INSECT ENEMIES OF EASTERN FORESTS 23 
Mechanical barriers placed around the trunk of the tree are very 
effective in preventing the ascent of leaf-eating caterpillars. A num- 
ber of materials have been succe ssfully used for this purpose, includ- 
ing burlap, cotton batting, fine-mesh screen, and sticky substances. 
Some sticky materials are on the market and, although more expensive 
than some other materials, are easily obtained and simple to apply. 
A good formula for a sticky banding material and its preparation for 
use » against the gypsy moth are described by Collins and Hood (102). 
TM: apply burlap or cotton batting, the bark should be smoothed, 
the material placed around the trunk and held firmly with a wire or 
string, and then the upper portion of the material turned down, so as 
to form a loose flange all the way around the tree. Johnson and 
Fenton (258) describe a method with paper bands. For some insects 
DDT sprayed around the lower trunk has been very effective.® 
TWIG OR STEM GIRDLERS 
Twigs or stems girdled by any of several species of insects causing 
this type of damage usually contain the borer in the severed portion 
of the twig. In some cases, however, the borers work toward the 
trunk, cutting off the portion of the twig behind them. In the former 
case gathering and burning of the girdled twigs is the most satisfactory 
means of preventing further damage, provided it is thoroughly done 
and extended some distance in the surrounding area. This form of 
control, however, is of very little value if the trees are growing adja- 
cent to wood lots where these girdlers are abundant. 
For those forms that girdle the twig behind them and bore down into 
the stem, prompt action in cutting the twig ahead of the borer and 
destroying it 1s the best remedy. The injection of a few drops of 
carbon disulfide into the hole, followed by plugging the stem, will 
also kill the borer. 
Carbon disulfide is inflammable and explosive when mixed with 
air in certain proportions, and is poisonous. The liquid should 
be handled with great care and never be exposed near fire in any 
form. Even hot steam pipes may ignite the gas. The fumes are 
poisonous and should not be inhaled. When applying the chlor- 
inated benzenes the hands should be protected with rubberized 
gloves, since the chemical might irritate the skin. Care should 
be taken to keep the vapor from the nose and eyes. 
ROOT BORERS 
Root borers are notoriously difficult to handle, but fortunately 
are not frequently encountered. Those attacking a tree at the ground 
line can often be destroyed by fumigating with ‘paradichlor obenzene. 
(See p. 25.) True soil-inhabiting insects that attack the roots of 
plants are treated in the discussion of insects affecting nursery plants 
(p. 28). 
Certain gall-forming insects can be controlled by sprays as men- 
tioned, but for many forms the only known method of control is to 
cut and destr oy the galls at that period of the year when they contain 
the living broods and thus prevent the adults from emerging and at- 
tacking the same or other trees. 
GALL MAKERS 
* For a full discussion of spraying and dusting, see pp. 51-57. 
