INSECT ENEMIES OF EASTERN FORESTS 31 
that have been under cultivation. Control is very difficult in soil 
where nursery stock is being grown, because treatments severe enough 
to affect the insects will pr obably destroy the seedlings also. 
Root Borers 
Occasionally where nurseries are planted on newly cleared land 
considerable damage is done by borers. The larvae of a species of 
long-horned beetle of the genus Prionus, which usually work in the 
roots of larger trees, may remain temporarily in the soil and feed on 
the roots of. seedlings. To avoid such damage, stump land, or land 
containing trees or brush, should be cultivated for a year or two before 
it is used for a nurser y site. 
FLATHEADED BORERS 
In hardwood seedlings held more than one season in the nursery, 
especially when they become crowded and in poor condition, serious 
damage may be caused by the flatheaded apple tree borer (Chrysobo- 
thris femorata ¥.). To avoid this injury trees should be kept in good 
growing condition and, if possible, should be moved from the nursery 
each season and planted out. 
Frequently young trees are injured by this borer during the first 
few years after their planting. The use of such protectors as thin 
veneer, paper matrix, or wire screen, placed around the base of the 
trees up to the first large branches, will prevent oviposition on the 
lower bole. The wrapping should be maintained in good condition 
from May to September for 2 years after planting. Results obtained 
from recent limited tests indicate that attack may be prevented by 
spraying the trunk with 5-percent DDT emulsion. Little dependence 
can be placed on repellents, poisoned washes, or chemicals to kill the 
eges and larvae. Since normal and vigorous trees are rarely injured 
by this borer, it is important to keep the trees healthy by good cultural 
methods. Burke (75), Chandler (83), and Johnson and Fenton (258) 
have discussed the control of these borers. 
COTTONWOOD BORERS 
Oviposition by the cottonwood borer (Plectrodera scalator) is best 
Deepens by barriers made of such material as burlap, wire screen, 
or tar paper, placed around the bases of the young cottonwood trees. 
Such barriers are needed for several years, or until the trees become 
large enough to resist or withstand attack. Later any borers can be 
cut out with a pocket knife if this is done by early September of the 
season of attack. After this time the borers may be too deep in the 
wood to be reached. Fumigants, such as the orthodichlorobenzene 
emulsion described on page 25 can be used to advantage. The emulsion 
should be poured or sprayed around the base of the tree between July 
15 and August 1 in quantities sufficient to saturate the bark around 
the egg scars. If too much of the emulsion is used it is apt to injure 
the roots. Milliken (304) has written on the control of the cottonwood 
borer. 
OTHER BORERS 
Several species of Melanophila and Agrilus likewise attack green 
trees weakened from various causes. Fumigant sprays have been 
tested against both these insects, but with indifferent success. 
792440°— 
