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BETTER FRUIT 



A II gust 



'Hf^m^m^^mf^sS' 



FRUIT CLEANER 

 AND GRADER 



The machine that puts the profit into the fruit business. 

 For descriptive matter and testimonials address 



OREGON FRUIT CLEANER CO., THE DALLES, OR[.,U.S.A. 



The Oak Fungus of Fruit Trees 



THE oak fungus disease or fungous 

 root rol, caused by the fungus 

 Armillaria mollea, is a very com- 

 mon and serious disease of orchard 

 trees in California. Its most striliing 

 characteristics are its marked localiza- 

 tion and slow progress. The fungus 

 which causes it probably existed in the 

 roots of wild trees, attacking living 

 roots, but working so slowly that vig- 

 orous trees were not killed, and also 

 persisting in the dead wood, causing the 

 roots to decay. It appears that many 

 wild trees are infected in nature, and 

 I do not have sutRcient evidence to say 

 that oaks are more subject to infection 

 naturally than other trees. Not all 

 roots in the soil are infected, so that 

 we cannot say that because an oak tree 

 grew in a given place oak fungus will 

 appear there. When the roots of a fruit 

 tree come suUiciently near to infected 

 wood in the soil the fungus grows over 

 and attacks the living rools. We must 

 believe that this may happen long after 

 the original clearing, because Ihe fun- 

 gus will not die out of the soil until 

 the root in which it lives is completely 

 decayed. It is probable that new in- 

 fections have appeared ten years after 

 planting an orchard. 



The course of the disease is now well 

 understood by fruitgrowers. Often 

 several trees have died before particu- 



By Professor W. T. Hoine, University of California 



lar attention is given to the trouble. It 

 is then found that two or three trees 

 nearest to those which have died are 

 dying or diseased. The trouble can be 

 recognized with certainty only by an 

 examination of the roots. Usually two 

 or three years will elapse after the first 

 signs of weakening have appeared be- 

 fore the tree dies, and after the first 

 collapse some part of the tree may start 

 up and continue to grow for an indefi- 

 nite time, finally to be blown over by 

 the wind or to die completely if it does 

 not first exhaust the grower's patience 

 and get pulled out. Two or three or 

 more years may pass before the disease 

 spreads to the next tree. It is thus seen 

 that the rate of spread is slow, but we 

 have maps of spots in citrus orchards 

 fifteen years old where 25 to 30 trees 

 have been lost. In some cases practi- 

 cally whole orchards have been sweiJt 

 over. Some have not been replanted. 

 Others have been replanted, ijart of the 

 replants living and others dying, so that 

 the result is very discouraging. After 

 Ihe disease has become well established 

 occasional new centers of infection 

 appear. It is believed that probably 

 such new infections arise from a dis- 

 eased root being carried along and, 

 before it dies, plowed under near a 

 healthy root. I have picked up from 

 the moist cover crop a piece of dis- 



eased root which had fallen from the 

 cart in which a dead tree was being 

 hauled from the orchard. If this root 

 had been plowed under so as to come 

 near a healthy root the fungus would 

 almost certainly have grown over into 

 the healthy root and in a few years 

 another tree would have died and a 

 new center of infection would have 

 been established. 



Toadstools or mushrooms appear 

 during early winter about most of the 

 sick and dead trees. These toadstools 

 may continue to come up on some 

 stiunps for at least five years. They 

 are light-tan color and are found in 

 large clumps. They arise directly from 

 the diseased roots and are the fruiting 

 bodies of the fungus. White spores are 

 found on them in immense numbers, 

 but prol)ably these spores do not cause 

 new infections in living trees, although 

 we have repeatedly grown them artifi- 

 cially. They might easily infect a de- 

 caying stump. 



If we examine carefully a root newly 

 killed 1).\- this fungus we see that its 

 hark is somewhat ])uffed and when 

 cut into is soft and moist. By care we 

 can separate it into layers, exposing 

 while plaques of fungus which are soft 

 felt> and tend to radiate out in fan- 

 shaped bodies. The ajjpearance will 

 vary somewhat according to the kind 



