PLANT DISEASES. 8l 



intricate character, and although the work has not gone far 

 enough to yield any definite results, valuable records have been 

 obtained which will be of use in the further experiments now 

 in progress. 



South Eastern Agricultural College, Wye. 



Lime-sulphur Wash. — The extended use of lime-sulphur wash 

 in this country as a preventive against the ravages of fungus 

 diseases, chiefly American gooseberry mildew, and to a less 

 extent apple scab, is largely due to the investigations of the 

 Advisory Mycologist attached to Wye College. The strengths 

 known as the " siunmer strength " and " half summer strength " 

 were determined as the result of spraying experiments extending 

 over several seasons. The provision on the EngHsh market of 

 brands of concentrated lime-sulphur washes of a i • 30 specific 

 gravity was due to the representations made by the College to 

 commercial firms to standardise the concentrated wash on a 

 specific gravity basis. During the work on lime-sulphur — which 

 is still proceeding—ra new and useful fungicide, ammonium 

 polysulphide, was discovered which is equal in fungicidal value 

 to lime sulphur, and superior in that it does not leave a visible 

 deposit on the sprayed part, thus making it possible to protect 

 from mildew gooseberries which are approaching ripeness. More 

 recently, attention has been given to the discovery of some 

 substance for use with lime -sulphur as a " spreader." Soap 

 cannot be used for chemical reasons. Two substances, viz., 

 saponin and calcium caseinate, were ultimately found to be 

 satisfactory, and are now being used with good results. The 

 chemical researches are at present being directed to another 

 matter of great practical importance, on which the farmer has 

 long awaited exact information, viz., the effect of mixing an 

 arsenical wash (an insecticide) with lime-sulphur. The outcome 

 of last season's experiments has shown that arsenic itself is a 

 powerful fungicide against " powdery mildews." 



Control of Bunt in Wheat. — Since 1919, plots of wheat grown 

 from seed heavily infected with " Bunt " {Tilletia tritici) have 

 been cultivated on the College farm for the purpose of investigat- 

 ing the effect of " pickling " the seed wheat before sowing. An 

 inquiry was first made into the effect of the usual method of 

 springing the seed wheat with a solution of " Bluestone " 

 (copper sulphate). It was found that this method when used on 

 certain varieties of wheat such as " Red Standard," severely 

 injures the germination of the wheat, in one case reducing the 

 percentage of germination from 98 per cent, to 60 per cent., 



