Host spectrum, reproduction, and survival of Neochetina eichhorniae (Coleoptera: Curculionidae) - A potential natural enemy for controlling water hyacinth (Eichhornia crassipes)

Neochetina eichhorniae (Coleoptera: Curculionidae) is a natural enemy of water hyacinth and its morphology as well as biology has been investigated previously. In this study, the host range of N. eichohorniae was examined using the following 7 groups of plants: Pontederiaceae (water hyacinth, Eichhornia crassipes; hastate-leaf pondweed, Monochoria hastata); food crops (rice, Oryza sativa; maize, Zea mays; sweet potato, Ipomoea batatas and cassava, Manihot esculenta); vegetables (cucumber, Cucumis sativus; mustard greens, Brassica juncea; turnip, Raphanus sativus; water spinach, Ipomoea aquatica; pepper elder, Peperomia pellucida; cabbage, Brassica oleracea var. capitata); herbaceous (boat lily, Tradescantia discolor, gotu kola, Centella asiatica, purple-heart, Tradescantia pallida); fruits (mango, Mangifera indica; longan, Dimocarpus longan; rambutan, Nephelium lappaceum); water plants (sacred lotus, Nelumbo nucifera; red water lily, Nymphaea rubra, yellow bur-head, Limnocharis flava) and industrial plants (sugarcane, Saccharum ssp.; peanut, Arachis hypogaea). The N. eichohorniae was found to be the only survivor that developed and completed its life cycle on water hyacinth. The N. eichohorniae caused only minimal damage to hastate-leaved pondweed and its life cycle was not completed on this weed. When fed with water hyacinth, N. eichohorniae female produced 358.9 eggs on average and the egg-laying period was 16 weeks. Forty three percent of eggs were laid from the 5th to the 8th weeks after females emerged from cocoons. The hatchability of N. eichohorniae eggs was 75.2% and 66.8% of the larvae could survive and became pupae. Approximately 79.1% of the pupae emerged as adults. Among the adults, the female ratio was 48.7%. These results indicated that N. eichohorniae could be considered as a natural enemy to be used for biological control of water hyacinth.

A Case Study of Waterhyacinth (Eichhornia crassipes) Control in Puerto Rico Using Glyphosate and Hand Removal

Waterhyacinth is an aquatic invasive plant that is widespread in Puerto Rico where it negatively effects estuaries, freshwater wetlands, potable water reservoirs, and wildlife refuges. Specifically, the tropical estuary San Juan Bay Estuary (SJBE) has been impacted with the presence of waterhyacinth. Infestations have led to a reduction of water circulation in the system as well as facilitating the establishment of invasive fauna. Therefore, a field study was conducted in a cove between Laguna San Jose and Peninsula Cantera to assess the use of glyphosate and hand removal as a management tool for waterhyacinth control. Aquatic macroinvertebrates and water quality were also monitored as a measure of environmental impact due to management activities. Results indicated that two weeks after glyphosate application, waterhyacinth biomass was significantly reduced to 0.27 kg DW m−2 at the treated plot as compared to untreated plot that yielded 0.62 kg DW m−2. Fresh weight of waterhyacinth decreased more than 90% when hand removal was used as compared to glyphosate treatment. Dissolved oxygen and water pH were not significantly different between sites however, water salinity increased to 8-9 ppt at both plots caused by tidal activity. The order Hemiptera followed by Sarcoptiformes were common at the aquatic macroinvertebrate community. Macroinvertebrate species found associated with waterhyacinth and considered natural enemies were: Orthogalumna terebrantis, Neochetina eichhorniae, Niphograpta albiguttalis. The use of glyphosate to manage waterhyacinth at the Laguna San Jose was useful as a short-term control method and its efficacy may be enhanced over time with follow up applications in combination with hand removal.

Chevroned Water Hyacinth weevil Neochetina bruchi Hustache (Insecta: Coleoptera: Curculionidae)

Neochetina bruchi Hustache is commonly referred to as the chevroned water hyacinth weevil and is a weed biological control agent used to manage water hyacinth, Pontederia crassipes Mart. [formely Eichhornia crassipes (Mart.) Solms (Pellegrini et al. 2018)], in more than 30 countries (Winston et al. 2014). Imported from Argentina, the insect was first introduced into the United States in Florida in 1974 and released in Louisiana later in 1974 (Manning 1979), Texas 1980, and California 1982 to 1983 (Winston et al. 2014). Now Neochetina bruchi occurs throughout the Gulf Coast States (Winston et al. 2014). The target weed of Neochetina bruchi, water hyacinth, is an invasive aquatic plant in the United States and is included on Florida’s list of prohibited aquatic plants. Neochetina bruchi is among four species of insect biological control agents that have been introduced into the United States to manage water hyacinth. The other three species include a weevil, Neochetina eichhorniae; a moth, Niphograptaalbiguttalis; and a planthopper, Megamelus scutellaris, which were introduced into the United States in 1972, 1977, and 2010, respectively (Tipping et al. 2014). Although the larvae and pupae of Neochetina bruchi and Neochetina eichhorniae have similar appearance and behavior and can be difficult to differentiate by casual observation (Deloach and Cordo 1976), the adult stages of the two species of water hyacinth weevils can be distinguished relatively easily based on the color patterns on their elytra (hardened fore wings).

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

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).

Impact of release of Neochetina spp. on growth and density of water hyacinth Eichhornia crassipes

Water hyacinth (<em>Eichhornia crassipes</em>) is an invasive aquatic macrophyte which creates several problems in irrigation system of rivers. To control their rapid distribution in water bodies the biological control method was carried by employing weevils <em>Neochetina bruchi</em> and <em>Neochetina eichhorniae</em> on river based field trial. The study demonstrates effectiveness of biocontrol weevil open field release on experimental site (Chittar river). When compared to first release in field, the weevil intensity was increased in numbers. Active scraping was observed in the leaves and decay spots were seen in the stems of weed. Both <em>N. bruchi</em> and <em>N. eichhorniae</em> (250 No) were introduced biyearly at experimental site for one year. During these two years of observation period, stunted growth and reduced population were observed in the study site. The study highlights importance of <em>Neochetina</em> spp. on the management of <em>E. crassipes.</em>

Implikasi keberadaan agens hayati Neochetina eichhorniae (Coleoptera: Curculionidae) terhadap eceng gondok

The effectiveness of Neochetina eichhorniae as a biocontrol agent of waterhyacinth was evaluated in West Java and DKI Jakarta. The objective of this research was to study the implication of the existence of N. eichhorniae on waterhyacinth. Research was conducted in several freshwater ecosystem infested by waterhyacinth and N. eichhorniae, including Cibinong and Lido lakes (Bogor District), Muara Angke Sanctuary (North Jakarta), and Citarum Hulu river (Purwakarta District), conducted during April to August 2004. The impact of N. eichhorniae on waterhyacinth was evaluated by leaf damage intensity and growth parameter of the plant. Results showed that there was no correlation between waterhyacinth and the occurrence of the N. eichhorniae. The population of N. eichhorniae adults was significantly low in any locations studied. Thus, the existence of the biocontrol agent can not result in decreasing of waterhyacinth population.