MICHIGAN EXPERIMENT STATION BULLETINS 339 



their development and, if at once cut off and burned, furtlier spread of the 

 disease will be sioiipod. In removinp; infected branches, the cuts should 

 be made, if possible, a foot or more below the knots, in order that the 

 diseased portions may be destroyed. When the knots are upon the trunks 

 or main branches of small trees, where it would be impossible to cut them 

 off without destroying the trees, the diseased tissues may be cut away 

 and, if the wounds are painted with linseed oil, or tincture of iodine, the 

 danger of stopping further growth of the tree or branch will be prevented. 

 While the removal of diseased branches is the only remedy that can be 

 depended on to prevent the spreading of the disease, yet, if the trees are 

 thoroughly sprayed with Bordeaux mixture, it will be impossible for the 

 spores to obtain lodgment upon the healthy branches. In several portions 

 of the state, it is reported that the knots are becoming very troublesome 

 and that they have destroyed many plum trees. In case the owners do not 

 take prompt action to check the disease, the fruit growlers of the locality 

 have in their hands the power to see that the knots are destroyed, as it 

 only requires a petition of ten free-holders to secure the appointment of 

 commissioners whose duty it will be to secure the destruction of all knots 

 and of the trees if badly affected. 



PEAR BLIGHT. 



The fire blight or " frozen sap blight " of the pear comes under the 

 operation of the yellows and spraying laws. This disease is of a bacterial 

 nature and is very troublesome in some seasons, particularly upon rapid- 

 growing trees, or on land that has been heavily manured, or that is natu- 

 rally rich in organic matter. The disease may appear upon the new growth, 

 upon fruit spurs, or at any openings upon the branches and trunk where 

 the bark has been cracked so as to permit the entrance of the germs. 

 They can also enter through the flowers, or through the soft succulent 

 tissues of the leaves or stems. The leaves upon the diseased portions 

 turn dark brown and dry up, but remain for a considerable time upon 

 the branches. The bark of the diseased portions also dries and becomes 

 nearly black in color. When the disease is at work in the tissu. -• ""he 

 bark cracks and a thick sap exudes. This has a distinct taste and ouor 

 of fermentation and the disease itself is nothing more than a fermentation, 

 brought about in the sap by the action of the bacteria. The remedy for 

 pear blight is much the same as for ''black knot," and, when any of 

 the leaves show the characteristic appearance of the blight, the branches 

 upon which they are should be cut off a foot or more below where any 

 signs of the disease can be seen, and immediately burned. By the prompt 

 removal of the diseased branches, the disease can generally be checked, 

 while, if this is not done, it may spread until all of the surrounding trees 

 are affected. 



