Larval Survival and Movement of Bluegrass Webworm in Mixed Stands of Endophytic Perennial Ryegrass and Kentucky Bluegrass

Abstract

Studies examined bluegrass webworm, Parapediasia teterrella (Zincken), larval pop- ulation density and movement in relation to the proportion of perennial ryegrass, Lolium perenne L., plants infected with the fungal endophyte Neotyphodium lolii Glenn, Bacon, Price & Hanlon (PR1), in mixed stands with Kentucky bluegrass, Poa pratensis L.) (KB), and the impact of endophyte infection on feeding preference, growth, and survival of P. teterrella larvae was evaluated. Inchoicetests, P.teterrella larvaedidnotdiscriminatebetweenKBandPR2,butbothwerepreferred over PR1. Larval survival and pupal mass did not differ between KB and PR2, but were significantly reduced on PR1. There was a negative linear relationship between larval population density and the proportion of PR1 in mixed stands with KB until that proportion reached 0.40, after which further reductions in larval populations were not significant. The percentage of larvae surviving in pots after 30 d was independent of initial larval density. Larval movement, as measured by emigration from pots in the greenhouse, increased as the proportion of PR1 increased but was never .50% of the larval population. Through increasing larval movement and mortality, mixed turfgrass stands containing as little as 40% PR1 should prove useful as a pest management tool for P. teterrella.