Abstract
Preventing a pest population from damaging an agricultural crop and, at the same time, preventing the development of pesticide resistance is a major challenge in crop protection. Understanding how farming practices and environmental factors interact with pest characteristics to influence the spread of resistance is a difficult and complex task. It is extremely challenging to investigate such interactions experimentally at realistic spatial and temporal scales. Mathematical modelling and computer simulation have, therefore, been used to analyse resistance evolution and to evaluate potential resistance management tactics. Of the many modelling approaches available, individual-based modelling of a pest population offers most flexibility to include and analyse numerous factors and their interactions. Here, a pollen beetle (Meligethes aeneus) population was modelled as an aggregate of individual insects inhabiting a spatially heterogeneous landscape. The development of the pest and host crop (oilseed rape) was driven by climatic variables. The agricultural land of the landscape was managed by farmers applying a specific rotation and crop protection strategy. The evolution of a single resistance allele to the pyrethroid lambda cyhalothrin was analysed for different combinations of crop management practices and for a recessive, intermediate and dominant resistance allele. While the spread of a recessive resistance allele was severely constrained, intermediate or dominant resistance alleles showed a similar response to the management regime imposed. Calendar treatments applied irrespective of pest density accelerated the development of resistance compared to ones applied in response to prescribed pest density thresholds. A greater proportion of spring-sown oilseed rape was also found to increase the speed of resistance as it increased the period of insecticide exposure. Our study demonstrates the flexibility and power of an individual-based model to simulate how farming practices affect pest population dynamics, and the consequent impact of different control strategies on the risk and speed of resistance development.
Highlights
The introduction of insecticides as a method of crop protection over the last 60 years has resulted in the development of many resistance cases amongst pest insects to several classes of active ingredient [1]
The interacting effects of factors underlying the evolution of insecticide resistance in the field are not fully understood, which impedes the development of new efficient resistance management approaches
We describe a spatially explicit individualbased model (IBM) that includes the important biological and environmental factors which affect the evolution of insecticide resistance, and which can be tailored to specific resistance problems by adopting appropriate parameter values
Summary
The introduction of insecticides as a method of crop protection over the last 60 years has resulted in the development of many resistance cases amongst pest insects to several classes of active ingredient [1]. The parameterised model was used to study the importance of environmental (crop rotations) and pest management (treatment thresholds) factors on the development of resistance in pollen beetle populations. Farmers can decide to treat their crops with an insecticide based either on calendar dates (e.g. 10 days after onset of flowering) or when the insect density exceeds a prescribed threshold (e.g. 15 adults/plant).
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