GM seeds may make pest monitoring more difficult
2.Seeds of change: corn seed mixtures for resistance management and integrated pest management - new study
NOTE: When Monsanto and Dow developed their stacked gene GMO 'SmartStax', incorporating 8 different transgenes, the U.S. Environmental Protection Agency responded by allowing farmers to reduce their refuge requirements. (EPA Reduces Refuge Requirement for Bt Corn)
Refuges have been required since 1999 in order to prevent or delay insect resistance to GM crops incorporating the insecticidal Bt proteins. Refuges are an area of non-GM plants where insects can live that will not evolve resistance to Bt, as no Bt is present in the crops. These refuge acres are meant to ensure that rare resistant insects that feed on Bt varieties will mate with susceptible insects and so slow the development of resistance.
Because SmartStax claims to protect plants against above-ground and below-ground pests via multiple GM (Bt) traits (including Monsanto's Yieldgard VT Triple and Dow's Herculex Xtra), the EPA reduced the refuge requirement for Bt corn from 20% to as little as 5%. Seed companies then went a step further by offering seed mixes that are 95% stacked GM corn and 5% non-GM corn hybrids. This removes the need for GM farmers to also plant a block of non-GM corn, by providing so-called 'in-field refuges'.
However, a new study (item 2), which considers the recommendation to use mixtures of GM Bt and non-GM seeds as 'in-field refuges' to prevent a Bt-resistant pest population building up, concludes that both the newer 'in-field refuges' and the older block refuges, where areas of the field are planted with non-Bt crops, present problems.
An article about the new study (item 1) says the EPA has acknowledged stacked GM toxins may not actually increase mortality in targeted pests. And if gene stacking doesn't improve pest mortality, then it has "much less value" for the management of pest resistance to Bt toxin. This means a drastic reduction in refuges is taking place on a false premise.
It looks as if the biotech industry's attempts to prolong the inherently pest-vulnerable monoculture model of agriculture is doomed to early failure. The industry's approach also encourages the deskilling of farmers - "there is less impetus than ever", as the article notes, "for growers or crop consultants to enter fields" in order to monitor crops and work out the most effective ways of dealing with pests.
But as one 'resistance management' method after another fails, GM farmers may inevitably be forced into a more resilient model of food production - polyculture, rotations, companion planting, and all the other techniques that agroecological farming keeps alive.
1. Biotech seeds may make pest monitoring more difficult
Jennifer Shike, University of Illinois
Western Farm Press, May 5 2011
As the use of biotechnology increases and more companies move forward with the U.S. Environmental Protection Agency's approval to begin full-scale commercialization of seed mixtures in transgenic insecticidal corn, many researchers believe pest monitoring will become even more difficult.
"Seed mixtures may make insect resistance management (IRM) risky because of larval behavior and greater adoption of insecticidal corn," said David Onstad, professor in the Department of Crop Sciences at the University of Illinois and lead author in a recent article published in the Journal of Economic Entomology.
On the other hand, Onstad said block refuges present a different suite of risks because of adult pest behavior and the lower compliance with IRM rules expected from farmers.
"It's likely that secondary pests not targeted by the insecticidal corn, as well as natural enemies, will respond differently to block refuges and seed mixtures," Onstad said.
The risk management approach to corn pest management has provided tangible benefits to producers in corn-producing regions where target pests were once abundant. For example, Bt corn hybrids have helped to greatly reduce the number of European corn borers, the authors said.
"However, the risk management approach tends to ignore many aspects of IPM, such as monitoring pest levels and concentrating treatments when or where appropriate, because there is an assumption that most pests are controlled throughout the season, regardless of pressure levels," he said. "Although field corn has never been considered an IPM-intensive cropping system, there is less impetus than ever for growers or crop consultants to enter fields."
Onstad said that growers will also have fewer choices in what hybrids they grow in their fields. Experts in integrated pest management are concerned that some seed companies will provide fewer options for regional needs, secondary pests, disease control and refuge plantings.
Onstad and the collaborating authors also questioned whether pyramided toxins would actually increase mortality in targeted pests.
"Without this increase in mortality through independent activity of each toxin, the pyramid has much less value for IRM," he said. "EPA recently acknowledged that a corn hybrid pyramided with two toxins active against corn rootworms does not significantly increase larval mortality."
Mike Gray, U of I Extension entomologist, said this research is important for stakeholders to consider as the industry transitions to the new paradigm of 95 to 5 seed blends across the Corn Belt.
"A significant consequence of the seed mixture infrastructure emerging within the corn insect protection arena is increasing pressure on the long-term sustainability of the soil insecticide market," Gray said. "As the number of refuges configured as blocks, strips, or separate fields declines, soil insecticide use should also be reduced. Ultimately, loss of soil insecticide products will result in reduced flexibility of producers to effectively manage economic infestations of white grubs, wireworms, and other soil insects."
In addition, if resistance develops to Bt hybrids and becomes widespread, growers will need to have some remaining tools to manage insect pests of corn, Gray added.
"It remains to be seen whether some groups within the agribusiness sector will maintain their investments in this competitive arena just in case resistance develops or to offer products targeted against secondary soil insect pests," Gray said.
Onstad's research, "Seeds of change: Corn seed mixtures for resistance management and integrated pest management," was published in the Journal of Economic Entomology. Collaborating researchers include P.D. Mitchell, T.M. Hurley, J.G. Lundgren, R.P. Porter, C.H. Krupke, J.L. Spencer, C.D. DiFonzo, T.S. Baute, R.L. Hellmich, L.L. Buschman, W.D. Hutchison and J.F. Tooker.
2. Seeds of change: corn seed mixtures for resistance management and integrated pest management
Onstad, D. W., P. D. Mitchell, et al. (2011). J Econ Entomol 104(2): 343-352.
The use of mixtures of transgenic insecticidal seed and nontransgenic seed to provide an in-field refuge for susceptible insects in insect-resistance-management (IRM) plans has been considered for at least two decades. However, the U.S. Environmental Protection Agency has only recently authorized the practice. This commentary explores issues that regulators, industry, and other stakeholders should consider as the use of biotechnology increases and seed mixtures are implemented as a major tactic for IRM. We discuss how block refuges and seed mixtures in transgenic insecticidal corn, Zea mays L., production will influence integrated pest management (IPM) and the evolution of pest resistance. We conclude that seed mixtures will make pest monitoring more difficult and that seed mixtures may make IRM riskier because of larval behavior and greater adoption of insecticidal corn. Conversely, block refuges present a different suite of risks because of adult pest behavior and the lower compliance with IRM rules expected from farmers. It is likely that secondary pests not targeted by the insecticidal corn as well as natural enemies will respond differently to block refuges and seed mixtures.