12 FUNGI AND FUNGICIDES. 



ROOT KNOT. 



No fungous disease is easier recognized than this. The very- 

 prominent black or brown wart-like excrescences upon the 

 trunk and roots, below ground, of all stone-fruit trees, readily 

 reveal its presence. 



Cut away the knot in the fall or winter and allow the wound 

 to dry, then with a swab apply a saturated solution of blue- 

 stone to the affected part.* This may be repeated two or more 

 times as long as the trees remain dormant. Never apply it to 

 the tree when the sap is flowing. After the knots have been 

 treated the soil is thrown back again, covering the exposed 

 roots. The Bordeaux mixture (formula A), applied in a sim- 

 ilar way, has also given good results. Instead of removing very 

 large knots it is better to bore an inch hole to the center of the 

 knot and fill this with either of the above solutions, which will 

 permeate the tissues of the knot and cause it to drop off after 

 a few months. 



OLIVE KNOT. 



One of the most serious diseases of the olive tree, in a few 

 counties of California, is the olive knot, or tuberculosis of the 

 olive, as it is sometimes called, which, like the pear blight, is 

 a bacterial and not a fungous disease. The tubercles, or knots, 

 which give this disease its name, are found singly and in rows 

 on branches of all ages. The bacteria which cause the disease 

 form a colony in the tissue of the sap-wood, which appears 

 like a small, transparent spot. This spot, when seen under a 

 high-power microscope, is found to consist of many bacteria. 

 From this spot soon develop, through different stages, the 

 tubercle knots. On the trunks and larger branches the knots 

 generally attain a large size. 



The diseased parts of affected trees should be carefully re- 

 moved and immediately burned. All wounds made by the 

 removal of the disease should be dressed with an antiseptic 

 paint. 



Cuttings from diseased trees should never be used for prop- 

 agating purposes. 



*A saturated solution of bluestone is all that water will dissolve. But it 

 is advisable to leave some undissolved bluestone in the bottom of the vessel, 

 as this will indicate that the water has taken up all the bluestone it can. 



