374 THE MONTHLY BULLETIN. 



CALENDAR OF INSECT PESTS AND PLANT 



DISEASES. 



By E. J. VosLER, Assistant Superintendent State Inse^tary. 



[Under the above heading the author aims to give brief, popular descriptions and 

 metliods of controlling insect pests and plant diseases as nearly as possible just prior 

 to or at the time when the suggestions given should be carried into effect by the 

 growers.] 



CITRUS FRUIT INSECTS. 



The Purple Scale. 



The female purple scales are long and oyster shaped, varying from 

 one sixteenth to one eighth of an inch in length. The color of the 

 scales varies from a reddish-brown to purple. This pest attacks the 

 leaves, branches and fruit of the citrus tree, causing the branches to 

 die and the leaves to drop. Because of the resistance of the eggs of 

 the purple scale to fumigation, it is one of the most difficult of the 

 citrus infesting scales to control. According to Quayle, Bulletin 214, 

 California Experiment Station, the period of egg deposition is from 

 three to four weeks, and from the time the eggs first appear until the 

 last ones hatch, there is, therefore, a period of about two months, so 

 that when two treatments are made for this scale about six weeks ought 

 to be allowed between fumigations. Fumigate with full schedule No. 1, 

 consisting of one and one half ounces of potassium cyanide to every 

 one hundred cubic feet of space, or three fourths of this dosage for 

 sodium cyanide, this fumigation usually being done when the black 

 scale is in the right stage to be destroyed. 



For details of fumigation the reader is referred to pages 318 to 336 

 of volume II, Nos. 1 and 2, of the Monthly Bulletin of the State Com- 

 mission of Horticulture, by E. 0.' Essig. 



The Red Scale. 



Another important scale enemy of the citrus tree is the red scale. 

 The injury from the red scale is due directly to the feeding, and 

 whether this is due to the loss of sap or to some toxic effect on the 

 tissues of the plant is not kno^^^l. The red scale does not give off 

 honey-dew like the black. This enemy is reddish, circular and flat, 

 the female scales being from one sixteenth to one eighth of an inch in 

 diameter. The young are usually produced from June to September, 

 or even longer in milder sections. It attacks all parts of the tree, 

 being particularly abundant on the twigs and branches. It is distrib- 

 uted throughout the southern citrus belt, particularly San Diego, 

 Orange, Los Angeles, Riverside, San Bernardino and Santa Barbara 

 counties. Fumigate with Schedule No. 1, made by R. S. Woglum of 

 the United States Bureau of Entomology. This dosage consists of one 

 and one half ounces of potassium cyanide, one and one half fluid ounces 

 of sulphuric acid and four and one half fluid ounces of water to every 

 one hundred cubic feet of air space. 



