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THE POLLINATION OF APPLE TREgS 



In many well-cared for orchards in '.iassachusetts there vrere blocks which bore 

 little or no fruit in 1952, hence, one can expect a heavy bloom in these blocks 

 in 1953. 



It is well knovm that such varieties as kclntosh, Delicious, R, I. Greening, 

 Cortland, and Spy reqxiire cross-pollination. Hence, much emphasis in the past, and 

 rightly so, has been placed on the importance of having a suitable cross-pollexiizer 

 within 80 to 100 feet of the variety to be pollinated. Experience has shown that 

 an arrangement of this sort is necessary as insurance against a crop failure in 

 years that are not favorable for bee flight. However, if weather conditions at 

 blossom time are favorable for bee flight and pollen germination (warm, sunny, 

 quiet) and a heavy bloom is present, over-pollination and an excessive set is a real 

 possibility. Such an overset leads to small apples, limb breakage, and biennial 

 bearing. Of course, to have an overset on Mcintosh the cross-pollenizing varieties, 

 such as Delicious, Cortland or 'wealthy, must be carrying a good bloom as vrell. 

 Since an apple tree with a heavy bloom needs to set but 3 to U per cent of its 

 blossoms to produce a full crop, it is not difficult to understand why oversetting 

 may occur in 1953. Also, in the absence of a crop in 1952 the trees are probably 

 high in food reserves which v/ill tend to increase the chances of over-setting. 



Many growers are in the habit of havitig hives of honey bees brought into the 

 orchard to aid in pollen transfer. It seems advisable to consider the removal of 

 such hives after one good day of pollinating weather in those blocks where the 

 bloom is heavy on Liclntosh, where there are an abundant number of blooming, cross- 

 pollinating varieties, and if the blossoming season is late enough so that fruit 

 losses by spring frosts are remote. Of course, we are assuming that these trees 

 are in a good state of vigor and are not deficient in the necessary nutrient 

 elements. It has been shown that a few hours of favorable weather for active bee 

 activity is all that is needed for sufficient cross-pollination to provide a good 

 crop of apples. Recently, it has been estimated on the basis of field records of 

 honey bee activity that it vrauld be theoretically possible for 7 bees to cross- 

 pollinate UOOO blossoms on a tree adjacent to a cross-pollenizer in one day or 

 enough to produce 25 to 30 bushels of fruit. This job could be accomplished if each 

 bee made eight trips per day and visited 150 blossoms per trip and spent half the 

 time on the Mcintosh tree and the rest of the day on the pollenizer. Under favor- 

 able weather conditions the number of bees per tree often greatly exceeds the 

 theoretical 7 that may be needed. Therefore, if conditions in an orchard are very 

 favorable for cross-pollination the removal of hives of bees from the orchard is 

 worthy of consideration after one day of active bee flight in blocks where one 

 is interested in reducing the chances of oversetting. However, even if hives of 

 honey bees are removed from the orchard an overset may still occur since wild bees 

 or even honey bees coming in from neighboring areas may be plentiful in the 

 orchard . 



The greater the amount of cross-pollination #iich occurs the greater the 

 number of flovrers that vfill develop into young fruits. To be sure, a large number 

 of these young fruits may fall during the June drop period but before this time 

 arrives these young fruits, through their utilization of food reserves in the tree, 

 will have an exhaustive effect on the tree. This influence will result in reducing 

 shoot grovrth, leaf area, and the chances of flovrer bud initiation for the 19^h crop, 



Vie realize that some may prefer to allow cross-pollination to proceed unhampered 

 and then rely on hand or chemical thinning to reduce an overset, if it occurs. How- 

 ever, hand thinning is usually done too late to influence biennial bearing and 

 chemical thinning is not risk-proof. 



F, "f. Southwj.ck 

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