Abstract
Chemical control of insect pests remains vital to agricultural productivity, but limited mechanistic understanding of the interactions between crop, pest and chemical control agent have restricted our capacity to respond to challenges such as the emergence of resistance and demands for tighter environmental regulation. Formulating effective control strategies that integrate chemical and non-chemical management for soil-dwelling pests is particularly problematic owing to the complexity of the soil-root-pest system and the variability that occurs between sites and between seasons. Here, we present a new concept, termed COMPASS, that integrates ecological knowledge on pest development and behaviour together with crop physiology and mechanistic understanding of chemical distribution and toxic action within the rhizosphere. The concept is tested using a two-dimensional systems model (COMPASS-Rootworm) that simulates root damage in maize from the corn rootworm Diabrotica spp. We evaluate COMPASS-Rootworm using 119 field trials that investigated the efficacy of insecticidal products and placement strategies at four sites in the USA over a period of ten years. Simulated root damage is consistent with measurements for 109 field trials. Moreover, we disentangle factors influencing root damage and pest control, including pest pressure, weather, insecticide distribution, and temporality between the emergence of crop roots and pests. The model can inform integrated pest management, optimize pest control strategies to reduce environmental burdens from pesticides, and improve the efficiency of insecticide development.
Highlights
Global crop production depends on efficient protection from insect damage
The efficacy to control root damage by corn rootworm of products tested in the 119 field trials used for model evaluation ranged from 0 to 99%; the value for each trial was calculated from averages given in reports, and assuming 0% efficacy for trials where the damage to plants in treated plots was equal to or greater than that in the untreated controls
Supplementary Data (SD) Fig. S1 illustrates the variability in the efficacy of products tested in each field trial by plotting the Node Injury Scale (NIS) damage values recorded in the treatment plots against those observed in the control plots
Summary
Global crop production depends on efficient protection from insect damage. Modern crop protection from insect pests is delivered through a combination of breeding and varietal selection, rotation, soil and crop husbandry, biological and microbial control, and chemical insecticides. Gianessi (2009) estimated that US growers spent $1.2 billion on insecticides in 2008 to treat 17% of the 1.1 million km of land cultivated with the 50 main crops, and that this resulted in a yield benefit of $22.9 billion. Compared with the earliest insecticides, modern active substances have improved mammalian toxicological profiles and greater selectivity; targeted placement into the crop, for example as a seed treatment or banded application, can achieve use rates lower than 50 g of active substance (a.s.)/ha (Lamberth et al, 2013)
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