THE COXTEOL OF TOMATO LEAF-SPOT 
15 
foliage and renews the films but does not adhere well. Copper-soap 
dusts 6 adhere much better than Bordeaux dust and protect the cov- 
ered parts from the action of parasites but do not renew the films 
well. Experiments now being conducted with different proportions 
of dry Bordeaux and copper-soap dusts may lead to the develop- 
ment of a more effective dust fungicide than either dry Bordeaux 
or copper-soap dust, but it is quite evident that much study of the 
fundamentals of both spraying and dusting is necessary to put this 
work on a highly effective basis. 
Although dusting has not given as good results on the average 
as liquid spray mixtures, it may ultimately replace spraying; in 
Fig. S. — A good bellows-type band duster. Several good crank and fan types are also 
on tbe market 
fact, dusting is now successful with some crops, and experiments 
with copper-soap dusts (10) on tomatoes seem promising. 
DEVELOPMENT OF RESISTANT VARIETIES 
The development of first-class blight-resistant varieties of toma- 
toes would give the best solution of the tomato leaf-spot problem. 
Unfortunately, all the domestic and foreign cultivated varieties 
which it has been possible to get from seedsmen and the numerous 
8 Tbese dusts are made from copper sulphate and salts of stearic and other high- 
melting fatty acids and contain from 4 to S per cent of metallic copper. 
