A DISEASE OF PINES CAUSED BY CRONARTIUM PYRIFORME. 17 



If it were possible to distinguish all of the diseased trees at the time 

 of planting, it would be an easy matter to discard them and thus 

 prevent the further spread of the disease. Such, however, is not the 

 case, since the disease may not become evident until three or four 

 years after the young trees are infected and until after they are planted 

 in the forest. This being the case, other means for the control of the 

 disease must be adopted. The most feasible plan to prevent further 

 infection in the nursery and the subsequent dissemination of the 

 disease through infected nursery stock appears to be the elimination 

 of all Comandra plants in the vicinity of the nursery. 



In order to protect the nursery from infection whenever the dis- 

 ease is present in adjacent forests, all diseased pines that can be 

 found within a radius of at least half a mile from the nursery should 

 be cut down. These can be selected most easily by a person familiar 

 with the fungus, at the time the secia mature in the pines. As pre- 

 viously stated, this period varies from the middle of May till in 

 August, depending upon both the latitude and the altitude of the 

 locality. This cutting-out process should be repeated each year until 

 no more diseased trees can be found in the proposed neutral zone. 



The elimination of all diseased pines will not suffice, however, 

 absolutely to control the disease in the nursery when Comandra plants 

 are in the vicinity, since it is quite certain that the fungus can spread 

 by the urediniospores from one Comandra plant to another for long 

 distances in one season. By this means the disease could be carried 

 from diseased pines outside of the neutral zone or belt of removal to 

 the young pines in the nursery. To protect the nursery against infec- 

 tion from this fungus all Comandra plants within 1,000 feet of the 

 outer boundaries of the nursery should be removed by digging them 

 out. 



Comandra plants are herbaceous perennials and spread primarily 

 by means of seeds and secondarily by means of underground runners. 

 The secondary method is the more common. The seeds, being 

 edible, are much liked by birds and rodents, and it is possible that 

 they may bo carried by these animals to a considerable distance from 

 the original place of growth, thus starting new plant colonies. The 

 eradication of Comandra plant colonies will be difficult, owing to the 

 numerous underground runners, any of which are liable to be broken 

 off and left in .the ground to start new plants. It will no doubt be 

 necessary to dig up the plants repeatedly before they can be com- 

 pletely eradicated. All species of Comandra are parasitic and derive 

 part of their food supply from other plants by a direct attachment 

 of the smaller side roots of Comandra to the roots of the host plants. 

 It is not yet known how many species of plants are thus parasitized, 

 but several widely different species are attacked. Species of Vac- 



