20 N. H. AGR. EXPERIMENT STATION. [Bulletin 203 



In yet another experiment on the relative value of different Bordeaux 

 mixtures and Burgundy mixture, the washes were apphed fortnightly under 

 90 pounds pressure. The following results were obtained: 



Degree of Control of Late Blight Obtained with Different Bordeaux 

 Mixtures and Burgundy Mixture 



While late blight was not severe in any of the fields in which experimental 

 spraying was carried on, it is nevertheless clear that Burgimdy mixture, 

 Ferret's formula and 4-4-50 Bordeaux mixture do not compare favorably 

 in protection with the 6-3-50 and 8-4-50 washes. The protection afforded 

 by a 6-3-50 Bordeaux mixture should, under conditions favorable to the 

 development of late blight, be less than that afforded by an 8-4-50 mixture 

 if the ideas expressed in a previous publication are true.* 



Under conditions of less severe infestation the two strengths would, as 

 in fact they did, afford a protection more nearly ahke. 



Effect of Siccatives on Seed Potatoes. WTien potatoes are cut before plant- 

 ing, it is a common practice, especially when they are to be machine sown, 

 to dust them with sulphur or gjTDSum or some other suitable substance to 

 dry the cut surface and protect the seed piece from decaying. Sulphur 

 is generally considered the best to use, though the reason for so considering 

 it is not obvious. 



^Vhen potatoes are machine planted, they go through the planter better 

 when the cut surface has been dried; but has a drier any other value besides 

 its siccative properties? Does sulphur, for instance, prevent decay of the 

 seed piece better than either gypsum or tricalcic phosphate? In an attempt 

 to answer this question Mr. Butler has for three successive years tested sul- 

 phur, gypsxim and tricalcic phosphate. The results obtained are indicated 

 in the following table: 



*Butler, 0. On the amount of copper required for the control of Fhytoph- 

 thoia infestans, Fhytopathology 10: 298-304. 1920. 



