Proceedings of the Third International Conference on Invasive ...

<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 4: Spartina Control and ManagementInfestation Rate ± SE1.0000.8000.6000.4000.200Emilie RueckerFox HillGreenwich CoveSuccotashTouisset0.000ChaetopsisLanguria taedataCalamomyia alternifloraeHaliaspisProkelisia / TrigonotylusOrchelimumFig. 3: Infestation rates <strong>of</strong> Spartina herbivores at five marshes. Feeding damage caused by Prokelisia spp. and that caused byTrigonotylus uhleri were not distinguishable.There were significant differences among sites in <strong>the</strong> rates <strong>of</strong>infestation by Chaetopsis spp. Loew (Diptera: Otitidae) (p =0.0007), Languria taedata LeConte (Coleoptera:Languriidae) (p = 0.0025), Calamomyia alterniflorae Gagne(Diptera: Cecidomyiidae) (p < 0.0001), Haliaspis spp.Takagi (Homoptera: Diaspididae) (p < 0.05), and <strong>of</strong> leafchewingdamage (p < 0.0001). Infestation by Chaetopsisspp. was associated with an average stem height reduction <strong>of</strong>24.8%, although <strong>the</strong>se results were not significant.DISCUSSIONThe results <strong>of</strong> vacuum sampling suggest that <strong>the</strong>re islittle variation in S. alterniflora herbivore communitycomposition among Rhode Island marshes. The apparentrarity <strong>of</strong> Orchelimum spp. and <strong>the</strong> absence <strong>of</strong> o<strong>the</strong>r speciesin vacuum samples was likely due to limitations <strong>of</strong> <strong>the</strong>sampling methods. Vacuum sampling used in this surveymay have provided more opportunity for evasion than sweepnetting used in previous studies (Davis and Gray 1966;Vince et al. 1981). Seasonal variation in communitystructure is also <strong>of</strong> importance as adult forms <strong>of</strong> many stemboringspecies are only present in limited intervals (Newton1984). To alleviate <strong>the</strong> inherent biases <strong>of</strong> this samplingmethod, surveys <strong>of</strong> community composition should include awider array <strong>of</strong> sampling methods and increased frequency <strong>of</strong>sampling throughout <strong>the</strong> season.Analysis <strong>of</strong> feeding damage to S. alterniflora stemsprovides sufficient evidence to warrant fur<strong>the</strong>r investigation<strong>of</strong> some species as possible biological control agents.Although sap-sucking insects caused <strong>the</strong> highest frequency<strong>of</strong> damage, <strong>the</strong>y did not cause <strong>the</strong> severity <strong>of</strong> damageassociated with <strong>the</strong> infestation by Chaetopsis aeneaWiedemann and C. apicalis Johnson. The larvae <strong>of</strong> <strong>the</strong>seflies destroy <strong>the</strong> shoot apical meristem <strong>of</strong> all infested stems,effectively stopping growth and preventing flowering. Thereexists, however, significant variation in <strong>the</strong> proportion <strong>of</strong>stems damaged by Chaetopsis spp. both among sites andwithin sites. This variation may be explained by differencesin variables such as plant nutrition, plant resistance, tidalfluctuation, and water salinity. Newton (1984) demonstratedthat salinity was strongly correlated to <strong>the</strong> infestation rates <strong>of</strong>several stem borers. Denno et al. (2000) investigated- 275 -