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Syrphids feed on multiple patches in heterogeneous agricultural landscapes during the autumn season, a period of food scarcity

Publication . Villa, María; Santos, Sónia A.P.; Marrão, Rosalina; Pinheiro, Lara Alina; López-Sáez, José António; Mexia, António; Bento, Albino; Pereira, J.A.

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.

2016Journal article

Open access

Olive volatiles from portuguese cultivars Cobrançosa, Madural and Verdeal Transmontana: role in oviposition preference of Bactrocera oleae (Rossi) (Diptera: Tephritidae)

Publication . Malheiro, Ricardo; Casal, Susana; Cunha, Sara C.; Baptista, Paula; Pereira, J.A.

The olive fly, Bactrocera oleae (Rossi), a serious threat to the olive crop worldwide, displays ovipositon preference for some olive cultivars but the causes are still unclear. In the present work, three Portuguese olive cultivars with different susceptibilities to olive fly (Cobrançosa, Madural, and Verdeal Transmontana) were studied, aiming to determine if the olive volatiles are implicated in this interaction. Olive volatiles were assessed by SPME-GC-MS in the three cultivars during maturation process to observe possible correlations with olive fly infestation levels. Overall, 34 volatiles were identified in the olives, from 7 chemical classes (alcohols, aldehydes, aromatic hydrocarbons, esters, ketones, sesquiterpenes, and terpenes). Generally, total volatile amounts decrease during maturation but toluene, the main compound, increased in all cultivars, particularly in those with higher susceptibility to olive fly. Sesquiterpenes also raised, mainly α-copaene. Toluene and α-copaene, recognized oviposition promoters to olive fly, were correlated with the infestation level of cvs. Madural and Verdeal Trasnmontana (intermediate and highly susceptible cultivars respectively), while no correlations were established with cv. Cobrançosa (less susceptible). No volatiles with inverse correlation were observed. Volatile composition of olives may be a decisive factor in the olive fly choice to oviposit and this could be the basis for the development of new control strategies for this pest.

2015Journal article

Open access

Physico-chemical characteristics of olive leaves and fruits and their relation with Bactrocera oleae (Rossi) cultivar oviposition preference

Publication . Malheiro, Ricardo; Casal, Susana; Baptista, Paula; Pereira, J.A.

Bactrocera oleae (Rossi) (Diptera: Tephritidae) oviposition preference to Portuguese olive cultivars with different susceptibilities (cvs. Cobrançosa, Madural, and Verdeal Transmontana) was studied by physical and chemical parameters. Physical parameters, maturation indices, infestation levels, and fatty acids profiles were recorded.Verdeal Transmontana olives revealed higher susceptibility to olive fly attack, while cv. Cobrançosa was the less affected cultivar. A faster maturation in cv. Cobrançosa and a slower one in cv. Verdeal Transmontana were observed. Verdeal Transmontana olives reported higher volume and lower elongation, while both olives and leaves reported higher lightness, all possible attractive cues for olive fly. Fatty acids composition revealed a characteristic profile in each cultivar with constant differences during crop season.Overall, maturation process influenced biometrical data and color of olive cultivars. The slower maturation process characteristic from cv. Verdeal Transmontana could modulate the composition and physical appearance of olives, therefore interfering with olive fly females oviposition preference.

2015Journal article

Open access

Biological control of Pseudomonas savastanoi pv. savastanoi by two bacterial isolated from olive tree phyllosphere

Publication . Diogo, Mina; Santos, Alba; Pereira, J.A.; Lino-Neto, Teresa; Baptista, Paula

Olive knot disease, caused by the bacterium Pseudomonas savastanoi pv. savastanoi (Psv), has been responsible for high economical crop losses in olive orchards, especially in Mediterranean countries. Olive knot cannot be eradicated once it is established in an orchard, and therefore its control is based on preventive measures. Laboratory experiments previously performed by us have showed the capacity of some bacterial species, isolated from olive tree phyllosphere, to inhibited Psv growth. In the present work, the two most promising bacterial isolates (i.e. Frondihabitans sp. and Paenibacillus sp.) were evaluated for the control of Psv in olive plantlets (Olea europaea L.) under greenhouse conditions, to predict their effect in a more natural condition. In pot experiments, two-year-old olive plants cv. Cobrançosa were inoculated with the antagonistic bacteria and Psv individually or in combination. Inoculations were performed in wounds previously made in three different sites of the main stem. Thirty replicate plants were used per strain. The plants were observed for symptom development and the number of bacteria on the inoculation sites was periodically evaluated, for up to 120 days after inoculation. To quantify the reduction of symptom expression, knots were excised from stems and their weights were compared between treatments. Inoculation with Psv resulted in the formation of knots with significantly higher weight values compared to plants inoculated simultaneously with Psv and antagonistic bacteria. Both tested bacterial also showed the capacity to reduce the amount of Psv in the inoculation sites, suggesting their effectiveness in controlling the multiplication of the pathogen. Data presented here demonstrate for the first time the potential of these bacteria for suppression of olive knot, and these two species should be considered in the future as potential biocontrol agents against Psv.

2017Conference object

Open access

Ground cover management affects parasitism of Prays oleae (Bernard)

Publication . Villa, María; Santos, Sónia A.P.; Mexia, António; Bento, Albino; Pereira, J.A.

Spontaneous ground covers comprise ecological infrastructures that may provide food, alternative hosts and shelter for parasitoids in olive groves, thus contributing to biological control of pests. This study investigated the effects of herbicide application, tillage, and conservation of spontaneous ground covers on parasitism of the anthophagous generation of the olive moth, Prays oleae (Bernard). The study was performed in northeast Portugal in 2011 and 2013 in 14 and 15 olive groves, respectively, with different management types. Generalized Estimating Equations (GEE) were used to analyze olive moth emergence, overall parasitism rate, relative abundance of parasitoid species, and total parasitismof olive moth larvae. Ageniaspis fuscicollis (Dalman) accounted for the majority of the parasitism, followed by Elasmus flabellatus (Fonscolombe). In both years, ground cover management type did not influence the emergence rate of P. oleae. However, overall parasitism rate, emergence of A. fuscicollis, and the number of A. fuscicollis emerging per olive moth larvae varied among years. In 2011, the latter response variables were significantly higher in groves with spontaneous ground cover than in those treated with herbicide, indicating a negative effect of herbicides on parasitoids. Although tilled groves obtained higher values for these variables in 2013, parasitism rates were generally very low. In sum, the management of ground covers seemed to influence the overall rate of P. oleae parasitism in some years, but longer-term experiments are needed to clarify this trend.

2016Journal article

Restricted access