2 BULLETIN 254, U. S. DEPARTMENT OF AGRICULTURE. 



ECONOMIC IMPORTANCE AND MODE OF INJURY. 



The economic importance of the Jassidse has never been fully appre- 

 ciated by the farmer and planter, nor have these insects been given 

 the attention which they deserve, even by entomologists. Especially 

 is this true of the sharp-headed grain jassid, one of the most widely 

 distributed species with a great variety of food plants. While it 

 probably may not become a destructive pest over wide areas, there 

 is always the possibility of local outbreaks which may cause serious 

 injury and temporary losses, as exemplified by the attack upon 180 

 acres of corn on the farm of Dr. O. R. Stewart, Palatka, Ark., during 

 July, 1912. It no doubt occurs in small numbers every year over its 

 entire range of distribution and causes secondary injury to grain 

 and pasture grasses by attacking vigorous growing plants, hindering 

 and interfering with their growth and development, and already weak- 

 ened and unhealthy plants, hastening their death or permanently 

 dwarfing them. 



The greatest damage inflicted by the sharp-headed leafhopper is to 

 young and tender gram crops by the feeding of nymphs and adults 

 during the fall and early spring months. To corn and other crops the 

 greater damage is done during the summer months. Because alfalfa 

 is of such rapid growth the apparent injury to the crop will probably 

 always be very slight. 



There are three classes of injury, the most important of which is 

 the direct injury caused by the feeding of nymphs and adults, in 

 puncturing leaf and stem tissue and sucking the juices therefrom. 

 An occasional feeding puncture in a leaf or stem would not of itself 

 do appreciable harm, but when there is a concentrated attack upon 

 a plant by from 10 to 50 nymphs or adults the injury becomes ap- 

 preciable. In many instances the author has observed leaves with- 

 ered throughout from this cause. The early stages of injury are in- 

 dicated by a yellowing of the tissue around the feeding punctures, 

 which are in themselves so small as to be hardly visible to the naked 

 eye. Following the yellowing there is a drying and deadening of 

 tissue which turns reddish brown, giving the leaf or stem a spotted 

 appearance. 



Ordinarily the feeding of the nymphs is more injurious to a plant 

 than that of the adults because usually there are to be found a great 

 many more nymphs than adults on the same plant. It is believed 

 that nymphs, after hatching from the eggs, often remain on the same 

 plant during the first two or three instars. The feeding of the 

 nymphs in grain is practically limited to the throats of the plants; 

 however, they will feed on almost any tender or succulent part. 

 In the case of alfalfa the feeding is done on the underside of the 

 leaves and upon young tender stems. The adults feed freely upon 



