Page 8 



BETTER FRUIT 



Jdiniarv 



Inio i)f the human bcin.y is true of all 

 living things, vegetable as well as ani- 

 nian. An abundant ninistuie supply is 

 essential to health anil a lack of it 

 means internal disorder. The greatest 

 number of genuinely non-parasitic dis- 

 eases in plants are induced by disturbed 

 water relations, and it is this group of 

 troubles we want to consider particu- 

 laiiy today. 



There is a very close analogy between 

 the prune orchard under the blazing 

 sun on a hot day in the middle of a 

 long summer and the laborer in the 

 harvest field under similar conditions. 

 The man perspires freely and so does 

 the tree, only scientists call it transpira- 

 tion in the case of plant life instead of 

 perspiration. The hotter the weather 

 the more the human being sweats. The 

 hotter and drier the weather the more 

 abundantly the trees and all vegetation 

 give off water. If the man brings with 

 him a suthcicnt supply of water or can 

 drink from a nearby spring when he is 

 thirsty, all is well with him. A tree, 

 however, cannot fetch water from a 

 distance nor yet go after it, but rooted 

 to the spot it must supply its needs from 

 the soil at its feet, and if it cannot get 

 enough water to balance the amount 

 given off from the foliage it must suffer. 

 Few of us realize, I think, the help- 

 lessness of the tree in the matter of 

 adapting itself to meeting extreme con- 

 ditions and we fail to appreciate the 

 importance of assisting the tree where 

 possible by our own intelligent efforts 

 at these critical times. A tree gives off 

 a surprising amount of water on a hot, 

 dry day and is almost as much at the 

 mercy of the atmosphere, as far as any- 

 thing it can do to stop this rapid loss 

 of moisture, as Monday's wash flap- 

 ping in the sunshine on the clothesline. 

 Dr. Ward, in England, once estimated 

 that a single oak tree gave off through 

 the foliage during five summer months 

 over 600 barrels of water, and a birch 

 tree on a hot summer day was found to 

 transpire to the extent of 14 to 18 bar- 

 rels in 24 hours. According to this an 

 acre of such trees would give off nearly 

 8,000 barrels in the course of a season. 

 It has been figured that the grass in a 

 hay field will give off six and one-half 

 tons per acre daily average through a 

 summer. I have not come across esti- 

 mates on the water loss from fruit 

 trees, but it is certainly probable that 

 their rate of transpiration is not vastly 

 different from that of other trees. To 

 replenish the loss of water vapor from 

 the leaves is the task which falls upon 

 the root system. Under ordinary con- 

 ditions the roots can meet the demand 

 on them very well, but under drouth 

 conditions let us see what happens. 



Normally the growth and develop- 

 ment of the root system keeps pace with 

 that of the top of the tree and supplies 

 that top with the amount of moisture 

 required. The root system, however, 

 cannot rapidly increase its rate of de- 

 velopment to meet sudden and severe 

 or prolonged periods of high foliar 

 water loss with entire success, and 

 under climatic conditions which tend 

 to exhaust the soil moisture rapidly 

 without replenishment a task may be 

 set for the root system which it is 



utterly incapable of jjerfonning. Tiien, 

 like the harvest hand in our illustration, 

 the tree must siill'ei-, and the hotter the 

 days and drier the air and soil the more 

 pronounced become the outward evi- 

 dences of that suffering. 



Let us look at some of the effects on 

 the tree of giving off water faster than 

 the roots can easily replace it. First, 

 there is a more or less wilted appear- 

 ance or rolling of the foliage, espe- 

 cially noticeable in the afternoon when 

 the thirst is greatest. This may, gradu- 

 ally become a fixed condition and the 

 prune trees may show what growers 

 term leaf roll, or sometimes leaf curl, 

 and this persists perhaps through the 

 balance of the season. Drouth is not 

 the only cause of this phenomenon. 

 Anything which interrupts or restricts 

 the water supply to all or to any part 

 of the top like root rot, borers, winter 

 injury, and most commonly of all, heart 

 rot may cause this appearance. Not 

 only do the leaves roll up, but they 

 also tend to assume a yellowish cast, 

 and in the severest cases this may be 

 followed by a dropping of leaves, which 

 results in a reduction in the evaporat- 

 ing surface of the tree and helps in this 

 way to preserve its life. 



Now it appears to be self-evident that 

 the trees which commence a season b\- 

 developing a large top and abundant 

 foliage will, unless they have an un- 

 usually extensive root system and a 

 deep, water-retentive soil on which to 

 draw, will suffer more in a season 

 when the water supply is low and the 

 rate of transpiration high than trees 

 that enter the summer with a more 

 moderate amount of foliage. The same 

 principle holds with different seasons. 

 In a year when abundant soil moisture 

 and plenty of warm days early in the 

 season induce a heavy foliage and shoot 

 growth the effect from a later drouth 

 period is much more severe than in 

 years marked by early drouth with its 

 natural retarding effect on leaf and twig 

 development. 



In 1918 in the Pacific Northwest the 

 dry weather struck us at the very out- 

 set of the season, thus checking to some 

 extent what might otherwise have been 

 a very heavy production of new foliage. 

 In view of the unparalleled long contin- 

 uance of the drouth this was probably 

 more fortunate than otherwise, for the 

 trees had a chance to adjust themselves 

 at the beginning to the sort of climate 

 which was to follow. Had this not been 

 the case it is very likely that far greater 

 damage would have resulted than or- 

 chardists actually experienced. As it 

 was, prune men saw a heavy set and 

 rapid development of the fruit. The 

 trees paid more attention, as it were, to 

 fruit prpoduction than to foliage pro- 

 duction. As the season wore on, how- 

 ever, the warm, dry, bright weather 

 continued practically unabated, gradu- 

 ally depleting the moisture from the soil 

 without material help from precipita- 

 tion in most sections. This brought on 

 a time of testing. The tremendously 

 active evaporation from the trees de- 

 manded heavy supplies of moisture 

 from the roots. Eventually the demand 

 became in some orchards greater than 

 the roots of some of the trees could 



supply, and evidences of trouble began 

 to assert themselves. 



It was some of the prune growers, I 

 think, who first nolicetl trouble. During 

 the last week in .Inly and the first day 

 or two in August there was, at least in 

 the central Willamette Valley, a marked 

 increase in the prevailing maximum 

 temperature. This placed a critical 

 strain on the orchards, and within a 

 very few days specimens of diseased 

 prune fruits in considerable numbers 

 were sent to the oHice of the Plant 

 Pathologist at the Agricultural College 

 and reports of damage came in from 

 widely-separated points in Western 

 Oregon. My own opportunity for se- 

 curing a thorough knowledge of the 

 situation was limited by the lack of an 

 opportunity to visit the orchard dis- 

 tricts, but from the information obtain- 

 able it was evident that considerable 

 losses were being experienced here and 

 there, although there were many or- 

 chards that seemed scarcely to have 

 been affected. 



The first conclusion of the orchard- 

 ists was that some sort of parasitic dis- 

 ease had struck the prunes. Careful 

 examination of the specimens received 

 indicated that such was not the case. 

 It was very evidently some sort of 

 non-parasitic trouble. The specimens 

 showed varying degrees of injury. In 

 some cases the prunes were affected by 

 what I have called, for want of a better 

 term, "gum spot." Examination shows 

 the exudation of gum through the skin 

 of the green prune in one or more 

 places or the collecting of gum within 

 the flesh in spots which have a watery 

 look through the skin. Cutting the fruit 

 open we find little brown specks in the 

 flesh always, or nearly always, in the 

 region of the network of veins or sap 

 conducting vessels lying a slight dis- 

 tance under the skin. It is evident that 

 some force has caused a collapse or 

 rupture of some of the cells, and that 

 this has been accompanied by the for- 

 mation of more or less colorless gum 

 which may accumulate in sufficient 

 quantity to break through the skin 

 under pressure and form on the outside 

 as a glistening bead. This sort of 

 trouble had been met with the season 

 previous, which had also been unusu- 

 ally dry, but in 1918 the amount of 

 broken-down tissue within the fruit 

 seemed on the average much greater 

 than before. 



Most of the specimens received, how- 

 ever, showed a much more severe effect. 

 The surface of the prune turned dark 

 colored as though prematurely ripen- 

 ing. Irregular depressed areas were 

 present over a greater or smaller por- 

 tion of the fruit surface and gave the 

 fruit an unnatural, corrugated appear- 

 ance. Upon opening up the flesh it was 

 found to be brownish underneath the 

 depressed spots, this browning of the 

 tissues varying in amount from a small 

 spot on one side of the fruit to a dis- 

 coloration which might involve nearly 

 the entire flesh. These tissues almost 

 invariably gave off a disagreeable fer- 

 mented or acid odor and the taste was 

 extremely unpleasant. Study of the 

 tissues showed a breaking down more 



Continued on page 24. 



