Pest Control
Modern agricultureuses worldwide about 2.5 million tons of pesticides annually (Wijnands 1997), and out of such quantity only about 0.4% reaches the targeted pests, according to Pimentel (Pimentel 1995), while losses through volatilization are on the order of 80-90% (Taylor and Spencer 1990).
Pesticides are considered a necessary evil; however, it has been estimated that without their use food expenditure for western families would more than double (Zilberman et al. 1991) and, much worse,food shortagewould be more acute in many third world countries: about 40% crop production would be lost, according to FAO. Pest and pesticide control is probably the sector where a really integrated view of farm management is most required: certainly, pest treatments by calendar as largely in use till a few years ago and still in use today here and there are unsustainable. The principles of targeting interventions according to real need as advocated
by the Integrated Pest Management (IPM) are much more reasonable, entailing only the shortcoming of some degree of risk.
It is not easy to define precisely IPM, since there is a variety of different definitions, originated by different approaches (almost 80 definitions can be found on the Web site of the Integrated Plant Protection Center, Oregon State University, http://www.ippc.orst.edu/IPM); IPM, however, is generally seen as a component of integratedfarming systemsrather than a component oforganic farming. It must be clearly appreciated that IPM is not organic farming. This is a critical point. IPM may provide a bottleneck to the adoption of organic farming and vice versa (Jeger 2000). IPM as advocated by the principles of organic farming in fact is a restricted version where the use of synthetic pesticides is totally banned, whereas IPM as commonly intended aims at reducing their use to the possible extent.
The principles of IPM are presently being objected in favour of a still more advanced view, somewhat integrating IPM, namely, the 'pro-active approach' seeking to minimize pest outbreaks by avoiding conditions conducive to their growth and dispersal (Chellemi 2000). Lewis et al. (1997) state in fact that the attempted solution becomes the problem ... application of external corrective actions into a system can be effective only for short term relief... the use of pesticides and other treat-the-symptoms approaches are unsustainable and should be the last rather than the first line of defense.
The main trouble with IPM in its presently adopted forms is how to determine the threshold beyond which an intervention is warranted, since the threshold depends on a multitude of factors such as pest population and its likely increase, the intensity of predators and their likely increase, crop damage functions for individual pests, crop susceptibility according to the particular phenophases, weather conditions and forecasts. The lower the threshold fixed for starting the intervention, the lower the risk of pest damage to the crop but the higher the cost in terms of economy and impact on the environment and the society, and as a consequence the threshold cannot be decided with a priori rules of thumb. The principle of a 'dynamic economic threshold', based on the modelling of the crop and pest evolution as impacted by pesticide sprayings and aimed to maximize profit, was developed by Bor (1997); the author suggested that future studies should enlarge the scope to include health and environment-related aspects. Doubtless, an intense scouting and management can greatly assist in safely raising the threshold level and reducing the external input.
Some objection is raised against the advocated solution of crop rotating to control pest development (Jeger 2000; Way and van Emden 2000). Leaving weeds grow on field margins to encourage predators can be a sound practice but can also encourage pests which nest there, according to Peet (1995), Gurr et al. (1998), Way and van Emden (2000). Opposite to these views, crop rotation and the presence of hedges are listed among the [k]ey aims, principles and management practices of organic farming for pest and disease control in a sort of handbook published by Greenpeace Environmental Trust (Parrot and Marsden 2002, p. 12). While this suggestion can be accepted, although with some limits, their final suggestion of 'hand picking' the pests (p. 12) is obviously absurd.
Successes of integrated pest management in the USA are illustrated by the leaflets released by SARE (http://www.sare.org/10yrsofsan/pest/pestmgt.htm); on the other side, the intensive monitoring, the relatively costly and sophisticated equipment required by IPM and the inherent higher risk for crops make it unsuitable for many developing countries, particularly in those areas where subsistence crops are grown to sustain the farmer families. It can also be argued that IPM has few probabilities of success at the other extreme, with very high-value crops, where no producer is willing to take a chance: at both extremes a realistic target which can be reasonably expected in the near future is just a reduction in pesticide input. An encouraging paper by van Lenteren, however, reports a considerable trend towards biological control expansion in Dutch greenhouses, even in the case of high-value ornamentals (van Lenteren 2000); he also comments that cost-benefit analyses in greenhouses show that biological control is the most cost-effective control method.
Sustainable approaches are those that are the least toxic and least energy intensive, and yet maintain productivity and profitability. Preventive strategies and other alternatives should be employed before using chemical inputs from any source. However, there may be situations where the use of synthetic chemicals would be more sustainable than a strictly nonchemical approach using toxic organic chemicals (SARE 1997). Lewis et al. (1997) stress this point: the fact that a product is natural and/or nontoxic does not necessarily mean it is less disruptive than synthetic products. The important thing is to work as much in harmony as possible with the system's inherent defenses.
Way and van Emden state that appropriate conventional synthetic insecticides will remain as important IPM components in many crop systems for the foreseeable future, as is evident from their continuing vital roles in some of our case histories. ... In summary, insecticides will continue to be widely used for the foreseeable future, but more as relatively expensive stilettos, never again as cheap panaceas (Way and van Emden 2000).
The efficacy of IPM in disease control, as opposed topest control, is debated: while Jeger is pessimistic (Biological control by natural enemies is a major component in the control of arthropod pests in IPM programmes. By contrast biological control of plant pathogens is still in its infancy and according to some sceptics will never be weaned let alone reach adolescence, Jeger 2000) van Lenteren is optimistic, at least for crops grown in greenhouses (van Lenteren 2000). Since the copper and sulphur-based fungicides can be noxious under various respects, the adoption of synthetic fungicides, at least under some circumstances, is presently unavoidable.
最近的进展集中在减少broad spectrum insecticides, toxic also to useful insects, and on the development of selective alternatives; on the use of pheromone traps, bails and phenology models; on the accurate monitoring of the crops to protect, including also the control of climatic conditions such as the relative humidity and the summation of degrees/day. Doubts can be cast, however, on the accuracy of the summation of degree/days procedure which fails to acknowledge the differences in temperature between the atmosphere and the plant canopies, the latter being during the day several degrees warmer or colder than atmosphere in dependence of plant water status.
The cost of the intensive scouting and monitoring may or may not exceed the savings from pesticide reduction (Fenemore and Norton 1985; Peet 2001; Walker et al. 1997, as reported by Way and van Emden 2000).
3.2.4.1 Impacts
•经济:Pimentel et al。(1993)相比的经济ic results for conventional and alternative pest management practices in tomato, concluding that potential reductions in herbicides were on the order of 80%, in conventional insecticides also of 80% and in fungicides of 50%, with corresponding cost increases (for mechanical cultivation, scouting and management) of 30%, 0% and 10%, respectively; apparently, they did not consider additional shortcomings depending on mechanical cultivation as mentioned above, however. An interesting research conducted by Clark et al. (1998) with tomato and corn showed that economic results obtained with organic and low-input management were basically the same, and both were differing from conventional management negatively for tomato (i.e. with higher costs) and positively for corn. Peet (1995, updated October 2001) reports thatinsect controlwith 'botanicals', namely chemicals extracted from plants, is more costly than with conventional pesticides both for the higher cost of botanicals themselves and for their shorter persistence requiring more frequent sprayings.
• Environmental: Clark et al. (1998) and Edwards-Jones and Howells (2001), applied the environmental impact quotient (EIQ) developed by Kovach et al.
(1992) to evaluate the environmental hazard of pesticides suggested for organic farming; the EIQ analyses three distinct categories of hazard, to farm workers, consumers and the environment. The conclusion of Clark et al. (1998) was that EIQ with organic farming is about half that withconventional farmingin corn while it is zero in tomato. The somewhat surprising conclusion of EdwardsJones and Howells (2001) was that generally, pesticides and fungicides permitted for use inorganic farmsare less hazardous than those used in conventional systems, but there are some clear exceptions to this rule. However, some evidence suggests that when toxicity and volume are considered in an overall pest management strategy, organic practices may have greater environmental hazard than conventional ones (Kovach et al. 1992). For these reasons, we can state that the crop protection activity of organic farming, and hence organic farming itself, is not absolutely sustainable.
Further objections can be moved to the rationale of permitting the use of broad-spectrum organic insecticides while prohibiting the more environmental-friendly selective synthetic insecticides:energy saving有时作为一个解释,not tenable because actually more energy is required by the production, the more frequent spraying and more intense scouting requested by the 'botanicals'. Furthermore, although it may come as a surprise, it must be acknowledged that 'botanicals' can be more toxic than conventional, super-blamed synthetic pesticides. Rotenone has an oral and dermal LD50 lower than both malathion and sevin, and a shorter persistence (Peet 2001), but the shorter persistence, in turn, obliges to more frequent treatments, which are not only directly harmful, but are also indirectly polluting for the energy requirement and the soil compaction, not to mention their higher cost.
edward jones的报价和豪厄尔斯报道above applies to insecticides and fungicides, since no herbicide is approved for organic farming: objections against this unreasonable banning were illustrated above when discussing the case of environmental damages from mechanical cultivation overwhelmingly exceeding those from the use of herbicides. Solomon et al. (2000) worked out an ecological risk assessment method based on the probabilistic theory, which permits to make decisions according to the accepted agrochemical risk level; their approach is interesting not only for the method itself but also because it implicitly emphasizes the principle, basic to probabilistic theory, that some level of risk, however small, is unavoidable. Including evaluation of hazards to the workers and the consumers, EIQ as mentioned above is a good indicator of social impact; however, focusing only on the pesticide action, it fails to consider the side impact of alternative solutions. For instance, the EIQ value of an alternative, organic, ecologically benign pesticide may well be less than that of the equivalent conventional, synthetic pesticide, but it is also important to evaluate the impact of the practices required to support the action of the environmentally benign pesticides, such as more cultivations or more targeted fertilizations (for instance, silica addition). In conclusion an integrated approach to the integrated management is needed, which is still missing
• Social: by far the most important social aspect is of course related tofood safetyand the permissible residue amounts. Tomassi and Gennaro (2002) report in their review that no pesticide residue above permitted limits was found in fruits of peach, plums and pears in a 2-year research conducted by the Italian Ministry of Agriculture. Leaving to ongoing research the difficult task of determining the safe limits to the presence of chemicals, it is worth quoting Haines (2000), referring to the risk of non-chemicals, i.e. 'botanicals': botanicals are often claimed by proponents to be environmentally safe and non-toxic to consumers because they are natural products. Such generalizations are clearly fallacious since many botanicals in crude or purified form (e.g. opium, nicotine, curare) have pharmacological, hallucinogenic or acutely toxic effects on humans and other organisms.
In order to issue reliable safety norms, the tolerable amounts of residues in the food must be assessed with certainty and the risk of the 'cocktail effect' must be fully evaluated. To this scope the ongoing updating of the 'Codex Alimentarius' standards, aimed at best serving the concerns of all (the rich and poor) regarding health, safety and trade in food (http://codexalimentarius.net/evaluation-en.stm) gives reasonable hope of a major progress, since the core FAO and WHO commission is collecting suggestions from a large number of governmental andnon-governmental organizationsworldwide.
3.2.4条分段——只有的综合a minor fraction of sprayed pesticides hits the intended target, while most of them pollute the environment; however, pesticides cannot be abandoned. IPM helps to enormously reduce their use and is presently progressing towards the 'proactive approach'. It is impossible to totally ban chemical pesticides, also because 'botanicals' and the other pesticides permitted byorganic agricultureare less effective and/or more polluting. One major problem is the determination of 'threshold values' for the treatments.
3.3 Discussion and Conclusions
Too many principles have gained dogmatic acceptance just because they have been endlessly repeated and acritically accepted, for instance that diversity is mandatory for ecosystem stability (experimental evidence and theoretical analysis reveal the notion that diversity causes stability as oversimplified at best, if not dead wrong, Dover and Talbot 1987; there is no reason to expect simple natural monocultures to be unstable, May 1975); that 'small is beautiful' (small can be beautiful but certainly is not useful if scale economies are disregarded); that organic food is richer in nutrients and vitamins (which results untrue); that reducing any external input to farms is highly desirable (the opposite is true, as demonstrated by Uhlin 1999a); that in large holdings, when capital (mechanization) is substituted for labor, this lowers yields more often than it raises them (Altieri 2002), which needs no comment, etc.
当然一个明智的解决方案对比这样的洪水of absurdities is to invest in multidisciplinary research and intense demonstration, and parallel activities of capacity building with the active participation of the stakeholders. When convinced producers become the sentinels of environmental quality obvious and durable advantages on the ground of social and environmental impacts will be achieved.
Considerations on the economic impact are clear-cut: unprofitable agricultural systems quite simply will never be accepted, and securing at least the same profit and the same risk of conventional systems is a prerequisite for the large-scale success of any sustainable system. The fact that growers accept for a while the rules of subsidized organic farming does not imply that they really support the organic farming principles: they just support the subsidy. The premium prices paid for organic products are volatile and not guaranteed in time, since while organic premiums are very high in a few markets, the global experience is somewhat less promising as more and larger producers enter this lucrative niche. ... Promises to farmers about enormous market profits may prove to be misleading, especially after the two-three years it typically takes to be certified (IFAD 2005).
And it is easy to observe that an agriculture based on subsidies is not sustainable, as demonstrated by many farmers who revert to conventional farming after the period of subsidy.
In any case, it can no longer be tolerated that such an important issue assustainable agriculturefalls prey to unskilled amateurs and dreamers (at best), while taxpayers' money goes to funding activities of a dubious utility or even harmful to the environment such as some of those supported by organic farming. It is reasonable to expect that the objective of the norms and subsidies be no longer to privilege niche producer and niche consumers who can afford to pay premium prices for an undemon-strated better food, but rather to (1) protect everybody's health; (2) encourage food production; and (3) effectively conserve the environment.
In the light of what has been discussed, pursuing sustainability in agricultural systems appears as a still ill-defined but inescapable task, to be based as far as possible on a global approach to farming systems, harmoniously combining all the resources offered by science and technology.
It is striking that, unlike in the USA where much attention is dedicated to soil, water and energy protection, in the rigid rules issued by the European Commission for organic agriculture (European Commission 2007), organic production and labelling of organic products, and in Regulation No 2092/91 and amendments (European Commission 2000, 2002) no specific, explicit provision is made for conserving soil, water and energy, nor to combatphysical pollution. Only generic, nebulous principles are enunciated to contrast physical pollution in spite of the so often displayed EU concern for the environment, while an obsessive care is dedicated to chemical pollution.
Although results obtained by researches are sometimes contradictory, due also to the enormous variety of experimental conditions and the uncertainty in some data, and their indications are sometimes biased, there is enough solid ground on which is possible to work confidently.
The complex problems require a cautious and flexible approach; however, a down-to-earth, information-rich paper by Reardon gives an illuminating example of the particular conditions to be faced when coping with a resource-poor agriculture and the possible need for adopting opposite solutions in contrasting situations (Reardon 1995). He comments that low-input systems are not necessarily benign to the environment: [P]oor farmers stay poor when they use few external inputs; but population still grows, sofood demandrises, pushing farmers to crop marginal lands of lower quality, which are easily degraded. Also Snapp et al. (1998), referring to Malawi and Zimbabwe, outline the shortcomings in single-minded approaches: Extension departments and non-governmental organizations have promoted the use of organic matter technologies such as green manures for over 70 years in southern Africa. ... Adoption of organic matter technologies has been nil. ... The technologies promoted require considerable labor inputs, and have often not met criteria of farmers. As Rasul and Thapa observe (referring to Bangladesh, but the observation is valid for most developing countries): Bangladesh cannot afford to provide subsidies to farmers to make up shortfalls in crop production caused by environmental conservation-orientated agriculture (Rasul and Thapa 2004). Of course their consideration applies to those strategies overlooking the 'economic pillar' of sustainability.
To some idealistic supporters of alternative farming, including the Soil Association (2002), Altieri (2002) and Ikerd (2008), increasing labour input and disregarding scale economies and reducing external inputs and fragmenting large farms into small family units are highly desirable, but elementary economic considerations as well as practical experience demonstrate the fallacy of their principles, both in developing and developed regions, not to mention the environmental damages which would be brought about by the advocated increases in highly polluting human energy input.
人是最理想的州长,不是energ生产国y for at least two good reasons: for a matter of human dignity (it is preposterous to insist that man should do the work that can be done by a donkey or a machine) and because man-developed energy is enormously more polluting than any other. This apart, any consideration on work affects economy and productivity.
Similarly, some idealistic supporters of alternative farming systems claim the goal of a totally unpolluted environment, unaware that in most cases it does not make economic sense to eliminate pollutants completely. That is, the cost of eliminating a minuscule level of contaminants may well exceed the benefits. ... The difficulty in assessing benefits of reductions in environmental damages has led the Environmental Protection Agency to establish maximum levels of acceptable pollution or environmental damage and to seek mechanisms to reach these levels at least cost (Zilberman et al. 1999). Kristin Kuntz-Duriseti (2004) with an acute analysis suggests solutions for a logically based integration of the precautionary principle into the cost-benefit analysis and presents three methods for incorporating a precautionary response to uncertainty into cost-benefit analysis in ways that balance economic growth and environmental protection.
Way and van Emden, in the discussion to their excellent review on IPM (Way and van Emden 2000), wrote: The most important message from this review is that priority should be given to application of the right kinds of applied ecological and associated behavioural work in real situations in the field. At present, the balance is wrong, with too high priority given to fashionable technologies. Yielding to fashion is probably one major reason for the inexplicable blind acceptance of illogical theories, while objecting to them is perceived as 'politically incorrect'.
Our duty, as responsible researchers, committed environmentalists and components of the civil community, is to seriously pursue the solutions appearing objectively more sustainable, without yielding to fashions, obtuse philosophies and, even worse, lobbies, be they on the side of industries or on that of the extreme environmentalists.
Organic farming can appear at a first glance as ideally suited to achieve a sustainable agriculture, and actually it is for some respects; the problem is that, in spite of the claims of its supporters, not always organic farming can reasonably be regarded as sustainable (Hodge 1993). Hodge's criticism lists only a part of the objections that can be raised against organic farming sustainability, as illustrated among others by MacCormack (1995), Kirchmann and Thorvaldson (2000), Rigby and Caceres (2001) and Edwards-Jones and Howells (2001). Elliot and Mumford (2002) comment that organic agriculture relies on price premiums in a niche market and prescribes certain technologies on ideological rather than pragmatic grounds and suggest the adoption of integrated farming, abandoning the more harmful technologies of conventional farming.
In order to counter criticism on the 'organic' term (all the agricultural systems are organic, it was objected), Scofield (1986) argued that 'organic' refers to the wholeness of the principles, which leads to the systematic connexion or co-ordination of parts in one whole. The explanation can be accepted, but then, as a consequence, the organic farming enthusiasts for a matter of coherence must accept to organically consider in their 'wholeness' all the factors that concur to sustainabil-ity, including those so far eluded or anecdotally and nebulously treated because they collide with some of their principles, such as energy saving and the impact of direct and indirect energy used in the farming systems, the sequestration of CO2 in soils and plants, soil protection against water andwind erosion,water conservationand of course the productivity level and the economic aspects of farming activity. Also some aspects of integrated pest management as advocated by organic farming principles are not exempt from criticism, as illustrated above and no satisfactorily, rational explanation yet has been given to their total refuse of synthetic chemicals (in the SAREP Web site it is reported: However, there may be situations where the use of synthetic chemicals would be more sustainable than a strictly nonchemical approach or an approach using toxic organic chemicals, SAREP 1997).
In this chapter there is no attempt to elaborate a new system for reaching sustainable agriculture: it is just an endeavour to work out a conceptual framework for focusing and organizing some basic principles. The principal of them is not to supinely accept any pre-conceived 'philosophy', but select in total freedom what is perceived the best solution for any particular case (admittedly, this too can be considered a philosophy). A rational, sustainable farming system in fact must be 'open' since farming systems are multi-purpose and multi-method and therefore highly dynamic; as a consequence, the process of elaborating an 'optimized' farming system must be able to flexibly integrate in a synergic mode all the relevant aspects, must be free from prejudice and dogmatism, and ready to promptly include any useful new principle or technological innovation and to reject less-than-rational solutions.
Only the adoption of elastic, advanced, rational strategies, to be selected in a participatory process from all the stakeholders, principally well-informed farmers, can secure a long-term and widespread acceptance of sustainable agriculture; this appears the only way to transform 'pragmatic' into 'committed' producers (Fairweather and Campbell 1996), or better to make the two categories overlap.
The task is evidently too challenging and the stake too important to indulge in emotional, non-rational approaches: all the resources of science and technology should concur in a coordinated, synergic effort towards the Holy Grail of sustainable agriculture. It seems fitting to report here in conclusion Thompson's warning that our society may collapse because of shortsighted stupidity on the part of the pro-growth, resource-exploiting power elites, but the collapse will only be tragic if it is shortsightedness or ignorance on the part of environmentally and ethically concerned people that helps bring it around (Thompson 1992).
Synthesis of Section 3.3 - To achieve sustainability cultural practices must be selected and combined independent of mainstream beliefs. Organic agriculture principles are unbalanced: too conservative for chemical pollution and too lenient for physical pollution, and this makes it unsustainable. Mostorganic farmersdo not really support organic farming but accept it for the sake of the state subsidy. It should not be permitted that taxpayers fund unreasonable practices: funding should be aimed at encouraging really sustainable farm management by convinced, educated, committed technicians and farmers free from obtuse ideological constraints.
Continue reading here:Definition and Global Situation of Organic Agriculture
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