10 MISC. PUBLICATION 303, U. 8S. DEPT. OF AGRICULTURE 
No species of woody plant is a pest throughout the country, and 
native species are far less troublesome than introduced ones. Sympho- 
ricarpos is considered a weed in places and a boon in others. Rubus 
and Smilaw are a nuisance where they cover large areas. Lonicera 
japonica is a very pernicious weed in woodlands, Campsis radicans 
and Potentilla fruticosa in pastures. Ailanthus aliissema has been 
known to supplant native forest trees, and Cytisus scoparius may 
run wild on sandy soil. 
Such plants as these form cover for soil and some produce a sec- 
ondary crop. Again, as with poisonous plants, common sense and 
caution should be used. If a species is really pernicious in a given 
region, if it easily escapes and quickly becomes widespread, and par- 
ticularly if other species can be used, the better decision would be 
to discard it. 
PLANTS HARBORING FUNGI OR INSECT PESTS 
At the present time there are nine Federal domestic quarantines 
affecting interstate movement of plants and plant products. These 
quarantines have been established to protect crops and forests from 
pests of major importance. Most regulations permit movement after 
inspection or treatment of the material to ensure freedom from 
infestation. The recognition by planting technicians of the fact that 
certain plants may assist In spreading diseases or insects that may 
cause serious loss of farm crops or forest trees as well as the plant- 
ings themselves, is essential. Familiarity with State and Federal 
regulations before plans are made is very necessary, and the techni- 
cian should cooperate in preventing the spread of pests. 
The recognition of rust hosts is of particular importance. Among 
the rust fungi the separate development of spore forms on unrelated 
hosts has taken place. Approximately one-twelfth of the species of 
rust fungi exhibits this character of heteroecism. ‘The completion of 
their life cycle depends on two host species, either or both of which 
may be an important or valued crop. It is thus evident that certain 
secondary hosts to economically important fungi must be eliminated 
from plans for planting woody species if the agricultural crop at- 
tacked by the fungus is of any importance in the vicinity of the 
planting. The more important woody species that act as secondary 
hosts are indicated in the list of woody plants. 
One of the measures taken to prevent the spread of rusts is the 
eradication of the secondary host that is of less importance eco- 
nomically. Such eradication programs are now in effect under vari- 
ous State agencies and the Bureau of Entomology and Plant Quaran- 
tine. Any technician engaged in planting operations should consult 
with State and Federal plant quarantine officials before making 
actual plantings whenever there is any doubt as to the legality of the 
operations. 
Hradication measures intended for the destruction of wild species 
known to harbor insect pests are also being carried on. Plants known 
to harbor a serious insect pest during that portion of the year in 
which nearby crops are materially damaged by that insect should be 
used with great discretion. Authorities of agencies engaged in con- 
trol and eradication of pests should always be consulted. 
