356 SEEDING AND PLANTING 



So far as possible all larvae should be destroyed in working the 

 soil in the formation of the beds. If the nursery is free from the 

 larvae they can be prevented from entry by surrounding the beds 

 with a trench. Starlings and other birds that feed upon the 

 grubs should be encouraged by hanging up nesting boxes around 

 the nursery. 



Although measures for exterminating the grubs must be un- 

 dertaken when evidences of damage are first discovered, the most 

 effective and least expensive methods for preventing loss are 

 cultural. Nursery beds are rarely seriously infested when the 

 soil has been free from vegetation for several months prior to their 

 formation. When sod or a heavy growth of weeds is plowed under, 

 potatoes or other cultivated farm or garden crops should be grown 

 for at least a season before the formation of the nursery beds. 



7. Protecting the Nursery from Injury by Parasitic Fungi. - 

 Various diseases due to parasitic fungi cause more or less serious 

 damage in forest nurseries. The most serious of these diseases in 

 the United States are damping-off and blister rust. Graves 1 calls 

 attention to the injury of coniferous seedlings in nurseries at Bilt- 

 more, N. C., by Ascochyta piniperda. Layerberg records a serious 

 disease of various species of forest nursery stock in Europe believed 

 to be caused by Pestalozzia hartwigii. It results in the death of 

 the cortex just above the ground and completely girdles the trees. 

 Hartley 2 records this or a similar disease under the name stem 

 girdle as appearing on the stems of 2- and 3-year conifers in the 

 United States. It attacks the plant just above the ground and 

 causes the death of the cambium. The stem is constricted at the 

 point of injury but abnormally large just above it. The trees 

 usually die the second year after the injury becomes apparent. 

 It has appeared in western nurseries on Scotch pine, yellow pine, 

 white fir, Douglas fir, and Norway spruce. The author has 

 observed this or a similar disease on white pine in various places in 

 New England, chiefly, however, in plantations and natural stands 

 on trees from 6 inches to 3 feet or more in height. 3 



1 Graves, A. H.: Notes on diseases of trees in the southern Appalachians. 

 (Phytopathology, vol. IV, p. 63. 1914.) 



2 Hartley, C.: The blights of coniferous nursery stock. (U. S. Dept. of 

 Agri., Bui. 44. 1913.) 



3 This disease of white pine in New England appears to be associated with 

 a large mound-building ant Formica exsectoides. Groups of diseased trees are 

 usually confined to the vicinity of the mounds formed by these ants. 



