






- New Yorx Agrioutturat Experment Station. 565 
pas COMPARISONS OF FUNGICIDES. 
For the purpose of investigating the question as to the com- 
parative merits of different fungicides, seven fungicides were 
tested, namely (~) copper sulphate (blue vitriol or blue stone), 
()) iron sulphate (copperas), (¢) zinc sulphate (white vitriol), (d@) 
Eau Celeste, ‘v) Bordeaux mixture, (7 mercuric chloride (corrosive 
sublimate), and ) ammoniacal solution of copper carbonate. ‘The 
best results were obtained from the use of iron sulphate, zinc 
sulphate and mercuric chloride but further experiments must 
be made before it can be definitely stated which of these is most 
effective. The formula for either the iron sulphate or the zine 
sulphate solution is one ounce of the sulphate to one gallon of 
water. The mercuric chloride formula is “ Dissolve two ounces 
of the chloride in two gallons of hot water, let it stand several 
hours, or over night, then dilute to fifteen gallons.” It should 
be remembered that the mercuric chloride is very poisonous. Only 
wooden vessels should be used in making any of these solutions. 
There is but slight difference in the cost of these three solutions— 
less than one cent per gailon in each case. 
| NATURE OF POTATO SCAB. 
Since the cause of potato scab has been definitely determined 
its treatment can be more intelligently studied than was formerly 
possible. The very careful work of Dr. Roland Thaxter at the 
- Connecticut Experiment Station and of Prof. H. L. Bolley of the 
North Dakota Experiment Station has shown that the cause of 
potato scab is a parasitic fungus. 
Regarding the question as to whether a distinction should be 
made between the so-called “surface” scab and “deep” scab it 
will be sufficient for our purpose to quote Prof. Bolley’s state- 
ment * that the economic interest of the subject is essentially 
centered about the establishment of the fact that the general 
first. cause of the disease is in parasitic plant action§ and his 
* Bull, 4, North Dakota Expt. Station, Dec., 1891, p. 6. 
§ Prof. Bolley states that ‘‘In order to understand the form which the scabs as such assume- 
one must keep in mind the structure of the potato tuber and the effort always made by living 


_ tissues to heal a wound. In plants this is most rapidly accomplished by the formation of bark 
rind or corky tissues composed of layers of tabular cells rapidly developed from the underlying 
soft tissues (parenchyma), The ultimate form which the scabs assume is the result of a con- 
tinuous formation of layers of cork below the area of disease, because of the irritating and erod- 
ing action of the parasite. These later cork formations push up, distort and rupture the disease 
eaten parts above.’’ See Bull. 4, North Dakota Experiment Station, Dec., 1891, pp. 8-9. 
