Biorational pest control agents, formulation and delivery

Biorational pest control agents, formulation and delivery

BookReviews Biorational Formulation Pest Control Agents, and Delivery, ed. by F.R. Hall and J.W. Barry. ISBN @8412cloth $84.95). 32261 (306 PP; Wash...

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BookReviews Biorational Formulation

Pest Control Agents, and Delivery, ed. by F.R.

Hall and J.W. Barry. ISBN @8412cloth $84.95). 32261 (306 PP; Washington DC, American Chemical Society, 1995 This book is based on a 1994 symposium sponsored by the Division of Agrochemicals of the American Chemical Society on the formulation and delivery of biorational pest control agents. The purpose of the symposium was to explore the current status of formulation and delivery of a broad range of pest and pathogen control agents, termed biorationals in the book. The uniqueness of the symposium and subsequent book is the interdisciplinary scope and the comprehensive treatment of biorational formulation and delivery. A theme throughout the book is the need to improve formulation and delivery, as well as to understand the basic ecology of the target pest and biology of the biorational. Scientists will benefit from formulation and delivery technologies used in disciplines other than those in which personal research may be underway. Policy makers and scientists alike will benefit from the chapters that detail regulation and registration considerations for biorationals. The book is divided into three general sections on registration needs, basic information needs, and delivery and environmental fate, and three biorational site-based sections, in addition to a thought-provoking introduction and overview by the editors. The three site-based sections: soil biorationals, foliar biorationals, and forest biorationals cover formulation and delivery of biorationals for specific pests, pathogens, and weeds of crops and forests. The first section on registration requirements considers for US Environmental Protection Agency (EPA) registration of biological pesticides and how formulation of the biorational can affect toxicity and risk to human health or the environment. In Canada, a generic approach to regulation is used to estimate and minimize the impact of an applied biorational on non-target species, based on the use of models and/or a field data base. Again, formulation and delivery of biorationals for forest insect control can affect the range of spray drift to non-target speciesor off-target sites and thus the extent of

regulation. Buffer zones based on operational conditions which promote maximum drift of the biorational formulation are established from the data base of extensive field tests or models for other pesticides, with emission spectra similar to that of the biorational in question. The two chapters in the basic information section focus on the need to understand the ecology of croppest systems in which the biorational would be applied. Use of the Pesticide Drop Simulation to model the dose transfer of Bacillus thuringiensis (Bt) toxin to the diamondback moth on cabbage revealed that the weak point in understanding the process is the behaviour of the pest target on the feeding surface. The third section on delivery and environmental fate has five chapters that outline application methodology, dispersal monitoring in forest canopies, and factors affecting environmental stability. Examples draw heavily from research with Bt as a biorational for the control of several pests. Development of suitable delivery systems for biorationals will be a significant challenge for successful adoption of pest and pathogen control agents. Traditional pesticide spray-application technology has been used for application of biorationals in forest canopies. Dispersal models for biorationals based on those developed for chemical pesticides have been evaluated and modified. Atomization of Bt preparations during spray application can reduce optimal droplet size and limit effectiveness. Field assessment of sample distribution of bio-rationals and subsequent model modification will improve delivery technology. Environmental fate is a critical issue for biorationals. Ideally, an effective biorational would persist long enough to control the target pest or pathogen, yet disappear when the target organism had been controlled. Biorationals are considered to be environmentally safe by definition, but field data on persistence and non-target effects will be required for adoption. Lack of persistence can often be a problem for biorationals. Sensitivity to UV radiation, and wash-off by rainfall has limited stability on foliage. Addition of optical brighteners has enhanced the activity of nuclear polyhedrosis viruses used for larval control. Biocontrol agents for soilborne plant

pathogens, and Metarhizium anisopliae and entomopathogenic nematodes for control of soil pests are described in three chapters under the soil biorational section. A comprehensive listing of biocontrol agents available for soilborne plant pathogens helps focus this area of research. To date, only limited success has been achieved in commercialization of biorationals for plant pathogens, but fermentation processes and delivery systems offer promise. Commercialization of M. anisopliae has been hampered by the lack of economic competitiveness, although several economically important pests are controlled. Problems of inconsistent performance, strain differences, and shelf life need refinement. Entomopathogenic nematodes such as Steinernema carpocupsae for soil pest control can now be formulated in an unique water dispersible granular that provides a suitable shelf life for commercial purposes. The section on foliar biorationals includes six chapters that cover pheromone formulations, entomopathogenio fungi, baculovirus biorationals, biological weed control, and formulation of foliar biorationals. Pheromones have been delivered in dispensers and in sprayable formulations. The dispensers provide month long efficacy but delivery to large acreage is time limiting. Spray formulations go on quickly but efficacy may be lost in a few days or weeks. Development of pheromone products is aimed at establishing economic incentives to growers for adoption. Entomopathogenic fungi in the genera Metarhizium and Beauveria are contact biorationals that produce conidia which must contact and penetrate the insect cuticle to infect and thus control the insect pest. A 2 year shelf life was a major consideration in the development of a unique cockroach infection chamber with Metarhizium. With baculovirus biorationals, a major limitation to development is the relatively long period (S-15 days) needed to kill the pest. Existing products have been used by US and Canadian forest services. In the future, genetic engineering to improve performance may offer a greater array of baculoviruses, provided environmental issues can be addressed by utilization of co-occlusion or preoccluded virus particles that do not persist in the environment. Two chapters on biological control

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Book reviews

for weeds examine factors involved in improving the formulation of biorational fungi and an overview of the USDA Agriculture Research Service program for introduction of natural enemies of weeds. A significant factor in formulation of biorational fungi for weed control is the need to maintain free moisture on the leaf surface for germination. UV blockers to prolong survival on leaf surfaces can extend the survival of biorational fungi prior to periods suitable for germination and infection. Approaches have included water-in-oil or invert emulsions, oilbased formulations, and microencapsulation in alginate or other materials. This section also includes a stimulating chapter on starch and flour formulation of biorationals that have been used successfully for Bt, baculoviruses, and both entomopathogenic and mycoparasitic fungi. Expansion of starch and flour formulation technology may lead to the next generation of biorational products. The final section contains two chapters on forest biorationals. Insect pheromones have only recently become economically feasible for forest pest management due to changes in public advances in pheromone perception, synthesis, and technological improvements in formulation and release dispensers. Strategies include mating disruption, mass trapping for isolated pest populations, and anti-aggregation for bark beetle pests. Use of a selected strain of Bacillus thuringiensis var. kurstaki for control of gypsy moth in hardwood forests of the USA will increase in the future. The final chapter looks at the success that has been achieved in the formulation and application of this biorational and the impact its use can have on non-target Lepidoptera both from the standpoint of direct toxicity, and indirectly through the Lepidoptera food chain. The editors, in their discussion and conclusions, call for national leadership in adoption of biorationals, and the need for consumer support of biorationals as safer alternatives to conventional pesticides. In the USA, the vehicle to accomplish this is the National IPM Plan wherein biorationals are the central component of an ecologicallybased approach to IPM. agents

North

D. Michael Benson Department of Plant Pathology Carolina State University, Raleigh, USA

Integrated Pest Management by David Dent. (xii + 356 pp; f45.00).

London, Chapman and Hall. Dent’s Integrated Pest Management might be more aptly titled Integrated

320

Pest Management Management, or posseven Integrated Integrated Pest Management Management, if such titles

ibly

could pass the scrutiny of editors and spell checkers. It is about managing integrated pest management (IPM) through interdisciplinary teams. It goes beyond the technical aspects of IPM and considers programme planning and organisational structures, amongst others. There are initial chapters on introduction, principles and control methods, brief overviews that may be useful for readers interested in the general subject of agricultural technology management, but without a specific background in pest management. Chapters 4-8 are the real core of the book. Defining the problem gets to the heart of the matter, what triggers the start of a pest management programme and what constrains it? The problem of excessively specialist scientists is raised as an important issue. He stresses goals and strategies and the need to backward chain, to work backwards from the goals to ensure a programme that will achieve them. Problem trees, in which the causes of problems are identified in immediate, direct steps down to final root causes are not mentioned, but otherwise there is a quite complete set of techniques for this critical phase. Programme planning and management advocates farmer participation and describes four models of how they can participate. Similar models could probably be devised for all the other potential participants in an IPM programme. The nature of this participation affects the goals and options of IPM. It seems rather strange that while this chapter has extensive coverage of such subjects as research group organisational structures (nets, matrices, radiating arms, etc) there is no mention of logical frameworks, one of the most common management and planning tools currently used, and required, by many funding organisations. Systems analysis is clearly a key to good planning. Dent predicts an increase in the use of models, despite recognising a general claim of dissatisfaction with the modelling approach in practice, citing a leading biocontol practitioner. I agree, but the emphasis on models in the future will be much more practically oriented to answering real questions. IPM is a paradigm, and as such it influences experimental procedures within it. IPM arose because people were unhappy with what preceded it. This is an interesting concept since what we were then dissatisfied with (chemical pest control) is what replaced what many now advocate returning to natural pest control. Abraham Lincoln observed that the only universally true statement anyone can make is ‘and this,

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too, will pass’. Dent predicts an imminent change in the paradigm that hostspecific parasitoids are essential features of biological control systems, a return to an old Arabian paradigm he describes in which predatory ants were successfully used on dates in medieval times. IPM implementation is a problem. Experience in many countries reveals ‘that the availability of an effective IPM product or technique alone is no guarantee that it will be adopted’. Unlike better mousetraps better, or even just effective, IPM will not sell itself. He mentions that many farmers are satisfied with what they do already and goes on to describe various ways to sell IPM under these circumstances (identifying and involving the ones who are dissatisficd, mainly). The book concludes with four chapters presenting examples of IPM in different cropping systems - olives, wheat, cotton and greenhouses. The olive example (by Walton) describes a large European programme involving considerable co-ordination of efforts in several countries. Examples are given of a number of control inputs for wheat pests all over the world (by Wratten and others in New Zealand and the USA), not as clearly integrated as the others. The chapter on cotton (by Gutierrez) is the epitome of a big ecology, top down approach based on a complete understanding of crop physiology to determine the problems and options. This provides an interesting contrast to the farmer first approach; Gutierrez categorises cotton farmers by greed, ignorance and obstinacy, with further inclinations to drink and lie in cotton growing countries in which alcohol is served. A temperance and redemption mission to benighted cotton producers seems the first priority. The greenhouse chapter (by van Lentern) follows more closely the overall run of the book, from the initial need for IPM to its development and adoption. Dent notes that the approaches taken in Decision Tools for Pest Management (Norton and Mumford, 1993, CAB1 International) ‘figure largely throughout this book’. His further combination is to concentrate on the development of R&D management, which he recommends as a complement to decision tools. I agree wholeheartedly that this is worthwile, though I do not agree that ‘decision-based approaches often assume and require the availability of extensive information’. All decisions involve both information and a decision process, and better results can be obtained by improving either, which Dent helps to achieve. John Mumford Centre for Environmental Technology Imperial College of Science, Technology and Medicine, London, UK