BODY AND BRANCH DISEASES AND INJURIES 57 



Several species of the genus Phoradendron attack the junipers 

 in southwestern and western United States. These mistletoes 

 are sometimes found also on fir, cypress and incense cedar. They 

 are much larger plants than the dwarf mistletoes and make a 

 part of their own food materials, since they have green leaves. 

 The main damaging effects of these mistletoes are the starving 

 of the portion of the limb from the point of attack outward 

 and the production of brittle swellings which allow the limbs 

 to be easily broken off by wind or excessive weight (Fig. 3). 



Practically all kinds of deciduous forest- and fruit-trees are 

 attacked by the mistletoe, Phoradendron flavescens, in southern 

 United States. This mistletoe is a large form and has green 

 leaves. The berries are sticky and are distributed by birds. 

 The roots from the germinating seed penetrate the wood and 

 establish the parasite. The chief damaging effects arise from 

 the starving of the branch beyond the point of attack and the 

 shading of the foliage of the host. The branch at the point 

 of attack becomes larger and greatly deformed. Sometimes 

 on certain hosts, abnormal branching occurs and witches'- 

 brooms are formed. 



Following is a list of the parasitic leafy mistletoes (species 

 of Phorodendron) of the United States arranged under the 

 kind of trees they attack : — ■ 



Alder 



P. Engelmanni Trelease. Texas 



P. macrophyllum Coekerell. Arizona 



P. longispicum Trelease. California and Arizona 

 Apple 



P. macrophyllum Coekerell. Arizona 



P. flavescens Nuttall. Central and southeastern states 

 Ash 



P macrotomum Trelease. Florida 

 . P. Eaioni Trelease. Florida 



P. macrophyllum Coekerell. Arizona 



P. Cockerellii Trelease. New Mexico and Texas 



P. longispicum Trelease. CaUfornia and Arizona 



P. flavescens Nuttall. Central and southeastern states 



