Assessing the oviposition preferences of predatory hoverflies is a key factor in the prediction of the success of these biological control agents against aphids in greenhouses, especially when using banker plant systems or in mixed-crop contexts. In this study, two aspects of the oviposition preferences of the American hoverfly, Eupeodes americanus (Wiedemann, 1830) (Diptera: Syrphidae), were evaluated. Firstly, the preference between the banker plant and the target crop was evaluated for three banker plant species (barley, finger millet, or corn) and two target crops (cucumber or pepper). Secondly, the preference between the same two target crops was assessed. Female oviposition preferences were evaluated via two-choice experiments using different plant/aphid systems. The results showed that, for the cucumber crops, the species of banker plant used drastically influenced the oviposition preference of the hoverfly, with a preference for barley over cucumber, cucumber over finger millet, and no preference between corn and cucumber. Unlike cucumber, when used with pepper, barley engendered a preference for the target crop. We conclude that the barley banker plant could be adequate for aphid control in pepper but not in cucumber crops. In a mixed-crop context, the American hoverfly had no preference between cucumber and pepper, which means it has the potential to protect both crops in a mixed-crop greenhouse context. This study shows that the banker plant system should be carefully chosen according to the crops/aphids present in the greenhouse to optimize the impact of the hoverfly as a biocontrol agent. Further work is required to confirm this choice of banker plant in semifield or field testing.

The American hoverfly Eupeodes americanus (Wiedemann) (Diptera: Syrphidae) is an aphidophagous predator during its larval stage and is currently being evaluated for inclusion in biocontrol programs as a new biocontrol agent. However, little is known about its reproductive aptitudes. The objective of the present study was to determine the reproductive parameters of E. americanus and to compare them with those of a commercialized and widely used biological control agent for aphids, the aphid midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae). The preoviposition period, oviposition period, adult longevity, lifetime and daily fecundity, egg hatching rate, and fertility were determined for E. americanus females and compared to those of A. aphidimyza. Trials were conducted under laboratory conditions in rearing cages on the broad bean plant Vicia faba L. (Fabaceae), infested with pea aphids Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). The results revealed that the preoviposition period, oviposition period, and adult longevity were significantly longer in E. americanus than in A. aphidimyza. The daily fecundity and egg-hatching rate were similar in both species. However, lifetime fecundity and fertility were considerably higher in E. americanus than in A. aphidimyza. This study demonstrates that the reproductive capacity of E. americanus is clearly superior to that of A. aphidimyza and therefore supports its inclusion in the aphid pest management program as a new biocontrol agent.

Hoverfly larvae are voracious predators of aphids but have limited dispersal capacity, so their survival depends critically on female selection of oviposition sites. For aphid control purposes, the ability of females to find small aphid colonies is especially valuable. In this study, the oviposition strategy and minimum aphid density triggering the oviposition of the American hoverfly, Eupeodes americanus (Wiedemann, 1830) (Diptera: Syrphidae), was compared with that of the aphid midge, Aphidoletes aphidimyza (Rondani, 1847) (Diptera: Cecidomyiidae), a predator commercially available in Canada as a reference. Oviposition behaviour was evaluated at densities of 0, 2, 5, 10, and 50 aphids per plant. This was tested on two economically significant plant/aphid systems: pepper plants infested by the green peach aphid, Myzus persicae (Sulzer 1776) (Hemiptera: Aphididae), and cucumber plants infested with the melon aphid, Aphis gossypii Glover 1877. Results showed that both predators lay their eggs in proportion to the size of the colony of aphids. Oviposition by E. americanus required a minimum density of 5 aphids on cucumber but only 2 on pepper, whereas for A. aphidimyza, it was also 5 aphids on cucumber, but 10 on pepper. The hoverfly laid more than twice as many eggs as A. aphidimyza on pepper. It also laid more eggs on pepper than on cucumber and the pattern is the opposite for A. aphidimyza. Therefore, the identity of the aphid‐host plant complex appears to modulate the oviposition of these predators. This study demonstrates the ability of E. americanus to respond to lower densities of aphids than A. aphidimyza early in the infestation on sweet pepper plants and shows that its oviposition rate is at least as effective as A. aphidimyza on cucumber. Consequently, these attributes of its oviposition behaviour indicate that E. americanus has great potential for use as an aphid biocontrol agent in these crops.

Syrphine hoverflies (Diptera: Syrphinae) are important predators of aphids in agricultural crops. While the use of flowering plants to enhance their efficacy is well established, recent research has developed an artificial diet for adult hoverflies consisting of a sugar solution and pollen in a dispenser. To ensure that the artificial diet is suitable to support hoverfly reproduction, a comparative analysis was conducted between a natural diet of flowering buckwheat plants versus an artificial diet consisting of artificial flowers (including honey solution and pollen), complemented by a sugar solution disperser. The study evaluated the fecundity, fertility, oviposition period, egg hatchability, and overall lifespan of the American hoverfly, Eupeodes americanus (Wiedemann 1830). The results indicate that the artificial diet does not negatively impact the reproductive parameters of E. americanus when compared to the buckwheat-based diet. Consequently, artificial diets emerge as a promising and more convenient alternative to flowering plants to support hoverflies in biological control strategies and for their mass rearing in research facilities and commercial insectaries.