Jorge Toledo's research while affiliated with El Colegio de la Frontera Sur and other places

Functional response and mutual interference are important attributes of natural enemies that should be analysed in species with the potential to be used as biological control agents in order to increase the predictive power of the possible benefits and/or consequences of their release in the field. Our main objective was to determine the functional response and mutual interference of Coptera haywardi (Oglobin), a pupal parasitoid of economically important fruit flies (Diptera: Tephritidae). The functional response of C. haywardi on A. ludens pupae corresponded to a type II model, with an attack rate of 0.0134 host pupa/h and a handling time of 1.843 h, which reveals a meticulous selection process of pupal hosts. The effect of mutual interference among foraging females was negatively correlated with increased parasitoid density in the experimental arena, showing a gradual decline in attack rate per individual female. The increase in the number of foraging females also had an impact on the number of oviposition scars per pupa and the number of immature parasitoids per dissected pupa, but not on the percentage of adult emergence or the sex ratio. Our results suggest that C. haywardi could act as a complementary parasitoid in the control of fruit fly pupae, since the random distribution of these pupae in the soil would decrease the possibility of aggregation and mutual interference between foraging females.

Fruit flies (Diptera: Tephritidae) are serious pests that affect fruit production and marketing. Both third instar larvae and pupae are biological stages that persist in the soil until adult emergence. Entomopathogenic nematodes (ENs) are biological control agents that are used to control agricultural pests in greenhouse or field conditions. Several studies have been carried out under laboratory and field conditions showing how ENs can be applied within an area-wide integrated pest management approach to control fruit fly species in orchards and backyard fruit trees. In this review, we analyze how soil physical characteristics and biotic factors affect the performance of these biological control agents. Of the reviewed papers, more than half evaluated the influence of soil texture, humidity, temperature, and other factors on the performance of infective juveniles (IJs). Abiotic factors that significantly influence the performance of IJs are temperature, humidity, and texture. Among the biotic factors that affect IJs are fungi, bacteria, mites, insects, and earthworms. We conclude that ENs have the potential to be applied in the drip area of fruit trees that are infested by fruit flies and contribute to their suppression. This approach, in conjunction with an area-wide pest management approach, may contribute to pest suppression and increase the sustainability of agroecosystems.

Knowledge on reproductive strategies and host use in insect parasitoids is fundamental for biological control purposes. Superparasitism and multiparasitism, oviposition in a previously parasitized host by a female of the same or different species, respectively, may impact pest management decisions. Our objective was to determine the occurrence of superparasitism and multiparasitism in three species of native larval−pupal solitary endoparasitoids that attack Anastrepha Shiner species (Diptera: Tephritidae) in the Neotropical region, and the possible effect on offspring fitness parameters. Doryctobracon crawfordi (Viereck), Utetes anastrephae (Viereck), and Opius hirtus (Fischer) occur in sympatry in Mexico, and are currently under consideration for use as biocontrol agents. Experiments were conducted under laboratory conditions with females acting alone (self-superparasitism), females in groups of the same species (conspecific superparasitism), and females in mixed groups (multiparasitism). Our results showed that self-superparasitism is an uncommon strategy in the three native species and is rare under conditions of intraspecific competition. In the case of multiparasitism, a higher number of immature stages of U. anastrephae was observed, compared to those of D. craw-fordi and O. hirtus. However, it is not clear yet if this was due to some adult female trait or to the competitive ability of the larvae. We conclude that most females of the native species studied appeared to avoid superparasitism, specifically when acting alone, suggesting a high discrimination ability, which is probably a result of a close relationship and evolutionary history with Anastrepha hosts.

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is a polyphagous pest that feeds upon more than 300 host plants, including fruits and vegetables. To eradicate this pest, the Mexican program (Programa Moscamed) targeting fruit flies applied a novel approach that works with the sterile insect technique (SIT) by inoculating sterile flies with fungal spores of a commercial formulation of Beauveria bassiana (Balsamo) Vuillemin. Dissemination occurs through contact with the sterile insect with wild populations. However, the fungus is known to reduce the homeostatic condition of the vector (sexual and aggressive interactions) to the point that it affects physical contact with the receptor. The objective was to evaluate the effect of B. bassiana on the sexual performance and survival of sterile males of the C. capitata strain VIENNA 8. Mating competition, induction of sterility, production of the sexual pheromone and survival were compared between inoculated and non‐inoculated sterile males. The parameters evaluated were fundamental to evaluate the success in the SIT. The results of the study indicated that the inoculated males with B. bassiana showed a gradual decrease in sexual performance (mating, induction of sterility and production of the sexual pheromone) and survival after treatment. We conclude that for SIT release programs, the effectiveness of targeted males is up to 5 days post‐inoculation. The implications of this biological control method in SIT are discussed.

The capacity of a parasitoid to discriminate hosts can favor the survival of its progeny as well as improve its efficacy as a biocontrol agent when it is used with another natural enemy, as this may result in greater control of the pest. Our aim was to characterize the discrimination ability of Coptera haywardi (Oglobin) (Hymenoptera: Diapriidae) females with respect to puparia of Anastrepha obliqua (Macquart) (Diptera: Tephritidae) treated with the fungus Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae), under three conditions: (1) no choice, separately exposing A. obliqua puparia treated 0, 24, 48, or 72 h prior to exposure to the parasitoid and without application of the fungus (absolute control); (2) with the possibility of choosing between untreated and treated puparia with the same times after fungus application; and (3) multiple choice, where parasitoids could select among puparia treated at different times. Observations were made to determine the discrimination behavior of the wasps as well the number of ovipositions by each female parasitoid; 14 observations were made. Coptera haywardi exhibited different levels of discrimination depending on the test. In the no‐choice test, discrimination was not observed; in the two‐choice test, females significantly discriminated the puparia treated 0, 24, and 72 h prior to exposure; and in the multiple‐choice test, females preferred the untreated puparia – behavior that was corroborated in the direct observations. Oviposition time ranged from 9 to 86 min and differences in average time among treatments were not significant. We conclude that the discrimination ability of C. haywardi allows the simultaneous use of B. bassiana, as females prefer healthy, untreated puparia without interfering with the fungus.

Spotted-Wing Drosophila (SWD), Drosophila suzukii Matsumura is an invasive fruit fly pest of soft-skinned fruits that causes serious economic losses in the berry growing areas of central Mexico. Effective attractants are necessary to detect its presence, to monitor populations where established, and to explore new strategies for pest control. The capture of D. suzukii in four food-based attractants was compared with apple cider vinegar (ACV) as the reference attractant in blackberry, raspberry, and blueberry crops. An active yeast-based lure, Fly Buster Powder®, resulted the most effective attractant capturing SWD flies in blackberry and blueberry. However, this attractant was similar to SuzukiiTrap® Max Captures, ACV and Pherocon® SWD, but less effective than a two-component attractant (2C trap) in raspberry. The specificity of attractants was variable among crops and experiments but Fly Buster Powder® tends to be highly selective in the capture of SWD with up to 70% of D. suzukii from all drosophilids captured. Fly Buster Powder® and 2C trap attractants were more effective trapping D. suzukii when aged for 7 days than when aged for 1 or 15 days. The specificity of both yeast-based attractants was significantly reduced when aged for 15 days than when aged for 1 or 7 days.

Separation of the sexes is necessary for the application of the sterile insect technique (SIT) in mosquitoes due to the hematophagous habits and disease vector activity of the females. In this review we analyze the history, current status, and future perspectives for the development of genetic sexing strains (GSS) of Aedes mosquitoes (Diptera: Culicidae). Various genetic control methods for mosquitoes are reviewed, as are their need for sex-separation methods. We focus on areas of opportunity where GSS developed with classical genetic methods can be used. Regulatory restrictions and social acceptance of various control methods are analyzed. We conclude that the development of GSS by classical methods represents the most viable option for separation of the sexes and the application of large-scale SIT programs within an area-wide integrated vector management (AW-IVM) approach.

The Sterile Insect Technique (SIT) has been successfully used for the control of fruit flies in a number of places in the world. One requirement for its successful application is that wild populations should be at low densities to achieve effective sterile to wild fly overflooding ratios. This has been an important reason that has limited its integration in fruit fly management in tropical fruit growing areas, where climate conditions and the availability of hosts all year-round results in high population densities. Here we report the results of a project where SIT integration into fruit fly management was evaluated under the tropical conditions of the mango growing area in the Soconusco region of Chiapas, Mexico. The basis for the area-wide integrated pest management (AW-IPM) approach was the knowledge of the population dynamics of the pest fruit flies in the region and of the fruit phenology. The main commercial mango growing areas are in the lowlands, where fruit fly populations are very low outside of the mango production season. Population densities are higher in the midlands and highlands, where alternate hosts are common in backyards and as part of the natural vegetation. We call these refuge areas, and the AW-IPM approach aimed at establishing a biological barrier with releases of parasitoids and sterile male fruit flies to suppress the fruit fly populations and prevent or minimize the dispersal of wild flies from the refuge areas to the mango orchards. In 2014, after two years of releases, fruit fly population densities were suppressed more than 70% in the release area and 65% in the entire area, including the lowlands with the mango orchards. With the support of fruit growers, state and federal governments, this project was continued and established as an operational AW-IPM programme. In 2016, after 4 years of programme implementation, the detection of wild flies was significantly reduced, and the number of batches of fruit that were rejected at the packing houses due to the detection of infested fruits was the lowest in the past 12 years, since the recording of these data was initiated. These indicators declined even further in 2017. The results obtained demonstrate that AW-IPM integrating the SIT can be applied successfully against fruit flies under tropical conditions with naturally high pest densities, providing there is adequate knowledge on the population dynamics of the fruit fly species present in the region.

Purpureocillium lilacinum is an entomopathogenic fungus. An experiment was conducted to see the sublethal effects of P. lilacinum on Anastrepha ludens adults. The infection of P. lilacinum reduced daily food consumption per fly ranging from 4.25 ± 0.28 to 6.44 ± 0.27 µl for infected flies, and from 6.30 ± 0.28 to 7.81 ± 0.22 µl for non-infected control flies. The age of treatment in males showed a significant effect on their ability to mate (χ2 = 5.32, P < 0.02). Early stage infection (4 days-old), reduced the male mating propensity significantly (10 ± 0.46 treated to 15.4 ± 0.26 untreated, F 8, 5.94 = 5.592, P < 0.01), compared to later stage (8 days-old) insignificant effect. No effect of fungal infection on an ability of male to inseminate the females was noticed, as fertility of the females mated with infected males was not declined. An inoculated single female (mixture of talc and P. lilacinum) was able to transmit conidia to four groups of 10 males within four days. Males exposed to females on the first day acquired in average 1.7 ⋅ 106, on the second day 1.7 ⋅ 105, on the third day 7.3 × 104 and the fourth day 3.5 ⋅ 104 conidia/ male; which resulted 67.5, 55.0, 20.0, and 7.5 % male mortality, respectively. Our study demonstrated that horizontal transmission through copulation could be used to suppress A. ludens populations.