The importance of using refuges

About 35 years ago -- when transgenesis technology was still embryonic -- I carried out a study (Modeling Insect Resistance to Insecticides Using Velvetbean Caterpillar (Anticarsia gemmatalis) as an Example) aiming to verify the factors that led to or prevented the development of insect resistance to insecticides (Link). A curiosity: at the time I used a “powerful” computer for the calculations, located at the Data Processing Center of the Federal Senate, in Brasília. Its processing capacity was much lower than the cell phone I use today!

One of the conclusions of that study was that the migration of insects from areas not treated with insecticide, or that received an insecticide with a different mode of action than that used in the studied area (avoiding cross-resistance), reduced the probability of resistance emerging. The most important factor was the dose of the insecticide-- which modulates the mortality rate in the field-- which mathematically demonstrated the importance of adjusting doses to obtain pest mortalities of around 80%, a conclusion that was intensely used at the time, in Embrapa recommendations for pest management programs.

There is an equivalence between the development of resistance of insects to insecticides and of plants to herbicides, or to insects. In the study above, migration is the effect of a refuge, with genetic exchange between specimens with some degree of resistance, and others that have not undergone selection for this characteristic. Thus, refuge, as a successful tactic in resistance management, precedes the emergence of transgenic varieties. In this text we will use the term variety although for some crops, such as soybeans, the correct term is cultivar and for others, such as corn, a hybrid.

Why avoid resistance?

There are several reasons, but let's list the central axis. Developing a transgenic plant, regardless of the desirable characteristic, takes many years. From the creation of a concept, through the development of an elite event (that characteristic that will benefit the farmer or society), release by official bodies, agronomic, environmental and health tests, until obtaining a commercial variety, with the Biosafety licenses last around 10 years. And its commercial use hardly reaches the following ten years, after launch.

Throughout the period referred to above, research and development costs are incurred, such as highly specialized personnel, state-of-the-art scientific facilities and equipment, multiple tests, permanent biosafety care. This cost needs to be reimbursed, under penalty of making the institution that developed it unviable, with the core of the royalties concept being the recovery of the investment made to obtain a transgenic variety. The value of royalties is calculated based on several parameters, the most important of which are the forecast of annual seed sales of the variety and the number of years of commercial viability.

If the pest (insect, disease or invasive plant) becomes resistant to the event that controls it, the varieties that use it may lose commercial viability. If the developer has been reimbursed for its creation and development costs, the problems are smaller. It can offer another variety, with the same characteristics, but with an innovative technology (if any), for which resistance has not yet developed. Either way, that particular technology is commercially impaired.

And if the payback of the variety for which resistance developed did not occur? In this case, the developer needs to find another way to compensate, under penalty of illiquidity or bankruptcy. Whichever way is found -- for example, adding the unreimbursed costs to the calculation of royalties for the new variety that will replace the previous one -- this will be charged to rural producers. And, in the new royalty calculations, the risk of loss of commercial viability due to the development of resistance will be considered, increasing its value.

In some cases, the technology may not be completely unfeasible, but the farmer will need to take specific management actions to control invasive plants or resistant pests.

Refuge is the best solution

Better from both a technical and financial, environmental and even productive stability point of view in the country. There are numerous recent examples of identification of resistance of insect pests to varieties developed for their control, as well as of invasive plants to full-action herbicides used in conjunction with herbicide-resistant varieties. Pests resistant to transgenic varieties are synonymous with higher production costs for the farmer, and therefore a lower margin.

In the case of insect pests, resistance to some insect proteins has developed. Bacillus thuringiensis expressed in varieties, such as Cry1F and Cry1Ac. Species of horseweed, wild peanut, ryegrass, palmeri pigweed, giant pigweed, white grass, crow's foot grass and sour grass are examples of invasive plants that are resistant to glyphosate.

The objective of this article is to present farmers with an overview of the problems caused by the development of resistance to varieties resistant to insects or herbicides. It is not our intention to guide, in detail, the use of refuge, but to highlight its transcendental importance for the farmer and for Brazilian agriculture.

For technical guidance on how to properly use the refuge, we suggest consulting specific technical publications from the variety developers, or the guidance provided by Embrapa, which can be found at Link; Link; Link; Link, or even consulting directly with Embrapa units.