Pests on agricultural crops can be a serious nuisance for farmers who do their best to keep the unwanted bugs in check. To limit impacts on the environment and human health, crop protection in the European Union relies increasingly on the use of biological control, pest-resistant plants, and ‘green’ pesticides containing natural compounds instead of synthetic compounds.
However, interactions among tactics can be unpredictable. In practice, Conflicting Pest Control emerges when botanicals suppress beneficial predators, resistant cultivars shift pest behavior, or sublethal doses accelerate resistance. Without coordinated timing, field monitoring, and refuge planning, these well-meant mixes can cancel each other out—triggering rebounds, secondary outbreaks, and higher costs. Rigorous trials, economic thresholds, and landscape-level design are essential to ensure combinations remain synergistic rather than counter-productive.
Wrong combinations
However, using the wrong combination of strategies ( Conflicting Pest Control practices) actually lead to an increase in crop pest populations. ‘Predator-prey models predict that resistance breeding and pesticides – with synthetic or natural – may hamper biological control to an extent that the level of overall crop protection will often decrease rather than increase’, says Dr. Merijn Kant of the Institute for Biodiversity and Ecosystems Dynamics.
Giving plants a helping hand by tweaking their genes through targeted breeding to create resistant plants might hinder the actions of biological control agents just as they hinder unwanted pests. One instance in which this can happen is when the plant is resistant because it is less palatable for insects. This will affect not only the harmful insects but also the beneficial ones since their prey will be of poorer quality.
Mathematical models predict that under these conditions harmful insects may actually escape predation better than if they feed on plants void of resistance. They can thus reach higher densities and inflict more damage to the crop. In this case, plants without defences may be defended better with biological control
Urgent risk
In an attempt to minimise Conflicting Pest Control practices, the EU has recently banned various popular pesticides, creating an open niche for breeders to invest in new resistances for their crops. The time is now for further research on conflicting environmentally friendly pest control strategies.
“’The counter-intuitive concept should be tested because the results can profoundly alter the rationale behind the design of integrated pest management strategies,” says Dr. Merijn Kant. “If we ignore this, we expect an enormous decrease in efficiency of environmentally friendly pest control, one that resistance breeding and ‘green’ pesticides cannot compensate for.”
Conflicting Pest Control leads to Defenceless defences
As the coordinator of the new European project Kant cooperates with scientists from three different research institutions in the Netherlands, Belgium and Spain. Together they assessed to which extent prey densities in a predator-prey system, i.e. a bio-control agent and its target pest, are influenced by chemical plant resistance traits and natural pesticides during a three-year project, entitled Defdef (short for ‘Defenseless defenses’). Source: University of Amsterdam
