European Weed Research Society working groups turn focus on biological control of Invasive Alien Plant species

CABI has shared its expertise at a workshop convened by the European Weed Research Society (EWRS) aimed at understanding the very latest science regarding the sustainable biological control of Invasive Alien Plant (IAP) species.

The scientists who attended the EWRS joint working group workshop (Credit: CABI).

The joint workshop of the ‘Invasive Alien Plant’ and ‘Biological Control’ working groups brought together researchers from eight countries to see how safer-to-use and more environmentally friendly biological control methods can help manage IAPs such as Parthenium hysterophorus and Commelina benghalensis.

Other IAP species that came under focus included Ambrosia psilostachya, Portulaca oleracea, Alopercurus myosuroides, and Lythrum hyssopifolia.

Serious negative consequences for their new environment

According to the European Commission (EC), Invasive Alien Species (IAS) are ‘animals and plants that are introduced accidentally or deliberately into a natural environment where they are not normally found, with serious negative consequences for their new environment.’

The EC states that they are a ‘major threat to native plants and animals in Europe and are one of the five major causes of biodiversity loss.

They can also cause significant adverse impacts on the economy (their economic impact in the EU was estimated at around EUR 12 billion per year) as well as human health, such as severe allergies and burns from, for example, giant hogweed.

At the workshop, which was held in Antalya, Turkey, Dr Marion Seier, Senior Plant Pathologist; Team Leader – Invasive Species, UK, and Dr Philip Weyl, Head of Weed Biological Control, Switzerland, gave a presentation entitled ‘Biological control of invasive alien plants in Europe – opportunities and challenges.’

Part of an integrated weed management strategy

They said biological control, being complimentary to other control strategies, lends itself to form part of an integrated weed management strategy.

The approach can be divided into three main methods – conservation biological control aiming to enhance population levels and activities of resident natural enemies; augmentative or inundative biological control based on the mass production and release of natural enemies in large numbers; and classical biological control (CBC) using co-evolved natural enemies from the native range of a species for control in its invasive range.

The latter approach is best suited for invasive alien plant species, whilst the former two are more applicable to native weeds in a cropping situation. In addition, botanicals, and plant-based products, as well as mycotoxins, also play a role in the biological weed control approach.

Dr Seier stated, ″In contrast to regions such as Australasia, North America and South Africa the use of biological control in weed management has been less widely practiced in Europe. Recently, however, the strategy has also gathered momentum in this region with several European countries actively pursuing research into and implementation of weed biological control.″

Classical biological control in the UK

Dr Seier also gave an overview of the classical biological control programme against invasive non-native plant species in the UK including Japanese knotweed (Reynoutria japonica), Himalayan balsam (Impatiens glandulifera), Australian swamp stonecrop (Crassula helmsii) and floating pennywort (Hydrocotyle ranunculoides).

This included mention of the four classical agents released against these target weeds in the UK which included the first fungal biocontrol agent (Puccinia komarovii var. glanduliferae) to be released against a weed (Himalayan balsam) in Europe. See more in the publication ‘Progress with Weed Biocontrol Projects.’

Dr Weyl then joined Dr Seier to give a final presentation entitled ‘Classical biological control of weeds: dealing with misconceptions and conflicts of interests.’

Dr Weyl said, ″A fundamental challenge of weed biological control is assessing the risk of non-target effects by a potential biological control agent. The long history of pre-release studies in weed biological control has significantly contributed to the development of risk assessment procedures (host specificity testing) with an overwhelming success rate.

″Yet, despite its wide application across the world, discussions about the risks involved in classical weed biological control are often dominated by misunderstandings and misconceptions.″

He added that biological control of weeds often has perceived conflicts of interests.

Leaf beetle Ophraella communa can significantly reduce pollen

In 2020, a CABI-led study published in the journal Nature Communications, found that the leaf beetle Ophraella communa can significantly reduce pollen of common ragweed (Ambrosia artemisiifolia) – which causes a range of symptoms from sneezing to itchy eyes and aggravates conditions such as asthma and eczema.

The interdisciplinary study – the first to quantify the economic benefits of biological control in Europe – argued that the costs inflicted by invasive species in Europe are ‘most probably seriously underestimated.’

The team of scientists from institutions including the University of Fribourg and ETH Zurich, Switzerland, the University of Worcester, UK, and Leiden University, NL, suggest countries in the Balkan Peninsula will benefit most from the leaf beetle as a biological control.

Tools to fight economically important crop pests and weeds

It was also reported in January 2024, that CABI is making good progress as part of its role in the EUR €6 million ADOPT-IPM project aimed at using Integrated Pest Management (IPM) tools to fight economically important crop pests and weeds affecting major crops across Europe and China.

CABI, together with partners, is leading the development of a web based IPM tool performance demonstrator and is also making valuable contributions to the creation and efficacy of IPM or biocontrol tools against two devastating invasive species, fall armyworm (Spodoptera frugiperda) and common ragweed.

Scientists from CABI’s centre in Switzerland this year added two new projects to their portfolio of invasive weed targets. These included, blueweed (Echium vulgare), also known as viper’s bugloss, and European frogbit (Hydrocharis morsus-ranae), both of which have many negative environmental and economic impacts.

Agents which have been released in Canada are also starting to show promise with early establishment for the Russian olive mite, Aceria angustifoliae and the root-and rhizome-feeding tortricid moth, Dichrorampha aeratana.

There has also been a massive push to release thousands of individuals of the stem-mining moths against phragmites in Canada, which has been very successful.

In the UK centre recent projects include work on the European native old man’s bear (Clematis vitalba) for New Zealand where the species is invasive.