Leaf hoppers suck on the sap supply of the leaves.
"The School Book of Forestry" by Charles Lathrop Pack
These are the leaf hoppers.
"The Insect Folk" by Margaret Warner Morley
The leaf-hoppers are a great nuisance.
"Little Busybodies" by Jeanette Augustus Marks and Julia Moody
Others are flat-headed apple borers, lace-wing fly, aphis, leaf hoppers.
"Northern Nut Growers Association Thirty-Fourth Annual Report 1943" by Various
Siphonata: = Homoptera or, more specifically, plant lice and leaf hoppers.
"Explanation of Terms Used in Entomology" by John. B. Smith
Figures 41 and 42 show the several life stages of the leaf-hopper.
"Manual of American Grape-Growing" by U. P. Hedrick
To this order belong the true bugs, the plant lice, leaf hoppers, frog hoppers, cicadas, etc.
"Handbook of Medical Entomology" by William Albert Riley
It is apparently spread by leaf hoppers.
"The Tomato" by Paul Work