AGRIS Sardegna DIRVE

Cagliari, Italy

AGRIS Sardegna DIRVE

Cagliari, Italy

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MacHtelinckx T.,Ghent University | Van Leeuwen T.,Ghent University | Van De Wiele T.,Ghent University | Boon N.,Ghent University | And 5 more authors.
BMC Microbiology | Year: 2012

Background: The predatory mirids of the genus Macrolophus are key natural enemies of various economically important agricultural pests. Both M. caliginosus and M. pygmaeus are commercially available for the augmentative biological control of arthropod pests in European greenhouses. The latter species is known to be infected with Wolbachia -inducing cytoplasmic incompatibility in its host- but the presence of other endosymbionts has not been demonstrated. In the present study, the microbial diversity was examined in various populations of M. caliginosus and M. pygmaeus by 16S rRNA sequencing and denaturing gradient gel electrophoresis. Results: Besides Wolbachia, a co-infection of 2 Rickettsia species was detected in all M. pygmaeus populations. Based on a concatenated alignment of the 16S rRNA gene, the gltA gene and the coxA gene, the first is phylogenetically related to Rickettsia bellii, whereas the other is closely related to Rickettsia limoniae. All M. caliginosus populations were infected with the same Wolbachia and limoniae-like Rickettsia strain as M. pygmaeus, but did not harbour the bellii-like Rickettsia strain. Interestingly, individuals with a single infection were not found. A PCR assay on the ovaries of M. pygmaeus and M. caliginosus indicated that all endosymbionts are vertically transmitted. The presence of Wolbachia and Rickettsia in oocytes was confirmed by a fluorescence in situ hybridisation. A bio-assay comparing an infected and an uninfected M. pygmaeus population suggested that the endosymbionts had minor effects on nymphal development of their insect host and did not influence its fecundity. Conclusion: Two species of the palaearctic mirid genus Macrolophus are infected with multiple endosymbionts, including Wolbachia and Rickettsia. Independent of the origin, all tested populations of both M. pygmaeus and M. caliginosus were infected with three and two endosymbionts, respectively. There was no indication that infection with endosymbiotic bacteria had a fitness cost in terms of development and fecundity of the predators. © 2012 Machtelinckx et al; licensee BioMed Central Ltd.


Nannini M.,AGRIS Sardegna DIRVE | Atzori F.,AGRIS Sardegna DIRVE | Murgia G.,AGRIS Sardegna DIRVE | Pisci R.,AGRIS Sardegna DIRVE | Sanna F.,AGRIS Sardegna DIRVE
EPPO Bulletin | Year: 2012

The introduction of Tuta absoluta in Sardinia (Italy) has caused an important increase in the number of insecticide treatments applied for pest management on greenhouse tomatoes, thus raising growers' demand for alternative control options. To evaluate the efficacy of releasing two specimens of Macrolophus pygmaeus or Nesidiocoris tenuis per m 2 for the control of tomato borer infestations, an investigation was conducted under field conditions between August 2010 and July 2011. The tests were carried out on 18 commercial greenhouse crops. Fifteen other greenhouses, where no biocontrol agents were released, were also surveyed as controls. The release of the mirid bugs resulted in poor population growth of predators, which reached a peak density of 1.79 individuals per plant. In approximately half of the cases, this was caused by the application of pesticides (usually abamectin and oxamyl) which are highly toxic to the predatory mirids. However, even in crops where only products regarded as harmless to beneficials were used (e.g. Bacillus thuringiensis-based insecticides), both M. pygmaeus and N. tenuis failed to achieve the levels necessary for effective pest control. Presumably factors other than pesticide-related mortality contributed significantly to delaying mirid population build-up. Further studies are necessary to evaluate the feasibility of improving the efficacy of releases of the predatory mirids by the implementation of measures that may contribute to enhancing the establishment of these beneficials on tomato crops. © 2012 The Authors. Journal compilation © 2012 OEPP/EPPO.


Marongiu G.,AGRIS Sardegna DIRVE | Sanna D.,AGRIS Sardegna DIRVE
Acta Horticulturae | Year: 2011

Tomato spotted wilt virus (TSWV) has recently been reported to cause severe damage to globe artichokes in Northern Sardinia (Italy). The disease is vectored by several thrips species previously regarded as secondary pests of this vegetable crop. For this reason, no specific control measures against thrips have been routinely adopted on globe artichokes. To evaluate their efficacy for the management of TSWV vectors, four insecticides currently registered in Italy for use on globe artichokes (spinosad, deltamethrin, lambda-cyhalothrin, and lufenuron), and two bio-insecticides used for thrips control on other crops (azadirachtin and a Beauveria bassiana-based product) were tested under semi-field conditions. While azadirachtin and B. bassiana were applied three times, all other products were sprayed twice. Twelve potted plants (4-10-leaf stage) were replicated four times in a completely randomized design. The mean number of live thrips present on four leaves randomly selected from each replicate was counted 3, 15, and 21 days after the first treatment. Infestation data were log-transformed prior to performing the ANOVA. The results achieved indicate deltamethrin and lambda-cyhalothrin to be the most active ingredients among the products tested. While spinosad and lufenuron proved effective after just two treatments, plants sprayed with B. bassiana and azadirachtin did not show any difference in terms of pest infestation compared to the controls. Although all the insecticides authorized for use on globe artichokes were found to be active against thrips, further studies are necessary to gather evidence of their efficacy for TSWV management. The two bio-insecticides tested here did not appear to be a reliable means of disease control.


Testa M.,AGRIS Sardegna DIRVE | Cadinu M.,AGRIS Sardegna DIRVE | Pilia R.,AGRIS Sardegna DIRVE | Pintore R.,AGRIS Sardegna DIRVE | Baghino L.,AGRIS Sardegna DIRVE
Acta Horticulturae | Year: 2013

Different extraction and detection methods were compared to evaluate the virus status of artichoke plants produced in vitro. These diagnostic procedures were performed to assess the efficacy of in vitro thermotherapy and/or meristem tips culture for obtaining virus-free plants. The viruses studied were: Artichoke Italian latent virus (AILV), Artichoke latent virus (ArLV), and Tomato spotted wilt virus (TSWV). In our experience, the most suitable detection method for in vivo analysis proved to be the tissue print hybridization on nylon membranes. This procedure is sufficiently sensitive and reliable, but at the same time less expensive than the other methods tested. When testing materials obtained in vitro, sometimes this method is not sufficiently sensitive, and false negatives frequently appear. The results of meristem tip culture showed that the excision of apices alone is generally insufficient to obtain AILV-free plants (3.3%), but better results were obtained for ArLV elimination (78.9% virus free plants ). The effectiveness of thermotherapy followed by meristem tip culture reached 100% for AILV and 0% for ArLV. For TSWV we have the result only of meristem tip culture, with percentage recovery of 98.51% (first Trial, subsequently abbreviated T1) and 45.95% (second Trial, subsequently abbreviated, T1R).


PubMed | Agris Sardegna DIRVE
Type: Journal Article | Journal: Communications in agricultural and applied biological sciences | Year: 2010

Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV) are among the most virulent pathogens of greenhouse tomatoes in Sardinia (Italy). To investigate the relationship between seasonal population trends of the vector Bemisia tabaci and the dynamics of TYLCD spread to susceptible crops, between May and October 2007 we carried out a survey in a tomato growing area located in the south of the island. On three farms specialized in the production of fresh market tomatoes we monitored, outside commercial greenhouses, the following parameters related to TYLCD epidemiology: mean weekly catches of the whiteflies B. tabaci and Trialeurodes voporariorum on yellow sticky traps, ratio between the two whitefly species and proportion of B. tabaci adults carrying TYLCSV/TYLCV in adult samples collected on hosts not susceptible to the disease, proportion of tomato plants infected by TYLCSV/TYLCV after a two-week exposure to open field conditions. Generally speaking, the flight activity of whiteflies increased during spring, reached a peak in May or June and gradually declined in summer. At the beginning of the survey, T. vaporariorum was found to be the prevalent species, but after a shift in composition of whitefly populations during July, B. tabaci became predominant. While the percentage of vector adults carrying the viral agents of the disease was relatively high up to July, with maximum values ranging between 14 and 25%, during the following months it decreased to less than 5%. The incidence of TYLCD in the plants exposed outside the greenhouses showed a similar trend in the sites surveyed, with two peaks roughly coinciding with the beginning and end of summer. Therefore, two distinct phases of TYLCD spread were observed: from spring to midsummer when the disease was transmitted by low 8. tabaci populations with relatively high proportions of virus carriers; from midsummer to autumn, when the disease was spread by larger vector populations with low percentages of individuals carrying the viruses. Further studies are necessary to gain a better understanding of the interactions among B. tabaci biotypes, TYLCSV/TYLCV and their hosts.


PubMed | Agris Sardegna DIRVE
Type: Journal Article | Journal: Communications in agricultural and applied biological sciences | Year: 2010

The whiteflies Bemisia tabaci and Trialeurodes vaporariorum and their associated viruses constitute a major threat to tomato crops in the Mediterranean region. Continuous host availability and mild climate are thought to be among the factors contributing to the outbreaks of whitefly-related problems in this area. We carried out a year-long survey to investigate the relative contribution of different plants, agricultural and not, and indoor/outdoor crops as hosts of the two whiteflies and the tomato yellow leaf curl disease (TYLCD) in a multi-crop system typical of tomato growing areas in southern Sardinia (S. Margherita di Pula, Cagliari, Italy). For this purpose, during 2005 we monitored whitefly population trends in different plots of a horticulture farm, evaluated seasonal changes in the infestation density of the two pests on the most represented host species and assessed the incidence of TYLCD on tomato crops and susceptible weeds. Whitefly catches on yellow sticky traps were found to be higher inside et along the external perimeter of greenhouses compared to open field crops or uncultivated areas, thus suggesting significant adult movement between indoor and outdoor patches. In most plots flight activity increased between late spring and late summer, peaking in July. The number of immatures of the two whitefly species showed similar dynamics, but while T. vaporariorum reached the highest densities in greenhouse tomato crops in June, peak levels of 8. tabaci were recorded between July and August in outdoor horticultural crops and weeds. The occurrence of TYLCD was detected all year round on weed hosts, but the highest number of infected plants was observed in June on long cycle tomato crops. The present survey has demonstrated the contribution of non-agricultural plants the maintenance of tomato yellow leaf curl disease in the study site. However, tomato crops established in summer as major reservoirs of TYLCD-associated viruses and presumably played a key role in the spread of the disease to autumn tomato crops. The implementation of a crop-free period between successive susceptible crops, or at least the avoiding of whitefly movement through greenhouse openings and the complete destruction of plants after final harvest, would probably reduce the severity of TYLCD epidemics in this area.


PubMed | Agris Sardegna DIRVE
Type: Journal Article | Journal: Communications in agricultural and applied biological sciences | Year: 2010

To evaluate the effectiveness of alternative options for biocontrol of whiteflies in greenhouse tomatoes, an experiment was carried out during the cropping season 2005-2006 in one of Sardinias major horticultural districts (S. Margherita di Pula, Cagliari, Italy). Twelve long-cycle and 17 short-cycle tomato crops (8 autumn and 9 spring crops) were surveyed. All of them were treated for insect pest control at the beginning of the growing season, but in 19 out of 29 cases whitefly natural enemies were also released (BCA greenhouses), at least four weeks after the last treatment. The following release programmes were tested: on autumn crops, 1 Macrolophus caliginosus and 12 Eretmocerus mundus/m2; on long-cycle crops, 1 M. caliginosus (released in autumn or spring) and 24 Encarsia formosa/m2 or 48 E. formosa/m2; on spring crops, 1 M. caliginosus and 24 E. formosa/m2 or 48 E. formosa/m2. The cost of each option was fixed at approximately 0.25 Euros/m2. The remaining greenhouses were maintained as controls (no BCA greenhouses). While whitefly and mirid populations were monitored monthly, whitefly species composition and mortality of immature stages were estimated at least twice during the growing season. On short-cycle autumn crops, the release of M. caliginosus and E. mundus produced negligible results in terms of Bemisia tabaci control. On long-cycle and spring crops, even though in June mortality rates in BCA greenhouses were found to be 2- to 3-fold higher than in no-BCA greenhouses, Trialeurodes vaporariorum population growth was not significantly affected by natural enemies. Among the beneficials tested, E. formosa proved to be the most effective; E. mundus and M. caliginosus did not establish well, probably owing to the persistence of insecticide residues, scarce prey availability and intense plant de-leafing. The presence of indigenous natural enemies of whiteflies was observed in most sites, but in general they contributed little to biological control. The present experiment showed that in Sardinian tomato greenhouses the use of beneficial insects may result in inadequate biocontrol of whiteflies. In particular, the application of cultural practices which may disrupt the establishment and development of predator and parasitoid populations should be critically reexamined.

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