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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



on pomegranate, nightshade, elm, and Enghsh walnut where these 

 occur near infested citrus. Its origin is at present unaccounted for, 

 but further studies may place it under some foreign form already de- 

 scribed. The fact that it is a pest at present of citrus entirely and has 

 not been taken on any native plant seems to indicate that it has been 

 introduced. 



The citricola scale has spread very rapidty in some sections. While 

 it was practically unknown in Tulare County two years ago, it now^ 

 occurs in most of the citrus sections of that county. It occurs in 

 such abundance in some groves there that, on account of the weaken- 

 ing effect on the tree, fruit production has fallen off as much as 50 to 

 75 per cent. Fumigation and scale control was unknown in that county 

 until the present year, but during this season a very general inaugura- 

 tion of such measures has been made. Excepting in a few localities, the 

 infestations in southern California are not so severe as in the San 

 Joaquin sections. The further fact that this scale is susceptible to 

 fumigation for so short a period makes it an important economic factor 

 / in the citrus industry of California. 



Aside from the general economic differences between this species 

 and C. hesperidum, the life-history and habits differ in the two species. 

 C. citricola always deposits eggs which may hatch immediately or after 

 a day or two. In C. hesperidum the young are brought forth alive. 

 There are several generations a year of C. hesperidum, while there is 

 but one or a partial second in the case of citricola. Many of hesperidum 

 may mature on the leaves, while citricola invariably migrates back to 

 the twigs. 



The young of C. citricola began to appear in 1914 about April 20 

 and continued until August. They settle on the leaves almost entirelj^, 

 and mostly on the under side. In November and later they migrate 

 back to the twigs. During the summer, fall and winter, they grow 

 but little but rapidly mature in the early spring. The first molt occurs 

 approximiately one month from birth and the second molt a month 

 later. 



The following identified species of parasites have been reared from 

 this scale: Coccophagus lunidatus How., C. lecanii, C. flavoscuiellum 

 How., Aphycus Jiea,r flavus. One or two others are not yet identified. 



A peculiarity in the control of this species is that it becomes very 

 resistant to fumigation after early in September. No evident changes 

 in the scale itself have been noted at this period. The black scale and 

 others at the same size would be very readily killed by fumigation. 

 Spraying has not proved to be very satisfactory, as is the case of all 

 spraying for scale insects on citrus trees. Fumigation, between July 

 15 and September 15, has proved satisfactory, and is the treatment rec- 

 ommended. 



