Hernández-Ortiz (2007) reported that A. obliqua has a marked preference for native plant species of Anacardiacea (the same family as the mango), while A. ludens is mainly found infesting species of the Rutacea or citrus family; however, the abundance of A. ludens (40,637 individuals) in this research is considerably higher than that presented by A. obliqua (504); 98.77% and 1.23% of the total, respectively; and differs from other studies in Mexico; Aluja et al. (1996), in the Soconusco region (0-250 m above sea level (asl)), (Chiapas, Mexico) captured 66.14% of A. obliqua and 30.41% of A. ludens. Martínez et al. (2004), in mamey sapote orchards, at Jalpa de Méndez (Tabasco, Mex.), at 10 m asl, found higher populations of A. obliqua, capturing 1,049 specimens in contrast to only 58 specimens of A. ludens. Rodríguez (2017) in Atoyac de Álvarez (Guerrero, Mex.), located at 40 m asl captured only 4 individuals of A. ludens compared to 418 of A. obliqua. This may be because A. ludens is mostly polyphagous in the study area, and because the higher altitudes of the sampled localities (834-1,166 m asl) were more favourable to this species, while the reduced abundance of A. obliqua is due to its distribution being associated with lower altitudes (0-250 m asl).The abundance of A. ludens has also been associated at high altitudes (> 500 m asl) in the states of Chiapas and Oaxaca (Aluja et al., 1996; Hernández-Ortiz, 2007; Antonio-Hernández, 2019). This coincides with the report of Aluja et al. (1990) in Mazapa de Madero (1,040 m asl), (Chiapas), who found a capture percentage of 65.2% for A. ludens and 30.1% for A. obliqua. Montoya et al. (2014), found a higher proportion of A. ludens to A. obliqua in mango in Hoyo del Aire, Taretan, (Michoacán, Mex.), located at an altitude of 900 m asl, and Rodríguez (2017) in Tetipac, (Guerrero), at an altitude of 1,660 m asl reported an abundance of 448 A. ludens and 326 A. obliqua.
Fruit flies per trap per day
The FTD index remained above 0.0100, so the category to which the three municipalities belong is one of high prevalence for the pest, the values obtained herein being above even the maximum MTD reported in other research: 0.250 in June in mango (Tucuch et al., 2008), 0.5–1.6 between April and June in mango (Montoya et al., 2014), 0.6726 in March in citrus (Vanoye-Eligio et al., 2015). In the case of A. obliqua, in Amatitán (0.079; September) and in San Cristóbal de la Barranca (0.0079 July; 0.0053 August; 0.0000 September) values corresponding to a low (< 0.0100) and even zero prevalence. However, even if the numbers of captured flies decrease, or even if the pest is not detected when the fruit is not available, it should not be assumed that the control actions have been effective because the pest tends to enter and leave the orchards in search of alternative food hosts (Celedonio-Hurtado et al., 1995; Aluja et al., 1996).
The correlation between precipitation (P-value = 0.001) and the abundance of A. ludens is positive, representing an increase in the capture of A. ludens, while the rainy season is established in the area. This agrees with Tucuch et al. (2008) in Campeche (Mex.) in mango crops, who found a highly positive correlation between precipitation and A. ludens populations, since its high populations coincided with the period of greatest precipitation in the region. Aluja et al. (2012), in Martínez de la Torre and Apazapan, (Veracruz, Mex.) reported that precipitation has a delayed effect on the population rates of A. ludens, concluding that when the seasonal difference in precipitation is maximal, the rate of population change should diminish. Likewise, Conde-Blanco et al. (2018), found that precipitation is the main covariate that influences the population fluctuation of Anastrepha spp. in Caranavi (Bolivia), showing a positive correlation, while Vanoye-Eligio et al. (2019) reported in Santa Engracia, (Tamaulipas, Mex.) that precipitation influences the population dynamics of A. ludens females in the field by benefiting their survival at high ambient temperatures.
The minimum temperature presented a significant correlation (P-value = 0.001) with the abundance of A. ludens, coinciding with that reported by Vanoye-Eligio et al. (2017) in Miquihuana and Bustamante (Tamaulipas, Mex.), who found a positive, weak but significant correlation between the minimum temperature and the capture of Anastrepha spp.; however, they mention that, in practical terms, it did not represent a functional relationship, and the lack of captures in the coldest months is related to the absence of food.
However, it must be understood that even if a correlation is found, it does not necessarily represent a cause-effect relationship (Celedonio-Hurtado et al., 1995) and that it should be interpreted according to the biology of the flies and the field conditions; a lack of rain can cause pupal dehydration in the soil or the adults die due to lack of food, in contrast, extreme rainfall can affect the quality of food for the adult fruit flies, decreasing their fecundity and longevity (Hendrichs et al. 1991, 1993; Aluja, 1994; as cited in Celedonio-Hurtado et al., 1995), or affect pupal survival by drowning (McPhail & Bliss 1933; Baker et al. 1944 as cited in Celedonio-Hurtado et al., 1995; Montoya et al., 2008). The results obtained contrast with those previously reported, as the sampling of this research was carried out in the harvest periods and early post-harvest periods – in which the food was abundant – giving even more relevance to the inferred relationships between the climatic variables (precipitation and low temperatures) with fruit fly abundance.
The present results also differ from those obtained by Celedonio-Hurtado et al. (1995) and Aluja et al. (1996) in the Soconusco region (Chiapas); Martínez et al. (2004) in Jalpa de Méndez (Tabasco); and those of Altafin et al. (2019) in Pindorama, São Paulo (Brazil), who mentioned that they did not find a significant correlation between the climatic variables and the collected fruit fly individuals. This difference may occur because in the tropical areas, where these studies were carried out, the climatic variables, among other factors, are different, particularly precipitation, which is greater than 1,500 mm per year, compared to the maximum average in our study area that did not exceed 1,100 mm.
The agronomic management had no significant correlation with the abundance of Anastrepha (P-value = 0.397); pest control could therefore be ineffective and promoting resistance to insecticides. Another reason is that any reduction of the A. ludens population by insecticide applications are quickly counteracted by immigration of individuals from neighboring orchards or for those from native hosts (Aluja et al., 2012). Consequently, efforts to control this pest should still be directed towards comprehensive pest management in all mango plots.
It is also important to mention that, although in this work the relationship between the abundance of Anastrepha spp and the phenology of the crop was not evaluated, it was observed that the highest captures of the insect coincided with the mango fruiting stage, a fact that had already been reported by other authors (Celedonio-Hurtado et al., 1995; Tucuch et al., 2008; Vanoye-Eligio et al., 2017).
The results of this research can be used as a reference for future studies in Mexico. Also, considering the dates of the highest incidence of the pest and the climatic conditions that prevailed when they appeared, these results can be used as a basis for decision-making in the integrated management of the fruit fly in “Barranqueño” mango plantations, in the state of Jalisco.