CONTENTS. 3 



Department Bulletin No. 931. — Corn-belt Farmers' Experience with 



Motor Trucks — Continued. Pag«. 



Tires 24 



Reliability 26 



Cost of operation 29 



Cost of hauling with trucks 30 



Saving of hired help 30 



Displacement of horses 31 



Farms on which tractors are owned 32 



Department Bulletin No. 932. — Life History of the Codling Moth in 

 the Grand Valley of Colorado : 



Introduction 1 



The Grand Valley of Colorado 2 



Explanation of terms 3 



Methods and rearing apparatus employed in the life-history studies— 7 



The insectary . 8 



Seasonal-history studies of 1915 9 



Codling-moth band studies of 1915 40 



Seasonal-history studies of 1916 45 



Codling-moth band studies of 1916 78 



Natural enemies of the codling moth 82 



Miscellaneous studies 83 



Review of seasonal-history studies of the codling moth in 1915 and 



1916 112 



Summary 115 



Department Bulletin No. 933. — Black Walnut : Its Growth and Man- 

 agement : 



Introduction 1 



Distribution of walnut 2 



Supply 6 



Description of the tree 15 



Silvical characteristics 18 



Growth of individual trees 22 



Growth of stands (yield per acre) 26 



Measuring logs and estimating standing timber 28 



Walnut plantations 31 



Establishing walnut plantations 40 



Department Bulletin No. 934. — Damping off in Forest Nurseries : 



Damping off in general 1 



Damping off of conifers 7 



Causal fungi 27 



Relative importance of the damping off fungi on conifers 65 



Damping off fungi as causes of root rot and late damping off 70 



Relation of environmental factors to damping off 73 



Density of sowing . 74 



Moisture and temperature factors 75 



Chemical factors 79 



Biologic factors 82 



Acknowledgments '%. 86 



Summary 86 



Literature cited 91 



Department Bulletin No. 935. — The Distribution of Northwestern 

 Boxed Apples : 



Introduction 1 



Production 2 



Preparation for market 4 



Transportation and storage facilities 5 



Rate of movement 6 



Marketing methods 7 



Distribution." 8 



Export shipments 8 



F. o. b. prices 9 



Appendix : Exhibits 1 to 11 11 



