Several surveys have been conducted which illustrate that leafhoppers (Cicadellidae) occur in great abundance in tall fescue pastures and are implicated in reductions in yield and forage quality. One species of froghopper (Cercopidae), the twolined spittlebug [Prosapia bicincta (Say)] also can be a serious pest of pastures in southeastern United States (Pass and Reed, 1965).

Like aphids, leafhoppers, and froghoppers feed on plant juices. Some species are known to be important virus vectors, although they are not known to transmit virus directly to tall fescue. In a survey of the leafhopper fauna of tall fescue fields in Missouri, 54 species from 37 genera were identified (Table 9-2), with eight species occurring in sufficient numbers to be considered economically important (Quisenberry et al., 1979). In controlled experiments with one species, Forcipata loca, decreases in yield, yield per tiller, and leaf elongation rate of tall fescue were recorded as a result of infestation (Quisenberry and Yonke, 1981a). Field trials have shown this species impinged on forage quality of tall fescue, increasing neutral detergent fiber, while lowering water soluble carbohydrate levels and in vitro digestibility (Quisenberry and Yonke, 1981b).

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Table 9-2. Major Ciccadellidae (leafhopper) and Cercopidae (froghopper) species found in abundance in three surveys of tall fescue in the United States (Quisenberry et al., 1979; Kirfman et al., 1986; Muegge et al., 1991) and the response of some species to endophyte.

Another survey, conducted in Tennessee in 1981, identified 32 cicadellid species belonging to 27 genera in tall fescue pastures (Kelly and Klostermayer, 1984). These authors reported that an application of insecticide to control the leafhoppers resulted in an increase in dry matter yield in one of the 2 yr of the study. Muegge et al. (1991), when monitoring populations throughout the year in Louisiana, found 27 species of leafhoppers and one froghopper species in field plots of ‘Georgia 5' tall fescue. Of these, six ciccadellid species and one cercopid comprised 80% of the specimens collected, with these insects occurring in greatest abundance between May and August. Applications of insecticide were unsuccessful in reducing populations, but a nematicide had a significant effect.

Effect of Endophyte

The response of leafhoppers and froghoppers to endophyte is similar to the response of aphids, with some species displaying sensitivity while there is no effect on others. The abundance of one leafhopper species, Draeculacephala antica (Walker), decreased with increasing endophyte infection rates in a survey of ‘Kentucky 31' tall fescue pastures conducted by Kirfman et al. (1986) (Table 9-2). In the same study, however, populations of the gray lawn leafhopper (Exitianus exitiosis) and an issid (Bruchomorpha spp.) were correlated positively with endophyte infection, and there was no apparent relationship between endophyte and the occurrence of two other species, Agallia constricta and Endria inimica. In another study (Muegge et al., 1991), the abundance of Draeculacephala spp. was reduced greatly by endophyte infection of Georgia 5 tall fescue. Agallia constricta was also more abundant in E- plots than in E+ plots, but the effect was less marked than for the former species. Populations of two other leafhopper species, E. exitiosus and Graminella nigrifons, and one froghopper, Prosapia bicincta, also were lower on E+ plots, with densities of the latter species particularly affected.

Aside from a direct effect of N. coenophialum infection on individual species, E+ tall fescue can contribute indirectly to reducing total leafhopper species diversity (Muegge et al., 1991). Leafhopper species diversity was related positively to diversity of plant species (Quisenberry et al., 1979), which was greater in E- tall fescue fields than in fields where E+ plants predominated, and exerted a competitive advantage over other plant species (Clay 1997).

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