THE PECAN NUT CASE-BEARER 11 



The data on the length of the pupal period of the first-brood 

 pupae for 1915 are incomplete, but in the case of the few indi- 

 viduals under observation the pupal period lasted from 10 to 11 days. 



NUMBER OF GENERATIONS 



Life-history studies have shown that under normal conditions the 

 pecan nut case-bearer has three generations annually, at Monticello, 

 Ma., and that it passes the winter in the immature larva stage of the 

 third generation. These third-brood larvae after feeding sparingly 

 for a few weeks migrate during the latter part of September or the 

 first part of October to the buds, where they construct small, com- 

 pactly woven hibernacula, in which they hibernate until the following 

 spring, when the buds on pecan trees are beginning to open. In con- 

 finement it may be possible for the pecan nut case-bearer to have four 

 generations. 



PARASITIC ENEMIES 



The writer has on several occasions reared a number of parasitic 

 insects from the larvae and pupae of the pecan nut case-bearer as 

 follows: Exorista {Nemorilla) pyste Walk., 3 Habrobracon variabilis 

 Cush., 4 Calliephialtes grapholithae Cress., 4 Cremastus (Zaleptopygus) 

 sp., 5 and Angitia sp. 4 The most effective parasite is the tachinid fly 

 Exorista pyste Walk., which was reared m large numbers from the 

 larvae and pupae, and is no doubt a very important factor in the 

 natural control of this pest. The braconid Habrobracon variabilis 

 also was frequently bred, and is perhaps second in importance among 

 the parasites of the pecan nut case-bearer. 



CONTROL MEASURES 



Investigations so far conducted show that the best method of 

 control against the pecan nut case-bearer is spraying with arsenate 

 of lead. 6 The arsenate should be used at the rate of 1 pound of the 

 powdered form, or 2 pounds of the paste form, to each 50 gallons of 

 water, to which should be added the milk of lime from 3 pounds of 

 slaked lime. The addition of lime is necessary to prevent arsenical 

 injury to the foliage and nuts. Three applications will be required 

 and should be at the following periods : 



1. Soon after the nuts have set, at which time they are about the 

 size of garden peas. 



2. One week or 10 days later. 



3. From four to five weeks after the second application. 



The date for the first application at Monticello, Fla., during the 

 season of 1915 was found to be May 15, and in 1916 it was May 12. 

 The time of spraying, however, will vary somewhat according to 

 latitude and the character of the season. The first and second appli- 

 cations are the most important in the control of the pecan nut case- 

 bearer, as most of the damage to the nuts is usually caused by the 

 larvae of the first generation. Since only a small portion of the nut 

 crop is attacked by the second-brood larvae, it is suggested that if 

 growers desire to reduce spraying of their orchards to a minimum 



'Determined by W. R. Walton. 



• Determined by R. A. Cushman. 



! Determined by K. A. f'ushman. The genus Cremastus now embraces the old genus Zaleptopygus. 



i in connection with Hfe-history Investigations, spraying experiments were conducted during 1916 and 

 l&ro, the results of which were reported in detail in Farmers' Bulletin W, of the United Slates Department 

 of Agriculture, pages 6 to 9. Further spraying experiments were begun in the spring of J Ul 7, but could not 

 |r- acce fully carried out on account of the mildness of tho infestation of the insect in tho orchard 

 selected for this work. 



