Effect of Cropping Systems on Insect Diversity, Abundance, and Their Role in the Dispersal of Aflatoxigenic Aspergillus Spp. In Pre-harvest Maize

Abstract

Maize (Zea mays) is a vital crop in Kenya, supporting millions of livelihoods. However, the persistent contamination of pre-harvest maize with Aspergillus and aflatoxins, facilitated by arthropods, poses a significant risk to food security, health, and the economy. Trials were conducted in Kisumu Makueni and Kilifi Counties in 2020 and 2021 aimed at determining the arthropods' diversity and abundance under different maize-legume cropping systems, the arthropods that could potentially spread viable Aspergillus inoculum in the field, and the identity and aflatoxigenic potential of the Aspergillus isolates recovered from insects. The field experiments were laid in an RCBD design with the four treatments: maize monocrop, maize/bean intercrop, maize/bean intercrop with Trichoderma harzianum, and push-pull technology. Insects were captured manually and by use of emergence traps, identified, and enumerated. Viable Aspergillus spores were recovered from the ten most abundant arthropod taxa and characterized using morphological, biochemical, and molecular techniques. The study documented over 300 arthropod taxa from the soil (Epigeic) and foliage of the maize-legume intercrops. The region, season, cropping system, the stage of crop development, and their interactions significantly (P ≤ 0.05) influenced the arthropod abundance and taxa diversity. The push-pull technology increased the arthropod diversity by adding beneficial taxa and significantly reduced the abundance of insect pests (fall armyworm and stem borers). Maize weevils, sap beetles, earwigs, and ants, were found to harbour spores of aflatoxigenic Aspergillus on their exoskeleton and gut. Mycotoxigenic fungi (Aspergillus, Fusarium, and Penicillium) were recovered from the insects in proportions that varied by region and season.