TREE PROTECTION 5 



15, 1941, they published recommendationsS which should materially facilitate 

 the operation of the war emergency work of tree programs. 



In brief, then, in view of the camouflage value of shade trees (Frontispiece), 

 municipal tree planting and protection programs previously developed for the 

 promotion of peaceful pursuits may nOw enable communities which were inter- 

 ested in living better, also to live longer. 



INVESTIGATIONS 



The present studies included forest and shade trees in all sections of the State, 

 with special attention to street plantings. The principal types of troubles found 

 are analyzed briefly. 



Fungus Diseases and Insect Pests. Insects'* contributing to tree injuries have 

 been found to include insects causing initial injury to healthy tissues, insects 

 associated with secondary injury to tissues previously weakened, and insects 

 which serve as vectors or carriers of other pests. Fungi and bacteria related to 

 tree injury include organisms which may kill trees promptly, induce ch onic 

 disease, or cause disintegration of portions of weakened trees. 



Dutch Elm Disease. The Dutch elm disease has been found in only seven trees 

 in Massachusetts, but mention of it is included here to call attention to the im- 

 portance of keeping this disease in check in any program concerned with the 

 elimination of hazardous trees. Extensive spread of the disease would doubtless 

 result in greatly increasing the number of dangerous street trees. (For additional 

 information see tailpiece.) 



Wood-destroying Fungi. It often happens that a limb broken from a tree dur- 

 ing a wind storm had been previously weakened as a result of decay following 

 invasion by wood-destroying fungi (Fig. 2). Sometimes evidence of this weakness 

 prior to the break may be completely lacking, but in many instances it might 

 have been detected had the tree been inspected. If a tree shows extensive signs 

 of decay, limbs which may be broken by the wind should be removed, as in the 

 case of the tree shown in figure 3. 



Physiological Disorders. Trees, like all other green plants, require water, 

 nutrients, sunlight, and air in order to function as living organisms. The lack 

 or excess of some of these essentials may result in injury or death. Thus, trees 

 sometimes suffer from drought, flood, alteration of water table, winter conditions, 

 shade, evaporation, non-availability of nutrients, and other inherent or induced 

 soil conditions. 



Chemical Injury. Calcium chloride and other chemicals stored or applied in 

 locations which permit contact with the soil about trees may cause injury to 

 roots. In the atmosphere, some of these materials may cause the burning of 

 foliage. 



Smoke Injury. Smoke and fumes frequently contain sulphur compounds or 

 other toxic substances which may injure trees with which they come in contact. 



^ Recommended Principles and Practices of Massachusetts Tree Wardens' and Foresters' 

 Association and Public Service Agencies. 



■* Inquiries concerning specific insect pests or their control should be addressed to the De- 

 partment of Entomology, Massachusetts State College, Amherst, Massachusetts. 



