An Analysis of Lethal Methods of Wild Animal Population Control: Invertebrates

Summary

If invertebrates are sentient beings they should be treated so that they do not suffer unnecessarily.1There is no general position on what constitutes “unnecessary” suffering for wild animals. In this context, I consider any human actions that increase the intensity of the suffering of wild animals or do not reduce the suffering associated with the natural causes of death of wild animals with a lesser form of suffering, to be “unnecessary”. Very rarely is the potential suffering of insects considered in agricultural population control. It is likely then that some of the current methods being used inflict significant suffering on target and nontarget insects. This paper tentatively suggests that fast-acting, broad-spectrum insecticides paired with artificial population regulation present an interim solution that may minimize insect suffering in agriculture.

Introduction

Population control is the policy or practice of limiting growth in numbers of a population (“Population control,” 2016). The most common method to removing invertebrate populations is to cull them. However, depending on the method, this may cause a significant amount of unnecessary suffering. If this is the case, we should consider slowing their rate of population growth as a viable alternative to killing overabundant animals. In this paper, I consider a broad spectrum of methods and discuss their impact on individual beings with the aim of understanding which methods are most effective at reducing the unnecessary suffering of invertebrates.

Section 3 begins with a summary of the ongoing debate as to whether insects can feel pain and follows on to look at the use of insecticides and the impact insects have on the agricultural industry. Section 4 then breaks down lethal population control into chemical and biological methods. Section 5 on chemical control methods provides an analysis of the physiological effects of insecticides, including the potential for suffering and length of suffering from contact or ingestion until death. This subsection suggests that broad-spectrum insecticides are possibly more humane than species-specific insecticides as they may reduce unnecessary suffering and sum total deaths. To understand if this is in fact the case, I consider the effects of broad-spectrum insecticides on predators, target insects, and nontarget insects, which reveals that they may not be as effective as they seem at first glance, but that their aggregate impact is still likely to reduce insect suffering overall. Section 7 on biological control methods describes the use of predation, parasitism, and disease to reduce target insect populations in agriculture. Lastly, section 8 presents viable alternatives to lethal population reduction through artificial population regulation. However, these alternatives — behaviour modification and sterile insect technique — by virtue of being species-specific, affect smaller populations of insects than broad-spectrum insecticides. It seems that whilst artificial population regulation has a reduced negative impact on target species, this benefit is not significantly large enough to outweigh the total impact of broad-spectrum insecticides. As such, I conclude that we need to engage in further research to better understand insect physiology and their capacity to suffer. In the interim a humane way to continue managing insect-populations is to partner the use of rapid broad-spectrum insecticides with artificial population regulation and invest more research and resources into improving both of these strategies.

Do insects suffer?

At this point the question cannot be conclusively answered. However, there is enough research to understand the physiological considerations at stake. It is unlikely that insects have subjective experiences similar to those in humans, but this does not deny the possibility that they have the capacity to generate subjective experiences of some kind. Insects have the capacity, known as nociception, to respond to adverse or harmful stimuli (Smith, 1991). For example, when exposed to temperatures beyond the normal range, contact with noxious chemicals, mechanical interference, or electric shock, insects responded just as vertebrates do: by withdrawing or escaping the experience (Smith, 1991; “The Importance of Insect Suffering | Essays on Reducing Suffering,” n.d.-a).

Whether these actions indicate the experience of pain or are purely motor responses is a crucial distinction in science and philosophy. It is suggested that “pain is different from nociception because pain is primarily a subjective experience of discomfort, despair and other negative affective states.” (Adamo, 2016/8) The subjective experience of pain is difficult to define in other species by virtue of its subjectivity. Research indicates that the complexity of central nervous systems and brain size are key, and the lack of protective behaviour towards injured body parts typically witnessed in insects suggests their central nervous systems may not be capable of generating the sensation of pain (Adamo, 2016/8). It is also possible that this distinction is unnecessarily narrow in its definition of consciousness, and that less complex animals have certain degrees of consciousness (“The Importance of Insect Suffering | Essays on Reducing Suffering,” n.d.-b).

Without being able to conclude one way or the other on the ability of insects to experience pain, we find ourselves in a situation where we can not be certain that insects can’t feel pain. If insects can feel pain, it is likely their painful experiences outweigh their non-painful ones over the course of a typical (often short) lifespan (“How Good or Bad Is the Life of an Insect? – Simon Knutsson,” n.d.). Therefore the approach likely to reduce the negative impact on the welfare of insects is a precautionary one, (“The Importance of Insect Suffering | Essays on Reducing Suffering,” n.d.-b) that is, an approach that focuses on minimising potential unnecessary suffering for insects. Reducing or removing populations of insects may be an important strategy in reducing the overall suffering of invertebrates.

Agriculture

This paper will focus on the use of lethal control methods in agriculture where the large scale culling of insects in routine. According to the Food and Agriculture Organisation (FAO) “herbivorous insects are said to be responsible for destroying one fifth of the world’s total crop production annually.” (Lewis, n.d.) However, a major reason pest insects are problematic to agriculture is because of the manner with which agriculture has shaped ecosystems (Lewis, n.d.). The selection of high yield crops receptive to large growth and grown in a confined space has attracted and promoted the population growth of herbivorous insects (Lewis, n.d.). Of the 10,000 species of crop-eating insects, approximately 700 species cause the predominance of damage both in field and storage (“An Introduction to Insecticides (4th edition),” n.d.-a).

The economic impact of crop-eating insects is difficult to ascertain since it involves not just the loss of damaged crop but also the cost involved in managing crop-eating insects. The Grains Research and Development Corporation conducted a study in 2013 on the six major Australian grain crops: wheat, barley, oats, canola, grain sorghum, and lupins. They found that “aggregated across the six major Australian grain crops, the estimated present annual loss due to invertebrate pests totalled $359.8 million…Present cultural and pesticide controls of invertebrate pests effectively reduced losses by $1,366.1 million, but “pest” management remained very dependent on pesticides. Nationally, pesticide treatment costs aggregated across all six crops totalled $159.1 million.” (Research & Corporation, n.d.) A study conducted around the same time in Brazil estimates that “insect pests cause an average annual loss of 7.7% in production in Brazil, which is a reduction of approximately 25 million tons of food, fiber, and biofuels. The total annual economic losses reach approximately US$ 17.7 billion.” (Oliveira, Auad, Mendes, & Frizzas, 2014/2) With such a strong motivator to eliminate pest insects, we are concerned that powerful insecticides are being employed on a massive scale with little to no consideration for the potential suffering they can cause.

Chemical control methods

Insecticides

An insecticide is a “pesticide used for the control of insects.” (Stephenson, Ferris, Holland, & Nordberg, n.d.) They “destroy, suppress, stupefy, inhibit the feeding of, or prevent infestations or attacks by, an insect [and] are used to control a wide variety of insects, including thrips, aphids, moths, fruit flies and locusts.” (“What are pesticides and how do they work? | NSW EPA,” n.d.)

Insecticides can be broadly categorized into two types: systemic and contact insecticides. Systemic insecticides are absorbed into the plant cell structure and kill insects when they eat the plant and ingest the insecticide (“Insecticide,” 2016). Because systemic insecticides are absorbed by plants, they are also present in pollen, nectar, and soil. This means they may harm nontarget insects, such as pollinators (Jennifer Hopwood, Mace Vaughan, Matthew Shepherd, David Biddinger, Eric Mader, Scott Hoffman Black, Celeste Mazzacano, 2012). Contact insecticides kill when they come into contact with the insect (“Insecticide,” 2016). By virtue of only requiring an insect come into contact with the insecticide, contact insecticides also kill non-target insects. Although both systemic or contact insecticides impact nontarget insects, it seems likely to me that the unrestricted manner with which contact insecticides reduce populations causes a higher number of deaths.

The chemical nature of the compound used in insecticides can take one of three forms:

  1. Inorganic e.g. arsenals and fluorides.
  2. Natural organics e.g. oils or botanical extracts.
  3. Synthetic organics e.g. organophosphates and carbamates (“Entomology – Pests and Insect Control – Insecticides,” n.d.).

Frequency of application

The number of insecticide treatments in one year is varied according to the crop type. One study found that “[o]n most crops the minimum number of treatments with insecticide was less than three, only on chrysanthemums the lowest number of treatments was 19. The maximum number of insecticide treatments varied from three treatments on sugar beets and beans to 181 treatments on chrysanthemums.” (van Drooge, Groeneveld, & Schipper, 2001) The frequency of applications has, in part, to do with the ability of target insects to build a resistance to the insecticide used (“Pesticide resistance,” 2016).

Types of insecticides

According to the United States Environmental Protection Agency, data gathered in 2001 found that the most commonly used insecticides as measured by land area were pyrethroids, carbamates and organophosphates (US EPA, ORD, Causal Analysis/Diagnosis Decision Information System, 2009). These three insecticides are not species-selective, meaning they may kill target and a wide range of nontarget insects. Therefore they can be classified ‘broad-spectrum insecticides’ (“UC IPM: Information about Selectivity of Insecticides and Miticides in Citrus,” n.d.). A later study conducted in 2007 found that the most commonly used insecticides in the agricultural market sector were organophosphates and carbamates (“Pesticide Industry Sales and Usage Report: 2006 and 2007 Market Estimates,” n.d.). Interestingly, pyrethroids, which were the most commonly used in 2001, were not featured in the agricultural market sector in 2007.

Organophosphates and carbamates

Organophosphates (OPs) and carbamates are contact insecticides, comparable to nerve gases that work by poisoning the nervous system (“An Introduction to Insecticides (4th edition),” n.d.-a). OPs and carbamates “inhibit certain important enzymes of the nervous system, namely cholinesterase (ChE). When ChE is inhibited by a carbamate, it is said to be carbamylated and when it is inhibited by OPs it is phosphorylated. This inhibition results in the accumulation of acetylcholine (ACh) at the neuron/neuron and neuron/muscle (neuromuscular) junctions or synapses, causing rapid twitching of voluntary muscles and finally paralysis.” (“An Introduction to Insecticides (4th edition),” n.d.-a) These insecticides are not species selective and as such are likely to be as lethal to non-target insects. In humans, overexposure to OPs and carbamates causes symptoms including headaches, muscle twitching, difficulty breathing, or swallowing and sweating (“How insecticides work,” n.d.). If we accept that insects may experience pain, it is unlikely that this form of death is free from suffering.

Pyrethroids

Pyrethroids “affect both the peripheral and central nervous system of the insect. Pyrethrum initially stimulates nerve cells to produce repetitive discharges, leading eventually to paralysis. Such effects are caused by their action on the sodium channel, a tiny hole through which sodium ions are permitted to enter the axon to cause excitation. These effects are produced in insect nerve cord, which contains ganglia and synapses, as well as in giant nerve fiber axons.” (“An Introduction to Insecticides (4th edition),” n.d.-b) Pyrethroids are described as extremely fast-acting, causing almost immediate paralysis (“An Introduction to Insecticides (4th edition),” n.d.-a). These are also not species-selective insecticides. If the fast-acting nature of pyrethroids also leads to a speedy death, then they may present one of the most humane ways to kill target and nontarget insects. However, it is certainly not clear that paralysis leads to a quick or pain-free death. Without having strong evidence to conclude that insects do suffer and if so, the extent to which they may suffer when exposed to pyrethroids, it is impossible to conclusively determine whether they present a solution in line with the precautionary principle to insect population control.2I would like to thank Jeffrey Lockwood for his input on the experience of pyrethroids on insects.

Neonicotinoid insecticides

Used predominantly on soft-bodied insects like caterpillars or aphids but also effective on other insects (“An Introduction to Insecticides (4th edition),” n.d.-a), neonicotinoids work on the central nervous system (“An Introduction to Insecticides (4th edition),” n.d.-a). Nicotinoids activate the nicotinic acetylcholine receptor persistently which leads to an “overstimulation of cholinergic synapses, and results in hyperexcitation, convulsions, paralysis, and death of the insect.” (“Insecticides: Chemistries and Characteristics 2nd Edition,” n.d.) Recent research on the impact of neonicotinoid insecticides on nontarget species found that they cause a susceptibility in honey bees to parasites and pathogens associated with colony collapse disorder (Jennifer Hopwood, Mace Vaughan, Matthew Shepherd, David Biddinger, Eric Mader, Scott Hoffman Black, Celeste Mazzacano, 2012). This has led to regulation on the use of some forms of neonicotinoids (“Neonicotinoid,” 2016).

Bacillus Thuringiensis

Bacillus thuringiensis (Bt) insecticides are larvicides which kill insects using bacterial toxins (“How insecticides work,” n.d.). There many strains of Bt insecticides which can kill a range of target insects (“How insecticides work,” n.d.). The toxins in Bt insecticides “paralyze the gut and rupture cells in the stomach lining of insects that ingest the poison.” (“How insecticides work,” n.d.) Death occurs “as spores and gut bacteria proliferate in the body.” (“How does Bt work?,” n.d.) It takes several days to kill the insect after ingestion (“An Introduction to Insecticides (4th edition),” n.d.-b). The description of death indicates that this may cause immense suffering over a number of days before death.

Insect Growth Regulators

Insect Growth Regulators (IGRs) can interfere with the development of an insect in two ways. As insects grow, they must shed their skin periodically. One effect of IGRs is to prevent this molting process from occurring, and the other is to prevent the insect from forming new skin at the right time (“How insecticides work,” n.d.). “Typical effects on developing larvae are the rupture of malformed cuticle or death by starvation.” (“Insecticides: Chemistries and Characteristics 2nd Edition,” n.d.) IGRs do not kill target insects immediately, instead, they have a “long-term debilitating effect.” (“How insecticides work,” n.d.) IGRs are popular because they  target processes so closely related to the insect’s survival, that it is less likely for insects to evolve resistance to them (“How insecticides work,” n.d.).

How effective are broad-spectrum insecticides?

If death caused by broad-spectrum insecticides is faster and causes less suffering than natural death by predation, starvation or parasitism, or a death caused by cultivation such as being crushed under a tractor (“Humane Insecticides | Essays on Reducing Suffering,” n.d.), it would be preferred to the alternatives. However, it is plausible that broad-spectrum insecticides are not as effective as they initially seem.

In an assessment of the environmental and economic costs of insecticide use, broad-spectrum insecticides that killed nontarget insects preying on target insects were found to create an environment for “pest” insect populations to thrive.

“For example, the following pests have reached outbreak levels in cotton and apple crops after the natural enemies were destroyed by pesticides: cotton = cotton bollworm, tobacco budworm, cotton aphid, spider mites, and cotton loopers; apples = European red mite, red-banded leaf roller, San Jose scale, oyster shell scale, rosy apple aphid, wooly apple aphid, white apple aphid, two-spotted spider mite, and apple rust mite. Major pest outbreaks have also occurred in other crops. Also, because parasitic and predaceous insects often have complex searching and attack behaviors, sub-lethal insecticide dosages may alter this behavior and in this way disrupt effective biological controls” (Pimentel, 2005).

Managing these outbreaks creates an additional expense for farmers. An associated effect of broad-spectrum insecticide use is the potential for target insects to build resistance to its effects. To manage increased resistance, additional applications are required which just compounds the problem (Pimentel, 2005). This is in contrast to insecticides like IGRs which target processes closely related to the insect’s survival, meaning building resistance is unlikely.

However, it seems unlikely, although there is room for more research, that resistance and potential outbreaks in populations occur regularly enough or are of numbers large enough to outweigh the effectiveness of broad-spectrum insecticides. If they were, such insecticide use would indeed be counterproductive, and different population control methods would be adopted by the agricultural industry.

Biological control methods

Biological control refers to the use of “natural enemies” to curb the population growth of pest insect species in agriculture. It is largely employed through the introduction, augmentation, and/or conservation of predators, parasites, and disease (“Biological pest control,” 2016). Biological control presents an alternative to the side-effects of broad-spectrum insecticide use such as increases in cost and the frequency of application. However, they are less effective at eradicating populations of target insects. Rather biocontrol methods manage target insect populations to reduce their densities (Agriculture, n.d.).

Predation

The most important predators for pest-insect management are arthropods, which include “lady beetles, ground beetles, syrphid flies, green lacewings, assassin bugs, predaceous bugs, minute pirate bugs, predatory mites, and spiders.” (Agriculture, n.d.) Predaceous insects are primarily generalist feeders, meaning they do not prey specifically on target insects. The predator’s method of killing its prey varies according to species. Assassin and ambush bugs are described as using their powerful beaks to “impale their prey and suck out the body fluids.” (Agriculture, n.d.) Similarly, lacewing adults use their large, sickle-shaped mandibles to “capture and hold prey as they suck out the body fluids.” (Agriculture, n.d.) It is unclear how successful predation is as a lethal form of population control relative to other biocontrol methods.

Parasitism

Parasites, generally certain wasp or fly species, are said to be more successful than predators at managing populations of pest insects because “many have a narrower host range, require only one host to complete development, have an excellent ability to locate and kill their host and can respond rapidly to increases in host populations.” (Agriculture, n.d.) Adult parasites lay eggs on or in their hosts’ bodies and the larvae feed on the hosts. Mature parasites may also “obtain nutrients by piercing the body of host insects and withdrawing fluids.” (Agriculture, n.d.) Almost all insects are attacked by one or more parasite species (Agriculture, n.d.). In this instance, even applying the precautionary principle, it has been observed that host insects do not always react aversively when attacked by parasites. (National Geographic, 2009) It is unclear whether the experience of parasitism causes greater suffering than that caused by chemical insecticides.

Disease

The following is an excellent description of the use of disease to manage pest insect populations prepared by the North Dakota State University.

“Insect diseases are caused by fungi, viruses, bacteria, protozoans, and other microorganisms. Insect-parasitic nematodes are also included in this group of natural enemies. Insect-parasitic nematodes are small worms that attack and kill insects that live in moist habitats…Both diseases and nematodes, like parasites, tend to be specific to certain species or groups of pests; they do not harm non-target organisms, such as beneficial insects, animals, humans, or plants. They can quickly spread through an insect population causing rapid mortality in a short period of time, and can be important in the natural control of pest populations.

Insect viral pathogens vary in how they attack and kill their host. Most insect viruses need to be ingested to successfully infect their host, though some can be transferred from the parent insect to the offspring through the egg. Symptoms usually occur within a few days after the virus is ingested. The infected insect will appear sluggish, feeding will stop, and the cuticle will have a pale discoloration and will often hang from its legs. The infected insect will die one to two days after the symptoms appear.

The bacteria most important in insect pest management are in the genus Bacillus. Species in this genus form spores that are toxic to the insect when ingested. Symptoms of infected insects include a loss of appetite, sluggishness, discharge from the mouth and anus, discoloration and liquefaction and putrefaction of the body tissues.

A beneficial soil bacterium, Saccharopolyspora spinosa, produces a natural metabolite, Spinosad3For more information on the use of spinosad as a biological form of pest control see Spinosad. (n.d.). In Wikipedia. Retrieved January 2, 2017, from https://en.wikipedia.org/wiki/Spinosad…Sickened insects stop feeding, become limp and are unable to move, and may appear to have weak tremors. Spinosad is effective against a wide spectrum of insect pests.

Insect pathogenic fungi produce spores that germinate when they come in contact with the insect cuticle and when temperature and moisture conditions are favorable. Germinating spores penetrate the insect cuticle and invade the body cavity. Hyphae rapidly grow, filling the body cavity with a fungal mass, killing the insect. The fungus also may produce a toxin. Hyphae penetrate outward through the softer parts of the insect and under favorable moisture conditions produce spores that ripen and are released into the environment to complete the life cycle.” (Agriculture, n.d.)

A possible alternative: regulating population growth

Rather than address the overabundance of insect populations through lethal means, it is possible that regulating population growth proves to be a more humane and environmentally sustainable approach. Two techniques I believe present promising alternatives are sterile insect technique and behavioural modification.

Sterile Insect Technique

Sterile Insect Technique (SIT) is defined by the FAO as “a method of pest control using area-wide inundative releases of sterile insects to reduce reproduction in a field population of the same species”. (Programme, n.d.) Similar to immunocontraceptives used on vertebrates, SIT is a form of contraception that prevents the female insects of target species from reproducing when they are inseminated by sterilised males (Programme, n.d.). Male insects are sterilised by being exposed to low doses of radiation and then released in infested areas. The number of sterilised males must outweigh the number of wild fertile males for the population to collapse (“The Sterile Insect Technique,” 1998). There is no information on whether the insects exposed to radiation suffer as a result. Radiation therapy in humans is said to be painless; however, there can be painful side-effects (Choices, 2016). In addition, the level of radiation relative to body size to sterilise insects is likely to be higher. Whether insects feel similar, stronger, or weaker symptoms is unclear. First developed in the US, SIT has been used for over 50 years and is common across six continents to suppress, eradicate, contain, and prevent populations of “fruit flies, moths, mosquitoes, tsetse flies and screwworm flies.” (Programme, n.d.) In South Australia, the use of SIT on the Mediterranean fruit fly has successfully eradicated eight fruit fly outbreaks since 2001 (“Sterile insect technique for fruit fly control | Department of Agriculture and Food,” n.d.) and has been successful with both the screwworm and pink bollworm in the US (“The Sterile Insect Release Method and Other Genetic Control Strategies,” n.d.). However, significant reductions in target insect populations through SIT programs are likely to take longer than lethal methods of population control, and these programs require interstate and sometimes international government implementation, regulation and monitoring (“The Sterile Insect Release Method and Other Genetic Control Strategies,” n.d.). This is unlikely to be a technique that can be successfully utilized by individuals or entities over privately-owned agricultural land.

Behavior modification

Behavior modification is a method of control that manipulates the behavior of pest insects so that they do not harm agricultural produce. Behavior can be manipulated in numerous ways, but it is done predominantly for the purpose of stimulating or inhibiting behaviors in order to protect crops (Foster & Harris, 1997). There are three key factors to behavior modification technology: “a behavior of the pest, a means by which the behavior is manipulated appropriately, and a method that utilizes the behavioral manipulation for protection of a resource from the pest.” (Foster & Harris, 1997) This technology is particularly useful with insects because their behavior is determined from a variety of external and internal inputs integrated by the central nervous system (Foster & Harris, 1997). Therefore, behavioral change can be effected by changing the external inputs, the internal inputs, or the way those inputs are processed by the central nervous system (Foster & Harris, 1997). Given the difficulty in attempting to the modify internal structures, behavioral modification technology has developed most successfully by adjusting external stimuli (Foster & Harris, 1997). Many insecticides, depending on the form of their delivery, utilize this technology. For example, systemic insecticides in the form of baits can be imbued with attractants, like food lures, to encourage their ingestion or sex pheromones which gather large populations of insects in mass traps.

Antifeedants

Antifeedants are a non-lethal form of behaviour modification technology. In agricultural use, they act as a deterrent to target insects. An antifeedant is a “behaviour modifying substance that deters feeding through direct action on peripheral sensilla in insect.” (Isman, 2002) Synthetic deterrents can be developed by understanding the chemical structures that establish defence mechanisms in some plants (Isman, 2002). One well-studied deterrent has been developed from extracts (called azadirachtin) of the neem tree (Isman, 2002). Azadirachtin, depending on the manner with which it is used and the dosage, can affect “behavior, growth regulation, ovarian development, fecundity, and fertility in insects.” (Foster & Harris, 1997) Azadirachtin is said to act as a particularly effective antifeedant. However, it has been suggested that evaluations of efficacy have fused azadirachtin’s IGR properties with its antifeedant effects, skewing the results (Isman, 2002). In addition, there are a number of other weaknesses identified with antifeedants. They have variable efficacy between insect species (Isman, 2002), and their deterrent effects may break down. In other words, the target insect may become desensitised to their effects after repeated exposure (Foster & Harris, 1997). The primary benefit of antifeedants is that they cause minimal to no harm to the insect. Deterring pest species from feeding on crops is likely to reduce their population on agricultural land, which as noted above, began to grow as a result of the selection of high yield crops receptive to large growth. However, it is unclear whether they will actually reduce populations of target insects or merely shift populations elsewhere. Antifeedants, then, are best utilised as part of a strategy that incorporates other forms of population control.

Mating disruption

Mating disruption is another form of non-lethal population control, involving the release of sex pheromones, through a dispenser, to prevent male insects finding females and mating (Peshin & Dhawan, 2009). Over the long-term the population of the target insect is reduced or kept at low levels. Mating disruption is said to be one of the “most successful applications of insect sex pheromones for direct pest control.” (Peshin & Dhawan, 2009) In addition, this technique causes little or no suffering to the individuals exposed to the synthetic pheromones. Mating disruption has been most successful with moth species, and has been used for almost two decades (Peshin & Dhawan, 2009). However, there are a few of drawbacks:

  • The technique has variable efficacy depending on the species, population density and level of exposure; and
  • It is unlikely to successfully reduce populations of pest insects alone (“Mating Disruption,” n.d.).

Yet, when partnered with a broad-spectrum insecticide, mating disruption presents a technique that can minimize the total deaths caused by insecticides by reducing population growth and requiring lower insecticide usage.

Conclusion

It is difficult to conclusively select a method of population control that addresses the complex interactions of target insects, nontarget herbivorous insects, soil invertebrates, and predators on agricultural land, and do so in a manner that humanely reduces the populations of all these beings. Very little research focused on crop-productivity considers the potential for suffering of insects which are killed directly or inadvertently. Broad-spectrum insecticides are more promising than species-specific insecticides and biological controls as fast-acting contact insecticides. However, we can’t discount the possibility that they induce a high degree of suffering which must be balanced against the duration suffering. Broad-spectrum insecticides are also susceptible to inefficacy. In addition to this, lethal methods of population control will have a greater negative impact on the individuals killed than artificial population regulation. Unfortunately, population regulation techniques for invertebrates are also imperfect. They can be lengthy, costly, and less effective than lethal solutions, meaning they are unlikely to be adopted as common practice. As such, we need to dedicate more research to understanding the experiences of insects so that we can improve current methods or develop new, more humane, techniques. In the meantime, we can advocate for an approach that partners the most humane broad-spectrum insecticides with behaviour modification technology and encourage governments to expand SIT programs where feasible.

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1. There is no general position on what constitutes “unnecessary” suffering for wild animals. In this context, I consider any human actions that increase the intensity of the suffering of wild animals or do not reduce the suffering associated with the natural causes of death of wild animals with a lesser form of suffering, to be “unnecessary”.
2. I would like to thank Jeffrey Lockwood for his input on the experience of pyrethroids on insects.
3. For more information on the use of spinosad as a biological form of pest control see Spinosad. (n.d.). In Wikipedia. Retrieved January 2, 2017, from https://en.wikipedia.org/wiki/Spinosad