HORTICULTURAL ENTOMOLOGY Black cutworm (Lepidoptera: Noctuidae) Larval Emigration and Biomass in Mixtures of Endophytic Perennial Ryegrass and Kentucky Bluegrass DOUGLAS S. RICHMOND 1 AND DAVID J. SHETLAR Department of Entomology, the Ohio State University, OARDC, Wooster, OH 44691 J. Econ. Entomol. 94(5): 1183Ð1186 (2001) ABSTRACT Studies examined the possibility that mixtures of endophytic perennial ryegrass and Kentucky bluegrass provide resistance against larvae of the black cutworm, Agrotis ipsilon (Hufna- gel). We hypothesized that resistance against A. ipsilon insuchstandswouldstemfromtheinßuence of Kentucky bluegrass on A. ipsilon growth and behavior rather than the inßuence of endophytic perennial ryegrass. In replicated greenhouse experiments, black cutworm larvae initially emigrated more quickly from pots containing monocultures of endophytic perennial ryegrass than from Kentucky bluegrass monocultures or polycultures of Kentucky bluegrass and endophytic perennial ryegrass. However, biomass of emigrating larvae decreased linearly as the proportion of Kentucky bluegrass increased. Turfgrass mixtures containing endophytic perennial ryegrass and Kentucky bluegrass may provide resistance against A. ipsilon mainly through the physiological effects of Kentucky bluegrass on A. ipsilon growth and development, but possibly through the inßuence of endophytic perennial ryegrass on A. ipsilon movement and foraging behavior as well. KEY WORDS Agrotis ipsilon, black cutworm, endophyte, perennial ryegrass FUNGI IN THE genus Neotyphodium (=Acremonium) formmutualisticsymbioseswithseveralimportantfor- age (Fletcher and Easton 1997), cereal (Bishop et al. 1997), and turfgrass (Breen 1994) species. These fungi dependonthegrasshostmainlyfornutritionwhilethe plant beneÞts from an array of defensive alkaloids that can provide both antibiosis and antixenosis resistance against leaf-feeding insects (Saikkonen et al. 1998). Studies have shown that turfgrass mixtures containing only a moderate proportion of endophytic plants can signiÞcantly reduce populations of insects such as sod webworms (Richmond and Shetlar 1999). However, larvae of the black cutworm, Agrotis ipsilon Hufnagel, areamongagrowinglistofherbivorousinsectsthatare relatively unaffected by the presence of fungal endo- phytes in plants (Williamson and Potter 1997). We may, therefore, expect turfgrass mixtures containing endophyte-infected grasses to provide little resistance against A. ipsilon. Conversely,Kentuckybluegrass, Poa pratensis L.,isresistantto A. ipsilon larvaeeventhough Neotyphodium endophytesarenotassociatedwiththis species (Williamson and Potter 1997). This implies that turfgrass mixtures containing both endophytic perennial ryegrass and Kentucky bluegrass may pro- vide some measure of resistance against A. ipsilon while maintaining resistance against other insects. However, the inßuence of Kentucky bluegrass-endo- phytic perennial ryegrass turfgrass mixtures on A. ip- silon has not been examined. It is generally accepted that interspersion of host and nonhost plants (i.e., polyculture) can lower insect population density through various mechanisms. These mechanisms include altering insect movement and foraging behavior, modifying host plant suitabil- ity, and enhancing the action of natural enemies (Coll and Bottrell 1994). With regard to insect movement, mixtures of host and nonhost plants can make suitable hosts difÞcult for insects to Þnd (Kareiva 1983) and increase their vulnerability to natural enemies while foraging (Bergelson and Lawton 1988). Similarly, be- cause of allelopathic, competitive, or beneÞcial inter- speciÞc effects, host plant quality may also differ be- tween monocultures and polycultures (Bach 1980) and the suitability of individual plants for herbivore growth and reproduction may be altered through in- teractions with conspeciÞcs. Although turfgrass mixtures have been used to en- hance turfgrass persistence and durability (Watschke and Schmidt 1992), very little has been done to de- terminehowmixedstandsofturfgrassinßuenceinsect pests. In particular, the use of turfgrass mixtures as a cultural management tool for A. ipsilon has not been examined. We conducted experiments to determine how mixtures of Kentucky bluegrass and perennial ryegrass, Lolium perenne L., infected with the fungal endophyte Neotyphodium lolii Glenn, Bacon, Price & Hanlon inßuence A. ipsilon foraging behavior and bio- mass. Experiments were conducted in the greenhouse using pots containing various combinations of endo- phytic perennial ryegrass and Kentucky bluegrass. Larval emigration from the pots was monitored over 1 E-mail: richmond.16@osu.edu. 0022-0493/01/1183Ð1186$02.00/0  2001 Entomological Society of America