Abstract
Simple SummaryThe mango fruit fly, Anastrepha obliqua, is one of the most important pests attacking mangos in Mexico and Central and South America. With the aim of identifying key factors that could help to better control/manage this pest, we determined the preferred sites in the fruit where A. obliqua females lay their eggs, registering if these sites were in the upper, middle, or lower sections of the fruit, if they were exposed to sunlight incidence, and if they had special concentrations of some nutritional and chemical compounds. Females mainly oviposited in shaded, upper fruit sections where the pulp was richer in carbohydrates than non-oviposited sections and, where mangiferin, a polyphenol known for its antioxidant properties, was in higher concentrations. The absence of abscisic acid (ABA) and dihydrophaseic acid glucoside, a by-product of ABA catabolism in non-oviposited sections, suggests that this chemical compound could play a role in fruit acceptance behaviors by female flies. We conclude that A. obliqua females prefer ovipositing in fruit sections, where fruit environmental and chemical conditions are optimal for egg and larval development and propose a management scheme directly based on this information.With the aim of identifying key factors that determine oviposition decisions by Anastrepha obliqua for management purposes, we conducted a behavioral study under natural/semi-natural field conditions to identify where exactly in the fruit (upper, middle, or lower sections) females preferred to lay eggs in a highly susceptible mango cultivar (“Criollo”), and whether sunlight incidence and fruit chemical compounds influenced oviposition site selection by this pestiferous fly. Females oviposited in shaded, upper fruit sections where pulp had higher total carbohydrate concentrations but similar total protein, lipid, and polyphenol concentrations than non-oviposited sections. Peel had higher overall nutrient and mangiferin/quercetin-3-D-galactoside (polyphenols) concentrations. An untargeted metabolomic analysis of oviposited and non-oviposited fruit sections identified abscisic acid (ABA) and dihydrophaseic acid glucoside, a by-product of ABA catabolism, as potential chemical markers that could play a role in fruit acceptance behaviors by female flies. We conclude that females preferentially oviposit in fruit sections with optimal chemical and environmental conditions for larval development: more carbohydrates and antioxidants such as mangiferin and ferulic acid and lesser sunlight exposure to avoid lethal egg/larval desiccation/overheating. We make specific recommendations for A. obliqua management based on female host selection behavior, a tree pruning scheme exposing fruit to direct sunlight, application of a host marking pheromone, and the use of egg sinks in the orchard.
Highlights
To successfully manage a pest taking advantage of vulnerable aspects/stages in its biological cycle, behavior, or population dynamics, field studies are critical [1,2,3,4]
Direct light incidence on the fruit had a clear effect on oviposition decisions by females
We did not measure fruit temperature, using light intensity as a proxy of temperature instead, we suggest that females prefer to oviposit in shaded areas with lower temperatures to avoid egg mortality due to desiccation or overheating [65,66], as when eggs are inserted into the fruit, the part where the respiratory horn is located remains partially exposed [39]
Summary
To successfully manage a pest taking advantage of vulnerable aspects/stages in its biological cycle, behavior, or population dynamics, field studies are critical [1,2,3,4]. Any insight gained on the factors that regulate/drive female oviposition decisions and what external abiotic (e.g., ambient temperature and humidity, incidence of sunlight/light intensity) or biotic factors (e.g., fruit chemistry) impinge the most on exactly where eggs are laid, will significantly improve our chances to efficiently control/manage the pest. To understand the factors that guide fruit fly (Diptera: Tephritidae) females during the catenary process of oviposition site selection once on a tree/fruit sensu [17,18], aspects such as fly age and egg load, aculeus wear, presence of conspecifics or predators, and host-quality, among others, have been studied [16,19,20,21]. Females can use fruit physical and chemical features from the host, such as sugar content, presence of toxic allelochemicals, and physical barriers (e.g., surface waxes, the width of the cuticle) to evaluate host quality [20,22,23,24,25]
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