Salvinia (Salvinia molesta) is one of the world’s most notorious aquatic weeds, with significant environmental and economic impacts. It is now established in tropical, subtropical, and temperate regions. It can tolerate a wide range of environmental conditions; however some abiotic environmental parameters appear to limit its spread. The primary biocontrol for this Weed of National Significance is the salvinia weevil (Cyrtobagous salviniae), which has had a high degree of success in tropical and subtropical regions. However, the efficacy of the salvinia weevil in controlling infestations of salvinia in temperate regions is less established, with evidence suggesting it is more variable. Identifying the most suitable method for controlling salvinia infestations and prioritising the areas that receive active control is necessarily complex and must consider site-specific characteristics of the colonised environment. Some environmental characteristics, such as shade and salinity, may serve to limit the spread of salvinia and may be considered passive control mechanisms, but how these abiotic elements affect the performance of biocontrol agents remains unknown for many weeds. We examined the interaction of shade and salinity to salvinia growth and the response of its biocontrol, the salvinia weevil, in several laboratory experiments. Salvinia was grown in water at six different concentrations of salt under either light or shade conditions, and plant growth, vigour and stress were measured. The tolerance of salvinia weevils to these conditions was also tested via choice experiments to determine whether they showed any preference for treatment type. Studies like these, which integrate attributes of the plant and the biotic and abiotic environment, may improve our understanding of the complex process of species invasions. This in turn, may lead to improved decision-making regarding which control methods to apply in heterogenous landscapes for a wide-spread and environmentally tolerant weed.