296 ^epori of i/te Committee on ^ear flight. 



Pear blight assumes different forms and has consequently different causes for its 

 origin. One form attacks trees gradually; its approach is slow and may be detected 

 for months, and often during the preceding season of growth, before the tree is fully 

 affected. This form, which may be termed gradual blight, is seen at all seasons 

 during the period of active vegetation, from early spring until September. Its 

 progress is usually arrested by a liberal top-dressing of liquid manure, so far as the 

 roots extend and a severe cutting back of the branches. This must be done when- 

 ever the tree assumes an unhealthy appearance. The cause, then, may be safely 

 attributed to exhaustion, and the remedy consists in replenishing the exhausted 

 supply of plant food. This form of blight is often noticed in orchards left unworked 

 and where the annual or biennial top dressing with fertilizing agents has been 

 withheld. 



Another, and this is the most fatal form, attacks a tree or a portion of it sud- 

 denly, causing the affected part to blacken in a few hours after the tree is struck ; 

 this is commonly termed Fire blight. This form is periodical in its attacks and 

 migratory, as it seldom remains permanent in a locality, but leaves an interval of 

 from ten to fifteen years between its occurrence. Its greatest intensity is on its 

 first appearance, which occurs usually when the fruit has attained half its size ; it 

 decreases as the season of vegetation advances, but reappears again the following 

 summer with less of its previous intensity. After decimating a section of country 

 during two consecutive seasons, there will be an interval of a series of years, during 

 which, blight in its oth'^r forms may occur, but there will not be a wholesale 

 destruction as during the prevalence of epidemic blight. Every observation tends 

 to the conclusion that fire blight is caused by zymotic fungus, whose presence is 

 not detected until life is destroyed in the affected parts. This form offers a wide 

 field for the investigation of microscopists, and from their future labors, we hope to 

 arrive one day at the origin of this fungoid growth. We are unable to arrive at a 

 satisfactory conclusion, as to what peculiarities of soil and temperature induce the 

 favorable conditions for the development of this fungoid vegetation. 



In the Experimental gardens of the Department of Agriculture at Washington, 

 the following mixture is prepared : Place a half-bushel of lime and six pounds of 

 sulphur in a close vessel, pour over it about six gallons of boiling water, adding 

 enough cold water to keep it in a semi-fluid state until cold. It is used as a wash 

 and applied to the trees and branches as high as can be reached. It should be 

 applied two or three times during the summer. Since this preparation was used, 

 no trees thus treated have been lost, although small limbs not coated with the mix- 

 ture were attacked and destroyed. Carbolic acid has also been used without any 

 perceptible difference in the result from the lime and sulphur mixture. Boiled 

 linseed oil, applied to the trunk and limbs has been tried near Norfolk, Va., with 

 marvelous cures, as reported. We mention this instance of the use of an extraor- 

 dinary ingredient resulting in good effects, as contrary to what is usually the result 

 when using this application upon the body of trees, its effects being to seriously 

 injure the tree if it does not destroy it. 



Still another form of blight is doubtless caused by mechanical action, by the 

 rupture of tissues consequent to a sudden superabundant flow of sap. This attacks 



