12 CIRCULAR 10 6, U. S. DEPARTMENT OF AGRICULTURE 



of the life cycle may be passed in the egg stage, since the earliest 

 eggs are deposited by the middle of July and the latest hatching 

 does not occur until the middle of May of the following year. 



DISSEMINATION 



Tree hoppers doubtless become introduced into distant territory 

 through the presence of the eggs in nursery stock. Adult insects 

 are also probably carried great distances in automobiles, bedding, 

 clothing, and fruit boxes which are transported from one part of 

 the country to another. The mature insect is also a strong flier, 

 and no doubt flies readily from one tree to another and from one 

 field or orchard to another. Upon hatching the young nymphs are 

 sometimes carried by the wind many feet through the air to lodge 

 upon barren soil or upon alfalfa or other food plants. 



NATURAL ENEMIES 



Two species of parasites have been reared from the eggs of the 

 green clover tree hopper (Stictocephala inermis). 8 Two determined 

 species of spiders 9 and other undetermined species, an ant 10 at least 

 two species of lady beetles, 11 several undetermined species of 

 syrphus-fly larvae, and predatory lacewing flies 12 have also often 

 been observed devouring the hatching nymphs of this species. Cer- 

 tain mites are known to destroy the eggs of both Stictocephala 

 inermis and the dark-colored tree hopper, Ceresa basalis. 13 Birds 

 and toads are also known to feed upon the tree hoppers both in their 

 nymphal and adult stages. 



PREVENTIVE AND CONTROL MEASURES 

 CLEAN CULTIVATION 



Since these insects are dependent in their developmental stages 

 upon the cover crop, such as alfalfa or sweetclover, or upon weeds 

 growing in the orchard, it is obvious that the removal of these from 

 the land before planting the orchard and keeping them out contin- 

 uously thereafter would be one of the surest methods of control. 14 



It has been found that clean-cultivated orchards are always free 

 of tree-hopper injury and that injury is most serious in orchards 

 in which alfalfa is grown as a cover crop. Under the cultural con- 

 ditions prevailing in orchards in the arid regions of the Pacific 

 Northwest, however, it is inadvisable to keep an orchard clean culti- 

 vated although the land should be freed of any such crops as alfalfa 

 before the trees are set out. 



8 Gonatocerus sp., Tetrastichus sp. 



9 PMlodromus minuta Bks. and Dendryphantes militaris Hentz. 



10 Formica fusca var. argentia Wheeler. 



11 Ad alia bipunctata L. and Hyperaspis quadrivittata Lee. 



12 Genera Hemerobius and Chrysopa. 



13 Genus Achorolophus, family Erythraeidae. 



"References to food habits and control do not apply to the crested, brown-mottled tree 

 hopper {HeUria rubidella), which occurs in considerable numbers in the Wenatchee Valley, 

 Wash., since this species feeds throughout its entire nymphal period upon the fruit trees 

 and is not dependent upon cover crops for its sustenance. Since this species also deposits 

 its eggs in the fruit-tree twigs, however, it is probable that all methods of control other 

 than clean cultivation, especially the use of dormant oil sprays, would prove equally 

 adequate for it. 



