LOUISIANA CIRCULAR No. 4. 13 



While the San Jose scale cannot be considered as a serious 

 pest of pecan, walnut and other fruit and forest trees, still it 

 must be remembered that such plants, when carrying the scale, 

 may serve as sources of infestation for peach or other orchards. 

 Even though the pest may breed for several generations upon a 

 nut or forest tree, barely maintaining its existence, when spread 

 or transferred from this unfavorable host plant to a favorable 

 one, such as a peach or plum tree, it again breeds as rapidly as 

 ever and becomes fully as destructive as if it had not been forced 

 to subsist for one or more generations under adverse conditions. 



Scale Insects Often Mistaken for the San Jose. 



The finding of scale insects in an orchard is not of itself 

 proof that the orchard is infested with San Jose scale, for there 

 are a number of other insects, native to Louisiana, that closely 

 resemble it. Among these may be mentioned the Cherry scale, 

 Putnam's scale, Gloomy scale and the Obscure scale. Unlike the 

 : San Jose scale these native species are preyed upon to a very con- 

 siderable extent by ladybugs and other predacious insects which 

 tend to hold them in check. Their rate of increase is not nearly 

 so great as that of the San Jose and hence they are not nearly so 

 injurious. 



The Cherry scale* can be found in almost any peach orchard 

 but usually in only limited numbers. While of nearly the same 

 size as the San Jose scale, it is more flattened and has the exuviae 

 (composing the central elevation of the scale itself) of an orange 

 red color. As a usual thing the individual scales of this species 

 are widely scattered over a tree and are parasitized to a marked 

 extent. In only one case have we seen this species abundant 

 enough to cause appreciable injury. Owing to the general oc- 

 currence of the Cherry scale, cases are often found where both 

 this scale and San Jose occur together upon the same tree. While 

 the two species have characters by which they are readily sepa- 

 rated when a microscopical examination is made, they are fre- 

 quently difficult to distinguish in the field, and in many case 

 cannot be distinguished except by one thoroughly familiar 

 scale-insects. 



* A apidiotus forbesi. 



