THE CITRUS THRIPS. 39 



The second application should be timed to prevent injury both 

 from larvae issuing from the very young fruits and from adults 

 emerging from the pupal stage existent at the time of the first appli- 

 cation. This renewed attack may be expected to reach the danger 

 point in from 10 to 14 days after the first spraying. The second 

 spraying should not be delayed too long, as comparatively few 

 larvse may, by constantly feeding in a circle about the base of the 

 fruit, cause deep ring scarring. Special effort should be made to 

 drench only the fruit and the remaining tender leaves. 



The third application may be delayed longer if the first two have 

 been thorough and well timed. It generally takes the insects from 

 three to four weeks to become dangerously numerous again, as 

 they reinfest the sprayed trees much more slowly after the second 

 spraying. 



All three applications should be completed by the time the fruit 

 is half grown, after which it rapidly loses its attractiveness for the 

 insects, which then find it necessary to spread out over the compara- 

 tively scant tender orange growth and miscellaneous food plants. 



During the latter part of August and early in September there is 

 usually another abundant growth of orange shoots, and upon this 

 the thrips congregate in large numbers. A fourth application during 

 this period is advisable in some seasons to prevent severe injury to 

 this growth, which is often the most abundant of the season. 



The first spray application to nursery stock should be made when 

 thrips become numerous on the spring growth and before their in- 

 jury becomes very evident, usually between April 15 and May 15. In 

 the case of trees budded in the fall the shoots springing from the 

 original stock should be cut back the following spring as soon as the 

 bud has attained a good growth. All the primings should be burned 

 to destroy contained eggs and larvse. In Tulare County this pruning 

 and burning usually can be accomplished during April. The grow- 

 ing scions must then be watched closely and as soon as thrips occur 

 in numbers spraying should begin. From two to four further ap- 

 plications should follow the first spraying, depending upon the num- 

 ber of growths and the degree of infestation. 



SUGGESTIONS FOE SPEAYING. 



The gasoline-power outfit, by reason of its large nozzle capacity, 

 reliability, and comparatively low cost of operation, is recommended 

 for spraying bearing orchards, young orchards in excess of 10 acres, 

 and large nurseries. Hand-power outfits, when of a type capable of 

 maintaining a pressure of not less than 125 pounds, are suitable for 

 spraying seed-bed and nursery stock and young orchards of small 

 acreage. 



The spraying outfit should be in perfect running order not later 

 than April 1, with the insecticide materials at hand and conveniently 



