**8. Applying insecticides on a when-needed basis**

Based on the description of EIL in IPM based approaches to pest management, Fig. 8a shows average pest population densities for the Scenario 2 simulations (see above) after including a pesticide spray application threshold ranging from 0-10% of the carrying ca‐ pacity (11,000 pest individuals) for the particular sampling universe (i.e. a field). In other words, it was assumed that sampling was conducted and that the average number of pests per plant was used as an action threshold for insecticide application. If the action threshold = 0, all pest generations were subjected to an insecticide application, while an action threshold = 2.5% meant that insecticide applications were only deployed if the esti‐ mated population density exceeded 275 pest individuals (or 2.5% of 11,000). Quite inter‐ estingly, the simulations suggested that using an action threshold led to slightly lower population density after 20 generations compared to a threshold = 0. In addition, the zero threshold showed a gradual increase in population densities from 18 generations and on‐ wards, while those simulations with a threshold showed a population density stabilizing after about 12 generations. More importantly, the increase in r allele frequency was mark‐ edly reduced when a threshold was used, and it stabilized at about 50%, while it contin‐ ued to increase in the scenarios without a threshold = 0 (Fig. 8b). Another interesting aspect of this analysis was that with 1,000 simulations and 20 generations, there was a to‐ tal of 20,000 combinations of generations and simulations, and: 1) threshold = 0 obviously triggered 20,000 insecticide applications, 2) threshold = 2.5% of carrying capacity triggered 13,890 insecticide applications, 3) threshold = 5.0% of carrying capacity triggered 13,340 in‐ secticide applications, and 4) threshold = 10% of carrying capacity triggered 12,517 insecti‐ cide applications. This means that, in addition to postponing complete insecticide failure (development of complete resistance development in the pest population), even a fairly low threshold of 2.5% of the carrying capacity reduced costs associated with insecticide applications by 31% [(20,000 - 13,890) × 100 / 20,000].

This exercise highlights some of the possible benefits of allowing some individuals of the homozygous susceptible genotype (with a higher reproductive fitness) to survive. They will obviously impose some level of crop damage and therefore cause yield losses, but their beneficial "dilution effect" is clearly outlined in the results from this simple exercise. In addition, it seems plausible that only spraying when the population density is above a certain threshold may enable natural enemies to become established and at least partially suppress the target pest populations. Incorporation of a pest density threshold as part of resistance management is analogous to the use of refuges as part of managing risk of ar‐

thropod resistance in transgenic crops (see [45] for review). Of course, the potential of tak‐ ing advantage of benefits from reduced insecticide application is based on the assumption that a combination of detection/monitoring and degree-day modelling can be converted into accurate and reliable decision support tools. Thus, it is paramount to envision the de‐ velopment of arthropod pest population growth models under field conditions as an es‐ sential part of optimizing use of insecticides – both in terms of when application is needed and as part of resistance management. among local populations). Thus, for long-term sustainable management of diamondback moth, it is highly important that its somewhat sporadic pest status is taken into account and that insecticides are only applied when and where they are deemed necessary. The important aspect of arthropod pest densities only occasionally leading to significant economic losses is that it provides justification for some times (in some growing seasons and/or in some cropping systems) NOT to apply insecticides, when pest populations are below a given threshold. However, diamondback moth being a sporadic pest in canola in Western Australia is by no means a unique pest–crop system, as most insect pests vary economic importance across seasons. A wide range of orchards pests [including a moth pest complex of peach [64] and *Acrobasis nuxvorella* Nuenzig (Lepidoptera: Pyralidae) in pecan [65], and field pests [including *Hypera postica* (Gyllenhal) (Coleoptera: Curculionidae) in alfalfa [66], and *Cylindrocopturus adspersus* (LeConte) (Coleoptera: Curculionidae) in sunflower [67], *Diabrotica virgifera* virgifera LeConte (Coleoptera: Chrysomelidae) adults in maize [68], and *Sitodiplosis mosellana* (Géhin) (Diptera: Cecidomyiidae) in wheat [69], there are well-established degree-day models to

becomes slightly drought stressed. During the last 10 years, seasonal weather patterns characterized by good summer and autumn

pest to develop resistance to DDT and Bt, and, as a species, it is considered resistant to at least 82 active ingredients (may vary

Figure 8. Effects of incorporating an action threshold **Figure 8.** Effects of incorporating an action threshold

predict "low risk"

models can be used very effectively to estimate whether a particular arthropod pest in a given growing season poses a threat to a certain crop system and provide strong founda‐ tion for only using insecticides on a when-needed basis. Only applying insecticides when needed may save growers money, and it will undoubtedly reduce the risk of insecticide

Based on the description of EIL in IPM based approaches to pest management, Fig. 8a shows average pest population densities for the Scenario 2 simulations (see above) after including a pesticide spray application threshold ranging from 0-10% of the carrying ca‐ pacity (11,000 pest individuals) for the particular sampling universe (i.e. a field). In other words, it was assumed that sampling was conducted and that the average number of pests per plant was used as an action threshold for insecticide application. If the action threshold = 0, all pest generations were subjected to an insecticide application, while an action threshold = 2.5% meant that insecticide applications were only deployed if the esti‐ mated population density exceeded 275 pest individuals (or 2.5% of 11,000). Quite inter‐ estingly, the simulations suggested that using an action threshold led to slightly lower population density after 20 generations compared to a threshold = 0. In addition, the zero threshold showed a gradual increase in population densities from 18 generations and on‐ wards, while those simulations with a threshold showed a population density stabilizing after about 12 generations. More importantly, the increase in r allele frequency was mark‐ edly reduced when a threshold was used, and it stabilized at about 50%, while it contin‐ ued to increase in the scenarios without a threshold = 0 (Fig. 8b). Another interesting aspect of this analysis was that with 1,000 simulations and 20 generations, there was a to‐ tal of 20,000 combinations of generations and simulations, and: 1) threshold = 0 obviously triggered 20,000 insecticide applications, 2) threshold = 2.5% of carrying capacity triggered 13,890 insecticide applications, 3) threshold = 5.0% of carrying capacity triggered 13,340 in‐ secticide applications, and 4) threshold = 10% of carrying capacity triggered 12,517 insecti‐ cide applications. This means that, in addition to postponing complete insecticide failure (development of complete resistance development in the pest population), even a fairly low threshold of 2.5% of the carrying capacity reduced costs associated with insecticide

This exercise highlights some of the possible benefits of allowing some individuals of the homozygous susceptible genotype (with a higher reproductive fitness) to survive. They will obviously impose some level of crop damage and therefore cause yield losses, but their beneficial "dilution effect" is clearly outlined in the results from this simple exercise. In addition, it seems plausible that only spraying when the population density is above a certain threshold may enable natural enemies to become established and at least partially suppress the target pest populations. Incorporation of a pest density threshold as part of resistance management is analogous to the use of refuges as part of managing risk of ar‐

**8. Applying insecticides on a when-needed basis**

218 Insecticides - Development of Safer and More Effective Technologies

applications by 31% [(20,000 - 13,890) × 100 / 20,000].

resistance.

#### importance can be predicted/forecasted based on quantitative models. Such models can be used very effectively to estimate whether a particular arthropod pest in a given growing season poses a threat to a certain crop system and provide strong **9. Pest infestations – symptoms rather than problems**

and it will undoubtedly reduce the risk of insecticide resistance. Above, it was established that, mainly as "peace of mind" or because of operational conven‐ ience and less as a response to actual emerging pest infestations, insecticides are being

foundation for only using insecticides on a when-needed basis. Only applying insecticides when needed may save growers money,

and "high risk" growing seasons. Such degree day models represent two important notions: 1) that the economic importance of a given pest shows considerable regional and seasonal variation, and 2) that the considerable spatio-temporal variation in economic

sprayed/applied more often than what is economically justifiable and/or necessary to control target pest populations below action thresholds. In addition, we highlighted some practical/ operational circumstances, like tank mix, which may justify insecticide application even without knowing whether emerging pest populations are present or not. It was also shown, based on detailed analysis of water sensitive spray cards deployed under commercial pesti‐ cide applications, that expected performance of spray applications may often be below opti‐ mal due to quite low spray coverage and canopy penetration. That is, we have outlined the heavy reliance on insecticide applications and also shown that most of the quantitative data available in published reports suggests that insecticide spray coverages are often quite low. In many situations, the benefits of applying insecticides are clear and pest control is being effective, but for other major pests chemical control does not seem to work. Further research into the biology and ecology of these pests can provide valuable clues to how we can reduce our reliance on insecticide based management of important pests. For example, in regions of southern Australia with summer rainfall, root-feeding larvae of scarab beetles at times can destroy all the roots of pasture grasses, so that the pasture can be rolled up like a carpet. During 1970-1975 some 20,000-40,000 ha pasture were estimated to be sprayed annually at a cost of about \$AUD 10 per ha. However, research showed the presence of potentially dam‐ aging populations was only evident after the damage had occurred and spraying at this time not only failed to prevent damage but also killed valuable natural enemies [70]. Larvae of the root-feeding scarab species selectively feed on living roots of the grasses in the soil [71], which initially causes a reduction in root growth, but a reduction in foliage growth was observed only when the plants were also defoliated (grazed), and these plants are vulnera‐ ble to any periods of water stress due to lack of rainfall [72]. At times when younger larvae are feeding actively and plants are growing well damage is not evident, and it is at a later time when older larvae are present that the plants may die due to drought. Spraying at this time does not prevent the appearance of damage because the plants were damaged previ‐ ously. In addition when roots are growing actively and larvae are feeding strongly it is the lower densities of larvae that cause greatest reduction in the root yield [72]. A model of the interaction between plant growth, sheep grazing and insect feeding indicate that greatest impacts of the insect on pastures are occurring at low grazing pressures and low insect den‐ sities when plants are growing well [73]. An adjustment of spraying strategy is needed for these root-feeding scarabs. The redlegged earth mite is a major foliage-feeding pest in re‐ gions of southern Australia with winter rainfall, feeding on annual clovers in pastures. Po‐ tential economic losses due to redlegged earth mite damage in pastures are estimated at \$200 million a year [74]. Pesticides are applied mainly in autumn as bare earth treatment be‐ fore the mites emerge or in autumn and spring as foliar sprays without any one approach to control being consistently superior. Mites feed on annual crops and pastures during the cooler wet winter but avoid the hot dry summer as diapausing eggs. Emergence of mites in autumn varies from year to year depending on rainfall and temperature, but the onset of di‐ apause in spring in this species remains the same for any one site from year to year [75]. A very accurate prediction for the onset of summer diapause was made for redlegged earth mites based on day length and length of long term growing season everywhere in southern Australia where this species was present [76]. This model was used to give an optimal

spring spray date for a single well timed spray, which has resulted in very effective control (over 95%) to the populations emerging the following autumn 8 months after the spray [77]. In both of these examples growers need to make decisions to control the pests long before the actual damage occurs. The mites are easier to see than the root-feeding scarabs which may make it easier to decide on the future risk of damage occurring but the strategy in both cases is to reduce the risk of damage occurring. Growth of plants also affects the plant-insect interaction. Grazing management can affect the populations of some pasture pests, as pas‐ tures have a carrying capacity for pests as they do for sheep. Heavy grazing can be used to suppress pest populations in the pasture [78, 79]. Other factors affecting plant growth will also interact with the populations of pests feeding on them. The risk of spider mite (Acari: Tetranychidae) infestations, have been shown to increase in response to crops being grown under drought stressed conditions [for sorghum, *Sorghum bicolor (L.)* Moench [80], cucum‐ ber, *Cucumis sativus* L. [81], pepper, *Capsicum spp.* [81] and strawberry, *Fragaria spp.* [81], or‐ namental plants [82], soybean, *Glycine max* L. [83], cowpea, *Vigna unguiculata* (L.) Walp [84], and maize (*Zea mays* L) [85, 86]. Thus, effective irrigation management could be considered a spider mite management tool. Numerous studies have demonstrated that nitrogen fertilizer tends to increase risk of spider mite infestations [87-90]. Thus application of nitrogen fertiliz‐ er will result in improved production but can lead also to the need for further cost inputs (pesticides). [91] reviewed over 2,000 studies regarding effects of potassium on pest and dis‐ ease incidence in plants. In about 63% of these studies, application of potassium led to a de‐ crease in pest pressure, but opposite and inconsistent effects of potassium applications have also been observed. The exact causes of a positive correlation between potassium deficiency level and susceptibility to pests are not fully understood, but there seems to be considerable evidence of potassium deficiency causing accumulation of soluble sugars and amino acids

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221

and interference with constituent host plant defence mechanisms [92].

Pest insects tend to feed mainly on one stage of growth of the plant. For many crop plants it is the seed which is harvested and sold and damage at this stage or post-harvest has a very direct impact on yield. Feeding damage by redlegged earth mite on seedlings can carry through to loss of seed yield by mature plants. In a carefully controlled study on yellow lu‐ pins (*Lupinus luteus*), redlegged earth mites at different known densities were allowed to feed for 14 days on seedlings and then removed, and the plants were grown to final seed yield 142 days after mite application [93]. This study revealed a clear negative correlation between redlegged earth mite density and yield with about 56% lower yields at the highest redlegged earth mite density. To avoid this damage the plants would have had to be sprayed with an effective miticide at the seedling stage. This is another example where the decision to spray has to be taken some time before any damage is evident. When the pest is feeding on the seed pod (as with pod borers) some plants are able to compensate. Popula‐ tion-level compensation is observed in cotton following feeding by *Helicoverpa* larvae (Lepi‐ doptera) [94], although obviously very considerable loss of seed yield due to this species can also be seen at other times. The examples above illustrate how insecticide applications should be based on extensive knowledge about the target pest's biology, and that overall management practices can dramatically influence the susceptibility of crops to pest species. It therefore seems possible to both time insecticide applications more accurately and also re‐ spring spray date for a single well timed spray, which has resulted in very effective control (over 95%) to the populations emerging the following autumn 8 months after the spray [77]. In both of these examples growers need to make decisions to control the pests long before the actual damage occurs. The mites are easier to see than the root-feeding scarabs which may make it easier to decide on the future risk of damage occurring but the strategy in both cases is to reduce the risk of damage occurring. Growth of plants also affects the plant-insect interaction. Grazing management can affect the populations of some pasture pests, as pas‐ tures have a carrying capacity for pests as they do for sheep. Heavy grazing can be used to suppress pest populations in the pasture [78, 79]. Other factors affecting plant growth will also interact with the populations of pests feeding on them. The risk of spider mite (Acari: Tetranychidae) infestations, have been shown to increase in response to crops being grown under drought stressed conditions [for sorghum, *Sorghum bicolor (L.)* Moench [80], cucum‐ ber, *Cucumis sativus* L. [81], pepper, *Capsicum spp.* [81] and strawberry, *Fragaria spp.* [81], or‐ namental plants [82], soybean, *Glycine max* L. [83], cowpea, *Vigna unguiculata* (L.) Walp [84], and maize (*Zea mays* L) [85, 86]. Thus, effective irrigation management could be considered a spider mite management tool. Numerous studies have demonstrated that nitrogen fertilizer tends to increase risk of spider mite infestations [87-90]. Thus application of nitrogen fertiliz‐ er will result in improved production but can lead also to the need for further cost inputs (pesticides). [91] reviewed over 2,000 studies regarding effects of potassium on pest and dis‐ ease incidence in plants. In about 63% of these studies, application of potassium led to a de‐ crease in pest pressure, but opposite and inconsistent effects of potassium applications have also been observed. The exact causes of a positive correlation between potassium deficiency level and susceptibility to pests are not fully understood, but there seems to be considerable evidence of potassium deficiency causing accumulation of soluble sugars and amino acids and interference with constituent host plant defence mechanisms [92].

sprayed/applied more often than what is economically justifiable and/or necessary to control target pest populations below action thresholds. In addition, we highlighted some practical/ operational circumstances, like tank mix, which may justify insecticide application even without knowing whether emerging pest populations are present or not. It was also shown, based on detailed analysis of water sensitive spray cards deployed under commercial pesti‐ cide applications, that expected performance of spray applications may often be below opti‐ mal due to quite low spray coverage and canopy penetration. That is, we have outlined the heavy reliance on insecticide applications and also shown that most of the quantitative data available in published reports suggests that insecticide spray coverages are often quite low. In many situations, the benefits of applying insecticides are clear and pest control is being effective, but for other major pests chemical control does not seem to work. Further research into the biology and ecology of these pests can provide valuable clues to how we can reduce our reliance on insecticide based management of important pests. For example, in regions of southern Australia with summer rainfall, root-feeding larvae of scarab beetles at times can destroy all the roots of pasture grasses, so that the pasture can be rolled up like a carpet. During 1970-1975 some 20,000-40,000 ha pasture were estimated to be sprayed annually at a cost of about \$AUD 10 per ha. However, research showed the presence of potentially dam‐ aging populations was only evident after the damage had occurred and spraying at this time not only failed to prevent damage but also killed valuable natural enemies [70]. Larvae of the root-feeding scarab species selectively feed on living roots of the grasses in the soil [71], which initially causes a reduction in root growth, but a reduction in foliage growth was observed only when the plants were also defoliated (grazed), and these plants are vulnera‐ ble to any periods of water stress due to lack of rainfall [72]. At times when younger larvae are feeding actively and plants are growing well damage is not evident, and it is at a later time when older larvae are present that the plants may die due to drought. Spraying at this time does not prevent the appearance of damage because the plants were damaged previ‐ ously. In addition when roots are growing actively and larvae are feeding strongly it is the lower densities of larvae that cause greatest reduction in the root yield [72]. A model of the interaction between plant growth, sheep grazing and insect feeding indicate that greatest impacts of the insect on pastures are occurring at low grazing pressures and low insect den‐ sities when plants are growing well [73]. An adjustment of spraying strategy is needed for these root-feeding scarabs. The redlegged earth mite is a major foliage-feeding pest in re‐ gions of southern Australia with winter rainfall, feeding on annual clovers in pastures. Po‐ tential economic losses due to redlegged earth mite damage in pastures are estimated at \$200 million a year [74]. Pesticides are applied mainly in autumn as bare earth treatment be‐ fore the mites emerge or in autumn and spring as foliar sprays without any one approach to control being consistently superior. Mites feed on annual crops and pastures during the cooler wet winter but avoid the hot dry summer as diapausing eggs. Emergence of mites in autumn varies from year to year depending on rainfall and temperature, but the onset of di‐ apause in spring in this species remains the same for any one site from year to year [75]. A very accurate prediction for the onset of summer diapause was made for redlegged earth mites based on day length and length of long term growing season everywhere in southern Australia where this species was present [76]. This model was used to give an optimal

220 Insecticides - Development of Safer and More Effective Technologies

Pest insects tend to feed mainly on one stage of growth of the plant. For many crop plants it is the seed which is harvested and sold and damage at this stage or post-harvest has a very direct impact on yield. Feeding damage by redlegged earth mite on seedlings can carry through to loss of seed yield by mature plants. In a carefully controlled study on yellow lu‐ pins (*Lupinus luteus*), redlegged earth mites at different known densities were allowed to feed for 14 days on seedlings and then removed, and the plants were grown to final seed yield 142 days after mite application [93]. This study revealed a clear negative correlation between redlegged earth mite density and yield with about 56% lower yields at the highest redlegged earth mite density. To avoid this damage the plants would have had to be sprayed with an effective miticide at the seedling stage. This is another example where the decision to spray has to be taken some time before any damage is evident. When the pest is feeding on the seed pod (as with pod borers) some plants are able to compensate. Popula‐ tion-level compensation is observed in cotton following feeding by *Helicoverpa* larvae (Lepi‐ doptera) [94], although obviously very considerable loss of seed yield due to this species can also be seen at other times. The examples above illustrate how insecticide applications should be based on extensive knowledge about the target pest's biology, and that overall management practices can dramatically influence the susceptibility of crops to pest species. It therefore seems possible to both time insecticide applications more accurately and also re‐ duce the number of applications by managing crops so that they are less likely to become infested. This approach will obviously reduce the number of insecticide applications, and therefore also decrease the likelihood of pest populations developing resistance. In this con‐ text, it is also important to highlight the adverse effect of insecticides on populations of ben‐ eficial insects. The example given here is for adverse effects on dung feeding beetles which provide ecosystem services by dispersing and burying dung and reducing populations of dung breeding nuisance flies. Avermectins are a family of drugs used to control internal parasites of cattle, horses and sheep. Residues from these compounds that are excreted in the dung of cattle can kill both the dung breeding nuisance fly pest, *Musca vetustissima,* and adversely affect the breeding of introduced scarab dung beetles [95]. Several authors have expressed concern that widespread use of avermectins as cattle drenches could adversely af‐ fect the populations of recently introduced scarab dung beetles [96]. Research has shown that scarab dung beetles in southern Australia breed mainly for 2-3 months in spring, and if farmers avoid using avermectins to drench cattle in these critical months an impact on dung beetle breeding would be minimised [97]. As can be seen from these examples, it is necessa‐ ry to have a good biological and ecological understanding of the pest and the crop plant in order to optimise the control of pests and reduce adverse effects of using insecticides.

created other problems. Even after more than 50 years of IPM, and with growing challenges with target pest populations developing resistance, it is somewhat striking that the number of documented IPM "successes" is fairly low. A simple scientific literature review search provided the following number of hits (based the literature search engine, Agricola, from 1972-2012): 1) "insecticide" = 17,629, 2) "insecticide resistance" = 4,900, 3), "IPM" = 2,243, and 4) "IPM" and "success" = 23. This recognition of our to-date inability to eliminate or com‐ pletely control pests leads to an important question–what benchmarks should be used to de‐ termine whether a pest management program was successful or not? [59] highlighted this

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It is indisputable, that insecticides are very important in our food production systems, and that they will continue to play a very important role far into the future. The purpose of this chapter is by no means to diminish their importance and the benefits associated with their usage in food production – in fact it is closer to the opposite: that exactly because of their importance and value, it is paramount that we understand how to use them effectively and that their performance is not being eroded due to resistance development. Another intended message from this chapter is that, when an insecticide "is not working" it is likely attributed to application failure rather than the insecticide not being effective against the given target pest. In short, we would be in serious trouble if we could not rely on insecticides, and that is precisely why they have to be used as wisely as possible. With the continuously growing list of insecticides becoming ineffective due to resistance, insecticides being faced out due to concerns about their adverse environmental effects, and with chemical companies having to spend increasing amounts of resources on getting new active ingredients registered for com‐ mercial use – it seems reasonable to reflect on the long-term sustainability of pest manage‐

aspect as being one of the leading short-comings in current IPM programs.

ment practices based almost exclusively on insecticide applications.

and Thomas James Ridsdill-Smith

The University of Western Australia, School of Animal Biology and the UWA Institute of

[1] Nansen C, Vaughn, K, Xue, Y, Rush, C, Workneh, F, Goolsby, J, Troxclair, N, Anciso, J, Gregory, A, Holman, D, Hammond, A, Mirkov, E, Tantravahi, P, Martini, X. A de‐ cision-support tool to predict spray deposition of insecticides in commercial potato fields and its implications for their performance. Journal of Economic Entomology

\*Address all correspondence to: christian.nansen@uwa.edu.au

Agriculture, Perth, Western Australia, Australia

**Author details**

Christian Nansen\*

**References**

2011;104:1138-45.

#### **10. Conclusions**

When concerns are raised about efficacy of currently available pest management programs, it is important to remember that humans have battled arthropod pests for as long as we have had agricultural production. There are 4,500-year old records of insecticide-based man‐ agement practices for control of insect pests in pre- and post-harvest agricultural products. Even biological control has been practiced for over 2,000 years [58, 59]. Yet, we have not been able to develop arthropod pest management Systems based on pesticide applications, which consistently (across many growing seasons and in most growing regions) maintain individual pest species below densities of economic concern. In stored grain, orchards, horti‐ culture, row crops. As a consequence, we are today researching management programs for the same pests as we did 50-100 years ago, or even before that. Despite incredible technolog‐ ical advances and scientific innovations during the development of human civilizations, we are still unable to "outsmart" the insects and mites in our food production, processing, and storage systems. On the other hand, there are several important examples of how classical biological control has provided almost complete control of different pests (i.e. weevils to control water hyacinth infestations in rivers and lakes, parasitoids to control cassava mealy‐ bugs in Western Africa, and moths to control prickly pear in Australia). Transgenic Bt tech‐ nology may be considered an encouraging exception, as it has provided remarkable control of several key coleopteran and lepidopteran pests with high levels of resistance to other in‐ secticides. However, even here there is widely reported documentation of Bt resistance (http://www.pesticideresistance.com/irac.php), and/or examples of how secondary pests, unaffected by Bt toxins, have adapted and taken advantage of the absence of Bt-controlled competitors. Thus for growers, Bt may have solved one pest problem but at the same time created other problems. Even after more than 50 years of IPM, and with growing challenges with target pest populations developing resistance, it is somewhat striking that the number of documented IPM "successes" is fairly low. A simple scientific literature review search provided the following number of hits (based the literature search engine, Agricola, from 1972-2012): 1) "insecticide" = 17,629, 2) "insecticide resistance" = 4,900, 3), "IPM" = 2,243, and 4) "IPM" and "success" = 23. This recognition of our to-date inability to eliminate or com‐ pletely control pests leads to an important question–what benchmarks should be used to de‐ termine whether a pest management program was successful or not? [59] highlighted this aspect as being one of the leading short-comings in current IPM programs.

It is indisputable, that insecticides are very important in our food production systems, and that they will continue to play a very important role far into the future. The purpose of this chapter is by no means to diminish their importance and the benefits associated with their usage in food production – in fact it is closer to the opposite: that exactly because of their importance and value, it is paramount that we understand how to use them effectively and that their performance is not being eroded due to resistance development. Another intended message from this chapter is that, when an insecticide "is not working" it is likely attributed to application failure rather than the insecticide not being effective against the given target pest. In short, we would be in serious trouble if we could not rely on insecticides, and that is precisely why they have to be used as wisely as possible. With the continuously growing list of insecticides becoming ineffective due to resistance, insecticides being faced out due to concerns about their adverse environmental effects, and with chemical companies having to spend increasing amounts of resources on getting new active ingredients registered for com‐ mercial use – it seems reasonable to reflect on the long-term sustainability of pest manage‐ ment practices based almost exclusively on insecticide applications.
