Exploration for candidate biological control agents of the submerged aquatic weed Hydrilla verticillata, in Asia and Australia 1996–2013

Abstract

Monoecious and dioecious forms of the submerged aquatic plant hydrilla, Hydrilla verticillata (Linn. f.) Royle (Hydrocharitaceae) are invasive weeds in the US. Surveys for biological control agents of hydrilla throughout its native range have been conducted since the 1970s. Surveys between 1996 and 2013 focused on China, Southeast Asia and Australia, with 425 collections of hydrilla made in seven countries. Most of the herbivores collected were typical of previous surveys and included three main feeding guilds and taxonomic groups: stem-boring Bagous weevils, leaf-mining Ephydridae flies and defoliating Crambidae moths. Preliminary testing of prioritized agents collected from 1996 to 2013 did not reveal candidates for use as biological control agents with those tested being polyphagous. Further surveys are currently in China and South Korea, where hydrilla forms/genotypes exist that match those found in the US.

Invasive Aquatic Vegetation in the Sacramento–San Joaquin Delta and Suisun Marsh: The History and Science of Control Efforts and Recommendations for the Path Forward

“…Aquatic insects that feed on SAV are less common and less diverse than their terrestrial counterparts, and to date there are no examples of species-specific SAV control from a biological agent (Cuda et al 2008;Hussner et al 2017). Several fly species have been identified and released to control H. verticillata in the southern US but established populations did not provide significant control (Purcell et al 2019). Grass carp (Ctenopharyngodon idella), made triploid and sterile by pressure treatment of eggs, have been used to control H. verticillata across the US and in other countries (Chilton and Muoneke 1992), including in canal systems of the Imperial Valley of California (Stocker and Hagstrom 1986).…”

Geographic and genetic variation in susceptibility of Butomus umbellatus to foliar fungal pathogens

“…For example, biological control agents of Hydrilla verticillata vary in performance between dioecious and monoecious genotypes in the US (i.e., host-genotype effects), genotypes which occur mostly in separate geographic areas (i.e., monoecious hydrilla has a northern US distribution and dioecious hydrilla has a southern distribution). This has generated interest in introducing agents that are better-adapted to specific host genotypes and led to additional overseas exploration for new agents (Grodowitz et al 2010;Harms and Grodowitz 2011;Harms et al 2017;Purcell et al 2019). Likewise, cryptic species of Diorhabda beetles were introduced for control of saltcedars (Tamarix spp.)…”

Enzymatic efficiency of the decomposing microbiota: what does really matter for aquatic macrophytes invasions?

“…Aggressive invaders can threaten biodiversity and ecosystem processes (Murphy et al 2019). The submerged Egeria densa, along with Hydrilla verticillata, are two of the main noxious aquatic weeds in reservoirs worldwide (Strange et al 2019), and (Purcell et al 2019). These plants present similar ecological strategies and growth forms that potentially occur in similar habitats and have a wide ecological range (Mony et al 2007).…”