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Title: STEMBORERS ASSOCIATED WITH SMOOTH CORDGRASS, SPARTINA ALTERNIFLORA (POACEAE), IN A NURSERY HABITAT

Author
item White, William
item Adamski, David
item FINE, G - USDA, NRCS
item Richard Jr, Edward

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2005
Publication Date: 11/11/2005
Citation: White, W.H., Adamski, D., Fine, G., Richard Jr, E.P. 2005. Stemborers Associated with Smooth Cordgrass, Spartina Alterniflora (Poaceae), in a Nursery Habitat. Florida Entomologist. 88(4):390-394.

Interpretive Summary: Smooth cordgrass is a native coastal grass of many Atlantic, Gulf, and Pacific intertidal marshes that is being used in Louisiana for shoreline and near-shore building, erosion control along shorelines and canal banks, and for stabilization of loose soil on mud flats and dredge-fill sites. As a result, a nursery industry is developing to meet the increased need for smooth cordgrass plant material. Currently, little is known of the insects that infest smooth cordgrass in these nursery situations, or of the potential of smooth cordgrass to serve as a host for introduction and distribution of potentially important pests such as stem borers to the Louisiana and rice sugarcane industries which border many of these nurseries. We surveyed nursery plots for the presence of stem boring insects and studied their feeding behavior on the plant. Six species of stemborers were found during our survey and these were found to utilize different areas of the plant. Two of the species found are considered pests of sugarcane and one of rice. This research is important to those individuals developing a cordgrass nursery industry because information on the insect species infesting cordgrass and their behavior would be critical to establishing effective control measures should they be needed. Additionally, this study is of benefit to regulatory agencies as it demonstrates the potential of important agricultural pests to be distributed with nursery material.

Technical 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 resource partitioning among stemborers infesting 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 stem, height of stem from ground level to top-visible dewlap, and condition of the stem meristem were documented. Stemborers representing six species of Lepidoptera were recovered. These species were: Blastobasis graminea (Lepidoptera: Coleophoridae); a four-species complex comprised of [Diatraea saccharalis (F.), Chilo demotellus Walker, Chilo plejadellus Walker, and Thaumatopsis probably actuella Barnes (Lepidoptera: Crambidae)]; and Donacaula probably unipunctella Robinson (Lepidoptera: Crambidae). Larvae were partitioned on the smooth cordgrass plant 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 (x' = 6.7 cm). The stemborer complex was the next most abundant (n=85; 35 %) and was always found within the stalk about mid-way up the stem (x' = 16.7 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 (x' = 23.6 cm). A total of 544 (52%) of the stems sampled had a dead stem meristem, but of the only 140 (26%) were infested. Stemborer species did not significantly affect the number of plants with and without deadhearts.