BLIGHT OF PEARS, APPLES, AND QUINCES 3 



from infected blossoms, twigs, and water sprouts. Invasion of large 

 branches, trunks, collars, and roots may result in the death of a part 

 or all of the tree. 



The disease is so destructive to the Clapp Favorite, Flemish Beauty, 

 Bartlett, and other high-quality pears that these varieties are grown 

 extensively in only a few favored localities. Although frequently 

 destructive to apples, it does not prevent the profitable growing of 

 susceptible varieties, such as Jonathan, Wealthy, and Yellow Trans- 

 parent. 



HOW IT OVERWINTERS 



Blight appears during the blossoming season and is generally active 

 until rapid growth of the tree ceases, usually about a month thereafter. 

 The bacterium causing blight winters over, chiefly in the areas of thick, 

 fleshy bark on large branches and trunks, and even roots, which it has 

 invaded during the previous year. Occasionally it may also live over 

 winter in twigs or small branches if conditions are such that the in- 

 fected places do not dry up during the summer. From these so-called 

 hold-over cankers the bacteria are carried to the open blossoms, and 

 from blossom to blossom and from tree to tree by insects visiting the 

 blossoms for nectar and pollen. From the diseased blossoms the 

 bacteria are carried to the twigs and water sprouts by insects and 

 probably to some extent by rain. Usually with the coming of 

 summer, the hardening of tissues and the occurrence of hot, dry weather 

 prevent new infections, and the old ones die out, except those so 

 favorably situated that drying out is prevented. These are chiefly 

 deep-seated infections in the thick bark of the larger branches, trunks, 

 and collars and in the roots ; they are the hold-over cankers mentioned 

 above. 



CONTROL 



In control the most important measure is the removal of the hold- 

 over blight. During the late summer the trees should be gone over at 

 least once and all blighted twigs cut out, the cut being made through 

 healthy wood well below the blighted part. Special care should be 

 taken to detect and cut out blighted areas on large limbs, trunks, and 

 collars, the cuts being run into healthy tissues and down into the roots, 

 if necessary. The trees should be reinspected in the fall or winter 

 after the leaves are off, and all hold-over areas that were previously 

 missed should be removed. Another inspection in early spring is 

 desirable. After every cutting operation the cut surfaces and tools 

 should be sterilized with corrosive sublimate, 1 part to 1,000 parts of 

 water, or with Reimer's solution, consisting of 1 ounce of corrosive 

 sublimate and 1 ounce of mercuric cyanide in 4 gallons of water. 

 Both of these chemicals can be obtained at drug stores. Corrosive 

 sublimate is sold in tablet form with directions for making up a 1-to- 

 1,000 solution. These chemicals are deadly poisons and should be 

 treated as such. Since these solutions will corrode metals they should 

 be kept in glass or wooden containers, and all tools should be carefully 

 cleaned after use. The solutions should be applied with a sponge or a 

 piece of cloth. 



Removing blighted blossoms and twigs as they appear in the 

 spring is usually impracticable, except when only a few trees are 

 affected. Even then, unless great care is taken to cut well below the 



