234 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



In dry sandy loam, bundles of stalks were buried with a larval ex- 

 pectation of at least fifty per bundle, and were taken and examined 

 at intervals. The results follow: — 



Date buried, Sept. 4. 



Dates removed. Sept. 20 Sept. 28 Oct. 12 Oct. 25 Nov. 2 Nov. 1. 

 53 8 4 5 2 1 larvae.^ 



Plowing must be done thoroughly so as to cover all stubble and debris. 

 This is materially helped by rolling immediately the crop is off, as roll- 

 ing crushes open from 95% to 97% of the stubble, flattens down the 

 stubble and weeds, kills some borers and destroys good wintering quar- 

 ters for others, because it greatly facilitates moisture getting into the 

 stalks and consequently, their earlier decay. Moreover, larvae leave 

 moist soil sooner than dry soil. Under dry conditions, the whole 

 season may be necessary to get all larvae in plowed under stubble, to 

 come to the surface. Early plowing kills some borers but is chiefly 

 of importance because it forces the vast majority of them to come to 

 the surface. If any debris is around, they enter it. 



On stubble land that has not been cleanly plowed down, rolling 

 after plowing vmdoubtedly forces some outstanding stalks under the 

 surface. Rolling of land that has been well and cleanly plowed, has 

 been found undesirable because it delays the movement upwards, of 

 the borers, and facilitates their migration to surrounding fields, when 

 they do com-C up. 



This movement upwards, of the larvae, is influenced by the type of 

 soil in which infested material is buried, by temperature and by moisture. 

 Just what these conditions are, has not been worked out yet. Reactions 

 vary according to the time and consequently the temperature of the 

 season. 



Comparison of rates of larvae leaving various types of soil, in order 

 of degree. Larvae used — at least 300 in each case. 



In some experiments the larvae died in material that was buried 

 early in August. In the m.ajority of cases, however, the earlier the 

 plowing, the sooner the larvae emerged from the soil. This shows that 

 in August, larvae emerged rapidly and migrated to neighbouring fields. 



