BETTER FRUIT 



AN ILLUSTRATED MAGAZINE PUBLISHED MONTHLY IN THE INTEREST OF MODERN, PROGRESSIVE FRUIT GROWING AND MARKETING 



The Abuse of Water on Fruit Trees 



By D. F. Fisher, Office of Fruit Disease Investigations, U. S. Department of Agriculture— Presented at the Annual Meeting of the 

 Washington State Horticultural Association, Kennewick, Washington, January 3, 1918 



IT may be somewhat surprising to 

 hear that irrigation water, which is 

 so essential to the production of 

 fruit in many parts of the Northwest, 

 can be and often is harmful both to 

 trees and fruit. The indictment of 

 water, however, cannot be limited to its 

 use in irrigalaion, for water is water, 

 whether applied in furrows or gratui- 

 tously supplied from the clouds. Per- 

 haps it would be putting it too strong to 

 say that fruit diseases due to soil moist- 

 ure conditions are more prevalent in 

 irrigated districts than elsewhere, but 

 certainly we may say that they appear 

 to be more aggravated and they have 

 been more closely studied. 



It is also true that such diseases can 

 be more nearly controlled under irri- 

 gation than under conditions of natural 

 rainfall, since the water supply is more 

 nearly under the control of the grower. 

 If irrigation practices were standard- 

 ized it would be comparatively easy to 

 point out in a general discussion such 

 as this just what phases of irrigation 

 are objectionable and the manner in 

 which they could be corrected. But 

 irrigation pracitces cannot be standard- 

 ized; different conditions require dif- 

 ferent treatment and growers are re- 

 quired to exercise their own judgment 

 in irrigating their orchards. This per- 

 mits of a wide variation in practice and 

 we find growers who would flood their 

 orchards continually if they could se- 

 cure the water, and others whose 

 orchards are in a constant state of 

 drouth, while in between the two ex- 

 tremes the balance of the growers fol- 

 low individual ideas, many scientifically 

 founded and highly beneficial, but some 

 positively harmful. Injury from the 

 use and abuse of water, however, is not 

 always a direct result of methods of 

 irrigation. But if other environmental 

 factors, dependent on, or caused by soil 

 moisture conditions, are concerned, 

 they are usually within the power of 

 the orchardist to remedy. 



While more progress is being made in 

 irrigated districts in the correction of 

 this class of diseases than elsewhere, 

 there is still a woeful lack of general 

 knowledge concerning these problems 

 and a failure to apply many of the prin- 

 ciples which have been established. In 

 every section we may still find the clean 

 cultivation "crank," who continues to 

 deplete his soil of plant food and ex- 

 haust the humus essential to the reten- 

 tion and penetration of irrigation water. 

 His trees become yellowish in appear- 

 ance, the foliage thin and sparse, the 

 new growth stunted and weak, while 

 the fruit crop constantly diminishes in 

 size and quality. In his attempts to 



correct these conditions he pours on 

 more and more water, but usually with- 

 out avail unless he resorts to subsoiling, 

 and then the relief is only temporary. 

 The surface of the soil may become sat- 

 urated, but without humus the water 

 will not penetrate to the roots. The 

 "plow-sole" becomes a kind of "hard- 

 pan" and is so cemented as to exclude 

 the water and starvation of the trees 

 very naturally results. 



We still find plenty of rosette in apple 

 orchards, usually under the conditions 

 just described, even though it is a gen- 

 erally accepted fact that an alfalfa 

 shade crop planted in such orchards 



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will in a short time correct this condi- 

 tion. While no definite study of this 

 disease is available for report it seems 

 probable that rosette is merely the re- 

 sponse to a soil moisture condition, pos- 

 sibly complicated by nutritive problems 

 or the poisonous effects of concentrated 

 soil solutions which are corrected by 

 the culture of alfalfa among the trees. 

 Alfalfa roots penetrate deeply and, in 

 decaying, humus is distributed through 

 the area occupied by the tree roots. 

 Channels for the penetration of irriga- 

 tion water are thus provided through 

 the "hardpan" and a balanced supply 

 of plant food for the trees is insured. 

 By this re-establishment of normal 

 growth conditions the tree affected with 

 rosette is soon able to overcome the 

 disease. 



j There are numerous other diseases 

 which are affected by the supply of 

 soil moisture, some of which are gen- 

 erally understood, but which it may be 

 profitable to review. The first class of 

 such diseases which conies to mind is 

 that caused by a lack of water or 

 drouth. A state of chronic drouth is 

 responsible for a lack of tree growth 

 and small-sized fruit. Water is essen- 



tial to the proper nutrition of the trees, 

 since all of the plant food obtained 

 from the soil is used in a water solu- 

 tion. Drouth, then, is starvation as 

 well as acute thirst. Water is essential 

 to the maintainance of turgor and activ- 

 ity of all the parts of the growing plant, 

 so that when the water supply fails the 

 plant not only starves but its cells dry 

 out and die. A chronic drouth may not 

 immediately kill the tree, but it causes 

 so much devitalization that even after 

 the return of proper soil moisture con- 

 ditions the tree remains for a long time 

 sick. Drouth kills the fine feeding roots 

 which supply the tree with food so that 

 the balance between roots and foliage 

 is destroyed. The leaf surface is then 

 reduced and new wood growth stunted. 

 Due to the destruction of the delicate 

 feeding roots the tree will require care- 

 ful nursing for a considerable period if 

 it is to completely recover from a pro- 

 longed drouth. Soil moisture condi- 

 tions must be carefully watched, for 

 the tree is then much more susceptible 

 to drouth than before. The reduced 

 foliage also invites sunscald and proper 

 shading should be resorted to in order 

 to prevent this injury. 



It sometimes happens that a sudden 

 and acute drouth is encountered fol- 

 lowing normal conditions of growth. 

 In this case the tree invokes the law of 

 self-preservation and extracts moisture 

 from the fruit for the maintenance of 

 its foliage and vegetative, parts. It is 

 more concerned in saving itself than in 

 propagating itself. We find that the 

 apples shrivel on the tree before the 

 leaves show signs of wilting. With the 

 early return of adequate soil moisture 

 conditions many varieties of apples will 

 recover their normal size and, appar- 

 ently, be none the worse for the expe- 

 rience. But in the case of certain vari- 

 eties, of the Winesap and Ben Davis 

 groups especially, the drouth is accom- 

 panied by a spotting of the fruit which 

 we have termed "drouth spot." Atfer a 

 certain stage in the drouth is reached 

 irregular reddish, water-soaked spots 

 appear on the apples and a sticky yel- 

 lowish exudate is formed on the spots. 

 This is sweetish to the taste and has 

 sometimes been mistaken as a sign of 

 blight infection on this account. But 

 the taste of the apple tissue from the 

 spot itself is extremely bitter, and this 

 has caused some people to regard it as 

 bitter rot. I know of cases where 

 growers have sprayed for this disease, 

 thinking it must be bitter rot because it 

 tastes bitter, and of others who were 

 on the point of pulling out their trees 

 because they were sure it was a case of 

 Continued on page 18 



