Mexico is the world’s leading producer and exporter of avocado, it has a cultivated area of 268,311 hectares and its production exceeding 2.7 million tons (FAO 2023; SIAP 2025). It is also considered the center of origin for this crop, as well as for many of its associated herbivores (Boheman 1845; Williams 1977). Nayarit ranks as the fourth-largest avocado-producing state in Mexico, with a production of 73,685 tons from 12,823 hectares. Seventy-eight percent of this production is concentrated in Tepic and Xalisco municipalities, making avocado the third most important perennial crop in the state, with an economic value exceeding 37 million dollars (SIAP 2025).

In Central America, two gall midge species have recently been reported causing direct damage to small avocado fruits: Asphondylia websteri Felt, 1917 (Diptera, Cecidomyiidae) and Bruggmanniella perseae Gagné, 2004 (Diptera, Cecidomyiidae) (Gagné et al. 2004; Hoddle 2008). Asphondylia websteri is a polyphagous species (Gagné and Jaschhof 2014), and Hoddle (2008) reported its larvae developing inside small fruits of the Hass avocado cultivar in Guatemala, causing fruit deformation. Additionally, Gagné and Jaschhof (2021) noted the distribution of A. websteri in Mexico on six hosts, including Persea americana Mill., 1768, but did not provide details on the affected organ or variety. This appears to be the only record of this gall-inducer on avocado in the Mexican territory.

Bruggmanniella perseae was first described and reported in avocado fruits in Colombia and Costa Rica (Gagné et al. 2004). To date, it has been reported infesting the Hass and Mendez cultivars in several Neotropical countries, including Mexico (Delgado-Ortiz et al. 2017; Gagné and Jaschhof 2021; Laureano-Ahuelicán et al. 2022; García-Escamilla et al. 2024). This gall midge causes deformation of small fruits (between 1 and 2 cm in length). The larva forms a chamber inside the fruit where it develops; the third instar excavates a tunnel and pupates near the exterior to facilitate adult emergence, which ultimately leads to the abortion of the damaged fruits (Gagné et al. 2004).

It is currently unknown whether a gall midge causes any significant economic damage to avocado, or if infestation and damage occur in fruits likely destined for natural abscission. Nonetheless, some natural enemies associated with gall midges have already been reported in avocado. For example, Laureano-Ahuelicán et al. (2022) found parasitoids of the genera Torymus Dalman, 1820 (Chalcidoidea, Torymidae), Paragaleopsomyia Girault, 1917 (Chalcidoidea, Eulophidae), and species from Pteromalidae in Mexico. Recently, Hansson and Hanson (2023), in a revision of the Galeopsomyia genus (Chalcidoidea, Eulophidae) from the Neotropical region, described four species that emerged from avocado fruits with gall midge damage (G. druparum Hansson, 2023; G. gonzalezi Hansson, 2023; G. leonae Hansson, 2023 and G. perseae Hansson, 2023), suggesting that at least one species could be a parasitoid of B. perseae; however, the specific role these wasps play within the fruit remains unknown. The same authors described the males of G. gonzalezi and G. leonae; therefore, the morphological characteristics of the males of G. perseae and G. druparum remain unknown.

In Mexico, B. perseae has been recorded from fruits of Hass and Mendez avocado cultivars in three central producing states (State of Mexico, Michoacán, and Morelos) (Delgado-Ortiz et al. 2017; Laureano-Ahuelicán et al. 2022; García-Escamilla et al. 2024). Asphondylia websteri has also been reported in the country (Gagné and Jaschhof 2021), although no further details are known regarding this gall inducer. More recently, the “Comité Estatal de Sanidad Vegetal de Nayarit (CESAVENAY)” (State Committee for Plant Health in Nayarit) detected damage in avocado fruits from different orchards that is consistent with that caused by gall midges, along with the presence of at least two species of parasitoids (Ing. Claudio Chavarín-Palacio, CESAVENAY, personal communication). The gall midge responsible is suspected to be the same species previously reported in central Mexico. Therefore, the objective of this study was to identify the gall midge species associated with immature avocado fruits and to identify the associated parasitoids.

A total of 944 avocado fruits were collected, of which 746 corresponded to the Mendez cultivar and 198 to Hass. A total of 192 adult gall midges emerged, predominantly from Mendez fruits (180 individuals) compared to Hass (12 individuals). Among non-emerged individuals, 127 larvae and 102 pupae were recorded in Mendez, whereas 116 larvae and 16 pupae were found in Hass. All specimens correspond to B. perseae, and representative images of larvae (Fig. 1A, B), pupae (Fig. 1C–E), and adults (Fig. 1F, G) are shown.

Regarding parasitoids, 147 adults emerged and 79 non-emerged individuals were recorded (Table 2). The parasitism rate per cultivar was higher in Mendez (31.49%) compared to Hass (12.20%). Six parasitoid species were identified, comprising two species of Rileya Ashmead, 1888, two of Galeopsomyia, and one species each of Torymus and Torymoides Walker, 1871 (Fig. 2). Rileya insularis (Ashmead, 1894) (Fig. 2A, B) exhibited the highest parasitism rate at four of the five sampling sites (El Rebaje 5.43%; San José Costilla 15.20%; El Ahuacate 20.86%; and San Carlos 21.67%). The second most prevalent species was T. umbilicatus (Gahan, 1919) (Fig. 2C, D) which was present at four sites; at El Rodeo it showed the highest parasitism rate (10%), followed by G. perseae (Fig. 2E, F) at 6.7% (Table 2).

A total of 36 specimens belonging to the genus Galeopsomyia were identified to species level. Of these, 13 specimens were identified as G. perseae (Fig. 2E, F), found at three of the five sampling sites, and 23 specimens belonged to G. gonzalezi (Fig. 2G, H), which emerged from the San Carlos locality in Tepic. Galeopsomyia gonzalezi ranked third in parasitism rate, followed by G. perseae (Table 2). The species with the lowest emergence were Torymoides sulcius (Walker, 1839) (Chalcidoidea, Torymidae) (Fig. 2I, J), with five specimens, and Rileya sp. (Chalcidoidea, Eurytomidae) (Fig. 2K, L), with four specimens. The latter could not be identified to species level and was recorded from the San Carlos and San José Costilla orchards.

The presence of B. perseae associated with deformed fruits of Hass and Mendez avocado cultivars was detected in Nayarit. Although the predominant cultivar in Nayarit is Hass (SIAP 2025), some additional sampling from the cv. Choquette, Booth 7, and Booth 8 were taken during April and July of 2025 to determine the distribution of B. perseae across those cultivars; however, a gall midge has not been found in them to date.

Although Gagné and Jaschhof (2021) reported the presence of A. websteri in Mexico, after examining 944 fruits from five sampling sites and different collection dates in Nayarit, this species has not been found. In contrast, B. perseae has been detected in Hass and Mendez cultivars in several Neotropical countries, including Mexico (Delgado-Ortiz et al. 2017; Gagné and Jaschhof 2021; Laureano-Ahuelicán et al. 2022). In some places of Costa Rica and Colombia, it has even been considered an emerging pest (Gagné et al. 2004). In the present study, intensive and systematic sampling to assess whether infestations cause economic damage in the study area was not conducted. However, in Nayarit, it was confirmed that the deformation of small fruits observed since the 2022–2023 harvest were caused by B. perseae. Furthermore, at least six species of parasitoids were detected that may be contributing to regulation of this gall midge’s population.

Parasitism rates have been reported in gall-inducing cecidomyiid species; for example, Doğanlar et al. (2011) reported parasitism levels of up to 66% in Dasineura oleae Angelini, 1831 and Lasioptera oleicola Skuhravá, 2011 (Diptera, Cecidomyiidae). Likewise, Chavalle et al. (2018) reported average parasitism rates of 22.3% for Sitodiplosis mosellana Géhin, 1857, 8% for Haplodiplosis marginata von Roser, 1840, and 2% for Contarinia tritici Kirby, 1798 (Diptera, Cecidomyiidae) in two cereal-growing regions of Belgium. Similarly, Batta and Doğanlar (2019) reported an overall parasitism rate of 36% for D. oleae across five olive-producing sites in Palestine. In the present study, the highest parasitism rates were recorded in the Mendez cultivar (23.41%, 30.21%, and 40.86%: Table 2).

Rileya insularis stood out as the species with highest emergence from fruits damaged by B. perseae in Nayarit, accounting for 16.70% of the total parasitism. This eurytomid has been associated to other gall midges, including at least 10 species of the genus Asphondylia Loew, 1850 and Neolasioptera impatientifolia (Felt, 1907) (Diptera, Cecidomyiidae) (Gates 2008). Therefore, the present study constitutes the first report of R. insularis associated with a different genus of gall midge. The distribution of R. insularis encompasses the entire Nearctic region, Central America, and South America, including Mexico (Gates 2008; UCD Community 2023).

Torymus umbilicatus ranked second in general parasitism (6.55%). The genus Torymus includes at least 410 species worldwide, Mexico has 27 reported species among which T. umbilicatus is included (UCD Community 2023). Most species are solitary ectoparasitoids, although some could be obligatory or facultative hyperparasitoids of concealed hosts, including some gall midges (Graham and Gijswijt 1998; Hanson 2006; Matsuo 2020). Three species of the genus Asphondylia and one of Lasioptera Meigen, 1818 (Diptera, Cecidomyiidae) are reported as primary hosts for T. umbilicatus (UCD Community 2023); therefore, this finding represents a new host record for this torymid species. In the present work, through dissection of fruits with gall midge damage, this species was observed developing as an ectoparasitoid of third-instar larvae of B. perseae. Recently, Laureano-Ahuelicán et al. (2022) mentioned a species of the genus Torymus associated to B. perseae in avocados in the State of Mexico. It is therefore important to examine the material to determine if it is the same species as that we found in Nayarit.

Two species of Galeopsomyia were found. This genus, distributed in tropical and subtropical regions of the New World, comprises 322 described species, most of which have been reared from gall midges (Hansson and Hanson 2023; UCD Community 2023), including four species that emerge from fruits presumably deformed by B. perseae (Hansson and Hanson 2023). In Mexico, another two species of Galeopsomyia had previously been reported, but none associated to avocado fruits (Ruíz-Cancino et al. 2001; UCD Community 2023). Galeopsomyia perseae and G. gonzalezi have been reared from B. perseae-deformed avocado fruits and are reported only from Costa Rica (Hansson and Hanson 2023). Therefore, both species represent the first records for Mexico.

Bruggmanniella perseae was the only gall midge species found causing deformation of Hass and Mendez avocado fruits in Nayarit, Mexico, during the 2024–2025 season. Six species of parasitoids associated with B. perseae were identified. Rileya insularis was the most frequent and abundant species, followed by T. umbilicatus, which was observed as an ectoparasitoid of third-instar B. perseae larvae. Galeopsomyia perseae and G. gonzalezi are reported for the first time in Mexico. Additionally, the male of G. perseae is characterized and illustrated for the first time.