62 PROTECTION OF WOODLANDS. 



Professor R. Hartig recommends, as a preventive measure and 

 special precaution against fungoid infection, the formation of Pine 

 nurseries in woods of broad-leaved species, or, at any rate, as far 

 away as possible from any cultural area infected with the leaf- 

 shedding disease. Particular care should also, he says, be taken to 

 avoid locating the seed-beds to the westward of infected areas, as 

 it is for the most part the rain-storms coming from that direction 

 which carry the spores to the young crops, and thereby cause 

 infection and spread of the disease. Hartig further recommends 

 the location of the nurseries at the edge of the forest, so that the 

 west winds may sweep over fields before reaching the former, the 

 formation of nurseries of a moderate size only, and their enclosure 

 with closely fitting boarding to a height of 6 or 7 feet on the wood- 

 ward side, so as to intercept the passage of the spores which are 

 wafted along in the layer of air close to the ground, and finally, 

 a light covering of foliage from broad-leaved species (leaves, not 

 needles) during the winter, in order to catch any spores that may 

 have been carried to the beds. 



Frosts have also been blamed as the cause of this disease, and 

 not only the early frosts occurring in autumn, but also hard 

 winter frost, followed by warm sunshine (according to Alers and 

 Nordlinger). The covering up of the seed-beds, or the lifting out 

 of plants early in autumn and storing them up in covered ditches, 

 or collecting them in beds and covering them up with a thin 

 layer of leaves, have been by them recommended as protective 

 measures, without having always the desired effect. 



Experience has shown that young plantations suffer less than 

 dense thickets formed by sowing, and that even in nursery seed- 

 beds, leaf-shedding is less destructive when the plants are further 

 apart, than when very close together ; two-year-old Pine seedlings 

 standing crowded in seed-beds almost invariably become infected 

 with this disease. 



Whilst the reasons for leaf-shedding may quite well be found 

 in one or other of these causes, the disease is probably very often 

 due to a combination of them. 



