Chapter 24 Common Ragweed Ambrosia artemisiifolia L. Zhongshi Zhou, Fanghao Wan, and Jianying Guo Abstract Ambrosia artemisiifolia L., an annual herb native to North America, has caused serious threat to native ecosystems, human health, agriculture and livestock breeding in China. In this chapter, we review the damages and invasion mechanisms of this invasive weed, as well as research progress in biological control and inte- grated management in China. Finally, we propose research perspectives on A. arte- misiifolia management in the future. Keywords Ambrosia artemisiifolia • Biological control • Replacement control • Biological control agent • Replacement plant 24.1 Introduction The common ragweed, Ambrosia artemisiifolia L. (Asterales: Asteraceae), is an annual herb native to southern parts of North America (Bassett and Crompton 1975). It is one of the most noxious weed in agriculture around the world (Chollet et al. 1999; Brückner et al. 2003; Török et al. 2003; Wan et al. 2005). In China, this weed was unintentionally introduced into southeastern coastal region in the 1930s (Wan et al. 1993), and has raised great awareness as an invasive plants since 1980s. Now, it has spread to 21 prov- inces in middle and eastern part of the country (Zhou et al. 2009, 2011a) (Fig. 24.1). It is a quarantine agricultural pest in China because of its significantly negative effects on agricultural loss, a notorious allergen to human health and impacts on biodiversity (Wan et al. 1995; Ma et al. 2008b; Ministry of Agriculture of China 2006). Artificial uprooting measure was conducted from late 1980s to early 1990s in order to suppress A. artemisiifolia populations in China. Thereafter, effective herbi- cides were used. However, despite the availability of chemical and mechanical methods, sustainable control strategies were not available before 2007 (Zhou et al. 2009). In the past decade, biological control of this weed has received more ­attention in China, and several classical biological control programs have been implemented Z. Zhou (*) • F. Wan • J. Guo State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2017 99 F. Wan et al. (eds.), Biological Invasions and Its Management in China, Invading Nature - Springer Series in Invasion Ecology 13, DOI 10.1007/978-981-10-3427-5_7 100 Z. Zhou et al. Fig. 24.1 Distribution of Ambrosia artemisiifolia L. (Zhou et al. 2015a, b) (Zhou et al. 2009). Due to the high efficiency, the use of natural enemies has been the sustainable management strategy of A. artemisiifolia in China. In this chapter, we briefly review the damages and invasion mechanisms of this invasive weed in China, as well as the research progress in biological control and IPM. 24.2 Damage of A. artemisiifolia Ambrosia artemisiifolia seeds can mix with crop seeds and then invade crop fields (e.g. corn and soybean fields). It can also invade vegetable fields, orchards, mul- berry fields, nursery and pasture,etc . (Fig. 24.2a). It strongly inhibits cultivated crops and wild plants because it has a strong root system and a large above-ground vegetative biomass (Ma et al. 2008a). Crop yield may be seriously reduced owing to intensive competition with A. artemisiifolia. For example, it was reported that the yield of corn (Wan et al. 2005), snap bean (Phaseolus vulgaris L.) (Evanylo and Zehnder 1989) and soybean (Wan et al. 2005) was significantly dropped when A. artemisiifolia occurred during the growth stage of these crops. Since A. artemisiifolia grows rapidly at late stages, it can remarkably suppress native annual plants and become dominant plant species. Diversity of native plants in invaded fields would decline significantly (Fig. 24.2b), further resulting in a sim- 24 Common Ragweed Ambrosia artemisiifolia L. 101 Fig. 24.2 Ambrosia artemisiifolia invades the corn field (a) and destroys diversity of native plants (b) ple community structure. In addition, diversity of soil animals also significantly decreased in the areas invaded by A. artemisiifolia in China (Sun et al. 2002, 2006). On the other hand, A. artemisiifolia pollen is one of the most problematic aero-­ allergens throughout its range (Wan et al. 1993, 2005; Karnkowski 1999; Zhou et al. 2015a, b), which can induce potential severe health problems (Bohren et al. 2006). In China, 2–3% of the population, ca. 14.5 million persons, in the A. artemisiifolia occurring regions may suffer from allergy, costing nearly 1.45 billion US dollars annually for prescription drugs in China (Zhou et al. 2011a). 24.3 Invasion Mechanisms 24.3.1 Spread of A. artemisiifolia Seeds A. artemisiifolia reproduces by seeds, and seeds can go into secondary dormancy and are capable of maintaining vitality in the soil for 5–30 years (Karnkowski 1999). Seeds can be dispersed by birds, water currents and strong winds. They can be also dispersed through exchanges of contaminated crop seeds, forage and fodder (Karnkowski 1999; Zhou et al. 2015a, b). A. artemisiifolia has a relatively high reproductivity, with one single plant capable of producing nearly 100,000 seeds. 24.3.2 Soil Ecological Environment Facilitate the Invasion and Expansion of A. artemisiifolia The invasion and expansion of A. artemisiifolia may depend on soil ecological condi- tions (soil microorganisms, nutrient availability, etc.). It is well known that arbuscular mycorrhizal fungi (AMF) may play important roles in invasion processes of some 102 Z. Zhou et al. plants. As A. artemisiifolia is known to be colonized its population by AMF within its native range, AMF was perceived to facilitate the invasion of this plant. Greenhouse experiment showed that AMF could positively affect growth and development of A. artemisiifolia (Fumanal et al. 2006). In addition, the symbiosis between A. artemisiifo- lia and AMF may increase the soil nitrogen acclimation, which enhances resource cap- ture of the plant by increasing specific leaf area, and this effect would be more significant at low soil nitrogen content. Therefore, the role of AMF for A. artemisiifolia growth was considered to be more evident in low-­nitrogen environments (Huang et al. 2010). In addition, the invasion of A. artemisiifolia can alter the soil microbial community at a certain degree that favors itself while inhibiting native plant species (Li et al. 2014). The change in the microbial community improved the activities of urase, phosphatase and invertase in the soil (Li et al. 2009). These enzymes can accelerate the accumulation of available N, P and K, thus concentrations of available N, P and K in the soil were significantly higher at the sites heavily invaded by A. artemisiifolia than at those with only native plants (Li et al. 2014). In addition, A. artemisiifolia plants secrete phytotoxic (allelopathic) substances that can inhibit the growth of native plants (Karnkowski 1999). 24.3.3 Benefit from the Escape of Natural Enemies The enemy release hypothesis support that invading species would benefit com- pared to their native counterparts if they lose their herbivores and pathogens during the invasion process (Agrawal et al. 2005). A total of 450 insect, mite and fungal species associated with A. artemisiifolia have been found since 1965, which had greatly suppressed the expansion of A. artemisiifolia in North and South America (Goeden and Andres 1999). In China, however, escape from natural enemies prob- ably has facilitated the population establishment of this plant (Ma et al. 2008a, b; Gerber et al. 2011). This was considered as one of the most important reasons for the successful expansion of A. artemisiifolia in this country. 24.4 Biological Control To control A. artemisiifolia, five beneficial insect herbivores were introduced into China from 1987 to 1989, i.e., Zygogramma suturalis (Fabricius) (Coleoptera: Chrysomelidae), Epiblema strenuana (Walker) (Lepidoptera: Tortricidae), Liothips sp. (Thysanoptera: Phlaeothripinae), Euaresta bella (Loew) (Diptera: Tephritidae) and Tarachidia candefacta Hübner (Lepidoptera: Noctuidae) (Wan et al. 1993, 2005; Ma et al. 2008a). Ophraella communa LeSage (Coleoptera: Chrysomelidae), native to North America (LeSage 1986; Futuyma 1990), is also a biological control agent of A. artemisiifolia (Goeden and Ricker 1985; LeSage 1986; Zhou et al. 2010). It was first detected in 2001 in the suburb of Nanjing city, Jiangsu province (Meng and Li 2005). It feeds on A. artemisiifolia leaves (Takizawa et al. 1999; Yamazaki et al. 24 Common Ragweed Ambrosia artemisiifolia L. 103 2000; Dernovici et al. 2006; Zhou et al. 2011b), killing plants when its adults and larvae reach a high density (Lesage 1986; Teshler et al. 2000, 2002; Zhou et al. 2009). Lots of work has been conducted for the use of these biological control agents, biological control agents have been employed in practice (Reznik 1991; Igrc et al. 1995; Goeden and Andres 1999; Wan et al. 1995; Ma et al. 2008b; Teshler et al. 1996, 2000; Moriya 1999; Zhou et al. 2011a). To better perform biological control of A. artemisiifolia, we introduced host specificity and mass rearing and control efficacy of these biological control agents in this section. 24.4.1 Specificity of Biological Control Agents Host specificity is a prerequisite condition that an insect herbivore can become a biological control agent of the weed. To confirm the safety of the introduced several insect herbivores of A. artemisiifolia, their host specificity was successively tested in the laboratory and in the field. Host specificity of Z. suturalis was tested on 74 plant species/varieties prior to field releases, where the beetle was found to feed only A. artemisiifolia. It did not accepted A. trifida, another invasive plant in China, as a host (Wan et al. 1989). In choice-tests, E. strenuana could attack sunflowers and produced adults on the plants in the greenhouse (Wan et al. 1995), but its larvae did not develop in a field cage test (Wan and Wang 2000).