354 SEEDING AND PLANTING 



species and cannot be reached by ordinary methods of poisoning. 

 The pine moth (Retina frustra) has seriously injured yellow pine in 

 some nurseries in western United States but no effective remedy 

 is yet known. 



Insects which injure the plants by sucking the sap from the 

 leaves or bark cannot be destroyed by ordinary methods of poison- 

 ing. A material which acts externally on the bodies of the insects 

 must be used. The standard materials for this purpose are kero- 

 sene emulsion, soap and water, and tobacco extract. The pine 

 bark aphis (Chermes pinicortids) , often found in forest nurseries 

 infesting white pine, is one of the most destructive of this class of 

 nursery pests. It can be effectively controlled by spraying with 

 kerosene emulsion. 



The common red spider (Tetranychus bimaculatus) often causes 

 considerable damage in forest nurseries in the United States, 

 particularly in the eastern states. Under favorable conditions 

 this pest infests nearly all kinds of nursery stock, but is par- 

 ticularly harmful in 2-year coniferous seedbeds. The insect is 

 minute and, when present in ordinary numbers, usually escapes 

 notice. When present in large numbers the leaves turn yellow and 

 have an unhealthy appearance. Close inspection of the plants 

 with a pocket lens shows these " spinning mites" as minute red 

 specks on the leaves and twigs. They injure the plants by pierc- 

 ing the epidermis and feeding on the sap. 



^ Serious injury from this insect seldom occurs except during dry 

 weather in late summer or autumn. When not overabundant it 

 can usually be held in check by drenching the beds with water at 

 frequent intervals. The water should be sprayed against the plants 

 with considerable force. Chittenderi 1 recommends the following 

 metlibcls of control for the red spider. 



a. Flowers of sulphur, mixed with water at the rate of an 

 ounce to a gallon, and sprayed over the infested plants. 



6. Potash, fish oil, whale oil, and other soap solutions at the rate of 

 1 pound to 20 or 30 gallons of water sprayed over the infested plants. 



c. A kerosene-soap emulsion prepared by combining 2 gallons 

 of kerosene and J pound of whale oil soap with 1 gallon of water. 

 The emulsion diluted with 10 parts of water is sprayed on the 

 infested plants. 



1 Chittenden, F. H.: The common red spider. (U. S. Dept. of Agriculture, 

 Bureau of Entomology, Cir. 104 1909.) 



