Laura Torres

Ants as predators of the egg parasitoid Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae) applied for biological control of the olive moth, Prays oleae (Lepidoptera: Plutellidae) in Portugal

The detrimental effect of predators on Trichogramma cacoeciae March. releases to control the olive moth, Prays oleae Bern., in the Trás-os-Montes region (Northeast of Portugal), was evaluated during three releases against the flower generation of the pest in 2002. At 1 and 3 h and at 1, 3, 7 and 14 days after each release, 30 Trichogramma releasing cards were examined in the field and predators were collected and identified. Furthermore, at 1, 3, 7 and 14 days after each release, the percentage of egg predation on the cards was also determined. Formicidae were the most abundant group of predators at 99.1% of the total individuals collected. Ten species were identified, Camponotus aethiops, C. lateralis, C. piceus, C. truncatus, Crematogaster auberti, C. scutellaris, Lasius niger, Leptotorax angustulus, Plagiolephis pygmaea and Tapinoma nigerrimum. T. nigerrimum was the most abundant species, both in total numbers as well as in the number of occupied cards. One day after release, the percentage of predation was 24.0% in the first release, 59.4% in the second and 38.0% in the third. Three days after release, the percentage of predation varied from 60.2 to 83.4% during the three release events. Seven days after release, the percentage of predation increased to 97.8% of the total eggs on cards.

Towards sustainable control of Lepidopterous pests in olive cultivation

Current olive growing practices range from the traditional Mediterranean olive grove to intensively managed olive plantations. Insecticides against major olive pests, like the olive moth (Prays oleae, Lep.: Yponomeutidae) and the jasmine moth, (Palpita unionalis, Lep.: Pyralidae) are still applied frequently. The European Union-funded international research project TRIPHELIO is aimed at the development of economically feasible and sustainable insecticide-free control methods for key Lepidopterous pests of olive. Main research activities focus on (1) the use of pheromones for mating disruption and improved monitoring of target pests, (2) habitat management strategies to enhance the activity of natural enemies in the olive grove, and (3) the use of inundative releases of mass-reared egg parasitoids of the genus Trichogramma. Moreover, tools for successful integration of the methods developed into an integrated pest management (IPM) strategy for olive pests were explored by optimising techniques for surveillance as well as considering potential side-effects of common pesticides on beneficial organisms. An intense exchange of scientific information and technology between European and North African countries was undertaken to create solutions for a wide range of olive growing regions. Key results and recommendations for further essential steps towards practical implementation are presented in this publication.ZusammenfassungTraditionelle, extensiv bearbeitete Olivenhaine, aber auch moderne Intensiv-Plantagen mit künstlicher Bewässerung und hohem Einsatz von Düngern bzw. chemischen Pflanzenschutzmitteln kennzeichnen die derzeitigen verschiedenen Anbauformen der Olive im Mittelmeerraum. Schadlepidopteren wie die Olivenmotte (Prays oleae, Lep.: Yponomeutidae) und die Jasminmotte (Palpita unionalis, Lep.: Pyralidae) werden durch regelmässigen Insektizideinsatz bekämpft. Das von der EU geförderte internationale Forschungsprojekt TRIPHELIO zielte auf die Entwicklung insektizidfreier Alternativmethoden durch (1) die Optimierung der pheromongestützten Überwachung und Verwirrtechnik, (2) der Anwendung von Habitatmanagement-Strategien zur Förderung natürlicher Gegenspieler, und (3) dem Einsatz von Trichogramma-Schlupfwespen. Zusätzlich wurden Module für eine optimale Anwendung biotechnischer und biologischer Methoden bezüglich der Phänologie der Schadinsekten und möglicher Nebenwirkungen von Pestiziden erarbeitet. Die intensive Kooperation zwischen Wissenschaftlern und Praktikern aus mehreren Ländern Europas und Nordafrikas erlaubte den Entwurf möglicher Lösungsansätze für verschiedene Anbaubedingungen und klimatische Regionen des Mittelmeerraumes. Die wichtigsten Ergebnisse und Ausblicke für eine zukünftige praktische Umsetzung werden in dieser Veröffentlichung beschrieben.

Evaluation of native plant flower characteristics for conservation biological control of Prays oleae.

Several studies have shown that manipulating flowering weeds within an agroecosystem can have an important role in pest control by natural enemies, by providing them nectar and pollen, which are significant sources of nutrition for adults. The aim of this study was to assess if the olive moth, Prays oleae (Bernard, 1788) (Lepidoptera: Praydidae), and five of its main natural enemies, the parasitoid species Chelonus elaeaphilus Silvestri (Hymenoptera: Braconidae), Apanteles xanthostigma (Haliday) (Hymenoptera: Braconidae), Ageniaspis fuscicollis (Dalman) (Hymenoptera: Encyrtidae) and Elasmus flabellatus (Fonscolombe) (Hymenoptera: Eulophidae), as well as the predator Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), can theoretically access the nectar from 21 flowering weeds that naturally occur in olive groves. Thus, the architecture of the flowers as well as the mouthpart structure and/or the head and thorax width of the pest and its enemies were analyzed. The results suggested that all beneficial insects were able to reach nectar of the plant species from Apiaceae family, i.e. Conopodium majus (Gouan) Loret, Daucus carota L. and Foeniculum vulgare Mill., as well as Asparagus acutifolius L., Echium plantagineum L., Capsella bursa-pastoris (L.) Medik., Raphanus raphanistrum L., Lonicera hispanica Boiss. et Reut., Silene gallica L., Spergula arvensis L., Hypericum perforatum L., Calamintha baetica Boiss. et Reut, Malva neglecta Wallr. and Linaria saxatilis (L.) Chaz. P. oleae was not able to access nectar from five plant species, namely: Andryala integrifolia L., Chondrilla juncea L., Dittrichia viscosa (L.) Greuter, Sonchus asper (L.) Hill and Lavandula stoechas L.

The use of the cumulative degree-days to predict olive fly, Bactrocera oleae (Rossi), activity in traditional olive groves from the northeast of Portugal

Terra Quente, situated in the province of Trás-os-Montes (northeast of Portugal), is one of the most important olive growing areas of Portugal. In this region, which is extremely hot and dry during summer, losses due to the olive fly, Bactrocera oleae (Rossi), are highly variable between years, with estimates ranging from 16.3 to 98.8% of infested fruits. The objective of this study was to test the use of the degree-days models, based in a daily accumulation of temperature (°DD) to predict insect activity in the field and timing control measures, in such a climatic condition. Seasonal flight activity periods and insect development were studied from 2005 to 2008 in traditional olive groves and a degree-day model was developed for predicting the development of olive fly second generation, which is the one that can cause losses. It was found that, while the use of these models could be hampered by high temperatures and low relative humidity prevailing during summer, they may have some potential as a tool for the management of B. oleae populations, allowing the identification with acceptable error of the main second generation events. Results indicated that, if adulticide sprays are to be used, the spray-window for their applications lasts between an accumulation, since January 1, of 1837.20xa0±xa035.82°DD8.99, which corresponds to the beginning of the insect second flight and 2045.87xa0±xa034.30°DD8.99, which corresponds to its main peak.

Effects of pollen, sugars and honeydew on lifespan and nutrient levels of Episyrphus balteatus

Hoverflies require pollen, nectar and honeydew during their adult stage, but little is known about the suitability and nutrient provision of each of those resources. Thus, in this study we assessed the effect of different types of food, such as carbohydrates (glucose, fructose, sucrose and honey), pollen, a mixture of honey and pollen, and honeydew on longevity and nutrient levels of Episyrphus balteatus (De Geer) (Diptera: Syrphidae). Glucose and the mixture of pollen and honey were the food sources that gave the highest longevities. Considering nutrient levels in the body of hoverflies, sucrose generated high levels of fructose, total sugars and glycogen while glucose generated high levels of lipids. This suggests that carbohydrates are important food components for the survival and energy supply of hoverflies, with glucose being the most effective. Honeydew can also be used by hoverflies, representing a significant sugar source that may replace nectar when suitable flowers are scarce in agroecosystems.

Effect of seven species of the family Asteraceae on longevity and nutrient levels of Episyrphus balteatus

Adult hoverflies feed on pollen, nectar and honeydews. Thus, the implementation of floristically diverse resources in agroecosystems can enhance biological control of pests by increasing populations of these natural enemies. The objective of this work was to study the effect of seven species of Asteraceae (Andryala integrifolia L., Anthemis arvensis L., Calendula arvensis L., Carduus tenuiflorus Curtis, Chamaemelum nobile (L.) All., Coleostephus myconis (L.) Rchb.f. and Crepis vesicaria L.) on adult longevity and nutrient levels of Episyrphus balteatus (De Geer) (Diptera: Syrphidae). Crepis vesicaria and C. nobile gave the highest mean longevities while, for the other plant species, longevities were not significantly different from those in the water only treatment. In addition, all species tested resulted in significantly lower longevities than the positive control (glucose). In terms of nutrient levels, C. nobile generated high levels of total sugars and C. vesicaria high levels of lipids which suggests the consumption of flower resources. However, the majority of the plants tested would not allow hoverflies to complete their life cycle. Thus, further experimentation needs to be done before considering these plants for implementation in agroecosystems.

Efficacy of spinosad bait sprays to control Bactrocera oleae and impact on non-target arthropods

A field study was conducted during 2005 and 2006 in Terra Quente, northeastern Portugal, to evaluate the efficacy of the spinosad-based insecticide Spintor Cebo® (Dow Agrosciences Ibérica, S.A.) against the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), as well as the impact of the treatments on non-target arthropods. Results suggest that this insecticide could be as effective as dimethoate and since it was reported as having more benign toxicological and ecological profiles, it seems to be a good alternative to control the pest in Continental Mediterranean climates such as Terra Quente. However, its use should be evaluated carefully, mainly in conditions that increase the arthropod biological control agents’ propensity for feeding on it (e.g. absence of pollen, nectar and honeydews) to identify unintended impacts on conservation biological control of olive pests as a result of its application.

Identification of predator-prey relationships between coccinellids and Saissetia oleae (Hemiptera: Coccidae), in olive groves, using an enzyme-linked immunosorbent assay

A polyclonal antiserum (AS) was developed and characterized for the detection of immature stages of the black-scale, Saissetia oleae, in whole body homogenized field-collected coccinellid species, using an indirect enzyme-linked immunosorbent assay (ELISA). The indirect ELISA showed to be sensitive to the S. oleae AS, detecting a protein content between 0.118 and 0.0374xa0μgxa0mL−1. The specificity of the ELISA was tested by assaying a range of sympatric predators and alternative preys with the S. oleae AS. Coccinellid larvae obtained the highest cross-reaction and a positive–negative threshold was established at 0.674xa0μgxa0mL−1 protein. A total of 1,322 coccinellids were field-collected in three olive groves located in Trás-os-Montes (northeast of Portugal) by the beating technique and were analyzed to detect S. oleae proteins in their guts. Field-collected coccinellids which attained a S. oleae protein concentration equivalent higher than the threshold were considered as a positive reaction. In the overall collected coccinellids, 21.2% reacted positively with the S. oleae AS. Chilocorus bipustulatus and coccinellid larvae obtained the highest percentages of positives with 43.4 and 40.8%, respectively. The greatest frequency of positive responses occurred at the beginning of July, mid-August, and mid-October coinciding with the occurrence of the first, second and third instar nymphs of S. oleae, respectively. Thus, in this study, the role of coccinellids as natural control agents of S. oleae was highlighted by the number of individuals and species that tested positive for S. oleae AS.

Effects of ten naturally occurring sugars on the reproductive success of the green lacewing, Chrysoperla carnea

The longevity and reproduction of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) when fed on ten naturally occurring sugars and on an artificial diet composed by honey and pollen (1:1) were evaluated. The effect of these diets differed between sexes. However insects of both sexes lived longer when fed on fructose than on sucrose, melezitose or raffinose. None of the females oviposited when offered raffinose, galactose or mannose. Moreover, lifetime fecundity of females fed on trehalose was not different from the artificial diet. The intrinsic rate of natural increase did not differ between trehalose, maltose, melibiose, fructose, glucose and artificial diet, being significantly lower for individuals fed on melezitose and sucrose. The importance of these results for the selection of natural sugar sources that enhance C. carnea effectiveness as a biological control agent against crop pests is discussed.

Natural mortality of immature stages of Bactrocera oleae (Diptera: Tephritidae) in traditional olive groves from north-eastern Portugal

Abstract From 2006 to 2008, we studied the natural mortality of olive fly, Bactrocera oleae (Rossi), eggs and larvae as collected in fruit on the tree, in two to five ‘traditional’ olive groves of Trás-os-Montes (north-eastern Portugal), per year. We also studied the fate of 2044 puparia that were buried in the soil from November to May for two seasons, by using exclusion cages to estimate predation. Mortality of eggs inside the fruit was estimated as between 5.4±2.4 and 16.6±6.1%, and as 10.7±2.1 and 100.0% for young larvae. Similarly, the estimated mortality of mature larvae was between 0 and 66.7±33.3%. The highest mortality levels for young larvae could reach 100% during August, and 47.4% during the first fortnight of December, coincident with high temperatures in summer or low temperatures at the end of autumn and early winter. Mortality (winter disappearance) of puparia was estimated at up to 98.5% of the population. Predation of eggs was low, at 0.6±0.3 to 6.3±4.0% in 2006, 0 to 4.1±1.1% in 2007, and 0 to 3.6±3.6% in 2008. Parasitism was insignificant during the study, and only one parasitoid was identified, the eulophid Pnigalio agraules (Walker). We also surveyed entomopathogenic fungi associated with the insect in 12 olive groves, and evaluated three of the latter against larvae, puparia, and adult B. oleae in the laboratory. Of the 15 fungal species identified from immature stages, three were considered to be entomopathogenic (i.e. Cordyceps bassiana, Penicillium corylophilum and Mucor hiemalis). We observed up to 20.0±3.2% and 94.0±2.5% mortality of larvae and puparia, respectively when treated with P. corylophilum and up to 32.5±11.1% of adults when treated with M. hiemalis.