The use of non-crop resources by natural enemies and their potentialities to enhance their effectiveness as pest control agents is increasing as a method for conservation biological control. Nevertheless, the effect of consumption of non-crop resources by pests has been generally overlooked being this knowledge crucial to favor natural enemies but not pests. In the present work, insect honeydews and flowers suitability as food resources for the olive tree key-pest Prays oleae were analyzed under laboratory conditions. The selected honeydews were excreted by Saissetia oleae and Euphyllura olivina, two olive pests, and the selected plants were seven abundant species in the olive grove agroecosystem that bloom simultaneously with the flight period of the anthophagous generation of P. oleae. In this work, some of these resources were identified as potential food sources for P. oleae. Despite the general findings, which indicate that honeydews have less nutritional value for insects than nectar, P. oleae reached the best survival and reproduction performance with the insects' honeydews. Several of the tested flowers were identified as potential food resources for P. oleae, being Malva sylvestris the one that originated the best performance. Moreover, our results suggest that P. oleae females are synovigenic and emerge with nutritional reserves for reproduction. We highly recommend accomplishing further research before establishing these resources in biological control methods in order to confirm their effect on pests in fields.

A B S T R A C TMany syrphid larvae are predators and have an important role as biological control agents of pests in agroecosystems. However, adults feed on non-prey resources such as pollen from flowers. Heterogeneous landscapes can provide syrphids with a great biodiversity of plants and ensure the existence of food resources. This is particularly important during periods of food scarcity, such as autumn, for syrphid species that spend those periods as adults. Nevertheless, the feeding habits of syrphid adults in resourcescarce agroecosystems are poorly known. In this study, the pollen consumption and preferences of Eupeodes corollae (Fabricius) and Episyrphus balteatus (De Geer) were analyzed in olive groves and surrounding herbaceous and woody patches in the autumns of 2012 and 2013 in northeastern Portugal. The guts were dissected, and the pollen types were identified and compared with the ground cover plants in the studied patches. Both species consumed and selected pollen types from herbaceous and woody vegetation that occurred in different patches, indicating that they flew between patches. These results highlight the importance of conserving heterogeneous agricultural landscapes to guarantee the existence of food resources for beneficial insects during periods of scarcity.

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1. Autoparasitoids are intraguild consumers that attack and kill heterospecific and conspecific parasitoids as well as immature stages of hemipteran hosts, such as aphids, whiteflies and soft scales. Field experiments assessing the importance of interspecific competition between autoparasitoids and primary parasitoids, as well as its impact on herbivore suppression, are scarcely found in the ecological literature.2. Using field data from 40 olive orchards, this study examined the mechanisms that regulate: (i) the interspecific competition between primary parasitoids of the genus Metaphycus and the autoparasitoid Coccophagus lycimnia; and (ii) the density of their shared herbivore host, the soft scale Saissetia oleae.3. Metaphycus parasitoids used smaller hosts than C. lycimnia, yet did not outcompete C. lycimnia. On the other hand, C. lycimnia preferred to use Metaphycus females as secondary hosts for producing males rather than their own females. This preference might explain why the autoparasitoid negatively affected the density of the primary parasitoids.4. Parasitism by the autoparasitoid C. lycimnia at the beginning of the season was the sole variable positively related to host mortality throughout the season, showing its greater effect on herbivore suppression. 5. In this study, an autoparasitoid, inferior at resource exploitation, was shown to outcompete a primary parasitoid without disrupting herbivore suppression.