Biological Control of Tephritid Fruit Flies in the Americas and Hawaii: A Review of the Use of Parasitoids and Predators

Simple Summary Biological control has been the most commonly researched control tactic within fruit fly management programs, and parasitoids have been the main natural enemies used against pestiferous fruit fly species. In view of this fact, it is important to highlight and compile the data on parasitoids with a certain frequency, aiming to facilitate the knowledge of all the researchers. Information regarding the activities of parasitoids and predators on pestiferous fruit flies in the Americas is limited; therefore, this study aimed to compile the diversity of parasitoids and predators associated with tephritid fruit flies, as well as providing the scientific evidence about the use of parasitoids and predators as biological control agents for fruit flies im the Americas and Hawaii. Abstract Biological control has been the most commonly researched control tactic within fruit fly management programs. For the first time, a review is carried out covering parasitoids and predators of fruit flies (Tephritidae) from the Americas and Hawaii, presenting the main biological control programs in this region. In this work, 31 species of fruit flies of economic importance are considered in the genera Anastrepha (11), Rhagoletis (14), Bactrocera (4), Ceratitis (1), and Zeugodacus (1). In this study, a total of 79 parasitoid species of fruit flies of economic importance are listed and, from these, 50 are native and 29 are introduced. A total of 56 species of fruit fly predators occur in the Americas and Hawaii.


Introduction
In the Americas, there are four genera of tephritid fruit flies, which include species of economic and quarantine importance. Anastrepha Schiner, 1868 is widely distributed in the neotropical region [1], and seven species are economically important in the tropics and subtropics due to their wide range of commercial host plants and distribution. The species include Anastrepha ludens (Loew) R. mendax (Curran), R. meiiginii (Loew), R. pomonella (Walsh), R. suavis (Loew), R. tabellaria (Fitch), R. zephyria Snow, and Z. curcubitae (Coquillett).
Information regarding the activities of parasitoids and predators on pestiferous fruit flies in the Americas is limited; therefore, this study aimed to compile a list of the diversity of parasitoid and predator species associated with tephritid fruit flies, as well as providing scientific evidence about the use of parasitoids and predators as biological control agents for fruit flies

Parasitoids
The parasitoids that deposit an egg in the host are either solitary, more than one, or gregarious. When the parasitoids develop inside the host, they are endoparasitoids, and when development occurs externally, they are ectoparasitoids. Parasitoids can be either idiobionts or koinobionts. The former refers to those who kill their hosts shortly after oviposition, preventing further development, while the latter characterizes those who allow develop in the living hosts and kill them at the end of their cycle [28].

Native Parasitoids
In the Americas, there is a richness of 51 species of native parasitoids of fruit flies (Diptera, Tephritidae) of frugivorous fruit flies with economic importance included in 20 genera of 7 families (Braconidae, Diapriidae, Eurytomidae, Figitidae, Ichneumonidae, Mymaridae, and Pteromalidae). The Braconidae and Figitidae account for 64.7% of the fruit fly parasitoid species on the American continent. The family with the highest species richness is the Braconidae, with 47.1% of the total, followed by Figitidae with 17.6%, Pteromalidae with 17.6%, and Diapriidae with 11.8%. Ichneumonidae, Eurytomidae, and Mymaridae are represented by only one species each (5.9% one species each).
Most parasitoid species (53%) are associated with the genus Anastrepha, while 35.3%, 31.4%, and 7.8% of all parasitoid species are associated with Rhagoletis, Ceratitis, and Bactrocera, respectively. Table 1 shows the relationship between the parasitoid genera and the tephritid genera.
Dicerataspis Ashmead, Eurytoma Illiger Lopheucoila Weld, Trichopria Ashmead, Tropideucoila Ashmead, and Rhoptromeris Förster are associated exclusively with Anastrepha, while Diachasma Foerster, Diachasmimorpha Viereck, and Eurytenes Foerster are solely associated with Rhagoletis. The exotic genera of fruit flies, Bactrocera and Ceratitis, have no exclusive genus of parasitoid. Doryctobracon Enderlein, with a greater species richness, is associated with both Anastrepha and Ceratitis. Coptera Say and Opius Wesmael are the only genus of parasitoids associated with the 4 genera of tephritid fruit flies of economic importance.
The native parasitoid species that has the largest number of hosts is Doryctobacon areolatus with 11 hosts (Anastrepha spp. and Ceratitis capitata), followed by Utetes anastrephae with 10 hosts (Anastrepha spp. and Cerattis capitata) ( Table 2). Anastrepha grandis is known as the South American cucurbit fruit fly, a quarantine pest and the main fruit fly pest of cucurbitaceous plants that has no parasitoid associated. The absence of knowledge of natural enemies of A. grandis (parasitoids and predators) is probably due to the following factors: (1) Few studies carried out with this species when compared with other species of fruit flies of economic importance, (2) parasitoids have difficulty ovipositing in A. grandis larvae and eggs because the ovipositors of native parasitoid species may be unable to pierce the thick epicarp of the host fruits of this fly (Cucurbitaceae), (3) the absence of studies of pupae parasitodes and predators of A. grandis.
Parasitoids of economic fruit flies have been recorded in 20 of the 35 countries that are part of the Americas. Brazil has 19 native parasitoids and continental USA has 15 parasitoids, followed by Argentina and Mexico with 14 each (Table 3). The greatest occurrence of parasitoids in these countries is mainly due to the fact of a higher intensity of fruit fly parasitoid surveys compared to other countries.
Most native parasitoids are solitary (81.1%), koinobionts (62.3%), or endoparasitoids (68.8%). The native species of Braconidae and Figitidae include endoparasitoid koinobionts that attack mainly larvae. The species of parasitoid idiobionts belong to the Diapriidae, Eurytomidae, and Pteromalidae. Ectoparasitism is found in the Eurytomidae and Pteromalidae. Most native parasitoids attack the larval stage (56.4%), pupa (32. 0%), and eggs (12.0%). There is no native parasitoid with a gregarious habit (Table 4). Table 1. Association between the genus of native parasitoids (Hymenoptera) and the genus of fruit flies with economic importance in the Americas.

Introduced Parasitoids
In the Americas and Hawaii, 29 species from 12 genera belonging to 7 families (Braconidae, Chalcididae, Diapriidae, Eulophidae, Figitidae, Ichneumonidae, and Pteromalidae) were introduced. Most introductions were species in the family Braconidae (72.4%). Psyttalia are associated with all fruit flies of economic importance, Fopius, Dirhinus, Tetrastichus, and Pachycrepoideus are associated with three fruit fly genera, Coptera and Aceratoneuromyia with two genera, while Bathyplectes, Bracon, and Utetes with only one genus (Table 5). Table 5. Association between genera of introduced parasitoids (Hymenoptera) with the genus of fruit flies with economic importance in the Americas and Hawaii.

Introduced Parasitoid Species Parasitism Modes Feeding Types Host Stage Attacked
Braconidae
Ants are a group of predatory insects that can be considered as pest control agents in some agroecosystems, regulating insect populations [198]. The predation of fruit flies by ants occurs when the larva leaves the fruit to bury itself in the soil for pupation [23]. Ants belonging to the genus Pachycondyla, Pheidole, Pogonomyrmex, and Solenopsis are important predators of A. fraterculus larvae in Brazil. Solenopsis saevissima was the most efficient species, with 42.86% of larvae removal in the field [25].

Biological Control Programs
Introduction of the invasive Zeugodacus cucurbitae (melon fly), Bactocera dorsalis (Hendel) (oriental fruit fly), and Bactrocera latifrons (Hendel) into Hawaii resulted initially in classical biological control programs, but later they became augmentative biological control programs [8,10,160,164]. Numerous parasitoid and predator species were introduced into Hawaii for classical biological control of Bactrocera spp. [69,178,179]. However, only the Asian-native larval parasitoid Psyttalia fletcheri (Silvestri) was successfully established in Hawaii on Z. cucurbitae with parasitism percentages that varied according to the host fruit species [8]. In an augmentative release program against the melon fly, P. fletcheri substantially reduced the number of emerged flies [155,199]. Other exotic parasitoid species, from Southern Asia and other regions, were successfully established on B. dorsalis in Hawaii, such as larval parasitoids Diachasmimorpha longicaudata (Ashmead), Psyttalia incisi (Silvestri), Fopius vandenboschi (Fullaway), and Tetrastichus giffardianus Silvestri, the egg-larval parasitoid Fopius arisanus (Sonan) and the pupal parasitoids Dirhinus giffardii (Silvestri) and Pachycrepoideus vindemmiae Rondani [154,200]. Augmentative releases of D. longicaudata made against B. dorsalis were inconsistent because they produced lower fly populations in the release plots one year and higher populations the next [10]. Although both D. longicaudata and F. vandenboschi were important biological control agents of B. dorsalis, F. arisanus has remained the most significant parasitoid of this tephritid species [8]. Because of the F. arisanus habit of attacking host eggs, which are more exposed below the fruit skin surface than larvae, this braconid parasitoid can achieve host parasitism percentages between 60% and 70% in the field [10]. In addition, F. arisanus was also the predominant species recovered from B. latifrons [158].
The establishment of the olive fruit fly B. oleae in California, USA, where it has spread to all commercial olive-producing areas since first being detected in 1998 [201], led to the development of a classical biological program control program in 2003 [167]. Several parasitoid species recovered from B. oleae collected from wild olives in Kenya, South Africa, Pakistan, or Namibia were imported to the USA. The introduced species were Bracon celer Szépligeti, Psyttalia humilis (Silvestri) (P. humilis from Kenya was previously referred to as P. cf. concolor) [165,202], P. lounsburyi (Silvestri), P. ponerophaga (Silvestri), and Utetes africanus (Silvestri) [117,118,165,[168][169][170]. In addition, three exotic parasitoid species, i.e., the Australian-native Fopius arisanus, Diachasmimorpha kraussii (Fullaway), and D. longicaudata, coming from colonies in Hawaii, were also evaluated as potential biological control agents for B. oleae [122,203]. Although both D. longicaudata and D. kraussii were efficient against B. oleae [122], they were not considered for field releases because both braconid species are host-generalists. Given this, more specialized species such as the larval parasitoids P. humilis and P. lounsburyi were chosen to release in California [168,204]. Field release and recovery efforts were conducted from 2006 to 2013; both parasitoid species were recovered post-release, but only P. lounsburyi was established in California coastal regions [167,205]. Given these results, the parasitoid P. lounsburyi was mass-reared for release on a larger scale in olive-producing areas of California [206].
An augmentative biological control program against the introduced B. carambolae, the carambola fruit fly, was carried out in Northern Brazil (Amapá state) by releasing millions of D. longicaudata specimens [151]. Although D. longicaudata adapted to the Amazonian environment [17], it did not have a substantial effect in controlling the tephritid target. The Asian-native parasitoid D. longicaudata was previously introduced in 1994 into Brazil from Gainesville, Florida, United States, for use against C. capitata and Anastrepha spp. [17]. In 2012, a new biological control program against B. carambolae was started by introducing F. arisanus into Brazil from Hawaii; currently, this braconid parasitoid is reared on C. capitata eggs in different Embrapa laboratories and in the Moscamed Brazil facility [151].
The first classical biological control programs against C. capitata generally involved the introduction of parasitoid and predator species not only for the control of this pest but also for using them against other pestiferous tephritid species, such as Bactrocera spp. [21] or Anastrepha spp. [11]. The earliest classical biological control programs against C. capitata were carried out in Hawaii and date as far back as 1913. Because of these biocontrol programs, several parasitoid species, such as the larval parasitoids Aceratoneuromyia indica (Silvestri), Diachasmimorpha fullawayi (Silvestri), D. tryoni (Cameron), D. longicaudata, F. vandenboschi, P. incisi, Aganaspis daci (Weld), Tetrastichus giffardianus Silvestri, the egg-larval parasitoid F. arisanus, the pupal parasitoids Coptera silvestrii (Kieffer), Dirhinus giffardii Silvestri, and P. vindemmiae, were introduced to Hawaii and most of those parasitoid species were successfully established on C. capitata [120]. However, the Asian-native F. arisanus, since its establishment in the late 1940s, became the major parasitoid of C. capitata through substantial reductions in the medfly population in some habitats, apart from controlling B. dorsalis [8,115,207]. In spite of this, the implementation of classic biological control programs in Hawaii did not meet the objectives expected for the control of pestiferous fruit fly species, which motivated the development of mass-rearing of different parasitoid species for their periodic augmentative release in the field [208][209][210]. Therefore, using augmentative releases of parasitoids as a strategy into integrated management programs to control C. capitata, as well as for other pestiferous fruit fly species, has been encouraged since the 1980s [149,154,211]. Thus, augmentative releases of D. tryoni were performed in the late 1980s in Hawaii, due to its simplicity for mass-rearing and its host preference for C. capitata rather than B. dorsalis [149]. Those augmentative releases of D. tryoni were able to suppress medfly populations and the combination with sterile male fly releases had a greater effect on the pest [212]. However, high medfly populations still occur in Hawaii mainly in coffee plantations and at higher elevations [213]. Newly classical biological control programs carried out against C. capitata in Hawaii focused on the introduction of more specific parasitoid species [214,215]. New introduced species were the larval parasitoid D. kraussii and the Eastern African-native egg-pupal parasitoids Fopius ceratitivorus Wharton and F. caudatus (Szépligeti) [213]. Among these parasitoid species, F. ceratitivorus would be the most promising for improving overall suppression of medfly in Hawaii, due to its host specificity, lack of non-target impacts, and ability to complement F. arisanus [158,213,216,217].
Since the establishment of C. capitata in Hawaii, this pestiferous fruit fly species has been periodically introduced and erradicated in California, Florida, and Texas (USA) as well in Southern Mexico, although high medfly populations still remain throughout Central and South America [121]. The northward spread of C. capitata from Central America into Mexico, and also into the United States, has been constantly monitored along the Mexican/Guatemalan border by the international organization Mosca del Mediterráneo (MOSCAMED) (United States, Mexico, and Guatemala) [121]. Predominantly in this region, the vast areas cultivated with coffee, Coffea arabica L., which extend through the highlands of Guatemala, maintain high medfly populations. In addition to the use of the Sterile Insect Technique (SIT) to control medfly populations, augmentative parasitoid releases have also been carried out. Diachasmimorpha tryoni has been augmentatively released from the air into coffee cultivated areas affected by C. capitata in Guatemala over two years, which led to parasitism levels of up to 84% [146]. Previously, Cancino et al. [218] showed the significant effects of D. longicaudata mass-releases on C. capitata populations infesting coffee berries on the Mexico-Guatemala border. Similarly, augmentative releases of the Asian-native parasitoid D. longicaudata against medfly were carried out in Chiapas, Southern Mexico, during 2001 and 2002 on over 9000 ha of coffee plantations, reaching parasitism peaks of 61% and 69%, respectively [138]. In addition, augmentative releases of D. krausii and F. arisanus, either together or in combination with medfly sterile males, were made inside large field cages erected over coffee grown at different locations and altitudes in Guatemala. Results showed that the inclusion of both parasitoid species provided significant medfly suppression and the effect was frequently substantial [121]. These outcomes indicate that augmentative releases of parasitoids could be a complementary tool to control high medfly populations within an area-wide integrated fruit fly management (AWIFFM) approach [219]. The introduction from Kenya of the medfly-specific parasitoid F. ceratitivorus to Guatemala, and its establishment in the USDA-APHIS/MOSCAMED quarantine facility at San Miguel Petapa, points to a new process to strengthen the use of parasitoids against these medflies [156]. Considering differences in weather conditions and medfly density throughout the area of the Mexican/Guatemalan border, several parasitoid species with different bioecological features have been reared in Guatemala by the MOSCAMED Program [121]. Not all parasitoid species are equally effective under all likely conditions; preferences for temperature, moisture, and/or host density may vary [76,78].
Costa Rica was the first Central American country to develop a biological control program against C. capitata by introducing numerous parasitoid species mainly from Hawaii in the 1950s. Thus, F. arisanus, D. longicaudata, A. indica, P. concolor, and P. vindemmiae were released and recovered in Costa Rica, but the impact on C. capitata was not significant [11]. In the 1980s, a classic biological control program facilitated the introduction to Costa Rica of four parasitoid species from Africa, i.e., Diachasmimorpha fullawayi, Psyttalia perproxima (Silvestri) (recorded as P. perproximus (Silvestri)) [119], Fopius caudatus, and F. silvestrii (Wharton); this last species was previously misidentified as F. caudatus [220]. The four braconid parasitoid species were directly released in the field but there was no recovery of them post-release [119]. Currently, both D. longicaudata and P. vindemmiae are mass-reared in Costa Rica for fruit fly biological control, although little information is available on their present status parasitizing C. capitata [133]. The fruit fly biological control program developed by Costa Rica in the 1950s was essential for promoting the use of parasitoids in other Latin American countries affected by the medfly. Thus, D. longicaudata, A. indica, and P. vindemmiae were mainly provided by Costa Rica to Nicaragua, Panamá, El Salvador, Guatemala, Trinidad and Tobago (Central America), Argentina, Bolivia, Colombia, Perú, and Venezuela (South America).
The larval parasitoid T. giffardianus was the first exotic species introduced into both Brazil and Argentina during the 30s and 40s, respectively, for C. capitata control. Low numbers of individuals were released in both countries. In Brazil, this eulophid parasitoid was recovered from medfly puparia after 60 years from its first release [17], but in Argentina there has been no evidence of its permanent establishment at any release site [16]. New biological control programs that involved the introduction of several exotic parasitoid species into Argentina from Mexico and Costa Rica were carried out between the 1960s and 1990s. The establishment on C. capitata of three released parasitoid species, D. longicaudata, A. indica, and P. vindemmiae, was verified in Argentina, although without exercising significant control on this tephritid pest [16]. However, open-field augmentative releases of D. longicaudata mass-reared on irradiated larvae of the tsl Vienna-8 medfly strain (named as "D. longicaudata tsl-Cc line") have recently been carried out in fruit-growing areas of Central-Western Argentina. Post-release data showed up to 75% of C. capitata mortality due to the D. longicaudata releases in fig crops [126,127]. Later, augmentative releases of the D. longicaudata tsl-Cc line were carried out to assess the effectiveness of parasitoid females in killing medfly larvae infesting peach and orange inside a field cage in the subtropical environment of the northwestern Argentina. Parasitoid effectiveness reached up to 50% in infested peaches [128]. Recent studies on the mass-rearing of the neotropical pupal parasitoid Coptera haywardii (Ogloblin) using gamma-irradiated larvae of the tsl Vienna-8 medfly strain as the host have been carried out at the BioPlanta San Juan facility [20]. Furthermore, the possibility of augmentative releases of C. haywardii for medfly control is currently being evaluated in Argentina. Augmentative releases of D. longicaudata against C. capitata were also carried out in different Brazilian regions, but recoveries of this braconid parasitoid were more associated with Anastrepha spp. [17,131,132]. This braconid parasitoid species has been previously introduced in 1994 into Brazil from Gainesville, Florida, United States, for use against C. capitata and Anastrepha spp. [151].
Historically, the introduction and release of exotic hymenopterous parasitoid species for biological control of native pestiferous Anastrepha species have been mainly standardized from the 1930s in Puerto Rico, Costa Rica, and Mexico, as well as in many Latin American countries. Most of these parasitoid species had first been introduced into Hawaii including D. longicaudata, D. fullawayi, D. tryoni, P. incisi, P. concolor, P. fletcheri, F. arisanus, F. vandenboschi, A. daci, T. giffardianus, D. giffardii, A. indica, and P. vindemmiae. A few species were able to establish in the released areas and they were able to control the target Anastrepha species. The status of all those introduced parasitoid species was discussed by Ovruski et al. [11].
Since 1992, Mexico has carried out the main biological control program against pestiferous Anastrepha species in the Americas. This national program, sponsored by the Mexican government, focuses on achieving free and/or low-prevalence areas of four economical and quarantined Anastrepha species, i.e., A. ludens, A. obliqua, A. serpentina, and A. striata [14]. Therefore, three exotic braconid parasitoid species, namely D. longicaudata, D. tryoni [221], and F. arisanus [152] have been mass-reared at the Moscafrut facility in Metapa de Dominguez, Chiapas, Mexico and released. Of the three parasitoids species, 50 million pupae parasitized by D. longicaudata were produced weekly [222]. The first parasitoid augmentative releases in Mexico started in the late 80s, when an average of 1500 D. longicaudata parasitoids per ha. was released on almost 200 ha in the Valle of Mazapa de Madero, Chiapas, Mexico. Significant reductions in Anastrepha species were recorded with an average of 60% parasitism. This test was performed in a diverse range of Anastrepha species [223]. This was an important step towards implementing an IPM program in Anastrepha populations in Mexico. Consequently, new augmentative area-wide releases of the D. longicaudata, mass-reared, have been carried out by air or from the ground in different Mexican states [14,15,222]. Releases of D. longicaudata have been continuously focused on wild areas and backyard orchards to prevent fruit fly dispersion into commercial crops, which has caused substantial reductions in numbers of Anastrepha adults [56,137,218,224,225]. However, despite the good outcomes achieved with D. longicaudata, the Mexican National Program against Anastrepha spp. fruit flies has turned attention to the many neotropical-native parasitoid candidates for augmentative release with the chance of strategically increasing the mortality inflicted on pestiferous Anastrepha species. Thus, native parasitoid species better adapted to certain natural environmental conditions to low host densities, or that may attack other developmental stages of the pest, can be used to complement exotic parasitoid species [146,[226][227][228]. Therefore, colonization of several neotropical parasitoid species and the mass-rearing of some of the species took place in Mexico [18,57,229]. Thus, the native C. haywardii is currently a suitable candidate for use with D. longicaudata in augmentative area-wide releases against Anastrepha spp. in Mexico [19,230,231].
The introduction of A. suspensa into Florida in 1965 led to the establishment of a biological control program which was developed by importing at least 11 parasitoid species from Hawaii, France, and Latin America between the early and late 1970s. Among introduced parasitoid species both D. longicaudata and the neotropical-native Doryctobracon areolatus (Szépligeti) has been successfully established into Florida [11]. Populations of A. suspensa decreased by 40% in some areas in the years following releases of the two braconid parasitoid species, but A. suspensa continued as a serious pest in Florida [159]. In view of this, a D. longicaudata mass-rearing and augmentative releases were carried out later, which generated significant reductions in A. suspensa populations in urban and suburban areas of Florida [144,232]. Because of these releases D longicaudata replaced D. areolatus as the major parasitoid of A. suspensa in the southern portion of Florida, while D. areolatus predominated in the northern sector [46,233].
In Brazil, the exotic D. longicaudata has shown the ability to adapt and settle in different environments, either in semi-arid or tropical areas, to control pestiferous Anastrepha species [17,[130][131][132]151]. Augmentative releases of D. longicaudata against A. fraterculus in wild vegetation areas near citrus crops in the State of São Paulo, Brazil caused a reduction of 30% in adult fly numbers [17]. Experimental studies under laboratory conditions showed the ability of F. arisanus to develop successfully in A. fraterculus eggs compared with C. capitata eggs [234]. This trait makes F. arisanus a complementary alternative to the use of D. longicaudata against A. fraterculus.
Parasitoid species introduced into Argentina for the biological control of C. capitata were also released against A. fraterculus. Three exotic species, D. longicaudata, A. indica, and P. vindemmiae were established after releases in different Argentinean fruit-growing areas [16]. In addition to the introduced parasitoid species, both Brazil and Argentina followed the initiative of the Mexican National Fruit Fly Program regarding the use of neotropical parasitoids for Anastrepha control. Thus, several native parasitoid species were colonized and lab-reared to be evaluated as biocontrol agents of A. fraterculus in Brazil, i.e., Aganaspis pelleranoi [235,236] and Doryctobracon brasiliensis [237,238], and in Argentina, C. haywardii [20,97,239], A. pelleranoi [240,241], Doryctobracon crawfordi [240], and Opius bellus [74,240].
In Peru, near to the border with Chile in the Department of Tacna, the National Medfly Program was releasing the parasitoid D. longicaudata weekly (reared in La Molina Facility in Lima) in the late 90s in order to reduce C. capitata populations in olive orchards. More than 50% parasitism was achieved during the two years with the periodical massive releases of D. longicaudata. The market quality of olives was maintained at a high level with the implementation of an of IPM program against C. capitata in which the biological control played an important role.
There is only one document that records the introduction and releases of parasitoid species during the 1950s into California against R. completa, R. indifferens, and R. fausta [161], but the results of these releases were unsatisfactory [242]. Much later, evaluations of the parasitism capability of Psyttalia humilis (referred to as P. cf. concolor) on R. completa were carried out only under laboratoty conditions; this parasitoid was introduced into California for B. oleae biological control [202].
In the Western United States there are two parasitoids, Opius lectoides Gahan and O. downesi, which generally attack Rhagoletis zephyria Snow and R. pomonella in Oregon. About 60% of pupae were parasitized by these parasitoids on native host plants, while less than 2% on apple were attacked. Both species of Opius have short ovipositors, which may not be long enough to reach host larvae in the larger apple fruits. Alternatively, Diachasma allaeum has a much longer ovipositor and has been very successful in parasitizing larvae in apples in the Eastern United States [243].
One of the major concerns in the use of predators in pest control is intraguild predation [24]. Intraguild predation occurs among natural enemies in biological control systems, where one natural enemy (the intraguild predator) attacks another species of natural enemy (the intraguild prey), whereas they also compete for the same pest [27]. There are two types of intraguild predation (PGI) between predators and parasitoids: (1) The predator can directly predate the parasitoid, feeding from the immature phase then externally to the host and adult phase; (2) the predator can predate the parasitic host, directly consuming the host and, indirectly, the larva of the parasitoid [244]. The effect of the presence of intraguild predators on the intraguild prey was often negative, but sometimes no significant effect was detected [27]. Although predators are not the focus of fruit fly biological control programs, they have a very important role in conservation biological control, and it is necessary to intensify studies that evaluate or use agricultural techniques that do not affect an assemblage of predators of fruit flies, such as the use of selective pesticides. [CrossRef] 29. Alvarado, L.; Medianero, E. Especies de parasitoides asociados a moscas de la fruta del género Anastrepha