GIVING MEDICINE TO TREES 



BY DR. CAROLINE RUMBOLD 



PATHOLOGIST, BUREAU OF PLANT INDUSTRY, UNITED STATES DEPARTMENT OF AGRICULTURE 



CAN a tree be cured of a disease by giving it medicine 

 internally? The usual method of combatting tree 

 diseases is through the external application of 

 sprays and fertilizers, or by cutting out and burning 

 diseased parts or entire trees. Many parasitic fungi 

 grow so deeply underneath the bark of a tree that any 

 external treatment is ineffective. This is the case with 

 chestnut blight, or the chest- 

 nut bark disease, as it is 

 more properly called. When 

 this fungus began to kill 

 chestnut trees by the tens 

 of thousands about fifteen 

 years ago, it was not un- 

 usual for an owner of a 

 prized ornamental chestnut 

 to offer a reward of a thou- 

 sand dollars to anyone who 

 would save the tree. Num- 

 erous quack "tree doctors" 

 advocated various alleged 

 remedies which failed mis- 

 erably when tested. Care- 

 ful experiments by plant 

 pathologists also failed to 

 develop a successful meth- 

 od of saving a tree after it 

 was attacked by the blight. 

 The disease advanced ruth- 

 lessly and all who valued 

 the chestnut trees were in 

 despair. 



In 191 1, the State of 

 Pennsylvania appointed a 

 special commission to con- 

 duct scientific investiga- 

 tions to determine the cause 

 of chestnut blight, and at 

 the same time to immedi- 

 ately attack the epidemic 

 by every means that seemed 

 to afford any possibility of 

 checking or delaying it. In 

 connection with other lines 

 of experimental work carried on by this commission, the 

 writer was employed to investigate the possibility of con- 

 trolling the disease by injecting chemical solutions into 

 chestnut trees. In 1913, the Pennsylvania Chestnut Tree 

 Blight Commission advised the Governor to discontinue 

 its work because the blight had advanced too far into 

 the State to make control practicable with the appropria- 

 tion available at that time. During the next two years 

 the writer continued the injection experiments under the 

 direction of the Office of Investigation in Forest Path- 



METHOD OF INJECTING SMALL TREES 



The chestnut trees in this orchard were infected with the chestnut blight, 

 and it was desired to find if the fungus under the bark could not be 

 killed by chemicals, without injury to the tree. As the tree absorbed 

 the solution it was siphoned out of the jar through the tube. 



ology, Bureau of Plant Industry, United States Depart- 

 ment of Agriculture. The University of Pennsylvania 

 furnished laboratory facilities and many supplies. The 

 credit for continuing these experiments to their present 

 stage is due to Mr. Harold Pierce, formerly Secretary 

 of the Pennsylvania Chestnut Tree Blight Commission, 

 who generously financed the work. 



The problem has been to 

 find a chemical agent which 

 would kill the fungus that 

 causes the blight, when a 

 solution was introduced 

 into a tree. The first dif- 

 ficulty encountered was in 

 getting the tree thoroughly 

 injected with any kind of 

 liquid. The sap of a tree 

 does not circulate like the 

 blood of an animal. The 

 wood of a tree contains 

 numerous vessels, or tube- 

 like cells, through which 

 the crude sap is conducted 

 to the leaves to be manufac- 

 tured into food which re- 

 turns to the roots and other 

 living parts through the in- 

 ner bark. A substance in 

 solution follows a vertical 

 path up the tree through 

 those vessels in the sap wood 

 that are close to the place 

 of injection. It can also de- 

 scend through those vessels, 

 but in all of this there is 

 lacking that persistent pass- 

 ing and return of a stream, 

 such as the blood stream, 

 which constantly bathes the 

 cells of the animal body. 

 This path in the tree 

 through which the injected 

 solution passes, usually is 

 but little wider than the 

 hole through which it is injected. Besides this, the 

 walls of the tubular cells act like blotting paper, with the 

 result that the farther the solution passes from the point 

 of injection, the weaker it becomes. So in order to 

 inject a tree evenly on all sides, it is necessary to make 

 a number of injections on different sides of the trunk, 

 and even on the limbs. This means that many quarts of 

 a very dilute chemical solution must be put into a tree 

 if the chemical is to reach all portions of the tree. Were 

 one to use only a small amount of concentrated solution, 



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