BLIGHTS OF CONIFEROUS NURSERY STOCK. 9 



of the nurseries, the writer is confident that the largest proportion of 

 the damage to pine, spruce, and fir nursery stock during the growing 

 season can be classed as sun scorch. 



HOW TO RECOGNIZE SUN SCORCH. 



The best way to tell whether or not an attack of blight is due to 

 sun scorch is to note the relation between the occurrence of the dis- 

 ease and crowding, shading, drying weather, sandiness of soil, lack of 

 soil moisture, and drought resistance of different species, as described 

 in the foregoing paragraphs. The only characteristic of value shown 

 by individual diseased plants is the simultaneous death of needles and 

 root tissue. When the character of the trouble is still in doubt, final 

 determination must rest with the nurseryman. The best method of 

 doing this is to lay out small plats in the beds at different points in 

 the nursery, giving some of them special shade and others regular, 

 heavy watering. If at the next attack of blight these treated plats 

 come out much better than the other beds near them, he can know 

 that the trouble is sun scorch and treat it accordingly. 



PREVENTIVE MEASURES. 



The best and only absolutely certain way to prevent sun scorch is 

 to water the nursery beds. When stock over two months old is 

 watered it should be watered heavily. The great trouble with arti- 

 ficial watering is that it is usually not done thoroughly. Most of 

 the water applied in sprinkling with the hose, as it is often done, 

 evaporates from the surface without reaching the roots at all, so that 

 even frequent sprinkling is of little value. At Halsey very crowded 

 beds must be heavily watered oftener than once a week in the most 

 drying weather to prevent all injury from sun scorch. With one ex- 

 ception there is no other nursery known to the writer where so much 

 watering is necessary. The density of the stand and the character 

 of the soil and climate must determine the amount of watering needed 

 to prevent trouble. In some nurseries on rather heavy soil no pre- 

 ventive is necessary except in most exceptional drought years. 



Objection has been made to much watering, on the ground that 

 it can be expected to make stock less hardy and less able to sur- 

 vive transplanting. Observation of the work of the disease has sug- 

 gested that the other extreme may also decrease hardiness. If the 

 trees are allowed to become too dry, many which are not killed en- 

 tirely and which may show little or no damage above ground appear 

 to have enough of their root systems killed to decrease their chance 

 for survival. 



At the nursery at Halsey, Nebr., the beds are flooded with water 

 obtained by a lift of a few feet from a river. At Monument, Colo.. 



13745°— Bull. 44—13 2 



