Of scientific obsolescence, ignorance, silver bullets, and agricultural waste: Understanding crop losses

 Ce qu’il fallait faire, c’était reconnaître clairement

ce qui devait être reconnu,

chasser enfin les ombres inutiles

 et prendre les mesures qui convenaient.

Albert Camus. La Peste


2014-01-15 10.09.30


by Serge Savary

Measuring, understanding and predicting crop losses to crop harmful organisms used to be a mainstream activity in plant health sciences. With the emergence of new and fascinating fronts of investigation, the field has become obsolete. Crop loss information – how much, exactly, is lost to plant diseases and pests – is taken for granted. This is a crucial mistake: because agriculture is changing at an ever-increasing pace, because the physical, biological, and socio-economic crop environments are evolving so fast, and because crop harmful organisms evolve and adapt, too, crop losses are constantly changing as well.

Ignorance has led to two seemingly opposed attitudes that have become pervasive among plant scientists and policy makers. One is the perception of a permanent, yet vague and non-quantified threat on food and fibre provision – the first of a range of agroecosystem services. The other is neglect in the face of outdated questions, reinforced by the confidence that quick fixes are at hand. One should not be surprised, then, to see arguments for silver-bullet solutions to plant protection flourish. These perceptions have provided grounds for the ‘Pesticide Revolution’to take root. They also generate the context of fatalism that led one well-known plant pathologist say: “Why analyze crop losses? – It’s too late anyway.” A physician would be ill-advised to make a similar statement about a patient dying of plague.

There are, in fact, many practical and important reasons to not drop the matter of crop loss assessment – instead, to consider it a worthwhile subject of investigation. Only four of these reasons, out of a range that have been widely documented in the literature, are briefly discussed here.

 It’s too late

Agricultural systems have evolved to cope with accidents, to varying degrees. Agriculture still exists, and still remains the basis of human societies today, because agricultural systems have built in mechanisms to compensate for, and survive, the vagaries of their environments, including diseases and pests. In agriculture, mishaps are the norm. Efficient recovery is not. Damage occurring on a crop reflects previous mistakes. The “it’s too late” argument negates the value of understanding and learning. Mistakes often arise from departures from the usual: an unusual

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What will happen soon

The mechanics of crop losses are usually non-linear. For most field crops, that is, the crops that feed the world, tipping points below which no harm is done, and beyond which all is lost, are very rare indeed. One deals with a progressive risk gradient, along which a decision must be made. While the decision of not acting now is often the best, it is bordered by the decision to act immediately, and that of not having ever to. A vision of what will, or could, happen soon is necessary to select an action from such choices. Understanding how and when crop losses build up and occur is the basis for such decisions.

Future losses

Crop losses build up along a decision chain. All too often, the chain considered by agronomists is limited to a single growing season. In doing so, built-in system mistakes are ignored. Cropping systems and regimens bring about inherent plant susceptibility and crop vulnerability that accumulate over growing seasons and across landscapes. As any engineered

input-output systems, agricultural systems can be decomposed and re-engineered to optimize resource use, minimize environmental disruptions, and reduce future losses to crop harmful organisms. Understanding the mechanics of crop losses is key in the process.

What did not happen yet

Because of the growing demand for agricultural products, notably food, world agricultures are taking risks. Because of agricultural changes and technology developments, quite a few crop health problems are subsiding. These changes however also bring about new or renewed crop health risks. Some of these appear to be compounded by climate change. As a set of technologies, agriculture is engaged on exploring uncharted grounds, where one certainty prevails: global change (economic, social, energetic), combined with climate change, will bring about new crop health challenges. In order to control the epidemic that has not yet started, knowledge of the vulnerability of agricultural systems in-the-making is essential: this is where crop loss research is needed. Ignoring this need would simply amount to drive future agricultural systems towards silver-bulleted pesticide non-choices. Plant scientists will then be right to say: “It’s too late”.