20 Direiictor's Report ojt thb 



suggestions as to the location and construction of fumigation 

 houses or chambers. 



Spraying fruit trees in Uoovi. — The effect of spraying fruit trees 

 when in bloom with the common insecticides and fungicides 

 which are used in orchards has been under investigation during 

 the past season. The work was carried on both in the labora- 

 tory and in the orchard. In the laboratory the germination of 

 pollen grains and the growth of pollen tubes in cultures which 

 contained none of the poisons used in spray mixtures were com- 

 pared with the germination and growth in cultures which con- 

 tained either some insecticide or some fungicide, or both. 



In these cultures both the Bordeaux mixture and copper 

 arsenite of the strength commonly used in spraying apple orch- 

 ards practically prohibited the germination of the pollen grains 

 with which they came in contact. In cultures containing but 

 2 per ct. of the 1-to-ll Bordeaux mixture pollen) germination 

 occurred only in rare cases; while even the presence of only 1 

 per ct. of this mixture had a decidedly adverse influence on 

 the germination of pollen and the development of pollen tubes. 



In the field investigation an effort was made to learn what 

 effect the spray mixtures have upon (a) the essential organs of 

 the flower, (b) upon the yield of fruit and (c) upon the fungous 

 diseases and insects which are injurious to the crop. 



In almost all cases where the blossoms were hit in the center 

 by the spray they failed to set fruit. In some cases the spray 

 caused the stamens and pistils to wither prematurely. Oc- 

 casionally when the spray hit the stigmatic surface the pistils 

 remained green for an unusually long time awaiting pollination, 

 but at last they withered and set no fruit. The laboratory cul- 

 tures showed that the pollen could not grow in the presence of 

 even quite dilute spray mixtures. It seems, therefore, that the 

 spray mixture on the stigmatic surfaces, in the cases just cited, 

 by preventing the growth of any pollen which may have reached 

 the stigmas caused the blossoms to fall away without setting 

 fruit. 



