IMPACT OF ISCHNODEMUS-FALICUS (HEMIPTERA, LYGAEIDAE) ON PHOTOSYNTHESIS AND PRODUCTION OF SPARTINA-PECTINATA WETLANDS

Wetlands dominated by the C-4 grass, Spartina pectinata (Link), were i nvestigated to quantify the effects of high densities of Ischnodemus f alicus (Say) on leaf-level photosynthesis and aboveground biomass prod uction. Photosynthetic rates of plants within heavily infested stands were greatly reduced from that of plants supporting low densities of I . folicus. In early May 1993, photosynthetic rates of S. pectinata wit h minor I. falicus presence were >30 mu mol m(-2) s-(1) with peak rate s of 45 mu mol m(-2) s(-1) in mid-June. In nearby infested S. pectinat a wetlands, individual plants had rates as low as 5 mu mol m(-2) s(-1) in early May and peak rates of 24 mu mol m(-2) s(-1) in mid-July. Alo ng with reduced photosynthetic rates, plants hosting high insect densi ties had lower aboveground production than did plants that had low ins ect densities. In 1994, when insect densities were ubiquitously low, t here were no differences in peak photosynthetic rates or biomass accum ulation between stands of S. pectinata that had been host to high vers us low densities of insects in 1993. Thus, although infestation of I. falicus on S. pectinata had significant short-term effects, the lack o f a long-term effect suggests that S. pectinata can successfully deal with periodic insect outbreaks.