Editorial (wileyonlinelibrary.com) DOI 10.1002/ps.3945
Are integrated pest management (IPM) and resistance management synonymous or antagonistic?* This issue contains three commissioned articles on IPM of the three major pest groups, pathogens, 1 insects, 2 and weeds. 3 The editorial board conceived these commissions following the presentation at a resistance symposium of an earlier version of the first paper showing that growers who used IPM for pathogen control had horrendous resistance problems, whereas those who did not practice IPM were still achieving adequate pathogen control. This seemed quite contrary to conventional wisdom that IPM and resistance management are synonymous. We wished to ascertain whether this discordance is/will be a general phenomenon of incompatibility between the two, and whether some issues in IPM need some rethinking. Despite all the hyperbole that IPM is the answer to long term sustainability in agriculture, there is the long experience that no agricultural practice has lasted forever – pest evolution has overcome all forms of mechanical and chemical control, and considerable tweaking is needed to stay ahead. Before the adoption of IPM by many but clearly not all growers, pest control was calendar based spraying, whether needed or not, irrespective of conditions, a technology still used by many. Detractors were sure that no farmer would adopt IPM based on the philosophy of KISS (keep it simple, stupid). Many farmers discovered that IPM saved time and money with fewer applications of less chemicals that were part and parcel of IPM systems, despite the scouting and calculating pest thresholds. KISS transformed to be ‘keep it sophisticated, smarty’. While we did not receive the general reviews we had hoped for, we received three fascinating manuscripts describing case histories that are perhaps more useful than generalities, because of the concrete evidence they contain. The vignettes they describe provide a multitude of insights on how IPM can become incompatible with resistance management. The lessons from hindsight suggest ways IPM might become more compatible if modified. As pointed out,2 there have been/are many definitions of IPM. Those in current use all seem to include two elements as part of the IPM strategies: reduced pesticide use and cost-effective pest control, and it is here where the incompatibilities enter, with theoretical underpinnings for support. “Cost-effective” typically means that the economic gains resulting from a pest control action action exceed costs of taking this action. Cost effectiveness has been measured by practitioners and academics over one or at most, a few seasons. Pesticide resistance typically takes 5–15 seasons to evolve inadequate control, depending on pest class and pesticide. When pesticide resistance raises its ugly head, control costs can skyrocket. There is a net loss from IPM when the increased control costs after resistance sets in are averaged with the savings
Pest Manag Sci 2015; 71: 329–330
www.soci.org
© 2015 Society of Chemical Industry
329
*Readers are invited to discuss the conundrum, especially with examples, on the Pest Management Science LinkedIn page: https:// www.linkedin.com/groups/Pest-Management-Science-4332010/about
from the IPM years. “Cost effective” has two components that facilitate the evolution of resistance: (1) using economic thresholds where the levels of pests that are left in the field when it costs more to control them than the economic damage they would immediately inflict; and (2) use the lowest rates of pesticide to achieve this cost-effective threshold. These considerations can be counterproductive for resistance management. If there is a fixed mutation frequency in a population for resistance, the more individuals in the field population, the more likely there will be a resistant individual selected for. If the field population prior to pesticide use is below the mutation frequency, the selection for resistant individuals is less likely. Not killing almost all individuals (by using short term economics to decide pest thresholds) leaves the numbers needed to select for these rare resistant individuals. Worse yet, these resistant individuals have many susceptibles available for mating. Thus, only mixed IPM strategies that assure very low pest reservoirs, whether seeds, eggs or spores, before pesticide treatments, can delay the evolution of resistance. The use of lower doses of pesticide with longer spacing between treatments in IPM has two effects: leaving more individuals (as discussed above) as well as having a greater range of ages and developmental states of pest individuals at the time of pesticide application. It is then likely that some individuals are old enough not to be killed by pesticides that do not kill all ages and stages with the same dose. There is ample evidence that stress increases the rate of mutations in the individuals that are heavily stressed, and then recover.4 Thus, not only do IPM strategies based on lower rates and longer spacing leave more individuals, these individuals may bear more mutations, including those for resistance. Therefore, it is of little wonder that the apple growers who used IPM based solely on economic threshold infections and a single fungicide have orchards full of resistant apple scab.1 The growers whose philosophy is the only good pest is a dead pest are free of the problem (so far). Clearly the IPM strategy used was an over-simplified perversion of IPM, which should depend on as many strategies as possible to deal with the pest. This is not an easy task in perennial orchards; the crop rotations that should be an important integral part of IPM are nigh impossible in orchards. Perhaps a multigene transgenic approach is a necessary component in orchard disease IPM. The multi-chemical treadmill of the Colorado potato beetle control, whether IPM or conventional has not been sustainable in most areas. Epidemiology is used, comparing different potato growing areas to try to ascertain what works and what fails.2 The lack of resistance in one area is due to regular high dose chemical applications (i.e. not very IPM oriented), but also may be due to a lack of genetic diversity in the beetle populations in that area, which renders it less evolutionarily adaptable. The greater use of crop rotation, greater distance between potato fields and large
www.soci.org numbers of volunteer potatoes not receiving pesticides that act as reservoirs of fit individuals that would compete with resistant ones should they evolve, all contribute to a lack of resistant populations in that area, compared to the others. The environmental benefits and lowered costs of using less tillage have resulted in greater chemical dependency on herbicides. One herbicide, glyphosate controls almost all weeds, and also happens to be the least expensive, resulting in vast overuse, especially in crops that have been transgenically rendered resistant.3 The willingness to blithely use so much was promoted by predictions of the manufacturer that its IPM compatible system was recalcitrant to the evolution of resistant weeds,5 which now cover ca. 5 million hectares of the USA alone. The authors of the paper in this issue claim that the principles of weed management that could have avoided this problem are known, but the “question is why growers defy sound science”.3 It is clear from all three papers that in order to be effective in the longer term, IPM must go from its present KISS to a longer KISSS – keep it super-sophisticated, smarty, with far more diversity of inputs, in a less patterned format to keep the pests at bay from rapid evolution. Only if we learn the lessons from these case histories and act accordingly can IPM and resistance management be synonymous. And even then, we will probably learn some new
Editorial
lessons (some the hard way) and then have to again modify the IPM strategies. Jonathan Gressel Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel E-mail: [email protected]
REFERENCES 1 Beckerman JL, Sundin GW and Rosenberger DA, Do some IPM concepts contribute to the development of fungicide resistance? Lessons learned from the apple scab pathosystem in the United States. Pest Manag Sci 71:331–342 (2015). 2 Alyokhin A, Mota-Sanchez D, Baker M, Snyder WE, Menasha S, Whalon M, Dively G and Moarsi WF, The Red Queen in a potato field: integrated pest management versus chemical dependency in Colorado potato beetle control. Pest Manag Sci 71:343–356 (2015). 3 Owen MDK, Beckie HJ, Leeson JY, Norsworthy JK and Steckel LF, Integrated pest management and weed management in the US and Canada. Pest Manag Sci 71: 357–376 (2015). 4 Gressel J, Low pesticide rates may hasten the evolution of resistance by increasing mutation frequency. Pest Manag Sci 67:253–257 (2011). 5 Bradshaw LD, Padgette SR, Kimball SL and Wells BH, Perspectives on glyphosate resistance. Weed Tech 11:189–198 (1997).
330 wileyonlinelibrary.com/journal/ps
© 2015 Society of Chemical Industry
Pest Manag Sci 2015; 71: 329–330
Are integrated pest management (IPM) and resistance management synonymous or antagonistic?* This issue contains three commissioned articles on IPM of the three major pest groups, pathogens, 1 insects, 2 and weeds. 3 The editorial board conceived these commissions following the presentation at a resistance symposium of an earlier version of the first paper showing that growers who used IPM for pathogen control had horrendous resistance problems, whereas those who did not practice IPM were still achieving adequate pathogen control. This seemed quite contrary to conventional wisdom that IPM and resistance management are synonymous. We wished to ascertain whether this discordance is/will be a general phenomenon of incompatibility between the two, and whether some issues in IPM need some rethinking. Despite all the hyperbole that IPM is the answer to long term sustainability in agriculture, there is the long experience that no agricultural practice has lasted forever – pest evolution has overcome all forms of mechanical and chemical control, and considerable tweaking is needed to stay ahead. Before the adoption of IPM by many but clearly not all growers, pest control was calendar based spraying, whether needed or not, irrespective of conditions, a technology still used by many. Detractors were sure that no farmer would adopt IPM based on the philosophy of KISS (keep it simple, stupid). Many farmers discovered that IPM saved time and money with fewer applications of less chemicals that were part and parcel of IPM systems, despite the scouting and calculating pest thresholds. KISS transformed to be ‘keep it sophisticated, smarty’. While we did not receive the general reviews we had hoped for, we received three fascinating manuscripts describing case histories that are perhaps more useful than generalities, because of the concrete evidence they contain. The vignettes they describe provide a multitude of insights on how IPM can become incompatible with resistance management. The lessons from hindsight suggest ways IPM might become more compatible if modified. As pointed out,2 there have been/are many definitions of IPM. Those in current use all seem to include two elements as part of the IPM strategies: reduced pesticide use and cost-effective pest control, and it is here where the incompatibilities enter, with theoretical underpinnings for support. “Cost-effective” typically means that the economic gains resulting from a pest control action action exceed costs of taking this action. Cost effectiveness has been measured by practitioners and academics over one or at most, a few seasons. Pesticide resistance typically takes 5–15 seasons to evolve inadequate control, depending on pest class and pesticide. When pesticide resistance raises its ugly head, control costs can skyrocket. There is a net loss from IPM when the increased control costs after resistance sets in are averaged with the savings
Pest Manag Sci 2015; 71: 329–330
www.soci.org
© 2015 Society of Chemical Industry
329
*Readers are invited to discuss the conundrum, especially with examples, on the Pest Management Science LinkedIn page: https:// www.linkedin.com/groups/Pest-Management-Science-4332010/about
from the IPM years. “Cost effective” has two components that facilitate the evolution of resistance: (1) using economic thresholds where the levels of pests that are left in the field when it costs more to control them than the economic damage they would immediately inflict; and (2) use the lowest rates of pesticide to achieve this cost-effective threshold. These considerations can be counterproductive for resistance management. If there is a fixed mutation frequency in a population for resistance, the more individuals in the field population, the more likely there will be a resistant individual selected for. If the field population prior to pesticide use is below the mutation frequency, the selection for resistant individuals is less likely. Not killing almost all individuals (by using short term economics to decide pest thresholds) leaves the numbers needed to select for these rare resistant individuals. Worse yet, these resistant individuals have many susceptibles available for mating. Thus, only mixed IPM strategies that assure very low pest reservoirs, whether seeds, eggs or spores, before pesticide treatments, can delay the evolution of resistance. The use of lower doses of pesticide with longer spacing between treatments in IPM has two effects: leaving more individuals (as discussed above) as well as having a greater range of ages and developmental states of pest individuals at the time of pesticide application. It is then likely that some individuals are old enough not to be killed by pesticides that do not kill all ages and stages with the same dose. There is ample evidence that stress increases the rate of mutations in the individuals that are heavily stressed, and then recover.4 Thus, not only do IPM strategies based on lower rates and longer spacing leave more individuals, these individuals may bear more mutations, including those for resistance. Therefore, it is of little wonder that the apple growers who used IPM based solely on economic threshold infections and a single fungicide have orchards full of resistant apple scab.1 The growers whose philosophy is the only good pest is a dead pest are free of the problem (so far). Clearly the IPM strategy used was an over-simplified perversion of IPM, which should depend on as many strategies as possible to deal with the pest. This is not an easy task in perennial orchards; the crop rotations that should be an important integral part of IPM are nigh impossible in orchards. Perhaps a multigene transgenic approach is a necessary component in orchard disease IPM. The multi-chemical treadmill of the Colorado potato beetle control, whether IPM or conventional has not been sustainable in most areas. Epidemiology is used, comparing different potato growing areas to try to ascertain what works and what fails.2 The lack of resistance in one area is due to regular high dose chemical applications (i.e. not very IPM oriented), but also may be due to a lack of genetic diversity in the beetle populations in that area, which renders it less evolutionarily adaptable. The greater use of crop rotation, greater distance between potato fields and large
www.soci.org numbers of volunteer potatoes not receiving pesticides that act as reservoirs of fit individuals that would compete with resistant ones should they evolve, all contribute to a lack of resistant populations in that area, compared to the others. The environmental benefits and lowered costs of using less tillage have resulted in greater chemical dependency on herbicides. One herbicide, glyphosate controls almost all weeds, and also happens to be the least expensive, resulting in vast overuse, especially in crops that have been transgenically rendered resistant.3 The willingness to blithely use so much was promoted by predictions of the manufacturer that its IPM compatible system was recalcitrant to the evolution of resistant weeds,5 which now cover ca. 5 million hectares of the USA alone. The authors of the paper in this issue claim that the principles of weed management that could have avoided this problem are known, but the “question is why growers defy sound science”.3 It is clear from all three papers that in order to be effective in the longer term, IPM must go from its present KISS to a longer KISSS – keep it super-sophisticated, smarty, with far more diversity of inputs, in a less patterned format to keep the pests at bay from rapid evolution. Only if we learn the lessons from these case histories and act accordingly can IPM and resistance management be synonymous. And even then, we will probably learn some new
Editorial
lessons (some the hard way) and then have to again modify the IPM strategies. Jonathan Gressel Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel E-mail: [email protected]
REFERENCES 1 Beckerman JL, Sundin GW and Rosenberger DA, Do some IPM concepts contribute to the development of fungicide resistance? Lessons learned from the apple scab pathosystem in the United States. Pest Manag Sci 71:331–342 (2015). 2 Alyokhin A, Mota-Sanchez D, Baker M, Snyder WE, Menasha S, Whalon M, Dively G and Moarsi WF, The Red Queen in a potato field: integrated pest management versus chemical dependency in Colorado potato beetle control. Pest Manag Sci 71:343–356 (2015). 3 Owen MDK, Beckie HJ, Leeson JY, Norsworthy JK and Steckel LF, Integrated pest management and weed management in the US and Canada. Pest Manag Sci 71: 357–376 (2015). 4 Gressel J, Low pesticide rates may hasten the evolution of resistance by increasing mutation frequency. Pest Manag Sci 67:253–257 (2011). 5 Bradshaw LD, Padgette SR, Kimball SL and Wells BH, Perspectives on glyphosate resistance. Weed Tech 11:189–198 (1997).
330 wileyonlinelibrary.com/journal/ps
© 2015 Society of Chemical Industry
Pest Manag Sci 2015; 71: 329–330
