Maize-Crotalaria spectabilis intercropping in organic system and relations with the insect community

Abstract

The objective of this study was to evaluate the canopy insect community associated with maize intercropped with different arrangements of Crotalaria spectabilis and the effects on the damage caused to maize by Spodoptera frugiperda and Helicoverpa zea. The treatments were intercropping systems of maize with Crotalaria spectabilis: CR - Crotalaria spectabilis sown on the same rows as maize; CBR - Crotalaria spectabilis sown between the rows of maize; CRBR - Crotalaria spectabilis sown on the rows and between the rows of maize, and M - maize monocrop. The experimental plot consisted of five rows of maize, five meters long, spaced 0.8 m apart. Assessments were made of the following parameters: insect community present in the maize canopy, leaf damage caused by the fall armyworm (S. frugiperda) and the corn earworm (H. zea), maize grain yield and shoot dry weight of maize and crotalaria. The CRBR intercropping system was characterized by the presence of predators and parasitoids, especially from the families Forficulidae and Braconidae: 79% and 82%, respectively. The maize monocrop, in turn, was mainly characterized by the presence of chewing and sucking phytophagous insects and predators. There was no influence of plant arrangements on the damage to maize caused by S. frugiperda (mean variation between 0.47 and 0.64 of damage) and H. zea (ranging between 6.42 and 7.49 of damage), neither on the grain yield of the crop (variation between 4129.57 kg ha-1 and 5653.77 kg ha-1). Our results suggest that C. spectablis sown in the rows and between the rows of maize has the potential to optimize conservative biological control, without, however, affecting the grain yield of the cereal