A16 Report oF THE HORTICULTURIST OF THE 
tobacco dust about the infested roots. If the 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 liceroccur 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 
Northern 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 Bouché, 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. 
