EXPERIMENT STATION BULLETINS. 367 



benefit during the season following the applications. The work of Prof. Taft 

 in Michigan shows that very beneficial results may be expected from the use of 

 one thorough spraying with copper sulphate solution two or three weeks before 

 the buds open. This treatment if given before April 1 should entirely prevent 

 the disease. 



BROWiV ROT. 



(Sclerotinia fructigena (Kze. & Schm.) Norton.) (See Plum.) 



CROWN GALL. 



(Dendrophagus globosus Toumey.) 



The disease known as crown gall has been noticed in Michigan only during 

 the past six or seven years but it is already recognized as a serious foe to the 

 culture of the peach. As its name indicates, trees affected with this disease 

 show galls or knots of soft, corky or spongy tissue located most frequently at the 

 crown of the root system, although they also occur on the roots and sometimes 

 on the stem above ground. These knots when young have the same color as the 

 roots but as they become older the surface darkens becoming rough and warty. 

 They may vary in size from that of a hazelnut to bunches as large as one's fist. 

 These galls usually begin to decay toward the end of the season and fall away, 

 being followed by new galls on other portion of the roots. Thus a new crop of 

 the galls is produced with each season. The effect of this disease on the trees 

 is such as to produce a spindling or stunted, sickly growth, and usually leads to 

 the death of the tree. Trees affected with crown gall when planted from the 

 nursery seldom reach bearing size but frequently die the first season. 



While many causes have been assigned for the formation of the galls character- 

 istic of this disease the true one has been found to exist in the presence of an 

 organism belonging to the myxomycetes, or slime molds. This matter has been 

 determined by Toumey in Arizona who used almond seedlings infected with the 

 disease for investigation. In its early stages the parasite consists of colorless 

 microscopic masses of protoplasm which inhabit the cells of the knot. Under 

 certain conditions these protoplasmic masses unite and come to the surface 

 of the galls where small rounded spore-producing bodies are formed. The 

 disease is spread most rapidly by means of infested nursery stock. There is 

 evidence also that the disease may spread through the soil for limited distances 

 and its contagious nature is clearly established. 



Treatment. — The nature of this disease gives small hope in the matter of a 

 cure, hence prevention is the chief source of relief. Some benefit has been derived 

 from the removal of the knots which form at the crown of the roots and painting 

 the wounds with a paste composed of copper sulphate and lime. Other galls 

 will form on the roots further underground but are not considered of as much 

 importance as those which occur on the crown. In most cases, however, it will 

 be better to dig out and burn affected trees. Careful inspection of nursery stock 

 should be made before planting and all affected trees rejected and burned. 

 Crown gall is also belived to be communicated to the peach from the raspberry 

 and blackberry but especially from the former. Hence the planting of raspberries 

 between the peach rows is to be avoided as galls are quite commonly found on 

 the former. 



SCAB. 



(Cladosporium carpophilum Thorn.) 



The disease known as peach scab, or merely "scab," causes dark colored velvety 

 spots which are frequently most numerous on one side of the fruit. "When the 

 spots are very numerous they run together and in bad cases cause the fruit to 

 harden and crack open. In such instances too the fruit often fails to develop 

 evenly but is one sided. The disease is especially common on certain kinds, some 

 seedling varieties seeming to be especially susceptible to its attacks. While the 

 peach scab, like that of the apple, is confined to the surface of the fruit its effects 

 may be such as to render the crop almost worthless and even in moderate cases 

 the market value of the fruit is apt to be materially reduced. This fungus also 

 sometimes causes spotting and shothole effects on the foliage. The disease is 

 most prevalent during rainy seasons. It also attacks the plum and cherry. 



