Plants as Affected by Animal Parasites. 161 
other cases. Attacks of this insect have also been success- 
fully prevented by surrounding the stem of the young plant 
with small cards of thin tarred paper. One of these cards, 
the tool used for cutting them, and the manner of using the 
tool are shown in Figs. 71, 72 and 73. 
310. Burrowers, as the term is 
here used, includes not only the so- 
called borers that burrow within the 
stems and roots of plants, but also 
the leaf-miners, that live between the 
surfaces of leaves, and the insects 
that pass their larval stage within 
fruits. Insects of this class are diffi- 
cult to control, since they are mostly | 
‘)_., beyond the reach of insecticides. 
_& ae 311. Borers that infest the 
Se ; ta 
_. . trunks and main branches of trees, 
Fig. 71. Tool for injecting 
poisonous liquids about the May often be kept out by applying 
See deh crepes strong alkaline washes to these parts. 
Soft soap, reduced to the consistency of thick paste 
by a strong solution of washing soda, applied to 
the trunk or branches forms a rather tenacious coating 
which repels the female insect. Painting the trunks of 
small apple trees a short distance above and below the sur- 
face of the ground with common paint, or pine tar, is said 
to prevent the entrance of the round-headed borer (306). 
Protecting the trunk with straw or lath, as recommended to 
prevent sun-scald (196) also tends to keep out these insects. 
Borers in the trunk may often be destroyed by probing 
their holes with a flexible twig. 
