FUNGOUS DISEASES AND SPRAYING 59 



SPECIAL DISEASES AND THEIR TREATMENT 



As has already been said, each cultivated plant may serve as 

 the host for numerous different species of fungi. Some fungi 

 are found on one species of host plant exclusively ; others live 

 on two or more nearly related species. Illustrations of the 

 former are the late blight of the potato and the black rot of 

 the grape ; of the latter, brown rot on peach and plum, and 

 smut on oats and barley. 



The symptoms of fungous diseases are various ; sometimes 

 the whole plant has a sickly appearance, being yellowish in 

 color and poorly developed. More frequently the disease is 

 manifested by the appearance of limited areas or spots, differ- 

 ing in color from the usual green of the part. The colors of 

 the diseased areas may be red, orange, yellow, purple, brown, 

 or black. Swellings and other defoi'mities are common. It 

 is sometimes difficult to distinguish between injuries due to 

 fungi and those due to insects ; but in case of the latter there 

 is either consumption or disappearance of parts ; or the insect 

 in some staoe mav be discovered on careful examination with 

 the naked eye. Most insects are large enough to be so de- 

 tected, while fungi are so small that they require a magnifier 

 to reveal their presence with certainty. It is important to 

 know which cause is producing the mischief, for the treatment 

 is different, fungicides will not serve for insecticides, nor in- 

 secticides for funi^icides. 



CD 



The followino- list of diseases embraces only the more im- 

 portaut ones occurring in New Hampshire : 



APPLE 



Apple Scab. Dark green or black, round velvety spots on 

 the fruit ; the spots are of appreciable thickness, justifying 

 the name " scab " ; the fungus develops just under the outer 

 layer of the skin, remnants of which, as whitish scales, may 

 often be seen on the surface of the scab ; appears early in the 

 season ; fruit may drop off or become one-sided and cracked. 

 On the leaves the fungus appears as dark green rounded 

 patches. 



Treatment. Spray with Bordeaux mixture as the buds are 



