Abstract
The establishment of invasive plants negatively affects natural environments. Invasive herbivores that attack weeds can be used as a form of biological control, but natural enemies of herbivores must be associated with this interaction to prevent the invasive phytophagous from become a local pest. We performed a greenhouse experiment to evaluate how the cotton aphid, Aphis gossypii, a ok and invasive herbivore, affects the performance of the weed Tithonia diversifolia, the Mexican sunflower. We also examined the relationship between the aphid and local natural enemies. Seedlings of T. diversifolia were divided in two groups: one infested by the aphid and another not infested. After 22 days, we assessed the relationship between aphid abundance and the presence of natural enemies (Coccinelidae and Aphidius platensis) on infested plants, and compared the vegetative performance of the two seedling groups. Both natural enemies were positively related to high aphid density on infested plants. Plants infested by the aphid presented foliar necrosis and senescence, and a reduction of around 50% in leaf number, foliar area, shoot length and shoot, root and total plant weight compared to non-infested plants. These results indicate potential biological control of Mexican sunflower seedlings by the cotton aphid, and control of this aphid by the studied natural enemies.
Highlights
The introduction of non-native species is one of the main causes of economic and biodiversity loss because it modifies local community structure and decreases crop productivity and establishment (Simberloff et al, 2013)
We investigated the relationship between an infestation of A. gossypii on seedlings of T. diversifolia and the presence of natural enemies in a greenhouse experiment
These impacts were reflected in approximately 50% higher values for leaf number, leaf area, stem length and stem, root and total plant weight in non-infested than infested T. diversifolia (Table 1)
Summary
The introduction of non-native species is one of the main causes of economic and biodiversity loss because it modifies local community structure and decreases crop productivity and establishment (Simberloff et al, 2013). Weed management is expensive due to high tolerance to many control methods and the absence of natural enemies in invaded environments (Bezemer, Harvey, & Cronin, 2014; van Kleunen, Dawson, & Maure, 2015; Cadotte, Campbell, Li, Sodhi, & Mandrak, 2018) Due to these impacts, and the challenges associated with eradication, many studies have explored alternative ways to suppress weeds in natural and anthropized areas. Weeds can be spontaneously attacked by invasive polyphagous herbivores already present in a natural area or near crops (Norris & Kogan, 2000) Such invasive species can contribute to reducing weed populations even in the absence of others efficient control agents (van Driesche, Hoddle, & Center, 2008; Tito & Torre-Mayorga, 2016)
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