CITRUS CULTURE IN HAWAII 



15 



scale (Ceroplastes rubens), and the cottony cushion scale (Icerya 

 purchasi) . 



Mealybugs 



Mealybugs (Pseudococcus filamentosus) , and possibly other 

 species) occasionally attack citrus trees, particularly young nur- 

 sery stock, principally in dry weather. Most species of mealy- 

 bugs are much alike in appearance, life history, and habits. The 

 adult female varies from one-fourth to three-eighths inch in 

 length, is about half as wide, and is covered with a white waxy 

 excretion. The males are smaller than the females. All parts 

 of the plant, including the roots, are attacked. 



Control — Several special emulsions have been successfully 

 tried at the station. Essig (10, p. 128) recommends a home- 

 made emulsion with the following formula: 



CARBOLIC ACID EMULSION 



Water 40 gallons 



Whale-oil soap 40 gallons 



Crude carbolic acid 5 gallons 



He states that the water should be brought to the boiling 

 point in an iron kettle, the soap thoroughly dissolved in it and 

 the crude carbolic acid added. The whole should be boiled for 

 10 or 15 minutes. The resulting mixture should be thick, light, 

 creamy, and of milky white color. A smaller amount of this 

 stock solution may be made by reducing the proportional parts. 

 For use as a spray 20 gallons of water should be added to 1 

 gallon of stock solution. Spraying thoroughly once or twice a 

 year, when growth is the least active, is recommended for mealy- 

 bug control. 



Aphis 



The aphis or black fly {Aphis sp.) is not considered a serious 

 pest of citrus in Hawaii, but nursery stock should be kept free 

 from it by spraying. These pests usually are found in masses 

 and suck the juice or sap from the tissues of the plant. They 

 may be identified by the honeydew they excrete on most parts of 

 the plant. 



Control — Aphis, mites, and thrips may be controlled by spray- 

 ing them with a mixture prepared according to the following 

 formula : 



NICOTINE-SULPHATE SOLUTION 



Nicotine-sulphate (tobacco-leaf extract) 2 ounces 



Whale-oil, or laundry soap 3 ounces 



Water 4 gallons 



The nicotine extract may be purchased in small quantities 

 and kept stored until it is needed. For small, tender plants, the 

 nicotine sulphate may be reduced to 1 ounce, and white soap 

 substituted for laundry soap. 



Orange Rust or Lemon Silver Mite 



The orange rust, or lemon silver mite (Phyllocoptes oleivorus) 

 sometimes attacks citrus in Hawaii. It injures mainly the stems, 

 foliage, and green fruit of orange trees, especially the fruit. The 



