94 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
ous scales, aphids, and bugs. Most of these insects, since they are 
enemies of larger trees as well, will be treated in later discussions. 
While the control of insect pests in forest nurseries is sometimes a 
difficult matter, the nurseryman, at least, has measures at his dis- 
posal which would be impractical to use under forest conditions. 
Some root-feeding insects can be controlled by applying a fumigant 
to the soil, or by using poisoned baits, but much can be done to avoid 
injury through regulating cultural methods. Transplant beds which 
have become | heavily infested should be plowed and allowed to re- 
main fallow for a year. If they are cultivated often enough to 
prevent the growth of any weeds, most of the insects will have been 
starved out In a year’s time, and the beds can be used again for a 
short period without serious injury to the transplants. Leaf- feeding 
insects usually are easily controlled by the use of sprays. 
To protect seedlings from root-feeding insects after they are set 
out is not so simple, and, so far as is known, no attempt has been 
made to control soil-inhabiting insects in plantations or forests in 
the Western States. 
KEY TO DIAGNOSIS OF INSECT INJURY TO SEEDLINGS 
A. Roots of seedlings chewed, injured. or dying. 
1. Rootlets completely bitten off or the bark badly chewed* by 
soil-inhabiting insects, appearing as 
a. Curled, white grubs with three pairs of prominent 
legs and with brown heads *______ white grubs, page 24. 
b. Small, curled. white grubs with small brown heads 
but without Jé@2s (2 ae root weevils, page 26. 
c. Long, slender, hard-shelied, yellow or brown “worms” 
with feebly developed legs ~_______ wireworms, page 26. 
d. Nearly hairless, soft. sluggish, dark-colored caterpil- 
lars working below surface of ground * 
cutworms, page 26. 
bo 
Tunnels or borings under bark of larger roots 
root bark beetles, page 27. 
3. Large, dark, soft-bodied aphids sucking sap from roots 
root aphids, page 28. 
B. Stems of young seedlings badly chewed or injured.° 
1. Stem bitten off, or bark badly chewed— 
a. Nearly hairless, sluggish caterpillars working at 
TB ne ee ee Se ee cutworms, page 26. 
6.-Grasshoppers. 2 te ee  Ss grasshoppers, page 164. 
2. Borings under bark of larger seedlings________ bark beetles, page 96. 
i: Leaves of seedlings either chewed. skeletonized, mined, discolored. or 
attacked by leaf-sucking inseets= 2225 ee defoliators, page 58. 
WHITE GRUBS 
White grubs (29) are probably more common in forest nurseries 
than any other soil-inhabiting insects. These are the larvae of 
June beetles (Scarabaeidae), which are widely distributed and feed 
on the roots of a great variety of plants. The adults are voracious 
feeders and in the Lake States and elsewhere are often very injurious 
to the leaves of plants. 
* Damage meeting this description is done also by root-feeding mammals such as 
gophers, moles, ete. é = 
*+These characters are not specific and sometimes noninjurious larvae of similar 
appearance may be confused with these forms. 
> Similar damage is often done by small animals, such as mice, squirrels, and porcu- 
pines. 
a 
a 
=. 
