12 N. H. AGR. EXPERIMENT STATION. [Bulletin 198 



tact insecticide. The study included also ex]ieriments in the effect of pyre- 

 thrum as a stomach poison, the check insects being house flies. 



The investigations of root maggots for the season of 1920 were designed to 

 include new aspects of the study suggested by the work of previous years. 



In order to assure a location where material would probably be abundant, 

 five different areas were selected and certain phases of the work were duplicated 

 in each of these. 



Since the studies prior to 1920 had proved the existence of definite insecticidal 

 properties in the combination of tobacco dust and lime, the work of 1920 was 

 planned to determine in detail the nature of these properties both with refer- 

 ence to the adults of the root maggots and with reference to the eggs and the 

 larviE. A series of special cages was constructed. Adults of the cabbage 

 maggot were introduced into these, and a detailed record of the repellent quali- 

 ties of tobacco dust on the adults was begun. In similar manner, the insecti- 

 cidal effects of the dry tobacco dust and hme on the egg stage and on the larval 

 stage were made the subject of detailed investigation. A further series of 

 experiments was begun to determine the effect of aqueous infusions of tobacco 

 dust and lime on the larval stage. All of these experiments are intended to 

 determine the natine and the meaning of the data that have been accumulated 

 in the work of the years prior to 1920. 



In general it may be stated that the investigation of root maggots has reached 

 the point. where the insecticidal value of tobacco dust and lime has been con- 

 clusively proved. The detailed reactions that take place are the matters that 

 are now being determined. 



Department of Horticulture. 



Fruit Bud Formation. — The season of 1920 represents the 13th year during 

 which this experiment has been in progress, and each successive season has 

 added new interest and brought out new evidence in this work. The project 

 is essentially two-fold in its aspect, namely — -practical or economic in its general 

 character and technical in its special applications. As indicated in the earlier 

 reports, this work is conducted in a seven-acre Baldwin apple orchard known 

 as the Woodman Orchard. A portion of it is plowed and cultivated each year 

 and a portion is in sod. In addition to tillage some plots have a green crop 

 plowed in annually and some also have various combinations of fertilizer 

 applied. For a number of years there was no apparent effect of the fertilizers 

 on the growth or yield of the trees, but the tillage gave immediate response in 

 both. For the past few years it has become evident that the fertilized blocks 

 of trees were outgrowing those which received no fertilizer, but only in the past 

 year, or possibly two, has there been any evidence that the jdeld would be 

 increased by the use of fertilizer in the cultivated parts of this orchard. Per- 

 haps the most outstanding feature of the season 1920 is the decided increase in 

 yield throughout all the fertilized plots as compared with the unfertilized ones. 

 In other words, it has taken twelve or thirteen years to obtain any increase 

 from fertilizers and it will require several years more to make the project suc- 

 cessful from this standpoint. But again let us point out that the value of ordi- 



