES, 



The best remedy known to me is to cultivate and protect the parasites 

 and enemies already described. The survival of the trees infested with 

 Pulvinaria in Davenport is undoubtedly due almost entirely to them. 

 At all events great care should be taken to preserve these enemies, 

 and caution should be used in destroying the injurious insects that we do 

 not destroy the beneficial ones also. 



Of artificial remedies the simplest is that of "heading in" the tree, 

 [i. e. cutting off the branches so as to leave only the trunk and larger 

 limbs), and then removing the lice from the remaining portion by hand 

 or otherwise. This appears to be the favorite method in use in Daven- 

 port, but it does not add anything to the beauty of the trees, though the 

 soft maples stand this severe ordeal very well. Tliis operation seems to 

 succeed best Avhen done in the early summer. On small trees the lice 

 can be removed without much difficulty by hand-picking, or crushing. 



In using liquid applications several facts must be taken into consider- 

 ation ; 1st, the effect on the Pulvinaria ; 2d, the effect on the parasites 

 and enemies ; 3d, the effect on the tree; 4th, the cost. Under the first 

 head I made a few tests, of the effects of various chemicals, such as 

 I happened to have at hand, upon the young larva, egg-nests and 

 adult females, and as a result I may state that alcohol and spirits, 

 chloroform, ether, turpentine or other oils, causes the death of the insect 

 in all stages even when fully protected by their waxen coats, while 

 water, acids (such as nitric and acetic) and alkaline solutions (such as 

 solution of potash) had no effect whatever even on the young larvae. 

 Very probably a prolonged submersion in these substances would cause 



