Non‐target impact of deltamethrin on soil arthropods of maize fields under conventional and no‐tillage cultivation

Abstract

Deltamethrin is a commonly used insecticide for controlling its key maize pest, the fall armyworm Spodoptera frugiperda (Lep., Noctuidae). Its toxicological profile is well known, but its impact on arthropods widely reported as bioindicators, mainly springtails (Collembola) and mites (Oribatida), is yet to be assessed in tropical maize fields. The treatments used to circumvent this shortcoming were conventional cultivation and no-tillage cultivation (with a presowing application of 2,4-D and glyphosate) systems with or without deltamethrin spraying. The deltamethrin residue analysis of soil samples by gas chromatography did not detect the insecticide 24 h after it was sprayed on the maize fields. There was no significant overall effect of deltamethrin based on principal component analysis. However, repeated-measures analyses of variance detected significant impact of deltamethrin in a species of Nitidulidae (Coleoptera). The cultivation system also provided significant impact on Oribatida and Gamasida soil mites and on the same Nitidulidae species referred above, which were more abundant in the conventional cultivation system. Springtails were also significantly affected by the cultivation system showing greater abundance in the conventional system, except Podumorpha. Analyses using only high taxonomic levels did not allow the detection of impact in the ant assemblage assessed. The results suggest that the impact of deltamethrin on soil arthropods from tropical fields varies among species and is lower than expected. The cultivation system imposes more drastic effects on arthropod assemblage.

Non‐target effects of insecticides, entomopathogenic fungi and nematodes applied against western corn rootworm larvae in maize

“…In another study investigating non‐target effects of pesticides used in tropical maize fields, Badji et al. () found that effects of another pyrethroid, deltamethrin, on soil arthropods are lower than expected. The authors concluded that the cultivation system imposes more drastic effects on arthropod assemblages.…”

Pezothrips kellyanus (Thysanoptera: Thripidae), nueva plaga en cítricos; comportamiento de sus poblaciones, muestreo y enemigos naturales

“…Broadspectrum pesticides, including organophosphates, were shown to decrease overall abundance and diversity of soil-dwelling mites (Koehler, 1992;BehanPelletier, 2003). Nevertheless, Badji et al (2007) observed that the impact of deltamethrin on soil arthropods from tropical maize fields varied among species and was lower than expected, and Koehler (1992) observed that some species are particularly susceptible, while others are not affected or can even show an increase. Definitely more studies, and during longer periods of time, are required in order to determine the effect of foliar pesticide applications on the soil-dwelling predatory mites.…”

Ecological Impacts of Insecticides

“…A commonly observed outcome of insecticide application is the release of prey species due to reduced predatory pressure. For example, springtails usually increase in numbers when fields are treated with recommended doses of OC and pyrethroid insecticides, since the mites that prey on them are more susceptible than their prey (Badji et al 2007). However, chlorpyrifos decimates springtail populations and changes the structure of their communities in soil, which take more than a year to recover.…”