88 ASSOCIATION OF ECONOMIC ENTOMOLOGISTS. 



the tender twigs of white ash shade trees growing upon the streets 

 of Denver. 



It may be stated that notwithstanding its occurrence upon shade 

 as well as fruit trees it is primarily the pest of the latter. In my 

 observations in Colorado this season I have taken the species upon 

 pear, prune, plum, almond, and apple, and at elevations above sea 

 level varying from a little over 4,000 feet to about 7,000 feet. 



Injury from infestation follows from two sources, (1) the dwarf- 

 ing and robbing of the trees of their sap substance, resulting in 

 retarded growth and cracking of the bark, and (2) an unsightly 

 pitting of the surface of the fruit itself , with more or less attendant 

 discoloration about the points of scale attachment. In the case of 

 yellow skinned plums these reddened blotches about the scale situs 

 are most noticeable and objectionable. With dark-colored plums and 

 prunes the scales appear as many small white specks scattered over 

 the surface, and with the pear deep pits are found in the skin, some 

 of these measuring nearly one-fourth inch deep and as wide across 

 at the top. Bartlett pears are especially subject to attack, as are 

 silver prunes, almonds, and wild goose plums. These varieties and 

 some others when infested and allowed to go without spraying will 

 in time become completely incrusted as in the case of the San Jose 

 scale. Early descriptions of this insect gave it as a pest principally 

 upon the fruit instead of the tree. The tendency to infest the fruit 

 itself is perhaps greater than with other species of this genus, but the 

 attack is also directed to bark, twigs, and leaves. A marked prefer- 

 ence is shown for Grimes Golden apples, this variety becoming 

 infested in orchards where all other varieties are exempt; in fact, 

 Grimes Golden and Geneton are the only varieties of apples observed 

 by me to be infested. By far the greatest injury, so far as my obser- 

 vations have extended, has been done to pear, and to the orchardist in 

 certain sections it is popularly known as the " pear scale." From its 

 variety of food plants the name Howard scale is more appropriate. 



Though Colorado, so far as known, is entirely free from the San 

 Jose scale, the life history and appearance of the scale has become 

 more or less familiar to many of the more progressive orchardists of 

 the State from literature published upon the pest. Upon the discov- 

 ery of the Howard scale in injurious numbers, however, it was a 

 natural mistake for them to assume the presence of the San Jose scale, 

 and this was what occurred. The two are of rather close resemblance 

 to the unpracticed eye, and both infest their host plants in about the 

 same manner. Both are of the same genus and subgenus, Diaspidio- 

 tus. The Howard scale, however, carries a much closer resemblance 

 to the Putnam scale (Aspidiotus ancylus Putn.) of maple and other 

 trees than to the San Jose scale. 



