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Abstract: Augmentative biocontrol constitutes a safe option to reduce pest populations through the enhancement of natural enemies’ activity. In this context, the aphidophagous syrphid Episyrphus baltetaus (De Geer) (Diptera: Syrphidae) is a promising candidate for aphid biological control: larvae of this syrphid attack and consume a wide range of aphid species and are found on many vegetable crops. Because natural populations of beneficial insects are not always sufficient to regulate the pest infestations, this work has focused on the conception of a biological control device containing syrphid eggs which ones can easily be introduced in fields or greenhouses. Using semiochemicals [E-(β)-farnesene, R-(+)-limonene and (Z)-3-hexenol], honeydews and “artificial honeydews” (10% or 30% aqueous solutions of sucrose, fructose and glucose), the syrphid oviposition was artificially induced on an inert surface. Specifically, E-(β)-farnesene and concentrated mono-sugars (30%) were identified as the most efficient ovipositional stimulants. To test and validate the biological control device described above, laboratory and field experiments were performed: a plastic lamella covered with syrphid eggs was suspended on aphid infested plants in order to measure the efficiency of the device. The results obtained were promising since populations of 500 aphids were eliminated in 10 days when 15 syrphid eggs were introduced. The use of such a biological control device could certainly contribute to the biological control to reduce the aphid infestations. [ABSTRACT FROM AUTHOR]

Abstract: The potential impact of nectar availability for biological pest control is of increasing relevance due to the disappearance of non-crop plants in intensified agricultural landscapes. However, little is known about how floral resources and their spatial distribution in and around crop fields influence cereal aphid parasitoid (Hymenoptera, Aphidiidae) survival and population dynamics. Cereal aphid parasitoids may be less dependent on flowers as they can use honeydew from their aphid hosts as an alternative food resource. However, honeydew appears to be less suitable as a food source for parasitoids when compared to nectar. Here the effects of flower distribution (nectar), aphid abundance (honeydew quantity) and honeydew quality on parasitoid life history parameters were explored using a spatially explicit, individual-based simulation model. In addition, effects of the availability of floral resources in field margins on parasitism levels in winter wheat were investigated in a field study. In the simulation study three flower distributions were compared: (i) flowers restricted to the field margin (most common in agricultural landscapes) or (ii) flowers in strips within the crop, and (iii) random flower distribution in the field. Simulations suggest that nectar feeding increases parasitoid longevity and parasitism at low aphid densities, but only in fields with randomly distributed flowers. In contrast, the spatial distribution of flowers did not affect the parasitoid longevity and parasitism rate at high aphid densities, where parasitoid feeding was restricted to the abundant honeydew resources. In simulations, parasitoid survival and the number of aphids parasitized were also affected by the nutritional quality of the honeydew, with low quality honeydew having a less positive effect on parasitoid longevity and parasitism rate. The field study did not indicate evidence of a significant relationship between flower cover in field margins and parasitism rates in wheat near the margins. This finding is compatible with results from simulations and suggests that honeydew feeding is more prevalent in cereal aphid parasitoids than nectar feeding. In conclusion, nectar may be an important factor for the potential biocontrol success of cereal aphid parasitoids, but most likely only at low aphid densities and especially when flowers are broadly distributed in the field. [Copyright &y& Elsevier]

Abstract: The majority of predators and parasitoids require non-prey food as part of their diet. The availability of suitable non-prey food can impact predator–prey and parasitoid–host dynamics and may be critical to the efficacy of biological pest control. A growing body of work addresses the role of floral nectar in conservation biological control programs. In comparison, we know relatively little about the role of honeydew as a sugar source for predators and parasitoids, in spite of the fact that honeydew is often the predominant sugar source in agroecosystems. Here we test the hypothesis that honeydew is a less suitable food source when compared with other sugar sources, using data from parasitoid literature. We also explore whether parasitoids of honeydew-producing insects show particular adaptations allowing them to optimize the exploitation of this suboptimal food source. A review of available literature supports the general hypothesis that honeydew is inferior to other sugar sources, although there is considerable variation in the quality of honeydew depending on the honeydew producer and its host plant. The accrued dataset is not consistent with our second hypothesis that parasitoids of honeydew-producing hosts fare better on this nutritionally inferior food source as compared with parasitoid species which exploit hosts that do not produce honeydew. Finally we review evidence on the use of honeydew by predators and parasitoids under field conditions and explore implications for biological pest control programs. [Copyright &y& Elsevier]

Abstract: We examined the effects of cotton aphid honeydew and buckwheat floral nectar on the lifespan and body carbohydrate nutrient levels of the phorid fly, Pseudacteon tricuspis (Diptera: Phoridae). Compared to flies provided with water only, cotton aphid honeydew modestly but significantly increased longevity of female and male P. tricuspis by about 1 day, with significant increases in the body levels of fructose, total sugars, and glycogen. Age had a positive effect on the levels of total sugars and glycogen in honeydew-fed flies. However, sex and mating had no significant effect on longevity and body nutrient levels. Body size (as measured by wing length) was positively correlated with glycogen levels in males, with larger males accumulating more glycogen from honeydew than smaller males. P. tricuspis flies were observed foraging on buckwheat flowers. However, no significant effects of buckwheat nectar on phorid fly longevity and body nutrient levels were detected. These results may suggest that buckwheat florets are morphologically incompatible with the mouthparts of phorid flies, or the possibility of innate behavioral characteristics of phorid flies that limit nectivory. Alternatively, buckwheat nectar may be quantitatively or qualitatively inferior to cotton aphid honeydew or may contain compounds that are mildly repellent to P. tricuspis. Future studies will investigate the mechanisms behind the observed reduced suitability of buckwheat nectar as a food source for P. tricuspis. Conservation of naturally occurring sugar sources in the field, including exposed sugar sources such as honeydew, may promote P. tricuspis lifespan and possibly, its impact as a biological control agent against imported fire ants, Solenopsis spp. (Hymenoptera: Formicidae). [Copyright &y& Elsevier]

Aphidius ervi (Haliday) (Hymenoptera: Braconidae) is a solitary aphid endoparasitoid. Adults feed on honeydew and possibly on other sugar sources such as nectar. Sugar sources can vary qualitatively and quantitatively according to biotic factors and environmental conditions. Experiments were conducted to determine the influence of quantitative variations of sugar sources on survival, feeding behavior, and consumption of A. ervi. A 1:1 glucose–fructose mixture was tested in a range of concentrations (0–70% (w/v)). The lifetime of both sexes increased significantly with increasing sugar concentration. The optimal lifetime was achieved by insects fed with 50 and 70% (w/v) of sugar solution for males and 70% (w/v) for females. Behavioral studies showed that sugar concentrations had a significant influence on feeding duration: for males and females feeding duration increased with sugar concentration. Longevity primarily depended on the concentration of the sugar solution, rather than the quantity of sugar solution ingested. In the last experiment, we studied the effect of feeding intervals on the lifetime of A. ervi females. Females fed with a 50% (w/v) 1:1 glucose–fructose mixture continuously or twice a day lived eight times longer than unfed parasitoids. In contrast, females fed every two days lived only half as long as those fed daily. We can thus conclude that females need at least two food intakes per day to attain maximum longevity. Our results provide insight into the nutritional requirements of A. ervi under laboratory conditions. Such information can be a basis to improving the longevity of this biocontrol agent by sugar feeding in the field and in greenhouses. [Copyright &y& Elsevier]

[Display omitted] • We review how ants affect pest abundance, and their natural enemies on citrus crops. • Ants affect the non-honeydew producing pests, but favour the honeydew producers. • Ants affect pests with edaphic stages, but favour pests without such stages. • The identity of the most abundant ant species affect the natural enemies. • Ants affect the generalist and winged natural enemies of honeydew-producing pests. Ants are one of the most abundant insect groups in citrus orchards. They help in controlling pests, but they can also facilitate the outbreak of other pests, such as those that produce honeydew. Moreover, ants can also affect natural enemies of pests. Here, we review how ants affect pest abundance, considering whether the pest produces honeydew and whether it spends part of its life-cycle in the soil (edaphic stages). We also investigated the effects of the presence of ants on natural enemies with a meta-analysis and how this effect is modified by honeydew production by the pest, the most abundant ant species, and the specialization and mode of dispersal (winged or wingless) of the natural enemy. The presence of ants decreased the abundance of non-honeydew producing pests, but increased the abundance of honeydew producers. Ants increased the abundance of pests without edaphic stages, but decreased pests with such stages. In addition, the identity of the most abundant ant species affected the abundance of natural enemies; the ants Iridomyrmex rufoniger and Lasius grandis had a negative impact whereas other ant species did not affect the abundance of natural enemies. Moreover, the presence of ants decreased the abundance of generalist and winged natural enemies of honeydew-producing pests. Our review provides crucial information on the effects of ants on biological control practices in citrus orchards, and increases our understanding of the relationships between ants, pests and their natural enemies. [ABSTRACT FROM AUTHOR]