Show black knot most serious disease must be carefully watched and controlled by spraying thoro there Is a disease of plum trees that bears tho the very descriptive name of black knot it la Is observed on tho the twigs of trees and sometimes on cherries where it causes a knot like it swelling that Is olive green in color in fit spring and black in tho the fall where tho the disease appears on tho swelling may extend up and down the branch branchi for as much as it foot while on fimi fruiting ting spurs it may exist as a knot no larger than a grain of wheat caused by fungus black knot la Is caused by a fungus that affects the wood causing it to swell into tho the rough defor deformed ined places it Is regarded its as a serious destructive disease and ono one that must bo care fully watched aud and kept under control damson plums are more subject ta black knot and varieties of the irlo flora group t tho 0 o least liable t to 13 buffer frer spores of tho the fungus aro are liberated berated il in spring from tho the galls ormed tho the year before when infection takes place the knots may m ay bo be observed in the fall but they hr are 0 ma more re consa conspicuous ICU in tile the spring with tho the beginning of growth in spring the linot knot swells rapidly and bursts tho the bark which at that time may uncover a yellowish surface which rather quickly turns to a n velvety dark green color tho the knot then Is covered with a mass of summer bummer spores which are carried by tile tho wind to spread tho the disease toward fall tile knot turns tura black and develops a now new crop of spores that are ro not liberated until tho the following spring these tire are called winter spores and differ very much in their origin from the summer spores most satisfactory control while spraying may bo be a safeguard against infection tho the most satisfactory control of black knot Is to prune off and immediately burn bum the tha infected twigs and limbs when this is lone done in tho the fall or winter the die source of in faction Is removed in doing this pruning it must be remembered that the tiny little knots so BO easy to overlook on tho the fruit spurs ore are capable of keeping up tho the infection watch for the little knots on anthe the twigs an and d cut them out bum ail all of the prun arun ings at once otherwise they will liberate spores just the same as if they had not been cut oft off |