INSECTS INJURIOUS TO CITRUS FRUITS 



623 



the growth of the plant. Injury to young fruits often results in a 

 large amount of dropping. Splitting and other deformation of the 

 fruit is another evil 

 effect of thrips in- 

 jury. 



The California 

 thrips is trans- 

 ported from place 

 to place for the most 

 part on young trees 

 where it is present 

 in the egg stage. 

 Local spread is the a 



result of the flight 

 of the adults. It 

 is not confined to 

 the citrus plants, 

 but feeds on several 

 others such as 

 grape, pomegran- 

 ate and apricot and 

 these may serve as 

 sources of infesta- 

 tion. The life cycle 

 requires about a c 



month and there FIG. 534. Citrus Thrips: a, Young nymph; 6, Full grown 

 are from six to eight n y m P h ; c, Adult. After Horton, U. S. Dept. of Agr. 



generations which overlap so that they are practically indistin- 

 guishable. The winter months are passed in the egg stage. The 

 Florida flower thrips is present everywhere and infests the 

 blossoms of many plants. 



Control. Natural enemies are an important factor in thrips 

 control. They include larvae of the lace-wing flies (Chrysopa 

 calif ornica Coq.), lady-bug larvae, some of the assassin-bugs 

 (Reduviidce) several species of spiders and a fungus disease. In 

 some years these enemies will render artificial control measures 

 unnecessary. 



Spraying is resorted to for control where any artificial measures 



