362 MAINE AGRICULTURAL EXPERIMENT STATION. IQIO. 



in the following pages together with the means of control so far 

 as these measures are understood. 



Black rot. This rot is caused by Sphacropsis malonim Pk. 

 which also causes a decay of pear and quince. The fungus at- 

 tacks apples both on the tree and in storage and is responsible 

 for much of the rot on the trees in this State. It is capable of 

 causing decay of green fruit but its progress is much moi'e 

 rapid in apples which are ripe or nearly ripe. Early apples are 

 especially susceptible. As a cause of storage decay, Sphacropsis 

 I)robabIy ranks second to Pcnicillium which is described below. 

 On account of the relation to leaf-spot, and limb cankers as well, 

 the black rot fungus in distribution and economic importance 

 l)robably ranks second in the State to that which causes apple 

 scab. 



Black rot of the apple takes its name from the appearance of 

 the fruit in the late stages of the decay. In early stages, the 

 decayed region is brown in color but the mycelium of the fungus 

 takes on a dark color with age and thus colors the apple. The 

 fungus usually enters the apple at either the blossom or stem 

 end, and, if the temperature is favorable for growth, spreads rap- 

 idly and causes the complete decay. The decaying region is 

 marked by concentric rings. When the mycelium has grown in 

 the apple for a sufficient length of time the threads begin to form 

 little aggregations just beneath the epidemis which develop into 

 the small black bodies which later break through the epidermis. 

 Ihe spores of the fungus are formed inside these bodies and es- 

 cape through an opening at the apex. The appearance of an ap- 

 ple in this stage of the decay is shown in Fig. 250. There is only 

 one other fungus (Phoma inali, see p 365) which in Maine 

 causes a similar appearance of decayed apples and the amount 

 of loss caused by that fungus is small as compared with the loss 

 caused by Sphacropsis. 



Since the fungus which causes the black rot of apples also 

 causes a disease of the wood and leaves, any means of control 

 of the rot must take into consideration these sources of infection 

 of the fruit. Old, diseased trees are almost certain to produce 

 Sphacropsis spores in large numbers on dead and dying limbs 

 and these spores are ready to infect the apples as they mature 

 and to cause their decay. One good means of control then is to 

 remove the source of infection by cutting out and burning all 



