IQ MISC. PUBLICATION 303, U. S. DEPT. OF AGRICULTURE 



No species of woody plant is a pest throughout the country, and 

 native species are far less troublesome than introduced ones. SympTw- 

 ricarpos is considered a weed in places and a boon in others. Rubus 

 and Smilase 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 altissima 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. 



Eradication 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. 



