10 FARMERS BULLETIN 862. 



80° F. or during the summer when the trees are hiden with immature 

 fruit. Should it appear advisable to employ a spray during the 

 summer, water under pressure should be used, as this can be applied 

 safely, even when the highest summer temperatures prevail. 



WATER SPRAYING. 



An increasing number of growers are using successfully water 

 under pressure so as to dislodge the mealybugs forcibly from citrus 

 trees. This method of control was demonstrated in several orchards 

 during the years 1915 and 1916, with varjdng degrees of success. 

 Control of mealybugs by water spraying is practicable in the case 

 of all citrus fruits excepting possibly the navel orange, but its suc- 

 cess depends on thorough and repeated applications. Especially is 

 this true of the navel orange, which requires such a large number of 

 applications that the method is generally impractical in extensive 

 and severe infestations. 



Water has one important advantage over all other sprays in that 

 it may be used with safety in unlimited quantities at any time 

 of the year, thus affording a means of combating mealybugs during 

 the summer months wdien practically all insecticides of value are 

 too injurious to fruit and foilage to justify their application. 



Several matters have a very important bearing on the successful 

 commercial use of water spraying. In orchards the cost can be 

 reduced materially by installing a system of piping, the power 

 being derived from the water main, a stationary piunp, or a power 

 sprayer. The piping should be of a diameter to give ample force. 

 The best type of nozzle allows an uninterrupted flow through an 

 aperture not larger than one-fourth of an inch. The writers 

 devised a very satisfactory direct-discharge nozzle having a rec- 

 tangular opening 6 by 2 millimeters and capable of delivering 6 to 

 7 gallons a minute under 100 pounds pressure. The common garden 

 type or a :^-inch fire nozzle, however, will serve the purpose. Nozzles 

 with small openings, as those of the Bordeaux type, are unsuitable 

 for water spraying, as the stream of water will strip the leaves and 

 cut off fruit. The tops of the trees should be sprayed from a ladder. 

 Twenty to thirty minutes are required for spraying thoroughly a 

 tree 10 to 15 years old. 



CONTROL BY NATURAL ENEMIES.' 



No important citrus insect pest in California seems to be attacked 

 by mpre natural enemies than the mealybug, and efficient control of 



1 The more effective enemies of this species, including both predators and parasites, 

 given in the order of their importance, are: SympJierobius barberi Banks, i?. caUforiiicua 

 Banks, Hnperaspis lateralis Muls., Crijptolacmus montrouzieri Muls., Chrysopa califor- 

 nica Banks, Lcucopis bclla Loew, and Paralcptomastix abnonnis Girault. 



II 



