Tritrophic interaction between the Mexican sunflower, the aphid Aphis gossypii and natural enemies in a greenhouse experiment

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.

Involvement of Allelopathy in the Invasive Potential of Tithonia diversifolia

“…Sesquterpene lactones and flavonoids of T. diversifolia probably act as defensive agents against herbivores [47] and pathogens [3,4,7,35]. Insecticidal properties of the extracts and compounds of T. diversifolia have also been reported [10,35,[48][49][50].…”

Melanaphis sorghi (Theobald, 1904) (Hemiptera: Aphididae), an invasive sorghum pest in the American continent, is a host of Aphidius platensis (Brèthes, 1913) (Hymenoptera: Braconidae: Aphidiinae) in Brazil

“…Despite the numerous mentions of A. colemani in Brazil and South America (Starý et al 2007), it is likely that the occurrences are of A. platensis (Tomanović et al 2014). In fact, after the report of Tomanović et al (2014), only A. platensis was reported in Brazil among the species that form the A. colemani species group (Souza et al 2019;Santos et al 2019;Venâncio et al 2020;Engel et al 2021).…”