We determined the release density, dispersal capacity, and optimal storage conditions for the parasitoid Telenomus remus Nixon to control Spodoptera frugiperda (J.E. Smith). Each of eighty plants within an 829-m² plot were artificially infested with one S. frugiperda egg mass in a maize field. These plants were distributed evenly along four concentric squares which allowed for 14 different distances from a central release point (range 3.6–20.3 m). Egg parasitoids were released at four densities (0; 100,000; 150,000; and 200,000 adults/ha) in two vegetative maize growth stages (V4-5 and V8-9). After a 48-h exposure, egg masses were retrieved to evaluate parasitism rates. Spodoptera frugiperda egg parasitism by T. remus did not differ among the three parasitoid release densities. Egg parasitism decreased linearly with increasing distance from the release point, but this was influenced by the crop’s phenological stage. Egg parasitism was 28% higher at the older than younger growth stages, and dispersal distance and area of dispersal were 35% and 16% lower, respectively, at the older stage. In the laboratory, we evaluated the effects of six storage periods (0, 3, 6, 9, 12, and 15 days) of S. frugiperda eggs at four temperatures (5, 10, 15, and 20°C) on T. remus adult emergence. Our results showed the highest emergence when eggs were stored at 15°C for ≤9 days. Altogether, we identified important mass release and rearing parameters for augmentative biocontrol of T. remus on S. frugiperda eggs that may help reduce production and marketing costs.

Lower elevations are generally thought to contain a greater abundance and diversity of insect communities and their natural enemies than higher elevations. It is less clear, however, how changes in seasons influence this pattern. We conducted a 2-year study (2013‒2014) in guava orchards located in a tropical Andean forest of Peru to investigate differences in fruit flies (Diptera: Tephritidae) and their parasitoid communities at two elevations and over two seasons. Fruit fly traps were installed, monitored, and guava fruits were sampled from eight orchards at low (800–950 m above sea level) and high (1,700–1,900 m above sea level) elevations and during the dry and rainy seasons. At each orchard, adult fruit fly trap captures and emergence of fruit flies and their parasitoids from guava fruit were quantified to determine their abundance and species composition. There was a greater abundance and species richness of fruit flies captured in traps at lower elevations, as well as higher abundance and species evenness of fruit flies that emerged from fruit, indicating that lower elevations are associated with larger fruit fly populations. The abundance, species richness and diversity of parasitoids were also greater at lower elevations. Consequently, guava fruit infestation and fruit fly parasitism rates were also greater at lower elevations. Seasonality also influenced fruit fly populations with a greater number of flies emerging from guava fruit and more fruit infested in the rainy season. However, seasonality had no effect on parasitoid population parameters or rate of parasitism, nor did it interact with elevation as an influence of populations of fruit flies or their parasitoids in guava orchards. This study highlights the importance of examining both elevation and seasonality for a better understanding of the population dynamics of fruit flies and their parasitoids in tropical agroecosystems.

Whether nutrient availability interacts with induced resistance to alter plant chemistry and, consequently, the preference and performance of herbivores on plants remains unclear. We hypothesized that changing fertilizer inputs modulates responses induced by exogenous application of the defensive phytohormone methyl jasmonate (MeJA) against Tuta absoluta, a devastating pest of tomatoes. We found that tomato plants grown at or 2-fold above optimal fertilizer rates had higher nutrient content and were more preferred by T. absoluta females for oviposition and were better hosts for their offspring. MeJA increased phenolic content and volatile emissions in plants, which correlated with lower T. absoluta oviposition preference and offspring performance. However, we found no significant interactions when fertilizer and MeJA were applied simultaneously, such that induced responses against T. absoluta in tomatoes were similar regardless of fertilizer rate. These results provide novel insights into the bottom-up effects of fertilization and induced resistance on plant-insect herbivore interactions.