PEAR DISEASES 



1629 



rainfall, the germs may have been dis- 

 tributed very widely. Had dry weather 

 continued the fact that the germ had be- 

 come widely distributed would not have 

 become apparent because countless in- 

 fections would not have taken. In very 

 dry weather the nectaries of blossoms 

 soon dry, and unless germs have gained 

 a strong foothold before drying takes 

 place no apparent infection results. The 

 above explanation should suffice to show 

 that the thunder and lightning theory 

 has no bearing whatever on the disease 

 known as pear blight. Consider the germ 

 In the light of a seed whose germination 

 is dependent upon the same environ- 

 mental conditions for all of its growth 

 activities. 



To one who knows something of the 

 theory of the disease, the matter of eradi- 

 cation often seems very simple. It is 

 usually a very easy thing to write about 

 the experiences of others and to tell in 

 considerable detail how blight should be 

 eradicated and controlled. The actual 

 field work is very difficult and tedious, 

 and a matter of days or months of train- 

 ing only will make an expert field man. 

 No one can become expert after a few 

 hours' work, even under competent in- 

 struction given by a trained man having 

 had years of experience. We do find 

 people, however, who are able to write 

 and instruct without having had any ex- 

 perience whatever. To the initiated, as 

 well as the uniniated, let me say that 

 the eradication of pear blight is one of 

 the most difficult problems known to 

 l)lant pathologists. Let no one say that 

 it is a simple thing. It is difficult, very 

 difficult. The reason for this difficulty 

 is that we are dealing with a consider- 

 able amount of ignorance and unbelief; 

 again, few farmers who have not had a 

 bacteriologist's training realize the pe- 

 culiar relation existing between the or- 

 ganism causing the disease and the host 

 plants. They fail to see that this rela- 

 tion is practically the same as that which 

 exists between the germ of tuberculosis 

 and man. On the one hand, antiseptic 

 precautions, and the removal of infec- 

 tions seems unimportant; on the otiier 



hand, however, long experience with this 

 dread human disease instills a sort or 

 fear, even tliough the true cause may not 

 be fully comprehended. If every fruit 

 grower could be made to feel that fruit 

 trees are living things very much In the 

 same sense as themselves, and that the 

 parasites attacking them should be 

 viewed in a corresponding light for both, 

 I am sure the whole matter of education 

 along the lines of pear blight control 

 would be solved. 



Treatment 

 The treatment for pear blight, or 

 rather the methods for controlling it. 

 may be divided into two classes, primary 

 and secondary. The primary method of 

 treating this disease consists of cutting 

 out thoroughly and antiseptically the 

 hold-over blight during the dormant sea- 

 son of the trees — that is, during the fall 

 and winter. It has been explained that 

 the hold-over blight may be found in the 

 larger limbs, the trunk and even the root 

 system. These hold-over cases have be- 

 come such through the various means of 

 infection pointed out, namely, through 

 blossoms, buds or water-sprouts, which 

 have become infected and through which 

 the blight has gained entrance to the 

 fleshy bark and cambium of the bodies 

 and roots. The other methods of en- 

 trance are through growth cracks, crown 

 galls, insect and bird punctures, or any 

 other way by which the epidermis may 

 be broken so as to expose the tissues 

 beneath. It has also been shown that 

 the pruning knife or other orchard in- 

 strument may be the means of spreading 

 the disease. If the work of removing 

 hold-over cases is done thoroughly it 

 leaves no opportunity for additional ad- 

 vantages from any other secondary 

 method. 



Remember that the important thing is 

 the removal of the source, or what will 

 be the source of infection the following 

 year. In the case of the pear or apple 

 it is important that this work be done 

 as skillfully as the work of a surgeon 

 in removing a member infected with 

 blood poison. Everyone realizes the 

 attention given to the source of a city's 



