New York Agricultural Experiment Station. 389 



be done by means of Paris green applied with a powder-gun. No 

 one of these three kinds ol injury appeared great but the sum of 

 the three was sufiSeient to make spraying very profitable. 



The fungi which cause the diseases early blight and late 

 blight, propagate themselves by means of minute spores which 

 may be carried from plant to plant by the wind. When one of 

 these spores falls upon a potato leaf and finds there a drop of 

 ^ew or other moisture it germinates and grows into the leaf, 

 produoing a new disease-spot. If the leaf is covered with a thin 

 coating of Bordeaux mixture the spore is unable to germinate 

 and in this way spraying prevents fungous diseases. It is evident 

 that any leaf which has none of the Bordeaux mixture will not 

 be protected. 



Bordeaux mixture will not kill either flea-beetles or Colorado 

 potato-beetles, but it is very distasteful to them. They will not 

 feed upon leaves covered with Bordeaux mixture if they can 

 avoid it; and when Paris green is added to the Bordeaux mix- 

 ture we have the best known remedy for both these insects. The 

 Bordeaux mixture, being very adhesive, holds the Paris green on 

 the leaves through quite heavy rains which would wash off Paris 

 green applied in any other way. For flea-beetles, Paris green 

 applied by the ordinary methods seems to be almost without 

 avail. It is a mistaken notion, however, that Paris green is not 

 poisonous to flea-beetles. It certainly will kill them if they eat 

 it, and it is probably that a goodly number of them are actually 

 killed by the Paris green applied in the ordinary way for potato- 

 beetles. But flea-beetles are very cautious insects and shun the 

 poison. If the Paris green is mixed with Bordeaux mixture and 

 applied in the form of a fine spray, the poison will reach nearly 

 every leaf and stick there for a long time, keeping the flea-beetles 

 at bay. 



'From this discussion it will be seen that the degree of success 

 attained in fighting flea-beetles by spraying depends upon the 

 thoroughness with which the spraying is done. Leaves which 

 are kept well covered with Bordeaux mixture and Paris green 

 will suffer very little from flea-beetle attacks. Such leaves will 

 suffer slightly from attacks made on the undersides, for flea- 



