LEAF HOPPERS INJURIOUS TO CEREAL AND FORAGE CROPS 3 



distribution or entrance to the plant tissues. In works on the sugar- 

 cane leaf hopper in Hawaii (3, p. 107; 12, p. 21) the insect is credited 

 with increasing attacks of the fungus. A similar condition is pre- 

 sented in the case of the fungous rice blast, which, according to 

 Fulton (8) , gains entrance to the plant tissue through punctures of 

 Oebalus pugnax Fab. 



In recent years much progress has been made in the determination 

 of the relation of leaf hoppers to plant diseases, and such notable 

 cases as the curly top in beets, carried by the beet leaf hopper (Eu- 

 tettix tenellus Baker), and the yellows of asters, which has been 

 shown to be carried by the 6-spotted leaf hopper (Cicadula 6-notata 

 Fall.), have brought the injury by these insects into much greater 

 prominence. It is very possible that many other plant diseases may 

 be found to have leaf hoppers as necessary factors in their introduc- 

 tion to the plant hosts. The leaf-hopper pests of the grasses, clover, 

 alfalfa, and soybean deserve thorough study with this possibility 

 in view. 



Still another phase of injury is to be noted in the effect produced 

 upon a seed crop by the attacks of leaf hoppers on the blossom or 

 the newly forming seed. Puncture of the unfertilized blossom will 

 easily make the pollination useless, as will also the sucking of a small 

 portion of the sap from a newly set seed cause it to wither or prevent 

 its maturity. Injuries of this sort in wheat, timothy, clover, alfalfa, 

 etc., are probably of much greater frequency than is generally 

 supposed. 



Whatever view may be taken as to the extent of damage and 

 relative importance of these insects, all who have studied the subject 

 will agree that the puncturing of the tissue and the removal of the 

 plant juices must result in more or less loss to and drain on the plant. 

 Their importance then will rest more on the abundance of the insects 

 that may attack any particular plant. It is evident that an insect 

 which simply pumps away the juices of the plant may go on with 

 this operation, constantly draining the plant and reducing its rate 

 of growth, without attracting the attention of the cultivator unless 

 the injury passes the point where the drain begins to cause actual 

 wilting, withering, or visibly unhealthy condition. Nevertheless, 

 this drain must show in reduction of the crop, lessening of available 

 pasturage or forage, and actual loss, none the less real because diffi- 

 cult to estimate in dollars and cents. 



In some estimates based on the abundance of insects actually col- 

 lected in given areas it has been claimed that from 25 to 50 per cent 

 of the growth of grass may go to feed these leaf hoppers and still 

 all this loss may occur without meadow or pasture actually showing 

 by wilted or withered plants that such a drain was occurring. Only 

 in periods of drought (and then this loss may commonly be charged 

 against a dry season) is the effect such as to be noticeable in meadows 

 and pastures. 



Some idea of the number of these insects can be gained from 

 various observations and counts and some appreciation of it by 

 walking through a pasture or meadow and noticing the clouds of 

 minute leaf hoppers that spring into the air in one's pathway. Esti- 

 mates based on various captures in Iowa amounted to from a half 

 million to a million insects per acre. In testing a hopperdozer for 



