1640 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



that soil moisture be retaiiu'd durin;; the 

 growing season of the trees. Some of the 

 moist, deep soils in the Sacramento river 

 districts, and perhaps in a few spots in 

 the Rogue River valley, retain their 

 moisture so well that pears get along 

 very well for a year or so without culti- 

 vation. On the other hand, practically 

 all of the lands in these districts need 

 thorough cultivation to bring them up to 

 anything like normal and to mature full 

 crops. 



The matter of fertilization is an impor- 

 tant one, especially where large crops 

 have been taken for several successive 

 years from an orchard. However, it is 

 known that nitrogenous fertilizers, such 

 as stable manure, as well as commercial 

 fertilizers containing large amounts of 

 readily available nitrates, tend to pro- 

 duce luxuriant growth, and hence, trees 

 so stimulated blight more seriously than 

 those not fertilized. Fertilizer must be 

 used, but it should be used in moderate 

 amounts. There is no advantage in using 

 an excess of potash to make the trees 

 more hardy and thus more resistant to 

 blight. The fondest hopes of some 

 would-be experimenters have been blast- 

 ed by trying to prevent blight injury 

 through the use of potash in the form 

 of muriate and sulphate. It is the same 

 old story, the blight must be controlled 

 by having no hold-overs present during 

 the infection period. I have seen large 

 commercial orchards practically ruined 

 in one year where potash was used as a 

 preventive against blight; so avoid using 

 it for any other purpose than adding 

 fertility to the soil. 



The whole subject of irrigation is so 

 broad that it will only be discussed here 

 in its connection with the control and 

 eradication of pear blight. While irriga- 

 tion cannot be considered in the same 

 light as rainfall, since it is merely water 

 applied to the root system, it is, never- 

 theless, important to understand it thor- 

 oughly, especially in connection witli 

 blight control. It has been pointed out 

 that periods of rainy weather during the 

 spring and summer produce what has 

 been termed infection periods, through 



the wetting of the trees, and thus per- 

 mitting a spread of the infection through 

 infected trees and making it possible for 

 the germs to be more readily distributed 

 over a considerable area in any district. 

 The warm, muggy weather, such as we 

 find common in tlie East following rainy 

 periods, further tends to influence the 

 spread of infection. Irrigation in no way 

 induces any of the above conditions, but, 

 on the other hand, its effect is noted in 

 the tendency of the trees to push very 

 rapidly under a normal water supply, and 

 to become sappy and less resistant to 

 blight. It is well, therefore, to have this 

 in mind, and to apply no more water 

 than is actually necessary for the produc- 

 tion of the crop or the maintaining of a 

 healthy condition in the tree. In cases 

 where a serious infection has made itself 

 apparent, the water should be immedi- 

 ately turned off and kept off until the 

 blight is under control. 



It is safe to say that in all irrigated 

 districts some harm usually results from 

 over-irrigation rather than under-irriga- 

 tion. The tendency to apply too much 

 water is especially the great fault with 

 beginners in irrigation. To irrigate 

 properly and scientifically one should 

 know soil conditions, soil depths and 

 drainage. Another important factor is a 

 knowledge of the duty of water; by this 

 it is to be understood the amount of 

 water which should be used to produce 

 the best results. It is well known that 

 the destruction of the pears by blight in 

 the San Joaquin valley, in California, 

 was due as much to maintaining too vig- 

 orous a growth by irrigation as it was 

 througli lack of the important detail 

 knowledge of fighting it scientifically. 

 Not only were the orchards lost, but 

 valuable soils were practically ruined by 

 over-irrigation. 



In the Eastern states it is a very com- 

 mon practice to sow a crop of cow peas, 

 sorglium, or sometimes even Indian corn 

 in the late spring. This is done to take 

 up the surplus moisture of the soil from 

 the trees, and has a tendency to check 

 luxuriant growth, and hence acts to 

 check pear blight. It must be under- 



