Search

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. info:eu-repo/semantics/publishedVersion

Syrphids provide valuable ecosystem services such as pollination, pest control or organic matter decomposition. In many cases, adults exploit pollen resources from the landscape to complete their life cycles. Yet, the knowledge about the most suitable plants for enhancing syrphid populations is still insufficient for most habitats. Also syrphid distribution across the landscape is understudied. In this work we analyzed: (i) syrphids distribution across different land uses and seasons in a Mediterranean landscape dominated by olive orchards, (ii) pollen resources exploited by the most abundant syrphid species and (iii) specific pollen resources relevant for egg production. Syrphids were captured weekly in spring, summer and autumn from April to November 2013 with a sweep net in patches with different land uses (olive orchards, herbaceous and scrubland patches). Nine species, generally with predatory aphidophagous larvae, were identified. The most abundant species was Sphaerophoria scripta (L.) followed by Melanostoma mellinum (L.). Sphaerophoria scripta was associated to olive orchards while M. mellinum was associated to herbaceous/scrubland patches. Pollen selection and consumption and number of eggs within gravid females for the most abundant species were determined through gut dissection and identified with a microscope. Several pollen types were showed a positive selection index by syrphid species. During spring and summer, the most ingested pollen types belonged to abundant plants in the patches of capture indicating that syrphids possibly do not need to fly among patches to feed during those periods. In spring, Asteraceae and Plantago type were particularly consumed by S. scripta and M. mellinum gravid females respectively while in summer feeding habits of males, gravid and non-gravid females did not differ. Females consumed more pollen than males but the number of eggs in gravid females was not related with the amount of ingested pollen grains. This study brings some insights about the seasonal variation of pollen feeding habits shown by adult syrphids across a Mediterranean heterogeneous landscape dominated by the olive orchard. In spring, dense flowering strips maintained within the olive orchards might attract and nourish adult syrphids while in summer syrphids might fly to non-crop areas to feed. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020), and project EXCL/AGR-PRO/0591/2012 “Olive crop protection in sustainable production under global climatic changes: linking ecological infrastructures to ecosystem functions.” and M.V. Postdoc grant (SFRH/BPD/119487/2016). info:eu-repo/semantics/publishedVersion

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. The authors are grateful to the Portuguese Foundation of Science and Technology for financial support through the project EXCL/AGR-PRO/0591/2012 ‘‘Olive crop protection in sustainable production under global climatic changes: linking ecological infrastructures to ecosystem functions’’ and Pest-C/EQB/ LA0006/2013. Maria Villa thanks FCT, POPH-QREN, and FSE for PhD grant (SFRH/BD/70693/2010). This manuscript is part of Maria Villa PhD Thesis. info:eu-repo/semantics/publishedVersion

Many 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 resource-scarce 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., The authors are grateful to the Foundation for Science and Technology (Portugal) and COMPETE/QREN/EU for financial support through the research project EXCL/AGR-PRO/0591/2012: Olive crop protection in sustainable production under global climatic changes: linking ecological infrastructures to ecosystem functions and for grant SFRH/BD/70693/2010 awarded to M. Villa

A cochonilha-negra, Saissetia oleae (Olivier) (Hemiptera: Coccidae), é uma praga importante da oliveira. Este fitófago é atacado por diferentes espécies de parasitoides cuja ação, em muitos casos, é suficiente para manter as populações de cochonilha considerados toleráveis. Com o presente trabalho pretendeu-se estudar as populações de cochonilha-negra em oliveira na região de Trás-os-Montes em diferentes períodos do ano; avaliar a diversidade de parasitoides associado a esta praga e sua relação com os diferentes estados de desenvolvimento do hospedeiro e período do ano; e por último procurar perceber a existência da relação entre o estado de desenvolvimento do hospedeiro, seus parâmetros biométricos e o parasitismo exercido. Neste contexto, em 40 olivais da região de Trás-os-Montes foram feitas amostragem em quatro períodos distintos (julho, setembro e novembro de 2011 e maio de 2012). Em cada olival foram amostradas 10 oliveiras, colhendo-se 20 folhas infestadas de cochonilha-negra/árvore. No laboratório, as folhas foram observadas, à lupa binocular, registado o número de exemplares em cada estado desenvolvimento da praga, a distribuição na folha (página superior ou inferior) e colocadas em tubos de ensaio que foram selados e colocados em condições controladas (22ºC, 70%HR, 16L:8D) até emergência de eventuais parasitoides. Os parasitoides emergidos foram identificados e procedeu-se à análise dos parâmetros biométricos do hospedeiro (comprimento, altura). Os resultados obtidos mostraram que foi na amostragem de verão (julho) onde se observou maiores números de indivíduos de cochonilha-negra, sendo na sua maioria ninfas do primeiro instar (aproximadamente 92% dos exemplares observados), que preferiam a página inferior da folha do hospedeiro. Foram identificadas sete espécies de parasitoides, designadamente Coccophagus lycimnia (Walker), C. semicircularis (Förster), Metaphycus flavus (Howard), M. helvolus (Compere), M. lounsburyi (Howard), Scutellista nigra (Fonscolombe), e S. caerulea (Merter) que e atuam de forma diferenciada de acordo com o estado de desenvolvimento do hospedeiro e a época do ano. C. lycimnia foi a espécie mais abundante e a que originou maiores taxas de parasitismo, principalmente nas ninfas do terceiro instar. As taxas de parasitismo nos diferentes períodos de amostragem oscilaram entre 3,61 e os 23,54%. Verificou-se também que o tamanho do hospedeiro influencia a escolha do parasitoide, sendo que os parasitoides do género Coccophagus que parasitam ninfas do segundo e terceiro instar preferiam hospedeiros com tamanhos superiores aos hospedeiros atacados pelos parasitoides do género Metaphycus Black scale, Saissetia oleae (Olivier) (Hemiptera: Coccidae), is an important pest of the olive tree. This pest is attacked by different species of parasitoids that in many cases, are sufficient to limit their populations. This work aims to study the black scale population in olive trees in Trás-os-Montes region in different periods of year, evaluated the parasitoids diversity associated with this pest and their relationship with the different development stages of host and period of year, and finally seek to realize the existence of the relationship between the development state of the host, their biometric parameters and parasitism exercised. In this context, in 40 olive groves in Trás-os-Montes region were made samples at four different times (July, September and November 2011 and May 2012). In each olive grove were sampled 10 olive trees and were collected 20 infested olive leaves by black scale per tree. In laboratory, leaves were observed by binocular microscope, recorded the number of individuals in each development stage of the pest, the distribution in leaf (page up or down) and placed in sealed test tubes under controlled conditions (22ºC, 70%HR, 16L:8D) until eventual parasitoid emergency. Parasitoids were identified and having proceeded to the analysis of the host biometric parameters (length, height). Results showed that it was in summer sample (July) where were observed the higher number of individuals of black scale, being mostly first instar nymphs (approximately 92 % of the individuals observed), that preferred the up page of the leaf. Were identified seven species of parasitoids namely Coccophagus lycimnia (Walker), C. semicircularis (Förster), Metaphycus flavus (Howard), M. helvolus (Compere), M. lounsburyi (Howard), Scutellista nigra (Fonscolombe), and S. caerulea (Merter) that act differently according the host stage development and season of the year. C. lycimnia was the most abundant species that originated the higher rates of parasitism, especially in nymphs of the third instar. Parasitism rates in different sampling periods ranged between 3.61 to 23.54%. It was also found that the size of the host influences the choice of the parasitoid, being the parasitoids of the genus Coccophagus that parasitize second and third instar nymphs preferred hosts with larger sizes than the hosts attacked by parasitoids of the genus Metaphycus.