Challenges to IPM Advancement : Pesticides , Biocontrol , Genetic Engineering

Integrated pest management (IPM) is widely promoted as the most sensible method of sustainable control of important agricultural pests. However, IPM is not widely practiced in commercial crops where this technology could be utilized. In crops where IPM is used, the sophistication of programmes with respect to the numbers of species, types of pests, and variety of control tactics simultaneously implemented are often simplistic and continued development of existing programmes for greater sophistication and management of multiple pest complexes is extremely challenging thus making progress slow. This situation for IPM may become more difficult to resolve in New Zealand, and elsewhere, as difficult and controversial pest management issues related to pesticide use, importation and utilization of exotic natural enemies, deployment of transgenic crops, invasive species, and a diminishing base of scientific talent and research funding become increasingly apparent and demanding of attention and resolution. Introduction Integrated pest management (IPM) had its genesis in the mid to late 1950’s when the detrimental effects of pesticide overuse became increasingly apparent. Continual and often excessive and unnecessary use of synthetic halogenated hydrocarbons were identified as the cause of resistance development, pest resurgence, the elimination of natural enemies that resulted in secondary pest outbreaks, pollution of water supplies, and lethal and sub-lethal impacts on charismatic wildlife (e.g., egg shell thinning in raptor species caused by DDT). Rachel Carson’s (1962) landmark book “Silent Spring” identified these problems, and raised the alarm about the unintended consequences of agricultural pesticide use, which ultimately gave these issues widespread and permanent public and political recognition. IPM or “integrated control” was “officially” conceived in seminal work by University of California researchers (i.e., Vern Stern (UC Riverside), Robert van den Bosch (originally UCR then UC Berkeley), Ray Smith (UCB), Ken Hagen (UCB), and Carl Huffaker (UCB)) that culminated in the landmark Hilgardia publication by Stern et al. (1959). However, some of the concepts formalized as essential cornerstones for IPM programmes were not novel, having been employed routinely by agriculturists prior to the invention and wholesale adoption of synthetic pesticides in the late 1940’s (Kogan 1998). The most common practice employed by pre-IPM farmers that forms a prominent cornerstone of modern IPM programmes is the exploitation of natural control, that is, the preservation and enhancement of resident natural enemies of pest species inhabiting crops. The strategy of deliberately manipulating generalist predator populations for pest control (e.g., ants and spiders) in some cropping systems (e.g., citrus (China) and dates (Yemen)) is hundreds of years old (Van Driesche & Bellows 1996). Upper trophic level organisms are primarily relied on for pest control in IPM, however, when scouting of key pest species indicates pest densities are approaching an a priori action threshold; carefully timed applications of pesticides are made to prevent economic injury to the harvestable product. Thus within the idealized IPM paradigm, biological and pesticidal control are “complementary” and can be utilized “harmoniously” (Kogan 1998). This synergism between natural and synthetic control can result in greater profitability for growers, improved environmental stewardship of farmland and surrounds, and sustainable management of organisms notorious for developing pesticide resistance. Despite the social, political, and intellectual appeal of the IPM approach to managing agricultural pest problems, widespread adoption New Zealand Entomologist 29: 77-88 (2006) New Zealand Entomologist 29: (2006) 78 and development of increasingly sophisticated IPM programmes that simultaneously manage several classes of pests (e.g., insects, mites, phytopathogens, and weeds) in diverse agroecosystems has generally not occurred to any significant extent (Kogan 1998). In many agricultural systems, the majority of IPM programmes target only one or two pests (e.g., mites and thrips that can be controlled with the same insecticide (e.g., abamectin) and are attacked by the same suite of generalist predators (e.g., phytoseiid mites)) or a pest complex (e.g., leaf rollers). While development of some IPM programmes has progressed significantly in some crops and countries, especially in relation to crops of high market or export value (e.g., kiwifruit and pip fruit production in New Zealand) the overall global situation for IPM has not changed greatly despite 50 years of research (Kogan 1998). Many of the impediments to IPM implementation and increased sophistication identified by Wearing (1988) are still relevant today, and the challenges for IPM are increasing, more varied, and for New Zealand agriculture, strongly influenced by overseas market trends (Whalon & Penman 1991). I perceive five major and interconnected factors affecting future IPM development, adoption, and sustainability: (1) pesticides, (2) biological control, (3) transgenic crops, (4) invasive pest species, and (5) recruiting, training, and retaining excellent IPM researchers and extension personnel, and providing productive programmes with stable moderate to long term funding for research and outreach. Pesticides Contamination of food and water and the psychological dependence of growers on chemicals for pest control are the consequences of over-reliance on pesticide applications in modern agriculture (van den Bosch 1978). In the highly controversial “The Pesticide Conspiracy” van den Bosch (1978) raises one extremely salient and poignant argument – the right of every consumer to “molecular privacy,” this being the right to eat food without synthetic residues that accumulate and/or have an unwanted effect in the consumer’s body. Given the litigious nature of U.S. society it is surprising that more lawsuits have not been filed on behalf of victims that have suffered “catastrophic” health consequences (perceived and realized) from agro-chemical residues on food that compromised their “molecular privacy.” The classic example of this kind of public outrage over perceived hazard from synthetic compounds was to Alar®, daminozide, a plant growth regulator used in apples in the U.S.A. (Rosenberg et al. 2001). Because of safety concerns over synthetic compounds being applied to foods, many broad-spectrum pesticide products (e.g., carbamates and OP’s) with known or suspected risks to human health are being phased as part in several countries (e.g., New Zealand and U.S.A.) as a result of legislation that is aimed at protecting food quality and consumer health. A growing body of scientific evidence coupled with experimental research is documenting the subtle but serious health consequences when “molecular privacy” is violated by exposure to trace residues (e.g., parts per billion) of some pesticides (Colborn et al. 1997; OSF 2005). Extremely small amounts of pesticide residues or byproducts of their environmental degradation can act as endogenous hormonal analogues adversely affecting development and behaviour in vertebrates (e.g., atrazine on amphibian development (Storrs & Kiesecker 2004)), including humans (e.g., endosulfan on the male reproductive system {Saiyed et al. 2003})). Accumulating knowledge of these phenomena led to the development of a revolutionary new biological theory – the environmental endocrine hypothesis (Krimsky 2000). Investigation of hormonal activity focuses on the tenet of how little of a compound is needed for an observed endocrine effect and is diametrically opposed to the cancer screening paradigm which assesses how much is needed to cause an adverse health effect. Overwhelming evidence for hormonal mimicry has led the U.S. Environmental Protection Agency (EPA) to mandate testing of new synthetic compounds for hormonal activity before wide-scale use outside of the laboratory (Wu 1998). Obviously, the need for protective chemistries that can aid crop production while not adversely affecting the consumer or other non-target organisms are needed in agriculture. “Reduced-risk” pesticides may be alternative chemistries that can obviate problems associated with more conventional pesticides used in agriculture. Addressing these well recognized health and environmental concerns should encourage the development of IPM programmes.