PLUM INSECTS 257 



Treatment. 



Unless occurring in excessive abundance this species will 

 rarely require treatment on plum. Kerosene emulsion, whale- 

 oil soap or tobacco extracts give satisfactory results, if applied 

 before the curling of the leaves makes it impossible to hit the 



insects. 



References 



Riley, Rept. U. S. Comm. Agr. for 1888, pp. 93-111. 



Cal. Agr. Exp. Sta. Bull. 160. 1904. 



Col. Agr. Exp. Sta. Bull. 133, pp. 40-41. 1908. 



The Plum Plant-louse 

 Myzus mahaleh Fonscolombe 



This yellowish-green plant-louse closely resembles the pre- 

 ceding species with which it has often been confused. It 

 belongs to a different genus and may be distinguished by the 

 structure of the head and antennae ; the frontal tubercles are 

 not prolonged into a slender tooth and the first antennal joint is 

 without the blunt tooth present in that species. It is not un- 

 usual to find both forms infesting the same tree. 



The life history of the two species is very similar, l)ut this 

 form does not migrate to the hop and is able to subsist during 

 the summer on a large number of plants among which may be 

 mentioned the pear, sunflower, dock, kohlrabi, chrysanthemum, 

 shepherd's purse, portulaca, etc. The winter eggs and spring 

 generations occur on both plum and peach. 



This plant-louse can b(^ controlled by timely spraying witli 

 '^ Black Leaf 40" tobacco extract, f pint in 100 gallons of 

 water, adding 3 or 4 pounds of soap to make the li(]uid stick 

 and spread better. Effective work can also be done with whale- 

 oil soap solution or with kerosene emulsion. 



Reference 

 Pergande, U. S. Bur. Ent. Bull. 7, pp. 52-59. 1897. 



