Insecticides could be replaced with pest-eating enemies

A conceptual study has revealed that natural pest-eating insects may be a potent way to keep pests away from crops without harm to the environment.

Andy Nelson/The Christian Science Monitor/File
Pineapple plants grow at a plantation near Ujarras, Costa Rica (2007). Pesticides used on pineapples and bananas have been observed by scientist in forest reserves and some believe their use may exacerbate the decline of reptiles and amphibians in the region. Natural pest-eaters might be a better solution.

Food Tank spoke with Dr. Mattias Jonsson, lead author of a paper on biological pest control. Biological control of pests is considered a key ecosystem service for the ecological intensification of agriculture.

The overall message: Biological control can vary according to land use. The authors present a conceptual ecological model for quantifying the ecosystem service of biological pest control across different production schemes in Sweden.

The research: The model predicted that biological control of aphid pests could reduce damage of cereal crops by 45-70 percent and that landscape complexity would magnify the effectiveness of biological control.

Food Tank (FT): Why is your research relevant for the transition to sustainable agriculture? What are two key points of your paper?

Mattias Jonsson (MJ): To reduce the reliance of agriculture on chemicals, it is important to provide evidence of the effectiveness of alternative approaches to crop protection. Such evidence is often lacking for biological control and this has hampered its use. First, our production function provides such evidence, by measuring the extent to which biological control services can reduce crop losses to pests and by showing that the composition of crop and non-crop habitats surrounding a field can have a strong influence on efficacy of biological control. Second, we hope that our conceptual framework will inspire other researchers to summarize the existing knowledge in other agricultural systems and develop further knowledge of biological control.

FT: How would you describe the results of your paper to a layman?

MJ: Our model shows that in Swedish barley fields, natural enemies of aphids can reduce crop damage by more than half. This effect is highly dependent on the composition of the surrounding landscape, ranging from about 45 percent reduction in landscapes dominated by annual crops to 70 percent in landscapes with little annual crop cover and a lot of grassland.

FT: Could you explain in laymen’s terms the importance of mapping biological control over different production systems? How do you expect the conceptual model you present in the paper to be adopted under different production schemes?

MJ: Mapping biological control potential in different landscapes can help to predict in which parts of the landscape aphid outbreaks are more likely to occur. For organic farming, mapping can reveal areas of the landscape where conversion to organic agriculture is most likely to be successful, due to low risk for pest damage. For conventional agriculture, the model can help reduce unnecessary insecticide application. This could be achieved by adapting the economic spray threshold to different parts of the landscape – it could be higher where biological control potential is high and lower where biological control potential is low. The model can also help to predict the best locations in the landscape to focus conservation management practices such as beetle banks or flower strips. Other studies have shown that the effect of such measures is likely to be highest in landscapes with relatively low effectiveness to biological control.

FT: How would you explain the effect of landscape complexity on biological control to a cereal farmer who is considering diversifying his or her farm?

MJ: Landscapes with a high complexity provide natural enemies with alternative food resources and shelter from disturbances. This increases both their abundance and diversity. Diversifying crop production can definitely contribute, but it is also important to preserve semi-natural habitat such as grasslands.

FT: We found your paper very exciting, because it seems to be one of the few that works to value the ecosystem service of biological pest control that sustains agricultural productivity. But some people say there is no need to assign a value to biological pest control, as it is already valued in the “benefit,” or total value of the crop; that this is essentially “double counting.”  How do you view this claim?

MJ: It would only be double counting if the value of regulating ecosystem services such as biological control were added on top of the value of the crop. However, biological control actually contributes to the value of crop production. By putting a value on biological control we highlight its importance for agricultural production, and by relating the value to different types of land uses, we can develop advice for sustainable agriculture with a minimized need for insecticide application.

FT: Could the conceptual model have implications for Payment for Ecosystem Services (PES) schemes? How will future research improve upon your model and integrate it with economic analyses?

MJ: The conceptual model highlights different processes that contribute to the value of biological control. Recommendations developed within this conceptual framework can be used to inform PES. Farms located in landscapes with high biological control potential might receive a higher payment that those located in landscapes with low potential for biological control. In the paper we list a number of ways in which the model can be improved. Integration of our model with economic models could help to relate biological control to other pest management options in different regions and landscape contexts. It could also include an assessment of the costs and benefits of preserving semi-natural grassland and other conservation management options at the landscape scale.

This article first appeared at Food Tank.

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