IQl6 



BETTER FRUIT 



Page II 



of approaching death. Though gener- 

 ally weaker, the long, slender spurs are 

 by no means always older than the 

 shorter ones. Stockiness or slenderness 

 of spurs in the prune tree is very largely 

 dependent upon the light received by 

 individual spurs. An abundant light 

 supply permits the elongated spur to 

 develop a good, well-lighted leaf system 

 with short internodes (joints close to- 

 gether). A poor light supply forces the 

 spurs to grow out long and slender in 

 order properly to expose their leaf sur- 

 face. This is probably the main reason 

 why the spurs in the very top of the 

 tree average much shorter and stockier 

 than those in the interior of the tree. 



The Ideal Distribution of Fruit-Spurs 

 in the Prune Tree 



We want not only a large number of 

 short, vigorous fruit-spurs in the ijrune 

 tree, but it is desirable that those spurs 

 be well distributed. A good distribution 

 of fruit-spurs means having a consider- 

 able amount of small fruiting branches 

 in the lower part of the tree and not 

 having them all crowded together in its 

 upper and outer portion. The trees of 

 many bearing iirune orchards consist 

 mainl> of barren scafl'old limbs, termi- 

 nating in large numbers of small spur- 

 bearing branches that occupy a com- 

 paratively narrow space around the 

 outside and that finite completely shade 

 the interior. In these trees the load of 

 fruit is borne at a considerable distance 

 from the main trunk, thereb\- placing 

 the greatest possible strain upon the 

 scafl'old limbs and crotches. Were this 

 load more evenly distributed over the 

 scafl'old limbs, as it would be if there 

 was fruiting wood in the lower and 

 interior portion of the tree, there would 

 be much less breaking of limbs and 

 splitting at the crotches than we now 

 find in our prune orchards. 



The same factor, limited light supph', 

 that causes individual fruit-spurs to be- 

 come weak and finally die, acts in the 

 same way upon fi-uiting branches. It 

 first forces them to grow long and 

 slender in order to reach up to the 

 light. Finally finding themselves out- 

 distanced in the struggle for existence, 

 these branches die olT and the scaffold 

 limbs are left with longer and longer 

 barren stretches. 



Pruninor That Keeps Individual Fruit- 

 Spurs .Stocky and Well Distributed 

 It will be inferred from the state- 

 ments that have been made that the 

 most important thing to do in pruning 

 the bearing jirune tree is to thin il suf- 

 ficiently to admit an abundant light 

 supply to the small fruiting branches 

 and to the individual fruit-spurs. There 

 is certainly good reason to believe that 

 this practice is one that most closely 

 harmonizes with and tends to improve 

 its natural fruiting habits. This is far 

 from stating that prune trees should 

 never be headed back. Without doubt, 

 the strong vegetative shoots that fre- 

 quently ap])ear even in old trees should 

 be judiciously headed back. Likewise, 

 individual fruit-spurs can often be 

 headed back to a lateral branch of tlic 



Figure .50 — An old Itali.in prune tree that two years af;o was in niin-li the 

 same condition as thai sliown in KiRiirc .53. At that time it was pruned in 

 the same manner as Hie tree shown in Figure 51. Note that not only have 

 the old fruiting branches and their fruit spurs l)een invigorated and made 

 more stocky, but a considerable amount of new fruiting wood has been 

 developed. Fienovalion can hartUy lu- said to be complete, but considerable 

 progress has been made in that direction, and that witliout sacrificing a 

 single fruit crop 



same spur and thus be made more 

 stocky, rather long, slender fruiting 

 limbs may be cut back to make them 

 more stocky. Neverthless, it wouki 

 seem that a large part of the pruning of 

 the bearing ijrunc tree should be a 

 judicious thinning out of the smaller 

 branches (brandies lialf an inch or less 



in diameter). This necessarily involves 

 the removal of a certain amount of 

 bearing wood; but if the amount re- 

 moved is not too great, the loss will be 

 more than compensated by the increased 

 stockiness and vigor of tlie remaining 

 fruit-spurs, and by the increased size of 

 the fruits tlitit fhev bear. 



Powdery Mildew of Apples 



[ Washington State Agricultural Experiment Station Bulletin ] 



THE pow(ler>' mildew of a|)i)le is due 

 to the parasitic fungus, Podos- 

 phaera leucolricha, the vegetative body 

 or mycelium of which develops as a 

 coating of minute interlacing whitish 

 filaments on the parts of the plants 

 attacked. The fungus produces two 

 spoi-c stages in its life history: the 

 conidial or summer spores wliich are 

 produced throughout the growing sea- 

 son anil give to all'ecled parts a whitish 

 powdery ap])earance; the ascigerous 

 stage, whicli gives rise to the asco- 

 spores. The latter is iiroduced only 

 upon (he twigs, and the bodies bearing 

 the ascospores may be found buried in 

 111!' daik-felleil mycelial mass toward 



the end of the growing season. The 

 conidia serve to spread the fungus 

 during the growing season. It is ap- 

 parent that the fungus is carried over 

 the winter by mycelium which hiber- 

 nates in the buds and also b\ the asco- 

 spores. The i)arl which the latter i)lay 

 in the life history of the fungus is 

 somewhat problematical. The mildew 

 confines its attacks in llie main to 

 \oiiiig shoots and blossom clusters. 

 Holh stem and leaves of shoots may be 

 alfected and either killed, deformed or 

 reduced in size and vigor. Blossom 

 clusters may be hlis-'hted and young 

 fruits may be nU'ected later than at the 

 blossoming pciioii. 'I he mildew is 



