Reforestation in Northern Arizona 101 



FIRE. 



The mature Western Yellow Pine is very fire resistant, but 

 the young trees are either injured or killed by fire. Fires are 

 not so prevalent now as formerly because of the greater efficiency 

 of fire patrol and better methods of fire fighting. Extensive 

 areas in the Transition type were burned over about thirty years 

 ago. It will be necessary to restock these areas artificially, if 

 they are to bear their best crop, since hardly any seed trees were 

 left. In a few places Aspen has taken the place of the former 

 stands of Douglas Fir; while over the rest of the area there is 

 no tree growth. 



TREE DISEASE. 



The mistletoe (Razoumofskya robusta (Engelm.) Kuntze.) 

 is a parasite which attacks both the mature and young Western 

 Yellow Pine, fastening itself on the branches of the trees. The 

 leaves of this mistletoe are reduced to mere bracts. The shoots 

 push out from the sub-epidermal portions of the host in the 

 latter part of April. Flowers are produced in June and July, 

 and seeds are matured in August and September. The fruit, is 

 a single-seeded berry which is attached to a short stalk. When 

 the berry ripens it bursts and expels the sticky seed which falls 

 on lower branches where it fastens itself and develops haustoria, 

 which penetrate longitudinally the tissues of the host. The 

 damage by mistletoe is serious; as high as three-fourths of the 

 trees are affected over extensive areas. 



INSECTS. 



Several species of the boring beetles belonging to the genus 

 Dendroctonus do considerable damage to young Western Yellow 

 Pine trees. The larvae in burrowing out of their egg galleries 

 make galleries all through the inner bark. The canals or bur- 

 rows made by the larvae sometimes completely girdle the tree 

 finally causing it to die. The work of the Dendroctonus beetles 

 is rather extensive in the Western Yellow Pine type. 



Another insect which has done considerable damage to re- 

 production is the Nantucket Pine Moth (Retinia frustrana). 

 The larvae completely destroy the growing tips of the young 

 trees by boring from the base of the current year's growth to 

 the terminal bud. Observations made on one Western Yellow 

 Pine about four feet high showed twenty-two out of thirty 



