Green Trends in Insect Control (RSC Green Chemistry)

375 Pages·2011·58.43 MB·English

by  Royal Society of Chemistry

Green Trends in Insect Control
RSC Green Chemistry
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George A Kraus, Department of Chemistry, Iowa State University, Iowa, USA
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6: Radical Reactions in Aqueous Media
7: Aqueous Microwave Chemistry
8: The Future of Glycerol: 2nd Edition
9: Transportation Biofuels: Novel Pathways for the Production of Ethanol,
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11: Green Trends in Insect Control
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Green Trends in Insect Control
Edited By
O´ scar Lo´pez and Jose´ G. Ferna´ndez-Bolan˜ os
Department of Organic Chemistry, Faculty of Chemistry,
University of Seville, Spain
RSC Green Chemistry No. 11
ISBN: 978-1-84973-149-2
ISSN: 1757-7039
A catalogue record for this book is available from the British Library
r Royal Society of Chemistry 2011
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Preface
This book is part of the Green Chemistry series published by the Royal Society
of Chemistry, and is designed to provide a modern overview of the current
status of insecticides. We present the current approaches for insect pest control
as green alternatives to classical agrochemicals, which should be of interest to a
vast group of researchers: agrochemists, biochemists, chemists, toxicologists,
etc. Throughout the book, the different approaches to pest control which
involve ‘‘greener chemicals’’ in particular are emphasized. In the literature
there are numerous examples of texts making a comprehensive treatment of
specific aspects of agrochemicals (such as toxicity, analytical measurements of
pesticides and their derivatives in the environment and in living organisms or
practical uses of insecticides), but there are few attempts of bringing together
the wide variety of topics covered in this book. With this publication, we
intend to provide a useful guide for a broadrange of readers, from students,to
teachers or professionals inthe agrochemical sector.
In each of the chapters, the following information is taken into account: a
description of useful synthetic and biorational insecticides, which highlights
environmentally-friendlyprocesses;themodeofaction,emphasizingselectivity
towards targeted species and environmental effects (e.g. toxicity, bioaccumu-
lation and metabolism and a comparison with classical insecticides); as well
as human and environmental risk assessments. Furthermore, formulation,
dispersal and persistence in the environment are covered as key aspects in
developing greener agrochemicals.
Therearenumerousinsectspeciesconsideredtobepestswhichcausehealth
problems in humans, cattle and crops, and even affect some human construc-
tions.Manyinsectsareknowntoactasvectorsinspreadingimportantdiseases
suchasmalaria,dengueortyphus,whichcontinuetoberesponsibleforalarge
number of deaths. Moreover, the crops devoted to human and cattle feeding
RSCGreenChemistryNo.11
GreenTrendsinInsectControl
EditedbyO´ scarLo´pezandJose´ G.Ferna´ndez-Bolan˜os
rRoyalSocietyofChemistry2011
PublishedbytheRoyalSocietyofChemistry,www.rsc.org
v
vi Preface
sufferfromimportantlossesinproductivityeveryseasonbecauseofinsectpests
acting on them.
Thecontrolofsuchpestshasbeenanarduoustaskthatcanbetracedbackto
the establishment of the first known civilizations, with numerous techniques
and approaches being employed over the centuries.
Historically,thefirstattemptstofightnon-beneficialinsectsincludedtheuse
ofnaturalsources,eithermineralsorbotanicalextracts,whichbecamethefirst
availablechemicalsubstancesagainstinsects.Afterthat,anarsenalofsynthetic
derivatives started to be commercially available in what seemed to be a
chemicalpanaceaforcontrollingpests.Itbecameevidentquitesoon,however,
that most of the compounds successfully applied to crops, cattle and even
humans exerted severe effects on the environment.
Many of the original chemicals, both natural and synthetic, were initially
used indiscriminately, and proved to be highly toxic against living organ-
isms, some of them acting indiscriminately on beneficial insects and other
animals. Many other insecticides were found to be highly persistent in the
environment, as a result of their slow environmental degradation and were
bioaccumulated through the trophic chain. Acute toxicological and long-
term effects included teratogenic damage, impairment of the central nervous
system and malfunctioning of numerous biological processes, among others.
Humanity slowly started to be conscious of the necessity of replacing the
classical approaches for insect control with ‘‘greener’’ substitutes, with an
increased selectivity and a reduced toxicity, as a way of minimising environ-
mental impacts. Furthermore, a deeper knowledge of insect physiology has
allowed the discovery of targets to which more selective insecticides can be
aimed (e.g. sodium channel, chloride channel, acetylcholinesterase, nicotinic
acetylcholine receptors, moulting processes, etc.).
The first chapter of this book (S. Manguin et al.) is devoted to a general
introductiontoentomology,withaspecialemphasisonthoseinsectsthatactas
vectorsindiseasescausedbymicrobialpathogens.Thischaptercoversthekey
biologicalaspectsofinsectvectors,suchastheirmorphology,habitats,feeding
andreproduction.Themaininsectsactingasvectorofdiseasescoveredinthis
sectionare:mosquitoes,bitingmidges,flies,fleasandlicewhichareresponsible
for spreading severe diseases such as malaria, typhus, lymphatic filariasis,
dengue, hemorrhagic fevers and certain encephalitis. The methods by which
insects spread infection and the most efficient strategies for fighting against
them are widely covered in Chapter 1. The information presented allows for a
logical understanding of the mode of action of insecticides, for the design of
novel, more efficient compounds.
Thesecondchapter(O´ .Lo´pezetal.)providesahistoricalreviewofclassical
insecticides,asexamplesofnon-greenagrochemicalsthatmustbereplacedand
their use revised. The chapter is divided into two main sections In the first
section, the approaches used for insect control before the development of
synthetic insecticides are covered. The use of non-rational insecticides,
developed from mainly mineral sources (e.g. sulfur, arsenicals, copper and
boron derivatives) and, in most cases, lacking specificity is widely reviewed.
Preface vii
The second part of the chapter is focused on the three main families of
synthetic insecticides that have dominated the agrochemical sector from
the 1940s to today: organochlorine, organophosphorus and carbamate
insecticides. The high efficiency and economic viability of such compounds
allowed an indiscriminate use on crops, households and cattle. Throughout
this chapter, however, it is strongly emphasized that many of these
insecticides are bioaccumulated and can provoke severe toxicological
effects in mammals, fish and beneficial insects, such as bees. The restric-
tions and bans exerted by highly recognized organizations (such as the
US EPA, the European Union Committees and the World Health
Organization) for the reduction and even the elimination of the use of such
insecticides are also discussed.
The rest of this book is devoted to the different approaches for over-
coming the adverse effects exerted by the classical insecticides. In this
context, the third chapter (Schleier and Peterson) focuses on pyrethroids, a
family of insecticides which emerged in the 1970s, inspired by natural
pyrethrins (botanical extracts from the Chrysanthemum genus) but lacking
their intrinsic photolability. Pyrethroids possess a series of features which
have been shown to be greener than the precedent organochlorine,
organophosphorous and carbamate insecticides; although pyrethroids
are lipophilic molecules, they do not undergo biomagnification and exert
no toxic effect on mammals. A critical overview of these compounds is
covered, in which they are compared with the parent pyrethrins and clas-
sical synthetic insecticides, in terms of toxicity, environmental stability and
future expectations.
Also inspired by botanical extracts, the neonicotinoids (Chapter 4, Nauen
andJeschke)arearelativelynewfamilyofinsecticidesdevelopedinthe1990s.
With a surprisingly fast growing market, the development of neonicotinoids
has allowed for the controlofsome of the mostdestructive crop insectpests.
Inthissection,thedifferentneonicotinoidgenerations,theirstrongspecificity
against insect pests and their low mammal toxicity are discussed. The
numerous advantages of this group of agrochemicals are reported, and they
are proposed as being one of the most promising insecticides in the near
future.
Chapters 5 (Dripps et al.) and 6 (Gomez et al.) describe work in which
DowAgrochemicalshasbeeninvolvedoverthelastfewyears.Thefirstofthese
chapters is devoted to spinosyns, macrocyclic lactones resulting from the
metabolism of the soil-dwelling bacteria of the Saccharopolyspora species,
which were discovered in the late 1980s and firstly marketed in the 1990s. The
authors highlight the green character of this kind of insecticide, not only in
terms of the production process (fermentation or semi-synthesis), but also in
terms of its environmental behaviour with regard to bioaccumulation and
selectivity. Spinosad and spinetoram insecticides received the Presidential
Green Chemistry Challenge Award in 1999 and 2008, respectively, and when
spinosad received its crop registration in 1997, it was among one of the first
insecticidestobeconsidered‘‘reduced-risk’’bytheUSEPA.Theauthorsgivea
viii Preface
detaileddescriptionofthemodeofaction,andQSARandbiologicalstudiesin
both targeted and not-targeted species.
An exampleof chemicals aimed atthe moulting process ofinsects,and thus
atinsectgrowthanddevelopment,isthebisacylhydrazines,whicharereviewed
in Chapter 6. The bisacylhydrazines are a non-steroidal family of Insect
Growth Regulators (IGRs), for whose initial development Rohm & Haas was
awarded the US EPA’s Presidential Green Chemistry Challenge Award in
1998.Structuralstudies,thedesignofnewexamples,environmentaleffectsand
formulations are covered in this chapter.
In Chapter 7 (Isman and Paluch) the use of botanical extracts as insec-
ticides is described. Although, when compared to some other families of
agrochemicals, the market of botanical insecticides is much more limited
(approximately 1% of total market sales), compounds such as terpenes
(from essential oils), or azadirachtin (from neem extracts), deserve attention
because of their beneficial biological properties. Plants provide an arsenal of
compounds which exert a variety of different insecticidal modes of action:
from direct toxicity to insects, to inhibitory properties on growth, devel-
opment, reproduction and feeding, as well as repellent activities. The
chances of developing and marketing new botanical insecticides are also
covered.
Besides conventional insecticides (based on the use of natural or synthetic
compounds), the use of living systems (e.g. viruses, bacteria, fungi, insect
predatorsandengineered-plants)ashighlyselectiveinsectcontrolmechanisms
is included in Chapter 8 (Sobero´n et al.). The mode of action, specificity,
environmentalriskassessmentsandapplicationindicationsarewidelycovered
in this chapter, with a particular emphasis on the most widely used bioinsec-
ticides, the endotoxins produced by the bacteria Bacillus thuringiensis. In
order to obtain more efficient insecticides from microbial sources, the use of
genetically-modified organisms is also reviewed.
Finally, the current philosophy in the agrochemical sector of the Integrated
Pest Management programmes (IPM) is introduced in Chapter 9 (Castle and
Prabhaker). IPMs attempt to reduce the use of synthetic pesticides while
keeping pest populations to an acceptable level. The authors claim that a
change in agricultural policies is needed for increasing crop production to the
rate required while competing with predatory pests. They suggest that key
aspectsinpestcontrolwhichareusuallydisregardedincludetheintensification
of crops, the appropriate selection of plant species and the appropriate use of
fertilizers. The main tactics of defence against pests from a green perspective
are also reviewed: the combination of bioengineered crops (e.g. producing
thebacterialendotoxinsdescribedinChapter8);anincreaseoftheplanttypes
in cropping systems; semiochemicals (e.g. repellents, antifeedants, sex pher-
omones, etc., usually in baits); and insect growth regulators. The authors
describe how the development of more ecological crops would help reduce
insect populations and at the same time our dependence on synthetic
insecticides.
Preface ix
Finally, we would like to express our gratitude to Dr. Manguin, Schleier,
Nauen, Dripps, Go´mez, Murray, Sobero´n and Castle, together with their
co-workers, firstly for their valuable contributions and also for their con-
structive discussions and suggestions for this book.
O´ scar Lo´pez and Jose´ G. Ferna´ndez-Bolan˜os
Seville