INJURING THE LEAVES. 



59 



m 



Fig. 25. Aphis. Magnified. 



that suck out the sap, and give the terminal portion 

 of the twigs a malformed appearance. These are 

 aphides or plant-lice. Two or 

 three species are known to 

 infest the plum, one of which 

 has been shown by Dr. C. V. 

 Riley to migrate during sum- 

 mer to the hop-plant. The 

 life-histories of the others are 

 not very well known. In a 

 general way they are similar 

 to the Apple Aphis, described on a previous page. 



Remedies. — Spraying with kerosene emulsion is 

 the most effective remedy for this insect. The ap- 

 plication should be made with a force pump and 

 spray nozzle ; and as soon after the insects are no- 

 ticed as possible. 



Plum Leaf Caterpillars. 



There are several kinds of caterpillars that occa- 

 sionally attack the plum, but they rarely occur in 

 sufficient numbers to do serious injury. Of these we 

 may mention the Plum Catocala (Catocala ultronea),. 

 the Polyphemus Moth (Telea polyphemus), the Horned 

 Span-worm (Nematocampa filamentaria), the Plum 

 Sphinx [Sphinx drupiferarum), the Gray Dagger-moth 

 (Apatela occidental is), and the Disippus Butterfly 

 (Limenitis disippus). These insects are all open to 

 destruction by spraying with the arsenites, and are 

 not likely to become injurious in orchards regularly 

 sprayed for the Plum Curculio. 

 4 



