AND OTHER INJURIOUS INSECTS OF I907 AND I908. 85 



tural Division. Acknowledgments are also due to Messrs. O. F. 

 Brand & Son of Faribault, and F. J. Butterfield of Long Lake for 

 courtesies extended to the Entomological Division in allowing the 

 use of their orchards for spraying experiments. Unfortunately 

 weather conditions in one case, and lateness in starting in the 

 other prevented any definite results from being obtained upon the 

 plums in those localities. The data upon which the following 

 suggestions are given were all obtained from work in the Experi- 

 ment Station orchard. 



The plum trees used in the experiment varied in age from five 

 to ten years, the average tree being capable of bearing a bushel 

 and a half of plums. They were of such varieties as Surprise, 

 Wyant, Cheney, De Sota, Compass-cherry, etc. Although at the 

 beginning of each season sixty or more trees were in the experi- 

 ment, fruit set well only on some twenty-five trees. 



Life History: The adult Plum Curculio, see Fig. 33, is a 

 Snout Beetle nearly ^4 of an inch in length. The female beetle 

 inserts her eggs beneath the skin of the fruit, and then turning 

 around, makes the characteristic crescent shaped mark on one side 

 of the egg, as seen in Fig. 33. From the egg hatches a little grub, 

 which feeds on the fruit, eventually causing it to drop. When the 

 grub is full grown it leaves the plum and enters the ground, soon 

 changing into a pupa. Late in the season the pupa changes into 

 the beetle, which passes the winter in protected places. 



In 1908 the adult beetles were not found until A^Iay 30th, although 

 observations were begun as early as May 1st. After their first ap- 

 pearance they were observed up to July 12th. It is possible that 

 they were present in small numbers several days before May 30th, 

 so that the actual Curculio season extended over a period of six 

 or seven weeks. 



In studying the habits of this insect one finds that in the spring 

 it feeds for a time upon the leaves and the young fruit. The theory 

 is, therefore, that if the leaves and young fruit are covered with a 

 poison spray during the time the Curculio is at work, many beetles 

 will be killed thereby. Plum leaves are very susceptible to burning 

 from Paris green, but we find that arsenate of lead, however strong 

 the mixture may be used, has no injurious effect upon the foliage, 

 and at the same time sticks much better than Paris green. Con- 

 sequently our experiments were carried on entirely with arsenate 

 of lead, or a combination of arsenate of lead and Bordeaux mixture. 

 Fig. 34 shows how well arsenate of lead sticks. The tree from 



