Prospects for biological control of Ambrosia artemisiifolia in Europe: learning from the past

Abstract

SummaryThe recent invasion by Ambrosia artemisiifolia (common ragweed) has, like no other plant, raised the awareness of invasive plants in Europe. The main concerns regarding this plant are that it produces a large amount of highly allergenic pollen that causes high rates of sensitisation among humans, but also A. artemisiifolia is increasingly becoming a major weed in agriculture. Recently, chemical and mechanical control methods have been developed and partially implemented in Europe, but sustainable control strategies to mitigate its spread into areas not yet invaded and to reduce its abundance in badly infested areas are lacking. One management tool, not yet implemented in Europe but successfully applied in Australia, is biological control. Almost all natural enemies that have colonised A. artemisiifolia in Europe are polyphagous and cause little damage, rendering them unsuitable for a system management approach. Two fungal pathogens have been reported to adversely impact A. artemisiifolia in the introduced range, but their biology makes them unsuitable for mass production and application as a mycoherbicide. In the native range of A. artemisiifolia, on the other hand, a number of herbivores and pathogens associated with this plant have a very narrow host range and reduce pollen and seed production, the stage most sensitive for long-term population management of this winter annual. We discuss and propose a prioritisation of these biological control candidates for a classical or inundative biological control approach against A. artemisiifolia in Europe, capitalising on past experiences from North America, Asia and Australia.

Is the recent decrease in airborne Ambrosia pollen in the Milan area due to the accidental introduction of the ragweed leaf beetle Ophraella communa?

“…Cannabis on ruderal habitats and agricultural land, and Urtica/Parietaria on ruderal habitats); (2) All host-range tests conducted so far indicate that O. communa is specific to the Asteraceae tribe Heliantheae (Palmer and Goeden 1991;Gerber et al 2011). As a result, Cannabaceae and Urticaceae populations could be affected by Ambrosia eradication measures in the Milan area, and concurrent decreases in airborne Cannabaceae and Urticaceae pollen are unlikely to be caused by beetle attacks.…”

“…The flight distance has been estimated to be approximately 25 km/day, with potential range expansion of 329 km/year (Yamamura et al 2007;Tanaka and Yamanaka 2009). Taking into account the selective host-feeding preferences, high fecundity and dispersal potential, it is suggested that O. communa may be a potential biological control agent against A. artemisiifolia (Teshler et al 2002) although Ophraella slobodkini was a preferred candidate species for the biological control of A. artemisiifolia in Europe, because it exclusively feeds on Ambrosia (Gerber et al 2011).…”

Weed biological control in the European Union: from serendipity to strategy

“…Since the 1960s, biological control had been considered as a management option against common ragweed in different parts of the world, including non-EU Member States in Europe (Gerber et al 2011). The noctuid moth Tarachidia candefacta (Hübner) (Lepidoptera: Noctuidae), which was released in Russia in 1969, was the first such intentional attempt to control common ragweed by biological means (Kovalev 1971), but so far with little impact.…”

“…Emphasis was put on biological control by promoting and coordinating studies on the host-specificity and impact of selected insect and fungal BCAs (Gerber et al 2011). In 2013, biological control efforts against common ragweed experienced an unexpected boost when the North American leaf beetle Ophraella communa LeSage (Coleoptera: Chrysomelidae) was detected in Northern Italy and Southern Switzerland Müller-Schärer et al 2014).…”

An early suitability assessment of two exotic Ophraella species (Coleoptera: Chrysomelidae) for biological control of invasive ragweed in Europe

“…Given its potential impact on common ragweed, O. communa had already been mentioned as the most promising candidate BC agent for Europe by Kiss (2007). It was, however, not regarded as a candidate by Gerber et al (2011) for Europe and had earlier been rejected as a candidate for Australia because of its wider fundamental host range including sunfl ower (Palmer & Goeden, 1991). Feeding on sunfl ower and a few other plant species from the same tribe (Heliantheae) has indeed been reported based on results from no-choice tests in the laboratory (Palmer & Goeden, 1991;Cao et al, 2011), and from fi eld surveys after its accidental introduction into Japan (Yamazaki et al, 2000).…”