Larval and Larval-Pupal Parasitoids Associated with Major Owlet Moth Pests of Soybean and Maize in the Brazilian Savanna: Measures to Preserve Them in Crop Succession.

Abstract

Owlet moths (Lepidoptera: Noctuoidea) are among the most threatening pests of soybean and maize systems under intensive cropping in tropical and subtropical regions. Their high dispersal, larval polyphagia, and voracious feeding behavior often lead to severe grain production losses. Many parasitoids are associated with owlet moths; however, the ecological importance of larval parasitism in the soybean-maize crop rotation of the Brazilian savanna remains uncertain. We assessed larval parasitism in major lepidopteran pests of soybean and maize crops over three agricultural seasons in eight fields across Brazil's central-west region. Parasitic wasps were more common than tachinids on larvae of all lepidopteran species in both soybean and maize fields over the years. The larval parasitism rate by wasps averaged 9.7% in soybean fields and 13.6% in maize fields, whereas tachinids accounted for only 1.7% of parasitized larvae across both crops. The parasitism rate of Anticarsia gemmatalis Hübner was low in all soybean fields (< 4.9%), in contrast to the ones for Chrysodeixis includens (Walker) (5.9 to 32.5%) and the Spodoptera Guenée complex (4.2 to 29.2%). In maize, parasitism rates of Spodoptera frugiperda (J.E. Smith) ranged from 8.4 to 26.0% among fields, primarily by Ichneumonidae. The consistent presence of wasps, such as Cotesia Cameron and Campoletis Förster, parasitizing multiple hosts across all soybean and maize fields and seasons highlights their role in the natural biological control of caterpillars in the soybean-maize crop succession. In this sense, this study discusses relevant aspects of conservation biological control within multiple cropping systems.