14 TENTH BIENNIAL REPORT 



Red Spider: (Tetranychus himacylatus Harv. and Bryohia pra- 

 tensis Garm.) This pest is present to some extent but has not done 

 a considerable amount of injury to the orchards and is easily con- 

 trolled by spraying. 



Aphids : (Many species.) These sucking insects occur in practic- 

 ally all the orchards and are of many different species. The green 

 aphids which feed on the leaves and growing twig tips are the most 

 common, but in some places' the woolly aphids, which feed both on 

 the roots and upper parts of the tree, are becoming established. The 

 green aphids can be controlled by spraying, but satisfactory results in 

 combating the woolly aphids are hard to secure. The total damage 

 to the fruit crop is not alarming. 



Physiological Conditions 



Many conditions are noticeable in Montana orchards, and else- 

 where, which cannot be attributed to any insect pest or to any specific 

 disease organism. While some of these conditions seem to be re- 

 sulting in considerable damage, others are not sufficiently wide- 

 spread or common enough to be a serious menace to the fruit in- 

 dustry. Chief among the conditions which may be for convenience 

 classed under this head are winter injury, malnutrition and brown 

 bark spot. 



Winter Injury: Winter injury is noticeable to a more or less 

 extent in all of the fruit growing districts and is also noticeable in 

 nearly all kinds and varieties of fruit. Some kinds like the sweet 

 cherry are much more easily affected by low temperature than others, 

 but no kind of fruit has entirely escaped injury. In the Bitter Root 

 valley the sweet cherry trees have almost become a memory, consid- 

 ered from the standpoint of commercial production. Only a few 

 tracts remain which are at all in good condition. The winter 

 injury to apple trees has not caused any serious damage in those 

 orchards which are well located and properly cared for, but in the 

 low lying areas many of the young orchards have been seriously set 

 back if not actually destroyed. It is impossible to avoid by any sort 

 of care the effects of low temperatures if conditions are right for 

 winter killing, but by proper cultivation, fertilization cf the soil and 

 irrigation it is possible to reduce the effect of bad winters very ma- 

 terially. 



