Dynamics of the Gut Bacteriome During a Laboratory Adaptation Process of the Mediterranean Fruit Fly, Ceratitis capitata.

Laboratory adaptation process used in sterile insect technique (SIT) programs can exert a significant impact on the insect-gut microbiome relationship, which may negatively impact the quality and performance of the fly. In the present study, changes in the gut microbiota that occur through laboratory adaptation of two Ceratitis capitata populations were investigated: Vienna 8 genetic sexing strain (GSS), a long-established control line, and a wild population recently introduced to laboratory conditions. The bacterial profiles were studied for both strains using amplicon sequencing of the 16S rRNA V3-V4 hypervariable region in larvae and in the gastrointestinal tract of teneral (1 day) and adults (5 and 15 days) reared under laboratory conditions for 14 generations (F0-F13). Findings demonstrated the development of distinct bacterial communities across the generations with differences in the bacterial composition, suggesting a strong impact of laboratory adaptation on the fly bacteriome. Moreover, different bacterial profiles were observed between wild and Vienna 8 FD-GSS displaying different patterns between the developmental stages. Proteobacteria, mainly members of the Enterobacteriaceae family, represented the major component of the bacterial community followed by Firmicutes (mainly in Vienna 8 FD-GSS adults) and Chlamydiae. The distribution of these communities is dynamic across the generations and seems to be strain- and age-specific. In the Vienna 8 FD-GSS population, Providencia exhibited high relative abundance in the first three generations and decreased significantly later, while Klebsiella was relatively stable. In the wild population, Klebsiella was dominant across most of the generations, indicating that the wild population was more resistant to artificial rearing conditions compared with the Vienna 8 FD-GSS colony. Analysis of the core bacteriome revealed the presence of nine shared taxa between most of the examined medfly samples including Klebsiella, Providencia, Pantoea, and Pseudomonas. In addition, the operational taxonomic unit co-occurrence and mutual exclusion networks of the wild population indicated that most of the interactions were classified as co-presence, while in the Vienna 8 FD-GSS population, the number of mutual exclusions and co-presence interactions was equally distributed. Obtained results provided a thorough study of the dynamics of gut-associated bacteria during the laboratory adaptation of different Ceratitis capitata populations, serving as guidance for the design of colonization protocols, improving the effectiveness of artificial rearing and the SIT application.

Sterile Insect Technique Programme against Mediterranean Fruit Fly in the Valencian Community (Spain).

The Mediterranean fruit fly, Ceratitis capitata (Wied.), is an endemic pest in fruit-growing areas of the Spanish Mediterranean coast. In the Valencian Community, it represents a serious problem in the cultivation of citrus and numerous species of fruit, such as peach, cherry, apricot, persimmon, etc. For over 50 years, the Department of Agriculture of Valencia has led, promoted, and carried out a C. capitata control programme to protect crops, especially citrus fruits, because this community is the largest national producer and the leading region for fresh citrus exports in the world. Traditionally, pest control has been based on the use of insecticides. However, a reduction of more than 90% of a target wild population was achieved in the frame of a pilot integrated pest management (IPM) project based on the sterile insect technique (SIT), which was implemented from 2003 to 2006. Based on this successful result, in 2007 the Department of Agriculture of Valencia initiated an area-wide integrated pest management (AW-IPM) programme for the suppression of C. capitata, using the SIT as the primary control method. Complementary activities are implemented periodically in hotspots and during different time periods depending on the pest population dynamics. As a result, there has been a reduction of more than 90% in the use of insecticides by aerial means to control C. capitata, as well as a growth trend in exports of citrus and fresh fruits from the Valencian Community in recent years. This paper provides a historical review of the Valencian programme and briefly describes how technological innovations and decision-making tools have contributed to programme efficiency.

Development of an attract-and-infect system to control Rhynchophorus ferrugineus with the entomopathogenic fungus Beauveria bassiana.

BACKGROUND: A new Beauveria bassiana-based attract and infect device (AID) to control Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) was developed. The virulence and persistence of the fungal formulation used in the AID were evaluated in the laboratory. Semi-field and field trials were carried out to validate the results and establish the potential of this device as a control tool. RESULTS: In laboratory conditions, a 50% lethal time (LT50 ) of 4.33 days was obtained when adults (7-10 days old) were exposed to the inoculation tunnel (IT) containing 1 × 1010 conidia g-1 in an oil-based fungal formulation. This formulation maintained conidium viability at 50% for up to 2 months. Moreover, when adults were exposed to 2.5-month field-aged ITs, mortality still reached 50% 40 days after exposure. In addition, no differences were observed between ITs aged in early spring and those aged in summer, suggesting that the fungal formulation is not strongly affected by environmental factors in Mediterranean basin conditions. Semi-field assays showed that the device allowed an easy transit of weevils through the IT, which were effectively attracted and infected. Using the AIDs in 4-ha plot field trials, a reduction of >50% in the percentage of infested sentinel palms was obtained. CONCLUSION: Based on the results obtained in terms of the efficacy and persistence of this new AID in the field and its potential in reducing R. ferrugineus populations and palm infestation, this device could become a key tool for the management of R. ferrugineus. © 2018 Society of Chemical Industry.

Mobility and efficacy of abamectin and imidacloprid against Rhynchophorus ferrugineus in Phoenix canariensis by different application methods.

BACKGROUND: Rhynchophorus ferrugineus is the most destructive pest of palms. As detection of early infestation stages is difficult, preventive measures, mostly chemical control, are crucial. Stipe injection of insecticides has developed rapidly as a suitable technique. However, pesticide movement within palms and palm reaction to wounding remain controversial. We used abamectin and imidacloprid applied by crown spray, stipe and frond injections to disentangle how these pesticides move within P. canariensis and how tissues wounded by injection heal. Furthermore, we established their lethal doses to larvae of R. ferrugineus. RESULTS: Maximum residues of imidacloprid (0.1 mg kg(-1) ) were detected in crown and frond samples for up to 2 months after stipe injection, whereas maximum residues of abamectin were found in frond tip samples (0.5 mg active substance kg(-1) ) 5 months after stipe injection. Based on the lethal concentrations calculated, these doses could satisfactorily protect palms for up to 3 months after treatment. No significant wound damage was observed 2 years after injection. CONCLUSION: Stipe injection, irrespective of the active substance considered, resulted in better distribution and higher persistence compared with frond injection and, especially, crown spray. As a consequence, our results point to stipe injection as a good alternative to control R. ferrugineus.

Potential of an indigenous strain of the entomopathogenic fungus Beauveria bassiana as a biological control agent against the Red Palm Weevil, Rhynchophorus ferrugineus.

The potential of a strain of Beauveria bassiana (Ascomycota: Clavicipitaceae) obtained from a naturally infected Rhynchophorus ferrugineus (Coleoptera: Curculionidae) pupa as a biological control agent against this weevil was evaluated both in the laboratory and in semi-field assays. Laboratory results indicate that this strain of B. bassiana can infect eggs, larvae and adults of R. ferrugineus (LC(50) from 6.3 x 10(7) to 3.0 x 10(9) conidia per ml). However, mortality was not the only indicator of treatment efficacy because adults of either sex inoculated with the fungus efficiently transmitted the disease to untreated adults of the opposite sex, with male-to-female and female-to-male rates of transmission of 55% and 60%, respectively. In addition, treatment with B. bassiana significantly reduced fecundity (up to 62.6%) and egg hatching (32.8%) in pairing combinations with fungus-challenged males, females or both sexes. Likewise, 30-35% increase in larval mortality was observed in larvae obtained from eggs from fungus-challenged females or from untreated females coupled with inoculated males, resulting in an overall 78% progeny reduction. Semi-field preventive assays on potted 5-year old Phoenix canariensis palms, with efficacies up to 85.7%, confirmed the potential of this strain as a biological control agent against R. ferrugineus.

Field efficacy of imidacloprid and Steinernema carpocapsae in a chitosan formulation against the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) in Phoenix canariensis.

BACKGROUND: The invasive red palm weevil, Rhynchophorus ferrugineus (Olivier), has become the major pest of palms in the Mediterranean Basin. Chemical control against this species is difficult because of its cryptic habits and is mainly based on the repeated application of large quantities of synthetic insecticides. The aim of this work has been to evaluate in the field the efficacy of imidacloprid (Confidor 240 OD) and Steinernema carpocapsae Weiser with chitosan (Biorend R Palmeras) as soil and stipe treatments respectively, alone or in combination, against this pest. RESULTS: All treatments significantly reduced the mean number of immature stages of R. ferrugineus per palm. However, there were no significant differences among the different treatments considered. Efficacies ranged from 83.8 to 99.7% for the mean number of immature stages found in the palms and resulted in a significant increase in palm survival compared with the untreated control (75.0-90.0% versus 16.5% respectively). CONCLUSION: Both imidacloprid and S. carpocapsae in a chitosan formulation proved highly effective against R. ferrugineus in the field, and their efficacies did not significantly change when used in combination.

Chemical alternatives to malathion for controlling Ceratitis capitata (Diptera: Tephritidae), and their side effects on natural enemies in Spanish citrus orchards.

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is one of the most important fruit pests worldwide. Mediterranean fruit fly control in Spain has been based on organophosphate sprays, especially malathion, mixed with protein baits. However, this insecticide has recently been excluded from annex 1 of the Directive 91/414 CEE, which lists authorized active ingredients for pest control in the European Union. This article reports on the efficacy of four alternative baited insecticides on Mediterranean fruit fly and their side effects on three natural enemies [Cryptolaemus montrouzieri (Mulsant), Neoseiulus californicus (McGregor), and Aphidius colemani (Viereck)] relevant for pest control in citrus agroecosystems. A high Mediterranean fruit fly mortality was obtained for all baited insecticides (phosmet and spinosad) except lambdacyhalothrin, which caused the lowest mortality and showed a novel disabling effect on surviving Mediterranean fruit fly adults. Spinosad proved to be the most selective bait treatment for C. montrouzieri and N. californicus, whereas for A. colemani the most selective bait was phosmet and lambda-cyhalothrin. These findings would contribute to a sustainable chemical control of C. capitata populations under an integrated pest management system in Spanish citrus orchards.

Survey of natural enemies of spider mites (Acari: Tetranychidae) in citrus orchards in eastern Spain.

Field surveys were conducted from 2004 to 2007 to determine the species composition and relative abundance of natural enemies associated with colonies of either the citrus red mite, Panonychus citri, or the two spotted spider mite, Tetranychus urticae, in Valencian citrus orchards (eastern Spain). Fourteen species were recorded, six phytoseiid mites and eight insect predators. Two of them are reported for the first time on citrus in Spain and two more are first reports as predators associated with T. urticae. The community of predators associated with T. urticae and P. citri was almost identical, and the Morisita-Horn index of similarity between both natural enemy complexes was close to one, suggesting that predators forage on both pest species. Quantifying the presence of many known spider mites predators in Valencian citrus orchards is an important first step towards spider mite control. A challenge for future studies will be to establish conservation and/or augmentation management strategies for these predators, especially to improve T. urticae biological control.

Efficacy of five selected acaricides against Tetranychus urticae (Acari: Tetranychidae) and their side effects on relevant natural enemies occurring in citrus orchards.

BACKGROUND: Three groups of natural enemies are fundamental in citrus IPM in Spain: coccinellid and phytoseiid predators and hymenopteran parasitoids. Tetranychus urticae Koch is an important pest affecting citrus, for which biological control has not yet been achieved; therefore, acaricides are commonly used to control it. The goal of this study was to measure the efficacy of different acaricides on this mite and their side effects on three natural enemies relevant for citrus (Cryptolaemus montrouzieri Mulsant, Neoseiulus californicus McGregor and Aphidius colemani Viereck). RESULTS: Some products proved highly effective against T. urticae and harmless to A. colemani (mineral oil, tebufenpyrad, clofentezine and fenazaquin). However, almost all products tested were slightly harmful for both the predators considered. Fenazaquin was even moderately harmful for N. californicus. CONCLUSION: Further studies, like that presented here, are necessary to gain a better understanding of integrating biological and chemical controls. When considering both efficacy and side effects on beneficial arthropods, the best options would seem to be mineral oil, tebufenpyrad and clofentezine. However, it is urgent to complete testing of the side effects of the acaricides used in citrus. This question is crucial if the fact that two recently introduced Tetranychidae are being controlled in citrus by chemical means exclusively is considered.