41 G Report of the Horticulturist of the 



tobacco dust about the infested roots. If tbe branches also are 

 attacked, they should be trimmed off where practicable and 

 burned. If considered more desirable, the lice may be killed by 

 spraying with a solution of whale oil soap, one pound to five 

 gallons of water, or kerosene emulsion, one part to five parts of 

 water. When but few lice occur in small colonies on the trunk 

 or large branches they may be easily and quickly killed by apply- 

 ing pure kerosene oil to the infested parts. 



Some Australian horticulturists hold that injury from the 

 woolly aphis can be avoided by selecting varieties the roots of 

 which are proof against these insects. Wickson states^^ that " the 

 ISTorthern Spy is on the whole the best, but it has been shown 

 that the roots of seedlings grown from Northern Spy seed vary 

 somewhat in degree of resistance." 



scale insects.^^ 



The scale insects include some of the most common and de- 

 structive insect pests of the orchard. Two species common in 

 the apple orchards of the State are the oyster-shell bark louse, 

 Mytilaspis pomorum Bouche, and the scurfy bark louse, Chionas- 

 pis furfurus Fitch. The San Jose scale, Aspidiotus perniciosus 

 Comst., also attacks the apple. These insects are especially in- 

 jurious to young orchard trees. The former two species pass the 

 winter in the egg stage, the eggs having been deposited under 

 the scales of the females. The eggs hatch in this climate in the 

 spring, varying according to the season, from late in April or early 

 May until June. The young lice soon settle down and insert their 

 sharp threadlike mouth parts into the tender bark from which they 

 suck the sap. The females form the oyster-shell-like scales, or, 

 in the case of the other species, the thinner, more oval, whitish 

 scales. The scales of the males of both species are more delicate, 

 nearly white, and larger and more slender. The adult males are 

 delicate two-winged insects. 



10 Univ. of Cal. Agr. Exp. Sta. Seed Bulletin, 1898-1899: 7. 



11 For a further discussion of these insects, see Bulletin 136 of this Station. 



