Stemborers Associated with Smooth Cordgrass, Spartina alterniflora (Poaceae), in a Nursery Habitat

Abstract

Extensive ecological studies have been conducted on insects inhabiting native stands of smooth cordgrass, Spartina alterniflora Loisel; however, this is not the case for insects found in smooth cordgrass in a nursery habitat. We investigated species composition and larval disposition among stemborers (Lepidoptera: Coleophoridae and Crambidae) infesting stems of smooth cordgrass in nursery plots. One thousand and forty stems of smooth cordgrass were randomly selected in 2003 and examined for presence of stemborer larvae. Height of larvae on or within stem, height of stem from ground level to top-visible dewlap, and condition of the leaf-whorl were documented. Stemborers representing six species of Lepidoptera were recovered. These species were Blastobasis graminea Adamski (Lepidoptera: Coleophoridae); a four-species complex comprised of Diatraea saccharalis (F.), Chilo demotellus Walker, Chilo plejadellus Zincken, and Thaumatopsis probably actuella Barnes & McDunnough (Lepidoptera: Crambidae); and Donacaula probably unipunctella Robinson (Lepidoptera: Crambidae). Larvae were generally on different parts of the stem and, with the possible exception of larvae of the four-species complex, seemed unlikely to contact one another. Blastobasis graminea was the most abundant species collected (n = 128; 52%) and was located at the base of the stem (eq x eqx- = 6.7 ± 5.4 cm). The four-species complex was the next most abundant (n = 85; 35%) and was always found within the stalk about mid-way up the stem (eq x = 16.7 ± 8.6 cm). Donacaula sp. was the least abundant species (n = 32; 13%) and was always found in the tight leaf-whorl just above the stem meristem (eq x = 23.6 ± 15.4 cm). A total of 544 (52%) of the stems sampled had a dead leaf-whorl, but only 140 (26%) were infested. Stemborer species did not significantly affect the number of plants with and without deadhearts.

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