544 research outputs found
The effect of distance between parasitoid and host on the parasitism of Psyttalia concolor (Szépligeti) in organic olive orchards
No full textBactrocera oleae (Rossi) is a major pest of olive fruits. Biological control of olive fruit fly mainly relies on the activity of the Braconid species Psyttalia concolor (Szépligeti), which parasitizes Bactrocera oleae at the larval stage. Parasitism tests have been carried out at the insect growing facility (insectariums) of the Mediterranean Agronomic Institute of Bari (C.I.H.E.A.M.). The critical point of the use of P. concolor as a biological control agent in organic olive crop is the assessment of its effectiveness against B. oleae. Its lower presence in fruits of cultivated olives rather than in small fruits of wild olives suggests an influence of the size of the fruit, and of the thickness of its pulp on the parasitization of P. concolor. Therefore, the aim of this research was to investigate the capacity of the females of P. concolor to lay their eggs into the target host according to the distance existing between the female and the host larva. In these tests, the substitution host Ceratitis capitata was used and parasitism of P. concolor was tested at different distances (0, 0.5, 1, 1.5, 2, 2.5 and 3 mm) to the host larvae at different times (7 min, 15 min, 30 min and 60 min) of interaction.
Predetermined distances between the parasitoids and the target larvae were arranged by locating the flying females into cubical cages of 40x40x40 cm with Plexiglas walls and the open roof covered with a tulle tissue in order to avoid that any insects from outside may enter the cages, and to allow the females to protrude their ovipositors. On these roofs, plastic cylinders containing the target larvae were placed with the open bases arranged with a tulle tissue, to allow the contact with the parasitoid females. Considering the width of the tissues negligible, distances were set by metal separators with increasing thickness.
Parasitism level at 7 min was not significantly different at 2, 2.5 and 3 mm distances. Parasitism level was the highest at 0, 0.5, and 1 mm distances with no significant changes. Parasitism at 15 min showed a high variability according to the distances. The highest level resulted at 0.5 and 1 mm distances, the lowest at 3 mm distance. At 30 min interaction, the highest level of parasitism was at 0 mm distance, whilst at 1 and 1.5 mm the level was lower with no significant changes. Again, parasitism level was the lowest at 3 mm distance. The highest level of parasitism at 60 min was detected at 1.5 mm distance and was as lower as the distance increased.
In conclusion, the study showed that the females of P. concolor were not able to parasite the target larvae at distances higher than 2.5 mm. Generally, the parasitism level decreases with the increase of the distance between target larvae and parasitoid females. At the lowest distances (0, 0.5 and 1 mm) hyper parasitism occurred and the target pupae were killed, but also the development of the parasitoids into adults was very difficult for nutrient unavailability. Biological control of P. concolor against B. oleae larvae may give satisfactory results only if the depth at which the target larvae are located into the olive drupes is not higher than 2 or 2.5 mm from the surfac
Mating behavior and vibrational communication of the meadow spittlebug Philaenus spumarius
No full textInfluenza delle caratteristiche chimico-fisiche del suolo e della gestione fitosanitaria sulla concentrazione di solfati in oliveti e vigneti biologici della Puglia
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Susceptibility of table grape varieties grown in south-eastern Italy to Drosophila suzukii
No full textSince 2008, Drosophila suzukii, the spotted wing drosophila, has colonized most of the
American and European continents, being able to adapt to very different climates. In
Italy, this pest has been captured from northern Alpine to southern Mediterranean
regions where it can infest a broad range of fruits, including wine grapes. Studies have
shown that oviposition levels and developmental rates of D. suzukii on wine grapes are
lower than on other berries, although recent observations indicate that grapes may
become a suitable host plant in particular conditions. Here, we report, for the first
time, the results of a series of no-choice oviposition experiments using berries of five
table grape varieties sampled in the provinces of Taranto and Bari (Apulia region,
south-eastern Italy) during 2013 from both organic and conventional farming systems.
The sugar content (SC) and skin hardness of each sample were analysed to assess the
influence of these physiological parameters on the susceptibility of table grapes to
D. suzukii infestation. A negative correlation was found between the number of eggs
laid and berry skin penetration force, whereas there was a positive one between the
number of eggs and Brix values, as well as sampling date. In organic grapes, SC and
skin hardness of two varieties (“Crimson” and “Scarlotta”) were measured, respectively,
higher and lower than in conventional grapes, thus making them more susceptible
to pest infestation. The study hence shows that in laboratory conditions D. suzukii
is able to heavily infest and develop on table grapes and that susceptibility to its infestation
significantly depends on both variety and farming system
Behavior-modifying and insecticidal effects of plant extracts on adults of Ceratitis capitata (Wiedemann) (Diptera Tephritidae)
No full textThe Mediterranean fruit fly Ceratitis capitata is a major pest of fruit orchards worldwide. In order to develop control methods based on natural products, particularly required in organic farming, a laboratory study was carried out to evaluate the response of adults to leaf extracts from four plant species: Ruta graveolens, Eriobotrya japonica, Rubus ulmifolius and Ficus carica. Air dried leaf powders were subjected to an ethanolic cold extraction. Chemical composition was assessed by GC/MS analysis. Extracts were tested in laboratory bioassays to assess the electroantennographic (EAG) response, attraction/repellence toward ovipositing females and induced mortality towards adults. Among the extracts tested, only R. graveolens elicited significant differences compared to the control in all the bioassays. This extract, whose main volatile compounds were 2-nonanone and 2-undecanone (45% of the total), recorded the greatest EAG response, and stimulated a positive oviposition response compared to the control. R. graveolens extract elicited a significant insecticidal activity, confirmed to be dose-dependent. LD50 and LD90 concentrations were 3.64% and 6.01% (v/v) respectively. To our knowledge this is the first study reporting a single plant extract, from R. graveolens, acting as attractant and oviposition stimulant, and at the same time having insecticidal properties toward C. capitata adults. The incorporation of such extract or its components into food bait could be useful in medfly “attract and kill” control strategies
Olive by-products as feed additives : in vitro evaluation on rumen fermentation parameters
No full textThe new technologies of olive fruits processing produce every year many tons of vegetable residues which must be disposed or recycled. Indeed, during the last decade, the use of olive by-products derived from the oil extractions has been intensively investigated in small ruminant feeding. However, these by-products have a low nutritional value by the presence of phenolics such as tannins, which may limit nutrient availability. Since numerous studies have highlight the beneficial effects of tannins at low levels of intake on efficiency of rumen microbial protein synthesis, the effects of olive fruits after oil extraction as feed additive on the in vitro rumen fermentation parameters were investigated. The batch culture incubation system was carried out with rumen fluid withdrawn from three rumen-fistulated not-lactating dairy cows. The rumen fluid was added to a mineral salt buffer, mixed in a bottle warmed at 39°C, purged whit anaerobic grade N2/CO2 (80/20, v/v) and standardized at pH 6.8 0.1. One hundred mL of solution were placed in glass bottles supplied whit a substrate for microbial growth (0.8 g/100ml alfalfa hay and 0.2 g/100ml corn meal). In this study, olive by-products were tested in duplicate at three different concentrations. The bottles were purged with anaerobic grade N2/CO2 (80/20, v/v), closed and incubated in a water shaking bath at 39°C for 9h. pH, VFA, ammonia N and Total Bacterial Count (TBC) were determined at 0 and 9h of incubation. Statistical analysis was performed using SAS. We tested olive fruits after oil extraction at low level of inclusion, as feed additive. Although, the NH3-N concentrations was not affected by this rich tannins waste, we evidenced a decreased in the total VFA concentration, significantly at the tested doses (P<0.001), showing a detrimental effect on rumen fermentation parameters. The hypothesis of their use as additives to modulate rumen fermentation was rejected. If they will be used for other purposes, these negative properties must be taken in account.This study was performed under European Community 6th Framework Program: EU Project SAFEWASTES n.513949
Behavioural responses of the egg parasitoid Trissolcus mitsukurii to the footprints of Halyomorpha halys and Nezara viridula
No full textTrissolcus mitsukurii is Asian egg parasitoids associated to different pentatomids such as Halyomorpha halys. Adventive populations of T. mitsukurii were found in Northern Italy showing a great impact on this pest, suggesting its exploitation as a biological control agent (BCA) against H. halys. Releasing an exotic parasitoid requires investigating the interaction BCA/environment, to avoid negative impacts on the entomofauna of the new habitat. Trissolcus mitsukurii is mainly associated to Nezara viridula in its native area, hence, we investigated the female parasitoid’s ability to distinguish between naturally released cues of H. halys and N. viridula and compared it with the foraging behaviour of Trissolcus japonicus. A single female parasitoid was exposed to contact kairomones of both pests, to evaluate its modifications in orthokinetic and locomotory behaviour. Additionally, for T. mitsukurii, synthetic compounds simulating the cues of the two pentatomids were used. The results confirmed the preference of T. japonicus for H. halys while T. mitsukurii preferred N. viridula’s cues. The significance and consequences of these results in the biological control of H. halys in invaded areas are discusse
Influence of distance from the host on parasitisation by Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae)
No full textThe olive fruit fly, Bactrocera oleae, is considered the main olive pest worldwide, and has been the target of biological control programmes through the release of the braconid parasitoid Psyttalia concolor. Laboratory tests were performed to evaluate the influence of distance from the host on parasitisation, placing larvae of the substitute host Ceratitis capitata at seven distances (0, 0.5, 1, 1.5, 2, 2.5, 3 mm) and four different time periods (7, 15, 30, 60 min). Moreover, field collected olives of Ogliarola Barese cultivar infested by B. oleae were exposed to P. concolor females to confirm its ability to parasitise B. oleae in small olives. Psyttalia concolor oviposition was inhibited at 2.5 and 3 mm due to the ovipositor length of the parasitoid females (2.7 mm). Hosts were easily parasitised at distances between 0 and 1.5 mm. The thin fruit pulp (up to 3.5 mm) of field collected olives allowed the parasitisation to occur also in mature fruits. At the best combination distance/time (0 mm, 30 min), tests performed with different larvae/parasitoid female ratio showed an increasing emergence of P. concolor (from 20% to 57%) with larvae/parasitoid ratio increasing from 0.11 to 0.74. The results of the present study might optimise the mass rearing of P. concolor, through a proper setting of its parameters, such as the host/parasitoid ratio, exposure distances, and interaction time
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