FORTY-FOURTH ANNUAL REPORT. 139 



FIRE BLIGHT. 



Fire Blight of Pears is a disease that Michigan frnit growers need to 

 dread more than any other disease of their trees. It affects pears, 

 apples, qninces and crabapples Avorst but is knoAvn to attack plums, haw- 

 thornes, apricots and several other plants. No variety of pear, apple, 

 quince or crab apple is immune to the disease but some are much more 

 susceptible than others. Of the apples, Alexander, Chenango, R. T. 

 Greening and Tolman Sweet ; of the pears. Bartlett, Clapp Favorite and 

 Flemish Beauty and of the crabapples, Transcendent, are usually the 

 most susceptible. 



The disease may attack any part of the tree, blossoms, fruit, twigs, 

 leaves, trunk, limbs, suckers and even roots. It is caused by a minute, 

 rod-shaped bacterium which lives mostly within the cambium tissue of 

 the plant where it is beyond the reach of any spray material. The only 

 way that spray material can be used in its control is to combat several 

 of the insects that are instrumental in its distribution. Among these, 

 the worst affected are the aphis or plant lice. While it is true that 

 trees standing in sod often blight badly, it must be conceded that trees 

 in luxuriant growing conditions, Avhether caused from cultivation, ex 

 cessive fertilization, excessive moisture or particularly favorable weather 

 conditions, are most susceptible to blight. Hence seeding down an or- 

 chard or withholding fertilization may be expected to and in a great many 

 cases has been, instrumental in preventing or checking the disease. 



Eradication and disinfection is the only safe method to pursue. The 

 disease is most apt to winter over in the canker spots on the limbs or 

 trunks but may winter over in the tAvigs. 



In the late winter or early spring all trees known to have blighted 

 during the past season, should be carefully gone over and every blighted 

 part removed. 



In the case of the new growth or rapidly growing limbs of older age, 

 the cuts should be ten to twelve inches back of the darkened and sunken 

 areas. In cases of fruit spurs, five or six inches may be sufficient while 

 in the case of the cankers, a quarter to a half inch is plenty. After every 

 cut, before another one is made, the tools and wounds should be disin- 

 fected with corrossive sublimate, one to one thousand or a five per cent 

 carbolic solution so that no bacteria can be carried from one part of 

 the tree to another or from one tree to another and any bacteria brought 

 by birds or insects to a fresh wound will be destroyed. 



Summer treatment is often very unsatisfactory for the reason that 

 new infections, invisible at the time the work is done, may develop in a 

 few days so that a week after the most thorough cutting out of the 

 blight, a new crop of infection is found appearing. In old trees when 

 the disease is distributed all over the tops, it is too much of a job to try 

 to cut out individual twigs affected but in young or medium aged trees 

 where there is so great danger of the twig being a half, third or entirely 

 killed, eternal vigilance must be practiced. 



One more very important feature I want to emphasize is that ''Fire 

 Blight Control" is not an individual fight, it is a community fight. One 

 fruit grower may do much to control- the disease in his own orchard but 

 as long as blight thrives or prevails in a neighbor's orchard, bees, flies, 

 wasps, birds, etc., may carry the infection back and forth almost at 

 their will. 



