Chemical Pest Control Technology: Benefits ... - ACS Publications

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Chemical Pest Control Technology: Benefits, Disadvantages, and Continuing Roles in Crop Production Systems Downloaded by PURDUE UNIV on August 29, 2014 | http://pubs.acs.org Publication Date: December 14, 2006 | doi: 10.1021/bk-2007-0947.ch001

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Allan S. Felsot and Kenneth D. Racke 1

Department of Entomology, Washington State University, 2710 University Drive, Richland, WA 99352 Dow AgroSciences, 9330 Zionsville Road, Building 308/2B, Indianapolis, I N 46268 2

In the U.S., certified organic agriculture has been clearly demarcated from conventional agriculture by regulatory rules under the National Organic Program. However, neither organic nor conventional agriculture has a clear scientific definition. From a public perspective, organic agriculture is often defined simplistically and contrasted with conventional agriculture by the non-use of pesticides. Furthermore, organic agriculture is often viewed as the epitome of sustainability. In reality, sustainable practices are not well defined because systems are dynamic and practices must be constantly adapting within the context of changing biotic and abiotic characteristics of a field or landscape. Sustainability is a concept best viewed as a goal of all growers, whether they associate themselves with the terms organic or conventional. Also, practices deployed by organic growers for pest control are increasingly practiced by conventional growers. Examples include the use of crop rotation for controlling soil borne pests (such as the corn rootworms, nematodes, and fungal diseases) and the use of pheromones for mating disruption of moths, especially in tree fruit. Pheromones are but one type of pesticide registered by the E P A and approved for use in certified organic agriculture. Others include certain formulations of spinosad and azadirachtin and certain

© 2007 American Chemical Society In Crop Protection Products for Organic Agriculture; Felsot, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2006.

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Downloaded by PURDUE UNIV on August 29, 2014 | http://pubs.acs.org Publication Date: December 14, 2006 | doi: 10.1021/bk-2007-0947.ch001

2 microbial pesticides based on non-genetically engineered cultures of Bacillus thuringiensis among other species. Considering that many agrichemical companies are now trying to develop and market EPA-approved reduced risk pesticides, a convergence in techniques may be taking place among all types of growers as they seek to manage the same problems consistent with a desire for environmental stewardship. Rather than further differentiate between organic and so-called conventional practices, this chapter seeks to understand common reasons for why growers use pesticides, the advantages and disadvantages of pesticides, and the continuing role of pesticides in crop protection regardless of agronomic practices. Over reliance on singular techniques in any agronomic system may lead to their eventual failure. To be sustainable, pest control must be conducted using the principles of integrated pest management (IPM) as a decision support system. The I P M strategy is based on a confluence of biological and economic information and is implemented by integrating multiple compatible control tactics.

The tools used to sustain a thriving agricultural enterprise are often viewed as the demarcating characteristic of different types of management systems. This perspective relegates any discussion of food production systems to a black or white perspective, best characterized by the cliché—pesticides bad, no pesticides good. Any production system using pesticides has been labeled as conventional and not viewed as sustainable. Furthermore, organic agriculture has become identified with "sustainable" agriculture. The reality is that all production techniques use pesticides or at least rely on the potential to use them. The difference among production systems is not the dichotomy of use but the specific types of products that are used. Unfortunately, the negative or favorable public opinions about agricultural practices based mainly on pesticide use (or non-use) hinder the understanding of agricultural impacts in a broader context and the convergence of all production systems toward sustainability. Integrated farm management seems to be the objective of all farming systems and specific practices are blurring among the different types of management schemes. For example, so-called conventional pome fruit (e.g., apple and pear) growers are using pheromone-based mating disruption techniques for controlling codling moth injury, but they still use cover sprays of organophosphorous insecticides and more increasingly reduced risk chloronicotinyls. Is this practice conventional or an alternative integrated technique in transition to a greater probability of future productivity? Similarity in practices also applies to soil management. Organic growers formerly relied heavily on tillage (cultural practices) for weed control, but have switched to

In Crop Protection Products for Organic Agriculture; Felsot, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2006.


3 reduced and no tillage practices that "conventional" growers in the Corn Belt adopted in great numbers over 20 years ago. Crop protection chemicals play a continuing role in modern agriculture, regardless of what techniques are deployed or how a commodity is marketed. One could even argue that plant breeding for antibiosis factors adversely affecting pest physiology is just a different strategy for deploying a chemical to aid crop protection. Nevertheless, to promote an understanding of the role of crop protection chemicals, this chapter provides a perspective on why growers use these tools, what advantages they confer, and a reckoning of their disadvantages. Necessarily, this chapter must cover some historical aspects of the evolution from integrated control to integrated pest management and the evolution of strategies for attaining technological competence that is compatible with environmental stewardship. Finally, issues associated with crop protection chemicals are comparatively examined in so-called conventional and certified organic production systems.

Why Producers Use Crop Protection Chemicals Numerous organic production advocacy websites, as well as refereed journal papers and review articles agree on one principle—optimizing agricultural productivity requires a crop protection technology. Certain agronomic practices (for example through the use of crop rotation, polycultures, host-plant resistance) achieve adequate control of some pests and are adaptable to organic and non organic production. Often, however, agronomic practices by themselves are insufficient to obtain economically successful production, especially in the highvalue per acre production of vegetables and fruit. Since the early 20 century inorganic and then later synthetic organic pesticides have closed the gap in pest control. But pesticides had been used since antiquity (7, 2). The key to understanding the need for management and a stopgap when agronomic techniques alone are inadequate lies in a comparison of natural and agricultural ecosystems (agroecosystems). Natural ecosystems are self-sustaining by virtue of their biotic diversity, having shaped and been shaped by the abiotic environment. The soil stores plant nutrients, which are continually recycled throughout components of the ecosystem. A combination of biotic diversity and soil fertility allows the system to respond to perturbations and re-establish its productivity. A good example of a natural ecosystem's ability to quickly re-establish productivity on a landscape and move through successional stages is the area around the Mt. St. Helens Volcano in Washington State. The catastrophic explosion of Mt. St. Helens in 1980 devastated a landscape that could be analogized to the destruction wrought by a nuclear bomb explosion. However, life reemerged in the vicinity and nearby affected areas of the volcano, proving the resilience of natural ecosystems to regenerate after perturbations. The lesson of Mt. St. Helens is that the biotic th



4 components of ecosystems may constantly change but natural ecosystems function as in a steady state and stable associations of species eventually develop. Such stability is called the climax state (5). Agroecosystems in contrast have significantly less biotic diversity than natural systems by virtue of the need to maximize production of a single species (4). Nutrients, especially nitrogenous forms, are annually removed from the agricultural system rather than recycled. The soil of field crops (corn, soybean, wheat, cotton, etc.) is continually disturbed and much of the biotic component must re-establish on an annual cycle. Orchards and other perennial crops lack wholesale annual disturbances but the biotic diversity is very limited and pollinators have to be imported to produce a crop. When diversity is lacking, the populations of just a few species can explode to dominate the system. When those species compete with us, they are pests needing control. Pests that become established in our agroecosystems may be either native to the ecosystems that the crops have replaced or they may have been accidentally imported from other countries (J). In the former case, native pest organisms (e.g., insects, plant pathogens) have a readily abundant food supply and populations can quickly increase i f the abiotic components (like weather) are favorable. Disturbed soil also provides opportunities for weeds to out compete crops. Native pests do have natural biotic regulatory factors (for example natural enemies like parasitoids, predators, and pathogens) but the lack of biotic diversity and frequent system perturbations can make these factors insufficient by themselves to prevent economic losses of crop yield. Imported (or exotic) pests, especially originating from places of similar latitude to the destination fields, experience conditions that allow them to thrive easily because their biotic regulatory factors are often missing or their other natural mortality factors are not operational. The conflict between the economic value of a crop and its susceptibility to damage from an explosive pest population demands the need for management of both the crop and the pest. The continual removal of nutrients from the soil by harvesting a crop and the comparatively short time interval between successive plantings necessitates the addition of readily available nutrients. In short, the structure and characteristics of an agricultural ecosystem and pest population ecology necessitate a high level of management and inputs to maintain soil fertility and protect the production of the harvestable seeds, fruit, and vegetation.

Benefits of Crop Protection Chemicals Economic and Environmental Benefits Pesticide and fertilizer use has been recorded since ancient times, suggesting that ecosystem management is not a recent cultural attribute. In the context of



5 production agriculture, the objectives of pesticide use are to increase production efficiency and yields; reduce cost of food and especially increase availability of fruits and vegetables; improve food quality and losses during transport and storage; improve soil conservation; and ensure a stable and predictable food supply (2). Pesticide use is widespread on farms, but more importantly, different classes of pesticides are differentially used (2, 6), suggesting that growers make decisions based on need rather than solely on prophylaxis. For example, during 2002 approximately 303 million acres of crops were harvested, and 95% were treated with some type of pesticide. However, 64% of the acreage was treated to control weeds (i.e., herbicide use), 22% to control insects (insecticide use), 6% to control diseases and nematodes (fungicide and nematicide use). Another 4% of the crop acreage was treated with a plant growth regulator for fruit thinning, growth control, or defoliation. The intensity of specific pesticide classes also varies significantly by crop. Grains tend to be disproportionately treated with herbicides, but fruit and vegetables mostly receive insecticide and fungicide applications (Table I). The benefits of crop protection chemicals for improving and protecting crop productivity is difficult to separate from the effects of hybrid seed technology and other plant breeding advances. Nevertheless, an examination of crop yields relative to land under production shows both types of technologies have had major contributions. For example, the greatest proportion of U.S. farmland is devoted to corn production. A historical examination of area of land, yields, and the introduction of different technologies over time suggests that insect control (mainly of the corn rootworm complex) has greatly enhanced the effectiveness of hybrid seed technology (Figure 1). Furthermore, the introduction of modern synthetic herbicides facilitated widespread adoption of conservation tillage in the Corn Belt that greatly reduced the number one problem of agriculture—soil erosion and sedimentation in rivers. Perhaps an even more compelling case for the role of crop protection chemicals, especially fungicides and fumigants, in crop production efficiency is suggested by potato production statistics. In 1900 nearly 3 million acres of potatoes were harvested yielding an average of 52 cwt/acre {10). In 1950, average yields were 153 cwt/acre. In crop year 2004, 1.2 million acres of harvested potatoes yielded an average 752 cwt/acre. Surely advances in plant breeding play an important role in production increases but by the 1950's fumigants for control of nematodes became widely available nearly coincidentally with the widespread adoption of mineralized fertilizers. But the production trends strongly suggest an environmental benefit in that only 40% of the total potato acreage planted in 1900 could produce in 2004 seven times more potatoes. The aggregate economic benefits associated with pesticide use have been subjected to various empirical modeling exercises and expressed as the loss of production i f pesticides were not used (2). Production losses during the mid-


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Table I. Percentage Use of Pesticide Classes on Major Crops During Crop Years 2003 or 2004 (7, *)


Crop

Herbicide

Corn Soybean Wheat Cotton Potato Apple

95 97 45 98 91 42

Acres Harvested

Insecticide

Fungicide

29 4 7 64 84 94

Chemical Pest Control Technology: Benefits ... - ACS Publications

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