Zoophytophagous mirids (Hemiptera: Miridae) are one of the most studied and successful group of natural enemies used as biological control agents in horticultural crops. When prey is scarce, some species, such as Nesidiocoris tenuis (Reuter) may damage plant tissue by increasing feeding on vegetative and reproductive organs. Despite the importance of mirids, the provision of a sugar source as an alternative or complement to plant feeding has never been addressed to reduce mirid phytophagy. Here we analyzed the nutritional status and phytophagy of N. tenuis in the presence of tomato plants with and without sugar dispensers. Our study demonstrated how nymphs and adults obtained carbohydrates when fed on tomato plants. Phytophagy was reduced more than two-fold with the provision of sugar dispensers. Both nymphs and adults contained higher carbohydrate levels when they had access to plants with sugar dispensers than without. Nymphs, which are generally responsible for more serious plant damage, had a higher content of carbohydrates than adults independently of the diet provided. Our findings contribute not only to improve the use of zoophytophagous predators as biological control agents, but also to understand the nutritional ecology of the Miridae, a group with a very diverse diet.

Herbivore suitability and quality for hymenopteran parasitoids is dynamic, varying with host development. Generally, within the same host species, large hosts (i.e. older instars) are considered of higher quality for progeny development. Studies of interespecific competition between parasitoids have considered the effect of host instar on indirect competition but its effect on interference competition remains unknown. Here, we report the first results on whether host instars (of different quality for immature development) might dictate the outcome of interference competition between sympatric parasitoids of the genus Aphytis Howard (Hymenoptera: Aphelinidae) when they attack low (second) and high quality (third) instars of their common host Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae). Oviposition behavior (host acceptance and clutch size) in low and high quality host instars was similar for both Aphytis species in the absence of competition. When they found heterospecific parasitized hosts of high quality, Aphytis melinus DeBach laid more eggs and accepted significantly more hosts than A. chrysomphali (Mercet), whereas there were no significant differences in the low quality instar. This result suggests that interference competition is mediated by host quality.However, the progeny proportion of both parasitoids in multiparasitized hosts (outcome of competition) was independent of host quality and A. melinus always emerged at higher rates.Therefore, the final result of interference competition between these sympatric parasitoids was not affected by host quality and this competition will contribute to the displacement of the native A. chrysomphali by the introduced A. melinus, as it has been observed in some areas of the Mediterranean basin.

Effect of host instar on host discrimination of heterospecific parasitized hosts by sympatric parasitoids