Fruit Setting and Pollination 253 



may prevent pollination. Bees are almost essential. 

 Other insects may be useful, but none is as active in carry- 

 ing pollen from flower to flower. The importance of delay- 

 ing the calyx application of lead arsenate until most of the 

 petals have fallen is now emphasized by most horticultur- 

 ists as a precaution against poisoning bees. Much has 

 been said about the importance of wind as a pollinizing 

 agent, useful in carrying the pollen from blossom to blos- 

 som and from tree to tree and much effort has been 

 expended in determining its effectiveness. Most author- 

 ities agree that fully 99 per cent of all fertilized blossoms 

 owe pollination to bees or other insects and less than 1 per 

 cent to the wind. As a direct agency, therefore, wind has 

 very little effect as far as carrying pollen is concerned. It 

 may, however, prevent bees from working on the windy 

 side of the tree and thereby cause a lighter set of fruit on 

 the exposed than on the sheltered side, (c) Eain or cold 

 weather is a factor affecting pollination. Cold, wet or 

 damp weather during the blooming period often checks 

 the activity of bees and sometimes prevents the germina- 

 tion and causes decomposition, or devitalization, of the 

 pollen-grains. Unfavorable weather at blooming is a very 

 important factor in reducing the set of fruit, particularly 

 through the central western states, and often in the East, 

 (d) Very hot and dry weather may also prevent proper 

 pollination, particularly if accompanied by wind. Excess- 

 ive heat may injure the stamens so seriously that they can 

 not properly mature their pollen or it may cause dehiscence 

 of the anthers before the pollen matures, (e) Excessively 

 windy weather. Strong winds, particularly if accom- 

 panied by rain are very injurious to the blossoms. The 

 rain is likely to wash away the pollen-grains and strong 



