Mottled Water Hyacinth Weevil Neochetina eichhorniae Warner (Insecta: Coleoptera: Curculionidae)

Abstract

Sometimes referred to as the ‘mottled water hyacinth weevil’, Neochetina eichhorniae Warner is a weevil that attacks the invasive, aquatic plant, water hyacinth, Eichhornia crassipes (Mart.) Solms. Water hyacinth is considered one of the most destructive plants in aquatic ecosystems in the United States and, as a result, is listed in both the federal noxious weed list and Florida’s list of prohibited aquatic plants. Neochetina eichhorniae is host specific and causes substantial damage to water hyacinth, making it a valuable biological control agent for this invasive weed in many parts of the world. The insect was first introduced into the United States from Argentina in 1972, when scientists released the insect in Broward County, Florida, to manage water hyacinth (Perkins 1973). Since then, the insect has been introduced in more than three dozen countries worldwide (Winston et al. 2014). Post-introduction studies indicate the insect substantially suppresses the growth of water hyacinth, significantly reducing biomass, flowers production, and water surface coverage (Grodowitz et al. 1991, Center et al. 1999, Tipping et al. 2014, Nesslage et al. 2016) and the need for herbicide applications (Haag 1986).

Optimization of Neochetina eichhorniae Warner and Neochetina bruchi Hustache for the management of water hyacinth, Eichhornia crassipes (Mart.) Solms in the Central Rift Valley lakes through the use of different nutrient levels in Ethiopia

“…The mean leaf loss of the E. crassipes increased with increasing water nutrient concentrations and decreased with a decrease in the weevil density (Figure 7A, B, and C). Similar to the current study, other studies reported that the E. crassipes leaf damage and loss were high as the density of N. bruchi and N. eichhorniae increased (Kariuki and Minteer, 2021), but E. crassipes productivity increased with a decrease in the feeding intensity of the herbivores when they were at a lower density (Bownes et al, 2010). The results imply that the biocontrol of E. crassipes is influenced by both herbivore densities and water nutrient levels.…”

“…Eichhornia crassipes plants in experimental buckets had a high adult density of N. bruchi and N. eichhorniae when they were treated with a high density of the weevils. The highest mean number (43) was obtained using a high adult density of weevils on E. crassipes plants that received the highest nutrient level (Table 2), which was substantially different from the lowest result. In a combined application of the weevil with white amur, Delfosse et al (1976) found a maximum of 89.4 N. eichhorniae per 388 E. crassipes plants in a pool per season, which is lower than the current result.…”