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German wasp | Vespula germanica

German wasp

Vespula germanica

Coral bush | Ardisia crenata

Coral bush

Ardisia crenata

Purple loosestrife | Lythrum salicaria

Purple loosestrife

Lythrum salicaria

Pom pom weed | Campuloclinium macrocephalum

Pom pom weed

Campuloclinium macrocephalum

Canarybird bush | Crotalaria agatiflora

Canarybird bush

Crotalaria agatiflora

Peanut butter cassia | Senna didymobotrya

Peanut butter cassia

Senna didymobotrya

Rubber vine | Cryptostegia grandiflora

Rubber vine

Cryptostegia grandiflora

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Environmental Programmes

In order to tackle our country’s socio-economic challenges, the government adopted the Outcomes based approach to improve government performance and providing focus on service delivery. find out more

Nutrient dynamics of Salvinia molesta in shaded and open areas: how does plant quality affect success of biological control by Cyrtobagous salviniae?

Nutrient dynamics of Salvinia molesta in shaded and open areas: how does plant quality affect success of biological control by Cyrtobagous salviniae?
Zolile Maseko, Julie A. Coetzee, Martin P. Hill
Zoology and Entomology Department, Rhodes University, Grahamstown

Cyrtobagous salviniae (Coleoptera: Curculionidae) has proved to be a very effective and deleterious grazer on the ubiquitous aquatic invader Salvinia molesta, which has been a global menace of freshwater systems. Despite the many successes of the weevil, it has however failed to record success in areas where salvinia grows as an understory species. Shallow waters which are still, or have low velocities and occur in the shade provide a haven for salvinia to establish. Previous studies have also highlighted the fact that there is failure to achieve biological control of salvinia under shade conditions. Therefore, the focus of this research is on the effects of shade on the nutrient dynamics of salvinia and how in turn this affects the success of biological control by C. salviniae. The study includes both field and controlled greenhouse studies. Variations in microclimates within the field setting will be investigated by comparing the shaded and open sites where variations in plant quality (tissue nitrogen concentration) could be attributed to the prevailing microclimates. The glasshouse controlled experiments will investigate the nutrient content of salvinia plants and control achieved by C. salviniae under three different levels of shade. The parameters to be investigated include total plant nitrogen, water nitrogen content, wet and dry biomass, plant damage, weevil population sizes, air and water temperatures, shade percentages and solar lux.

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General News Updates

2019 National Symposium on Biological Invasio…


This is your invitation to South Africa's 2019 National Symposium on Biological Invasions. The convention is hosted by the Centre for Invasion Biology (CIB), University of Stellenbosch, and the Biolo... Read more

2019 Invasive Species Training


During the past five years (2014-2018), ISSA invasive species trainers have trained 4 000 in the identification of invasive species and laws pertaining to invasive species across South Africa.  ... Read more

Alien Grass Working Group


Who are we? The South African National Alien Grass Working Group was jointly initiated by the South African Biodiversity Institute (SANBI) and the Centre for Excellence in Invasion Biology (C·I·B) in... Read more

Permits for planting indigenous Cynodon?


On 16 February, 2018, South Africa's Department of Environmental Affairs issued amendments to the regulations and lists relating to the National List of Invasive Species.  Updates to the draft&n... Read more

Invasive species training 2018 dates released


Interested in invasive species?  How much do you know about NEMBA invasive species compliance for landowners and organs of state? The South African Green Industries Council (SAGIC) have released... Read more

Communications post for Africa advertised


The Nature Conservancy has advertised a brand new post:  Communications Manager, Africa Region. Knowledge of invasive species and water would be an asset in this post. See details below:    Job Titl... Read more