12 N. H. AGR. EXPERIMENT STATION [Bulletin 208 



1. Adult flies of the cabbage root maggot do not lay eggs freely on or 

 near plants freshly treated with the tobacco-dust-lime mixture. 



2. When eggs are laid in contact with tobacco-dust-lime mixture, a large 

 percentage of non-hatch results. In the work of 1922 the non-hatch was 

 100% in the case of eggs placed in contact with the mixture, whereas the 

 non-hatch was 0% in the checks, where eggs were placed in contact with 

 soil. 



3. The heavy percentage of non-hatch persists whether the eggs are 

 placed on the surface of the mixture or are inserted slightly below the 

 surface. 



4. The percentage of non-hatch is high whether the material remains 

 dry or is wet down. The results indicated no difference due to the addition 

 of moisture. 



5. Protection to cabbage plants in the field from the use of the mixture 

 diminishes rapidly when heavy rains intervene. This appears to be due 

 largely to the fact that rain packs the mixture down and the movement 

 of the cabbage plant in the wind then opens a small space next to the stem. 

 The female fly drops eggs down into this space. 



6. Protection of cabbage plants during the first two or three weeks after 

 they are set out is the most important phase of the treatment. The plants 

 will withstand heavy attack by maggots after they have established their 

 root system. This protection of newly-set plants is readily attained by the 

 use of the tobacco-dust-lime mixture. 



7. Protection of plants that are drilled in, such as radishes, is easily se- 

 cured by the use of the mixture. Such plants do not sway in the wind as 

 do cabbage plants. In 1922 the percentage of radishes free from maggot 

 attack or only slightly infested in the treated rows was 81.2, whereas the 

 percentage in the untreated rows was 45.5. 



The department believes that the investigation has now resulted in a prac- 

 tical treatment for cabbage, radishes, turnips and cauliflowers, which will 

 give them reasonable protection without in any way injuring the plants or 

 retarding their growth. The treatment is easily and quickly applied. The 

 ingredients are cheap. In the case of cabbage and cauliflower the protec- 

 tion afforded carries the plants through the critical period following trans- 

 planting; in the case of radish and turnip it affords a satisfactory means 

 of insuring a marketable and profitable crop. 



The tobacco-dust-lime phase of the root maggot studies is considered to 

 be ready for publication, and a bulletin is in preparation. 



How Bordeaux Mixture Stimulates Plants. 



The past year has seen the completion of the studies on the stimulatory 

 action of Bordeaux mixture. The investigations of O. Butler (Botany) 

 in this field show that the physiological response of plants to the mixture 

 depends on the intensity of the shadow cast by the wash. The amount of 

 lime present in the mixture proved the important factor here. Bordeaux 

 mixture 1:1 was found to act as a depressant but Bordeaux mixture con- 

 taining just enough lime to give an alkaline reaction permitted normal de- 



