294 MINNESOTA STATE HORTICULTURAL SOCIETY. 



Frequently an entire limb or even the trunk will be affected for 

 only a short distance, while the top will be entirely free from the 

 disease, and this can only be understood when we speak of how the 

 disease is spread. 



More frequently upon the pear several limbs and even the whole 

 trunk will be affected, and when this is the case the tree should be 

 cut out root- and branch. 



If the young shoots of a tree affected with blight be examined, 

 small drops of sticky, thick fluid will be found exuding from the 

 edge of the diseased area. If ©ne of these drops be examined with 

 a high power microscope, myriads of little oblong bodies will 

 be seen, some separate, some in short chains. These are bacteria. 

 Arthur proved that these bodies, inoculated into a sound tree by a 

 needle, would produce the disease. Waite proved to us beyond dis- 

 pute that insects, especially bees, are the main instruments in their 

 dissemination. They are attracted by the viscid sap, suck up part or 

 all of the drop, and then carry thousands of these germs with them 

 to inoculate flowers, shoots or wounded places in the bark. Un- 

 doubtedly heavy currents of wind assist in spreading the disease and 

 probably account for the commonness of "twig blight." The ques- 

 tion comes right here: Shall I keep bees if I have an orchard? 

 Certainly, and for two reasons. First, the honey and the revenue 

 derived from it are often no small object to the farmer. Second, 

 the bees are absolutely needed to assist in proper cross-fertilization, 

 or pollination, of the flowers. This leads us to the subject of reme- 

 dies, for preventives there are none. 



REMEDIES. 



As soon as the bacteria are carried to young flower or wound, 

 they effect entrance and, living upon the sap and starch, multiply 

 rapidly. If they gain entrance along a limb or trunk, they live in 

 the inner bark and cambium-layer, that layer which adds yearly to 

 the growth of both bark and wood. 



It can readily be seen from this that they are well covered, and 

 consequently spraying does no good. The only remedy thus far 

 found has been and is the careful and continuous use of the saw 

 and pruning knife. All diseased shoots and limbs should be cut 

 off at from six inches to one foot below the place of evident infec- 

 tion or injury, as the bacteria have always gone down deeper into 

 the limb than seems to be the case from the outside. Many pruners 

 have the habit of splitting down the bark to see how far the 

 disease has proceeded, but this practice is to be condemned, as 

 they never see how far the disease has proceeded, and the in- 

 cision of the knife mav carrv the bacteria from diseased to 



