Managing Crops for Climate Change Can Also Manage Pests

The impacts of climate change are already being felt by farmers in many parts of the world. As such, it is important for us to determine which strategies may help protect crops and stabilize yields in the face of these changes.

Emphasis in the literature is placed on cropping practices that may help to mitigate or improve crop resistance to the abiotic effects of climate change, such as drought, temperature, or erosion from increased frequency of storm events. However, climate change is also predicted to affect the biological communities in cropping systems. One such biological community is the insects, both pest and beneficial species, that damage and manages productivity in crops, respectively.

Fortunately, a review of the recent literature found that many of the agricultural practices recommended to mitigate climate change (primarily by reducing greenhouse gas emissions), or to improve crop resilience under climate change conditions, may also help to reduce insect pest pressure.  Reducing the amount of tillage in cropping systems can help to increase abundance and evenness of important ground-dwelling pest predators, such as spiders, ground beetles, and rove beetles.  When rotating crops, planting a perennial crop species even for two years can increase pest predators not only in the perennial crop but also in the annual crop planted after the perennial species.  Fertilizing crops with manure can also reduce pest populations, or slow their growth, compared to fields in which synthetic fertilizers are applied.  The System of Rice Intensification (SRI), a planting strategy for rice fields that spaces plants more widely and reduces the number of times the field is flooded, not only reduces methane emissions from the fields but also reduces infestation by multiple insect pest species.

However, the story is not always clear-cut whether a practice aimed to improve crop resilience to climate change will manage or facilitate pest damage.  For example, the practice of conservation tillage – that is, leaving crop residue on the soil surface after harvest – reduces soil erosion and increases soil moisture retention.  This practice can provide better habitat for predatory insects, but it may also increase habitat for pest insect species, particularly in corn and wheat fields.  Whether pests or predators benefit more from this practice seems to depend on the individual cropping system.  Similarly, irrigation and fertilizing crops with compost have variable effects on pest damage and pest management.

The fact that many farming practices aimed at improving crop resilience to climate change may also help manage pests within these systems is heartening.  The next question to be addressed is whether these practices will continue to manage pests under forecasted climatic conditions.  This is a more difficult question to answer, as climate change is predicted to directly affect insects: their development rates, foraging behaviors, swarming frequencies, and population dynamics.  To date, only two studies have specifically tested effects of different farming practices on biological control under projected climate change conditions.  Our challenge, as a scientific community, is to put more farming practices to the test, so that we can predict which practices will continue effectively improve crop resilience and manage pests in the coming years.

These findings are described in the article “Can agricultural practices that mitigate or improve crop resilience to climate change also manage crop pests?”, recently published in the journal Current Opinion in Insect Science. This work was conducted by Ebony G. Murrell while at Pennsylvania State University, currently employed by The Land Institute.

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