DISEASES OP PLANTS. 567 



composted manure in favoring- the development of potato scab, and the 

 comparative value of corrosive sublimate, lysol, and sulphur in pre- 

 venting - scab upon clean land. 



In the first experiment the seed used was completely infested with 

 scab. The tubers were washed, divided into 5 lots, and treated with 

 lysol, 0.1, 0.5, and 1 per cent solutions and a corrosive sublimate solu- 

 tion (1 oz. to G gal. of water). 



Alter treatment the seed potatoes were spread out to dry, and cut 

 and planted as usual. The external effect of the lysol was very marked. 

 In the case of the two stronger solutions the etiolated sprouts were of 

 a pale brownish-red color, while the green sprouts were uninjured, 

 except the young leaf buds, which were blackened. 



Observations on the growth of the plants showed no very marked 

 irregularities except where a 1 per cent solution had been used. These 

 plants were 3 or 4 days later than the others in appearing above ground. 

 Some hills failed entirely. The crop was light and composed of very 

 small tubers. 



The potatoes were all dug August 28 and graded. The yields from 

 the different plats are tabulated. From the tabulation it is seen that 

 corrosive sublimate as a preventive of potato scab gave the best results. 

 TheO.l per cent solutiou of lysol was not sufficient to secure disinfection 

 of the seed, and the others materially injured the seed and lessened 

 the crop. 



In connection with these experiments the fungicidal and insecticidal 

 value of lysol and Bordeaux mixture was tested. As an insecticide 

 lysol possessed little value as compared with Paris green, and as a 

 fungicide it failed to check the early blight of potatoes. Dry Bordeaux 

 mixture mixed with Paris green and dusted over the potato plants 

 proved inferior both as a fungicide and an insecticide to Bordeaux 

 mixture used in liquid form. 



In the experiment to test the comparative value upon infested land 

 of corrosive sublimate, lysol, and sulphur the seed was soaked for an 

 hour and a half in 0.1, 0.5, and 1 per cent lysol solutions; rolled iu 

 sulphur, aud sulphur sown in each hill; or soaked in corrosive sub- 

 limate solutiou. The plat where this trial was conducted produced 

 the previous year a crop of potatoes 75 per cent of which was scabby. 

 The results of this experiment are tabulated and summarized by the 

 author as follows: 



"(1) Where the soil is infested with scab fungus the crop of tubers will be seri- 

 ously diseased if no preventive treatment is applied. The disease will be further 

 aggravated under such conditions by the use of scabby seed. The use of infested 

 land for potatoes should therefore be discountenanced. 



"(2) Lysol used in 1 per cent solution injures the seed when the latter is allowed 

 to remain 11 hours in contact with it. "Weaker solutions are almost inoperative 

 when used upon either (lean or scabby seed planted on infested land. 



"(3) Sulphur is an unsatisfactory preventive of potato scat), no matter what the 

 quality of the seed, when the soil is infested. It further tends to roughen the sur- 

 face of tubers growing iu contact with it. 



