CHAPTER I. 



INSECTS INJURIOUS TO CITRUS TREES. 



THE BLACK SCALE. 



{Leeanium o^ete— Bernard.) Order, Hem- 

 iptera; sub-order, Homoptera; family, 

 Coccidce. 



[A dark brown hemispherical scale in- 

 sect, or bark-loiise, which infests all va- 

 rieties of citrus trees, and nearly all 

 varieties of deciduous fruit trees, and 

 many shrubs, vines, etc.] 



The black scale is more generally found 

 in the orchards and gardens of California 

 than any other species of the Coccidce. 



It infests the orange, lemon, lime, olive, 

 apple, pear, peach, apricot, plum, prune, 

 clieiry and pomegranate trees. In the 

 garden it infests the honeysuckle, chrys- 

 anthemum, rose, oleander, and many 

 other plants ; and this, or a closely allied 

 species, infests the forest trees. The pres- 

 ence of this species can be readiU^' de- 

 ^ tected by the appearance on the branches, 

 foliage and fruit of a black smut, known 

 to scientists as Fumago sciiicina, and the 

 cause of its production is a question upoii 

 which authorities ditiV^r. I am convinced, 

 from practical investigation, and also from 

 information received from Mr. Alexander 

 Craw, and Mr. Wolfskill, of Los Angeles, 

 and the late A. B. Clark, of Orange, Los 

 Angeles countv, that the black smut is 

 caused by a honeydew exuded by the 

 females of the black scale insect, in the 

 stage of their life between the first forma- 

 tion of the calcareous secretion by which 

 the insect is covered, and their reaching 

 maturity or becoming fixed to any part of 

 the plant. 



In relation to this smut or fungus, Pro- 

 fessor Barlow writes : "The result of our 

 examination of the diseased orange and 

 olive leaves is briefly as follows : The 

 disease, although first attracting the eye 

 by the presence of the black fungus, is 

 not caused by it, but rather by the attack 

 of some insect which itself deposits some 

 gummy substance on the leaf and bark, 



or so wounds the tree as to cause somo^ 

 sticky exudation on which the fungus 

 especially thrives. It is not denied, 

 that the growth of the fungus great- 

 ly aggravates the trouble already 

 existing by encasing the leaves, thus 

 preventing the action of the sun- 

 light. We only say that in seeking a 

 remedy we are to look further back than 

 the fungus, itself, to the insect, or what- 

 ever it may be, which lias made the lux- 

 uriant growth of the fungus possiVjle. 



The smut or fungus is found on the- 

 branches, foliage and fruit of orange^ 

 lemon, lime and olive trees infested by 

 the black scale. I have also seen apricots 

 and peaches, taken from trees infested by 

 this insect, so thoroughly covered by this 

 smut that it destroyed their market value 

 for canning purposes. 



Natural History.— The black scale 

 when full grown is of a dayk brown color,, 

 neaily hemispherical in form, but is 

 slightly longer than broad ; length, from 

 two to two and a half lines^'^; width, about 

 two-thirds of the length ; height, one and 

 one-half lines ; there are two ridges or 

 bars across the body, apparently dividinj4; 

 it into three parts, the middle being the 

 largest; a sliort ridge along the back joins 

 the two cross ridges, forming lines resem- 

 bling the letter H; the edge of the cover- 

 ing of the insect resting on the wood,, 

 foliage, etc., is margined, and has a 

 grooved or fiuted appearance nearly one- 

 half the height of the insect. 



The eggs are ovai in form ; when first 

 laid, whitish ; before hatching, a reddish 

 yellow. From seventy-five to one hun- 

 dred and seventy-five are deposited by 

 each female of this species. 



The larva is one-seventy-fifth of an inch 

 long; width, five-eighths of length; form, 

 oval; antennae, six or seven jointed. From 

 the time the secretions begin to form until 



*A " line " as here used is one-twelfth of an inch 



