100 Diseases of Greenhouse Crops 



wind and insects. In the greenhouse, these two 

 agencies are practically shut out. With forced cu- 

 cumbers, the difficulty is often overcome by install- 

 ing beehives in the house. Bees are very active 

 imder high temperature conditions, and perfect pol- 

 lination is the result. The usual practice is to sup- 

 ply a beehive to every 200 feet of house. The 

 hives should be placed on platforms several feet 

 above the bed to protect the bees from becoming 

 drenched during the watering or sprinkling of the 

 beds. We should bear in mind that the hives must 

 be taken out whenever the house is fumigated with 

 potassium cyanide. Nicotine fumes do not seem 

 to injure the bees, especially if the fumigation is 

 carried on at night. Bees may be used to pollinate 

 practically every crop grown in the forcing house. 

 It seems, however, that bees refuse to work on to- 

 matoes, perhaps because of a dislike for their nec- 

 tar. In this case, then, it is necessary to pollinate 

 by hand. The investigations of Fletcher and 

 Gregg* and others have shown that the setting of a 

 good crop of smooth heavy tomatoes depends largely 

 on the proper distribution of pollen over the stigma. 

 A lack of pollination will of course result in no crop. 

 An uneven distribution of pollen will result in too 

 large or irregular fruit. During the winter and on 

 sunny days, it will pay to go over the plants and 

 tap each blossom with the finger or with a stick on 

 which is fastened a small glass rod or spoon. This 



•Fletcher, S. W., and Gregg, O. T., Michigan Agr. Expt Sta., 

 Special Bui. 39: z-io, 1907. 



