Impact of Ischnodemus falicus (Hemiptera: Lygaeidae) on Photosynthesis and Production of Spartina pectinata Wetlands

Abstract

Wetlands dominated by the C4 grass. Spartina pectinata (Link), were investigated to quantity the effects of high densities of lsehnodemus falicus (Say) on leaf-level photosynthesis and aboveground biomass production. Photosynthetic rates of plants within heavily infested stands were greatly reduced from that of plants supporting low densities of I. falicus . In early May 1993, photosynthetic rates of S. pectinata with minor I. falicus presence were >30 μmol m−2 s−1 with peak rates of 45 μmo1 m−2 s−1 in mid-June. In nearby infested S. pectinata wetlands, individual plants had rates as low as 5 μmol m−2 s−1 in early May and peak rates of 24 μmol m−2 s−1 in mid-July. Along with reduced photosynthetic rates, plants hosting high insect densities had lower aboveground production than did plants that had low insect densities. In 1994, when insect densities were ubiquitously low, there were no differences in peak photosynthetic rates or biomass accumulation between stands of S. pectinata that had been host to high versus low densities of insects in 1993. Thus, although infestation of I. falicus on S. pectinata had significant short–term effects, the lack of a long–term effect suggests that S. pectinata can successfully deal with periodic insect outbreaks.