518 FUNDAMENTALS OF FRUIT PRODUCTION 



is not made for the purpose of minimizing the importance of "rainy 

 weather" at blossoming in reducing the fruit crop. It is desirable, 

 however, that there be a correct understanding of the relative importance 

 of the different factors that usually constitute "rainy weather" and that 

 there be a realization that even a hard rain, if of short duration and not 

 accompanied by very low temperatures, is not ordinarily a serious limit- 

 ing factor in this connection. 



Wind. — The average fruit grower regards wind as one of the most 

 important agents in the transfer of pollen from stamen to stigma. Many 

 plants, such as the walnuts, oaks, hickories and hazels, are wind-polli- 

 nated and with these a reasonable amount of wind at blossoming is a 

 distinct aid in securing a good set of fruit. However, the majority of 

 the deciduous fruit crops are insect-pollinated. With these, wind hinders 

 rather than helps pollination, since bees and other pollen-carrying insects 

 work most effectively in a still atmosphere and in a strong wind they 

 refuse to work at all. Abundant evidence on this point may be found 

 in orchards with some exposed and some protected situations. Other con- 

 ditions equal, there will be a much better set of fruit where the trees are 

 protected from the full sweep of the wind and in exposed places there is often 

 a much better set on the leeward than on the windward side of the trees. 

 In addition to the indirect effect of wind through interfering with 

 the work of pollen-carrjdng insects, it may operate more directly in whip- 

 ping about the flowers and causing mechanical injuries. It may also cause 

 the stigmatic fluid to dry prematurely and thus prevent the germination 

 of the pollen grains. In some species at least, the action of wind is more 

 pronounced early in the usual period of pistil maturity than later. ^^ 



There are many cases in which the protection afforded the fruit 

 plantation at the time of blossoming is of greater importance than any 

 other service rendered by a windbreak. 



Fungous and Bacterial Diseases. — The flowers of many species are 

 subject to the attacks of various fungous and bacterial diseases and often 

 their work at this time is serious enough greatly to reduce the set of 

 fruit. Thus fire blight is generally recognized as one of the most impor- 

 tant factors in limiting the set of fruit in pears; the apple and the pear 

 scab are responsible for the falling of many flowers of those fruits at or 

 shortly after blossoming; brown rot attacks the blossoms of practically 

 all the stone fruits; black rot works on grape blossoms, causing many 

 to drop; the flowers of the mango^"® are attacked frequently by an 

 anthracnose; the list might be extended almost indefinitely. Naturally 

 the losses occasioned by these fungous and bacterial attacks at the time 

 of fruit setting vary greatly with locality, variety and seasonal conditions. 

 For instance, there are certain restricted areas where fire blight of the 

 pear and apple is not found, though the disease may levy a very heavy 

 toll on pear blossoms a hundred miles distant. The Grimes apple is but 



