ENTOMOLOGY. 417 



I have a list of over forty species of insects which are found 

 in Minnesota, injurious to the plum. Many of them do not occur 

 everj^ year in large numbers, others are constantly present, but 

 have to be favored by suitable conditions to exert their full powers 

 as destructive insects, while others are common every year and 

 take a large part of our crop. For this meeting- I will mention 

 only a few and give their life histories, which must guide us in 

 choosing the remedies w^e can apply w^ith success. To use insect- 

 icides at random does little good, and frequently more harm 

 than good, and without knowing exactly the habits of our foes we 

 cannot expect to conquer them. Besides, the plum is a tree that 

 is very readilj^ injured by all kinds of arsenical poisons, more so 

 than anj^ other cultivated plant we have in Minnesota. Moreover, 

 the tree is at different times more readily injured than at others, 

 and the use of any arsenical poison has to be restricted as much as 

 possible and be guided with inuch caution, or instead of killing the 

 insects, we kill the tree. 



I had during the summer a very peculiar experience with a new 

 insecticide sent out by a Chicago firiu, of course, with the usual 

 high sounding claims supported by manj^ testimonials. The direc- 

 tions were given how to'use this material; and as some trees in my 

 yard had large numbers of leaf-lice upon them I was stupid enovigh 

 to try an experiment upon my own trees. Result: living lice crawl- 

 ing away; leaves all dead; twigs and smaller branches, ditto; dead 

 foliage of all kinds of plants as far as the spray reached; bad temper; 

 bad language — btit no testimonial for the firm expressed in the 

 usual polite terms. Prof. Snj^der, of our station, kindly determined 

 the composition of the fluid and found it to contain about equal 

 parts of soluble arsenous acid and caustic potash. The tin can con- 

 taining the fluid, having been kept upon a painted porch, left a 

 mark upon it by having eaten away the paint. The can was thrown 

 away among rubbish in the neighboring woods, causing the death 

 of several trees and of everything living in a radius of over four feet. 

 Perhaps, some of you gentlemen will in future offer me the use of 

 some trees for trial of new insecticides! If j^ou do, please give me 

 your address and a written release from all possible damages. 



The four most destructive insects to plums and plum trees are 

 Plum Gouger, Plum Curculio, Plum Aphis and Plum Gall Mite. 



It is hardl}^ necessary to speak in detail about the first two insects 

 as they are too well know^n, and you can hardly open ah entomolo- 

 gical bulletin issued by any of the Eastern, Central or Southern 

 states without finding a description of the one or the other, and of 

 the remedies that will kill them. As far as such remedies are con- 

 cerned I am afraid that much more is claimed for them than is war- 

 ranted by facts. Now-a-days Paris green and Bordeaux mixture are 

 a sort of cure-all, and all ills that plum trees are heir to are said to 

 be cured by them. We could only be glad if such were the case, 

 but the millennium has not yet been reached, and some of the older 

 methods of fighting insects have to be used in addition. 



The Plum Curculio ( Conotrachelus nenuphar ) eats all tender 

 parts of the tree, such as green bark, buds, leaves, flowers and fruit. 



