Suppression of Salvinia molesta Mitchell in Texas and Louisiana by Cyrtobagous salviniae Calder and Sands

Release and evaluation studies of the Brazil population of Cyrtobagous salviniae on Salvinia molesta were conducted originally at 18 sites in Texas and Louisiana from 1999 through 2005. However, overall project results could only be continually evaluated at two release and two control sites because the remainder were eventually destroyed or corrupted by floods, droughts, or herbicides. Mean fresh weight biomass of S. molesta ranged from 15.5 kg FW m−2 during the summer to as low as 2.1 kg FW m−2 during the winter prior to the release of C. salviniae. Insect populations established within a year of release and initially spread slowly. Damage to S. molesta increased with increasing C. salviniae detections while S. molesta biomass and surface coverage declined at both release sites by more than 99% while remaining unchanged at the control sites. Water in release sites registered higher levels of dissolved oxygen, higher temperatures, and higher pH than water in control sites. This study provides another example of the effectiveness of C. salviniae against S. molesta even in more temperate climates.