THE BROWN ROT OF STONE FRUITS. 



We have lately entei'ed upon a new era in our 

 knowledge of the economy and methods of fighting 

 the multitudinous fungus diseases which plants are 

 heir to. Twenty, or even ten years ago, very few of 

 these rusts, smuts, blights, mildews and rots were 

 understood, and for still fewer was there known any 

 successful remedy. But now, thanks to botanical 

 investigations and experiments, we have brought 

 under control a number of these insidious foes, and 

 there is good reason for hoping that to many others 

 we shall soon be able to say : "Thus far shalt thou 

 go, but no farther." 



One of the most destructive of thefee diseases is 

 that known as the brown rot of stone 

 fruits. It attacks plums, cherries, 

 peaches, and occasionally even ap- 

 ples ; and nearly every year causes 

 serious losses to the fruit growers of 

 the country. Where it is present, the 

 fruit, while yet green and immature, 

 begins to turn brown and 

 shrivel, as shown at Fig. 

 I ; and in a few days the 

 skin becomes covered with 

 a brown velvety down, 

 which consists 

 simply of the 



Fig. I. Plums attacked by Rot. 



fruit or spores of the fungus. If a small quantity 

 of this velvety material be placed under a high 

 magnifying power, it will be seen to consist of 

 threads of cells, as shown at Fig. 2. These cells 

 are the spores or productive bodies of the fungus. 

 If a plum covered by the velvety down mentioned 

 above be lightly shaken over a piece of glass, and 

 the glass put under the microscope, it will be found 

 that a great many of the spores have fallen away 



from the threads, and the field of the microscope 

 will present the appearance shown at Fig. 3. It is 

 by means of these spores that the disease spreads. 



Threads 

 Spores. 



The wind blows them all 

 through the orchard, many 

 falling upon healthy plums, 

 where they germinate b y 

 sending a minute tube which 

 enters the fruit. Once in- 

 side the fruit, this tube con- 

 tinues to develop into mycel- 

 iuiii which penetrates all the 

 tissues of the plum and Fig. 2. 

 causes it to turn brown. 

 This mycelium eventually develops a crop of spores, 

 and causes the plums to become withered and dry, 

 and to remain upon the trees in a mummied or 

 dried condition. (See Fig. 4, page 166.) In this 

 way the fungus stays on the trees all winter and even 

 until the next year's crop of fruit ripens. 



At the Ohio Experiment Station the past year, 

 we attempted to keep this fungus in check. In our 

 treatment of the plum orchard, we began late in 

 March by picking and burying all the mummied 

 plums on the trees. Then we sprayed them early 

 in April, before the leaves came out, with a simple 

 solution of copper sulphate ; and twice during May 

 (15th and 25th), the first time with London purple 

 alone (to kill the curculio), and the second with 

 a combination of London purple and the Bor- 

 deaux mixture, which treatment was repeated 

 June I. 



After these sprayings, the fruit was fairly 

 \ well covered with the copper sulphate and lime, 

 which stayed on despite the many rains until 



00 



6 ft^.- 



4' 



0 ' 

 0 



it ripened in 

 Septemb e r — 

 a period of 

 nearly four 

 months. A t 

 the time o f 

 picking, an unde- 

 sirable amo u n t 

 was still present 

 — so much that it 

 was necessary to 

 wash the fruit. 

 This year I in- 

 tend trying some other compound of copper instead 



00. 'M. 



0 



Fig. 3. Spores. 



