The ground beetle Pseudophonus rufipes revealed as predator of Ceratitis capitata in citrus orchards

The Mediterranean fruit fly Ceratitis capitata (Wiedemann) is a major citrus pest in Spain. Although medfly is being controlled chemically, alternative biorational strategies should be developed, like those based on conservation biological control of polyphagous predators. The ground beetle Pseudophonus rufipes (De Geer) is the most abundant carabid inhabiting the ground of citrus orchards in eastern Spain. However, little is known about its activity-density and predatory role against C. capitata in the citrus agroecosystem. Here, we report on its predatory potential on the medfly's developmental stages that take place in the citrus ground. This carabid species preyed efficiently on C. capitata third instar larvae and especially on pupae but not on teneral adults. Moreover, predation under field conditions was evaluated by detecting C. capitata DNA remains using PCR-based gut-content analysis. Half-life DNA detectability of C. capitata was of 32.33 h. Pseudophonus rufipes specimens were field-collected after C. capitata sterilized pupae were deployed in a commercial citrus orchard. Thereafter, the carabids captured by pitfall traps were analyzed, being DNA-remains of C. capitata detected in 22.2% of them. Data reported here clearly suggest that P. rufipes could play an important role in regulating medfly populations in citrus orchards. This information is particularly useful when biological control conservation strategies are being considered to control this pest

A Minor Role of Host Fruit on the Parasitic Performance of Aganaspis daci (Hymenoptera: Figitidae) on Medfly Larvae

Host fruit is known to strongly affect the performance of both fruit pests and their potential natural enemies. This is particularly important in the control of tephritid fruit flies, whose larvae develop inside the fruit and thus create a set of foraging problems for parasitoids. In the present study, we assessed the response of female Aganaspis daci (Weld) (Hymenoptera: Figitidae), one of the most promising parasitoids for tephritid biocontrol in the Mediterranean Basin, to different potential host fruit species. We measured the olfactory response to medfly-infested and uninfested fruits, and several biological parameters of A. daci when different infested fruits were offered under both laboratory and greenhouse conditions. Our results showed that this parasitoid was significantly more attracted to apples and uninfested fruit. Moreover, parasitic activity was similar among the tested fruits under both conditions, showing very high values in the laboratory and a much poorer performance when conditions were variable. This suggests that A. daci may be a good candidate to be included in mass releases against the medfly regardless of the affected crop, but only when climate conditions are not expected to hinder its normal activity

Improving the Sterile Sperm Identification Method for Its Implementation in the Area-Wide Sterile Insect Technique Program Against Ceratitis capitata (Diptera: Tephritidae) in Spain

The success of sterile males in area-wide sterile insect technique (aw-SIT) programs against Ceratitis capitata (Wiedemann) is currently measured by using indirect methods as the wild: sterile male ratio captured in monitoring traps. In the past decade, molecular techniques have been used to improve these methods. The development of a polymerase chain reaction-restriction fragment-length polymorphism-based method to identify the transfer of sterile sperm to wild females, the target of SIT, was considered a significant step in this direction. This method relies on identification of sperm by detecting the presence of Y chromosomes in spermathecae DNA extract complemented by the identification of the genetic origin of this sperm: Vienna-8 males or wild haplotype. However, the application of this protocol to aw-SIT programs is limited by handling time and personnel cost. The objective of this work was to obtain a high-throughput protocol to facilitate the routine measurement in a pest population of sterile sperm presence in wild females. The polymerase chain reaction-restriction fragment-length polymorphism markers previously developed were validated in Mediterranean fruit fly samples collected from various locations worldwide. A laboratory protocol previously published was modified to allow for the analysis of more samples at the same time. Preservation methods and preservation times commonly used for Mediterranean fruit fly female samples were assessed for their influence on the correct molecular detection of sterile sperm. This high-throughput methodology, as well as the results of sample management presented here, provide a robust, efficient, fast, and economical sterile sperm identification method ready to be used in all Mediterranean fruit fly SIT programs

Molecular tools in the evaluation of SIT programmes success against Ceratitis capitata in Spain: a review

Background: The success of sterile insect technique (SIT) programs against many tephritid fruit flies, including Ceratitis capitata (Wiedemann), relies on the mating success of released sterile males in the field. Since its´ development in an area-wide concept, this control program is evaluated by the recapture ratio of sterile versus wild flies. This measure neither takes into account the real target of the SIT that is the wild female, nor does it give any clue about the success of released sterile males. Thus, the contribution of released sterile males to reduce the wild population still remains as a key issue. In this work we review recent findings on how sterile males contribute to reduce wild populations by means of analyzing the sperm content of wild females, as the real target of the SIT program. Methods: A mating competition test was initially performed in laboratory and then under semi-natural conditions, with different Ceratitis capitata Vienna-8 tsl release ratios. The efficacy of the SIT and its contribution to reduce wild population was assessed by determining the percentage of females mated with sterile male, with a sperm ID molecular test, and by linking to offspring production on sentinel hosts. Results: Statistical methods have been developed with the obtained data of sperm ID in the spermathecae of captured females and with data of viable offspring produced in sentinel fruits, revealing that both can be predicted using release ratio and mean temperature. Moreover, humidity arose also as a factor influencing the female capture in lured traps. A strong negative relationship was established between the proportion of Vienna-8 mated females and Ceratitis capitata offspring production, being a key point for a model to predict the SIT program success. Conclusions: The statistical models developed should contribute to enhance the efficacy of SIT programs against Ceratitis capitata by means of modulation of release ratios by season temperature and by checking wild female’s sterile sperm content

Life History Parameters of Diachasmimorpha longicaudata on Ceratitis capitata Under Laboratory Conditions: Implications for Mass Rearing and Biological Control

The Mediterranean fruit fly, Ceratitis capitata, is considered one of the most destructive pests worldwide. The braconid Diachasmimorpha longicaudata is the most widely used parasitoid in biological control programs of tephritids. It has been mass-reared and used in augmentative releases against major fruit fly species in tropical and subtropical countries, and recently in the Mediterranean Basin. After its introduction into Spain and then Tunisia, reproductive and demographic parameters have been studied on C. capitata under laboratory conditions. These parameters were compared to those published elsewhere. The role of artificial diet for rearing the host is discussed. Our findings showed the good fitness of the parasitoids produced on C. capitata in laboratory with a generation time of 28.1 days, a reproductive rate of 39.2, an intrinsic rate of increase of 0.125, a doubling time of 5.2 days and the finite rate of increase (per day) was 1. Involvements on the biological control of the Mediterranean fruit fly in Tunisia are discussed