|Author||H.G. Hewitt and Richard P. Oliver|
Fungicides in Crop Protection
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Fungicides in Crop
Richard P. Oliver
Curtin University, Australia
H. Geoffrey Hewitt
Formerly School of Plant Sciences, University of Reading, UK
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Library of Congress Cataloging-in-Publication Data
Oliver, R. P.
Fungicides in crop protection / by Richard P. Oliver, Curtin University, Australia, and
H. Geoffrey Hewitt, formerly School of Plant Sciences, University of Reading, UK. -- 2nd
Includes bibliographical references and index.
ISBN 978-1-78064-166-9 (hardback : alk. paper) -- ISBN 978-1-78064-167-6 (pbk. : alk.
paper) 1. Fungicides. I. Hewitt, H. G. II. Title.
ISBN-13: 978 1 78064 166 9 (hbk)
978 1 78064 167 6 (pbk)
Commissioning editor: Rachel Cutts
Editorial assistant: Alexandra Lainsbury
Production editors: Lauren Povey and Tracy Head
Typeset by SPi, Pondicherry, India.
Printed and bound by Gutenberg Press Ltd, Tarxien, Malta.
Preface to the First Editionvii
Preface to the Second Editionix
2 Plant Pathology and Plant Pathogens
3 The Fungicides Market
4 Fungicide Discovery
5 Fungicide Performance
6 Fungicide Resistance
7 Strategy and Tactics in the Use of Fungicides
8 Legislation and Regulation
9 The Future Prospects for Fungicides and Fungal Disease Control
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Preface to the First Edition
Fungal diseases of crops limit our ability to produce food safely in sufficient quantity
and of an acceptable quality to satisfy a rapidly expanding and discerning world population. The discovery and development of effective chemical control emerged only in the
mid-19th century and did not become a significant part of crop production until comparatively recently. Current methods of agriculture and horticulture rely heavily upon
the use of fungicides to the extent that some crops cannot be grown in their absence.
All crops are host to a range of fungal pathogens, many of which cause severe
economic damage under suitable conditions. However, fungicide development is
driven not by the occasional or regional fungal problems of crops, but by their global
value to the manufacturing industry. The need to return sufficient profit from a
research investment is becoming more difficult to fulfil under ever increasing legislative
stringency and spiralling costs of product development. More and more, the potential
benefits of fungicides to growers are being challenged as the levels of economic return
to the industry hasten their withdrawal from low-value crops.
This book approaches the subject of fungicide use from an economic standpoint.
Discovery and development are shown to be dependent firstly upon the capacity of
new products to support further research investment, and secondly upon biology.
Much of the text describes the chemistry and biochemical mode of action of a wide
range of fungicides, but the emphasis is predominantly biological and demonstrates
that growers do not purchase clever chemistry but practical performance.
Other important features are described which highlight the continuing diversification of an industry seeking to integrate the opportunities available in the use of natural
products and their derivatives with biological control systems and in the application
of biotechnology to crop protection. Because of the weakening reliance on traditional
fungicide use, the industry is now more correctly called a crop protection business.
Inevitably there have been casualties in the number of companies trading in chemical
control. The drive to continue to fund the discovery and development of new products
urges companies to acquire or form partnerships with others in order to gain market
size and hence to fund research and registration expenditure.
It is from this background of proven benefit, economic constraint, industry change
and new technical opportunity that the text launches a description of fungicide use in
crop protection. Little weight is placed on application technology or on those aspects
of the fungicide industry that are common to herbicides and insecticides, although
comparisons are made between the value of each agrochemical sector.
I gratefully acknowledge the encouragement and guidance given to me by colleagues
from the agrochemicals industry and academia, especially Dr Mike Smith, Research
and Development Manager, Novartis (UK) and Professor Peter Ayres, Department of
Biological Sciences, Lancaster University. It is also appropriate to thank everyone
who, over the last 20 years, has played a key role in showing me that plant science
and its application to crop protection is exciting and worthwhile. In that respect, I
single out Dr Len Copping for his unfailing support and wit.
There were times when I was tempted to abandon the effort and if, in reading the
book, you find it useful in any way, then your thanks must go to my wife and family
for persuading me to do otherwise.
The contribution of Zeneca Agrochemicals in providing the cover illustration of
Azoxystrobin (© ZENECA Limited) is gratefully acknowledged.
H. Geoffrey Hewitt
Preface to the Second Edition
It is 15 years since the first edition of Fungicides in Crop Protection was published. These
15 years have seen very significant changes in the world of crop protection in general
and in fungicides in particular that more than justify the need for an update of this
book. The most significant of these changes is the growth in demand for food crops.
The world’s population has risen from about 6 billion to 7 billion in that period.
Many people eat more meat than before and hence the demand for grain is growing
even faster than the population. In clear contrast to the 1990s, we no longer hear
about food surpluses. There is an undoubted and urgent need to grow more food, on
less land, using less water, fertilizer and other resources and it is clear that fungicides
have a major role to play in this.
Fungicide utilization has grown significantly in the last decades. In 1998, fungicide
use was dominated by Europe and Japan but is now much more widespread. Fungicides
are widely used in Asia, Australia, New Zealand and the Americas. Use is particularly
heavy in regions producing vulnerable crops such as grape vines and bananas.
In some countries, regulations limiting the use of fungicides are becoming ever
more rigorous. This is particularly true of the European Union. As a result, about
50% of the pesticides available in 1990 have now been withdrawn.
While many of the fungicide classes in use in 1998 are still providing good value,
several new classes, especially the quinone outside inhibitor (QoI) and succinate
dehydrogenase inhibitor (SDHI) groups, have been introduced. There is a strong
pipeline of new compounds especially to combat Oomycota and powdery mildews.
The underlying sciences have advanced in important ways. We now have a firm
understanding of the evolution of the major groups of target organisms. Oomycota have
been clearly differentiated from the true Fungi and we no longer talk about Deuteromycota
or the Fungi Imperfecti.
Fifteen years ago, it was widely predicted that many crop cultivars would carry
transgenes conveying disease resistance. While the area grown to genetically modified
(GM) crops has expanded rapidly, these crops generally carry only two GM traits,
herbicide resistance and insect tolerance. The failure to develop and release GM disease resistance traits is partly due to the inherent difficulty of developing useful genes,
but also due to the widespread public antipathy to GM technology. As a result the
regulations are very stringent and so the costs associated with developing GM traits
are very high. It remains to be seen whether the next 15 years will witness the widespread introduction of GM disease resistance.
The major challenges for the fungicide industry in 2014 are interlinked. It is
increasingly more difficult to discover new fungicides and especially new modes of
action and to bring such compounds to market. Resistance to fungicides is now a
major concern. Genomics is now central to the discovery of new fungicides, determining modes of action and in resistance management. This new edition is designed
to introduce this exciting and critical world of fungicide use in crop protection.
I gratefully acknowledge the cooperation of Geoff Hewitt, the author of the first edition. This edition has been prepared with the help of many people in the fungicide
industry who have provided me with insight into the world of fungicides over the last
15 years. These include Andy Leadbeater, Derek Hollomon, Craig White, Craig
Ruchs, Craig Pensini, Jenny Davidson, Doug Wilson, Fran Lopez, Frank van den
Bosch, Gavin Heard, Geoff Robertson, Gerd Stammler, Hans Cools, Ian Dry, Kithsiri
Jayasena, Ken McKee, Kevin Bodnaruk, Lise Nystrup Jørgensen, Michael Csukai,
Naomi Pain, Neil Paveley, Nick Poole, Paul Chatfield, Peter Hobbelen, Rick Horbury,
Scott Paton, Geoff Thomas, John Lucas, Bart Fraaije, Andy Corran, James Brown
and many others. I am grateful to Rothamsted Research for help in selecting images
for the front cover. Thanks also go to Kasia Rybak, Wesley Mair and Fran Lopez for
supplying photographs and tables. Research in the author’s laboratory is funded
mainly by the Australian Grains Research and Development Corporation and the
Grape and Wine Research and Development Corporation.
Richard P. Oliver
Fungicides are agents, of natural or synthetic origin, which act to protect plants
against invasion by fungi and/or to eradicate established fungal infection. With herbicides, insecticides and plant growth regulators, they form the battery of agrochemicals (also known as pesticides) that is available to protect crops and maintain their
yield potential, measured as the quantity or quality of produce. Diseases of crops are
caused by a vast range of organisms that include the true fungi (e.g. Ascomycota and
Basidiomycota), fungal-like but unrelated Oomycota (e.g. Phytophthora and
Pythium), Plasmodiophora, bacteria, viruses and nematodes. The term fungicide is
conventionally taken to mean compounds that control the true fungi, Plasmodiophora
and the Oomycota. It does not include chemicals that control bacteria (these compounds are conventionally called antibiotics), viruses (mainly controlled by insecticides) or nematodes (mainly controlled by genetic and cultural methods).
Since the discovery of the various types of pesticide, several factors have
ensured their continued use and the growth of the pesticide businesses. They
include an increasing world population, higher incomes and direct benefits both to
the grower, such as lower labour costs, higher yields and greater profit, and to the
consumer, such as a higher consistency of food quality, increased variety of produce
and lower prices.
Population Growth and Food Production
For most of recorded history, the global population growth rate has been below
0.2% per annum. However, the early 19th century witnessed the beginning of an
accelerating advance in the control of human disease and in the consistent ability
of growers to produce cheaper, higher quality food and a varied diet, which initiated a reduction in mortality rates. In industrialized countries birth rates remained
high initially, resulting in a rapid increase in population growth. What we know as
the ‘developed’ world passed through that initial phase and has a low growth rate
once again. However, the population of the ‘developing’ world is still expanding
The world population is currently estimated at 7 billion, having increased from
6 billion just 15 years ago (http://esa.un.org/wpp/unpp/panel_population.htm).
There is clearly a need for more food to be produced and delivered to the world’s
population; currently an estimated 25,000 persons die from malnutrition each day
(Skamnioti and Gurr, 2009). Conservative estimates predict a world population of
10 billion by 2060. An increasing proportion of the world’s population is demanding
a diet that is higher in dairy and meat produce. The animals are increasingly fed on
grain. The area of land available to grow all these crops is under threat from urbanization, pollution and climate change. There is a clear and urgent need to produce
© R.P. Oliver and H.G. Hewitt 2014. Fungicides in Crop Protection, 2nd Edition
(R.P. Oliver and H.G. Hewitt)
more food that is nutritious and safe on less land, using less water and fertilizers.
And the evidence is convincing that fungicides have had and will increasingly have
a major role to play.
Historically, the world’s demand for food has been met largely through an
expansion of the area under cropping and by improvements in the food distribution network. The increased food needs of Western Europe in the 19th century, for
example, were supplied by the expansion of production in the Americas and
Australasia. The 20th century introduced a technological revolution into agriculture which has made possible a rapid rate of growth of food production to feed a
historically unprecedented growth of world population. Central to the growth in
food production was the development of artificial fertilizers and high-yielding crop
varieties – the Green Revolution (Evenson and Gollin, 2003). The high yields
increased disease levels. This both increased the need for fungicides and justified
Agriculture makes a significant impact on global warming (Berry et al., 2010).
About a seventh of all greenhouse gas (GHG) emissions can be ascribed to agriculture. These include direct use of fossil fuels for transport and tillage, indirect use
of fossil fuels for nitrogen fertilizer production, and GHG emission due to soil
microbe release of methane and nitrogen oxides. It is therefore possible to quantify
food production not just on a tonne per hectare basis but also on a tonne per GHG
emission basis. Such studies consistently show that the disease control and green
leaf area d
uration promoted by appropriate use of fungicides maximizes both food
production per hectare and per GHG equivalent (Berry et al., 2008). It is therefore
provocatively argued that fungicide-based agriculture is the most
Recent studies of disease losses and fungicide use have been made in Australia
(Murray and Brennan, 2009, 2010). Australia has a generally low rainfall and poor
soils, giving average cereal yields in the range of 1–2 t/ha. These are conditions in
which disease levels would be expected to be low by world standards. It is sobering
that even under these close-to-ideal conditions, pathogens still cause percentage losses
in major, highly researched crops of up to 30% (Table 1.1). Table 1.2 details the absolute actual loss in Australian dollars in comparison to the loss expected if no control
methods (genetics, cultural or fungicide) were applied. The difference between the
potential loss and the actual has been apportioned to each of the major control
methods. It is clear that fungicides have a very significant role in protecting yield. This
varies between disease, crop, variety and season, but overall the annual AUS$250
million expenditure on fungicides in Australia generates a return of AUS$2000 million;
an 8 to 1 ratio.
Table 1.1. Current estimates of losses due to
disease in major crops in Australia. (Modified
from Murray and Brennan, 2009, 2010.)
% yield lost to diseases
Table 1.2. Breakdown of losses to disease and gains to genetic, cultural and chemical
disease control in selected grain crop diseases in Australia; all figures are in AUS$ million.
The ‘potential loss’ is the loss incurred if no control measures were in place; the ‘actual
loss’ is the current estimate. The difference between potential and actual is assigned to
either genetic control, cultural practices or fungicide control. It is clear even in low-input,
sustainable agriculture situations like Australia that fungicides contribute heavily to disease
control. (From Murray and Brennan, 2009, 2010.)
Agricultural Technology and the Impact of Fungicide Use
Crop production is a process governed by a series of limiting factors which interrelate. These are crop variety (i.e. the varying degree of genetic disease resistance),
nutrition, water supply and crop management (pest, weed and disease control, cultivation). Each factor may assume a dominant, yield-limiting role, depending upon the
crop, husbandry practices and the region. For example, water availability is the major
factor governing plant distribution and in crops it is often the determining factor in
yield production. Historically, the combined action of early improvements in irrigation and the introduction of new varieties with higher genetic potential for yield
resulted in dramatic yield increases. Later, the use of fertilizers relieved the limitations
to yield dictated by nutrient deficiency and allowed the inherent yield capacity of the
crop to be realized to a point that was limited by weed populations, insect infestation
and disease. In the 20th century, intensive breeding programmes have further
improved the genetic potential for yield in many crops and their capability to respond
to other inputs such as fertilizers and agrochemicals.
One of the consequences of increased fertilizer use is more frequent and damaging
attacks by fungi, and in intensively grown crops their control is a significant factor in
yield determination. However, to a large extent the development and use of pesticides
have permitted an even greater use of fertilizer and further increases in yield.
Since the 1940s, the search for new fungicides has intensified and the total value
of the crop protection business, as fungicide sales, now stands at US$13 billion, compared with US$6 billion in 1995 (http://www.amisglobal.com/).
The economics of pesticide use vary from crop to crop, between targets and
according to the levels of weed, insect or disease infestation. Recent studies in
Australia document the gain of AUS$8 for every AUS$1 spent on fungicides (Murray
and Brennan, 2009, 2010). This figure is driven by the sharp reductions in the cost
to farmers for some fungicides in the last 10–15 years. The cost of off-patent fungicides has fallen to less than AUS$5/ha and so disease gains need only be small to
justify the costs. The value gained from the use of small amounts of fungicide to
control seed-borne diseases is very large. More modest but still significant gains are
obtained when controlling foliar diseases. The use of cereal fungicides in Western
Europe probably accounts for an extra 2–3 million t of grain annually, equal to
US$400–600 million. In some cases the benefit gained through fungicide use is more
critical to the extent that certain crops cannot be cultivated in the absence of disease
control. By the late 1800s coffee rust epidemics were a serious and frequent problem
in India, Sri Lanka and Africa. Eventually, production levels became uneconomic
and stimulated a change in cropping from coffee to tea. The recovery of the coffee
industry was, and remains, totally dependent on the use of fungicides.
The impact of fungicide use on wheat in the UK is illustrated in Fig. 1.1. The
average yield of wheat in the UK increased from about 4 to 8 t/ha from 1960 to 2004.
During this period, first methyl benzimidazole carbamate (MBC), then demethylation
inhibitor (DMI) and finally quinone outside inhibitor (QoI) fungicides were introduced.
Each introduction coincided with a further increase in yield.
The History of Fungicide Use
The devastating social effects of plant disease are a common feature of history,
extending into Biblical times and beyond with references to ‘blasting and mildew’ in
the books of Deuteronomy and Amos (Large, 1940/2003). Wheat rusts were known
% of crops sprayed
Fig. 1.1. Average wheat yields in the UK, 1960 to 2004 (
; original data
source: Cereal Production Surveys, Defra), introduction of the main fungicide groups
(arrowed; MBCs, methyl benzimidazole carbamates; DMIs, demethylation inhibitors;
QoIs, quinone outside inhibitors) and percentage of crops sprayed with fungicides ( ▲ ;
original data source: Polley and Thomas, 1991; Crop Monitor, Defra/CSL). (From Lucas,
2006 with permission from HGCA.)
at least from Roman times and were considered so important that their occurrence
was attributed to divine action. Regular festivals to appease the gods Robigus and
Robigo were held in the hope that cereal rust disease could be prevented. However,
the gods were clearly not to be trusted and some rudimentary chemical disease control was also practised, the therapeutic but mysterious nature of sulfur being passed
down from the ancient Greeks.
Other than crop failure, fungal disease can have a dramatic and direct effect upon
human welfare. In 943, a European chronicler described the ‘wailing and writhing’
of men in the street suffering from a disease which came to be known as ‘St Anthony’s
fire’, named after the behaviour of people who, in hope of a cure, visited the shrine
of St Anthony in France. The cause is now known to be rye grain contaminated with
the alkaloids present in the ergot fungus Claviceps purpurea.
By 1750, cereal diseases had attained such a significant economic status in Europe
that the French Academy of Arts and Sciences volunteered a prize for the best treatise
describing the cause and control of wheat bunt. The solution was not forthcoming and
10 years later up to half of the French wheat crop failed because of bunt and smut
(Ustilago nuda) diseases. Mathieu Tillet eventually characterized the causal organism
of bunt, which carries his name, Tilletia tritici, and went on to describe the life cycle
of the fungus. Of equal importance was the work, based on a series of field experiments, which examined the efficacy of various treatments against T. tritici. It was
demonstrated that crops treated with various materials mixed with lime or putrefied
urine could be maintained relatively free from bunt disease and these treatments came
to be of major economic importance in France.
The catalogue of incidents of fungal disease during the 19th century is extensive (Table 1.3).
However, the social impact of plant disease was at its greatest where potatoes were the
staple diet. In those regions threats of famine were common and in Eastern Europe and
Ireland reached dramatic reality. In Ireland alone, in the 15 years from 1845, over 1 million
people died and 1.5 million were forced to emigrate as a direct result, mainly to the USA.
Table 1.3. Major outbreaks of fungal disease in the 19th century.
Claviceps purpurea (ergot)
Sphaerotheca humuli (powdery mildew)
Phytophthora infestans (late blight)
Uncinula necator (powdery mildew)
U. necator (powdery mildew)
U. necator (powdery mildew)
Plasmopara viticola (downy mildew)
Hemileia vastatrix (coffee rust)
Guignardia bidwellii (black rot)
Puccinia spp. (rust)
Puccinia spp. (rust)
Puccinia spp. (rust)
Puccinia spp. (rust)
South Africa, India
Commercially, plant disease was a critical factor in the survival of some industries. The vine industry, for example, was under continual attack; first from grape
powdery mildew (UNCNEC – see Chapter 2 for pathogen abbreviations), initially
observed in England in 1845, and then followed in the late 1860s by grape downy
mildew (PLASVIT). Out of necessity, this period also witnessed the beginnings of
modern fungicide use. Observations by the gardener who first reported UNCNEC
in England suggested that applications of sulfur could be used to control the disease. Although his findings were confirmed by Professor Duchartre of the Institut
Agronomique, Versailles, the challenge to produce a product that could be applied
easily to an extensive area of vineyards was not successful until 1855, when
Bequerel produced a fine form of sulfur that could be used to achieve effective plant
Similar advances were made in 1885 with Millardet’s invention of Bordeaux
mixture, copper sulfate and lime, for the control of PLASVIT, later shown to be
effective against late blight in potatoes (PHYTIN). Several versions of the treatment
were explored but the mixture is still in use today for the control of fungal diseases on
a wide range of crops.
The technology developed in France in response to the frequency and severity of
crop disease, especially in vines, became the stimulus for other international investigations. This led, in 1886, to a large programme of trials in the USA to evaluate all
the leading French fungicides against black rot, Guignardia bidwellii, on vines; apple
scab, VENTIN; gooseberry mildew, Sphaerotheca fuliginea; and several vegetable
pathogens. This collaboration between the US Department of Agriculture (USDA)
and French experts was one of the first to examine the relationship of dose–response,
cost of spray per hectare, optimum timing and phytotoxicity.
However, the problem of cereal rust disease that had persisted throughout this
period of fungicide development evaded similar attempts at control. Farmers
resorted to the use of resistant varieties and altered crop management practices to
combat the disease. Little success was achieved and by the turn of the 19th century,
world wheat production could be severely limited by rust infection, a situation destined to remain until the advent of systemic fungicides in the mid-1960s. Other
crops also suffered from rust diseases. In 1869, coffee rust was reported in what
became Sri Lanka, and in 10 years reduced average yields by over 50% to 251 kg/ha.
The effective destruction of the coffee industry led to investment in a replacement
crop, tea. Henceforth, the cultivation of coffee in India and Sri Lanka was totally
dependent on the use of fungicides to control rust disease. An excellent and lively
introduction to the social history of plant pathology can be found in Money (2006).
The use of complex organic chemistry began with the introduction of new seed
treatments designed for the control of wheat bunt. Studies in the pharmaceutical
industry which developed medicinal compounds made from arsenic and various dyestuff intermediates stimulated similar research by German plant pathologists, and
resulted in the synthesis of several phenolic fungicides containing metallic elements
such as mercury, copper and tin. The discovery by the Bayer Company of a compound containing mercury and chlorinated phenol, active against wheat bunt,
prompted the intensive development of organomercury seed treatments; the first,
Uspulam, being introduced in 1915 by Bayer, followed by Ceresan from ICI (1929)
and Agrosan G, also from ICI (1933). The efficacy of these products ensured their
widespread popularity in the farming community and they led the cereal seed-treatment
market until mercury-based products were banned in the 1970s and 1980s on the
grounds of adverse toxicology.
The establishment of the commercial organizations that would become the major
companies in the agrochemicals industry began in the late 1850s, but significant development did not occur until the late 1940s. During the First World War (1914–1918)
in Europe agriculture had responded to the need for self-sufficiency, but after the crisis
the incentives were reduced and agriculture retreated into its former uncertainty
fuelled by poor wages and fluctuating prices. It was not until after the Second World
War (1939–1945) that the potential of fungicide use in crop protection and the maintenance of yield were realized, and it is generally accepted that this marks the real
beginning of crop fungicide technology.
The early fungicides business was founded on the control of crop diseases that
previously had been unchecked and competition between companies was relatively
light. Most of the products that were introduced were in response to clear needs of
growers and they created new markets by exploiting latent demand. Later products
improved on existing control and were established at the expense of their lesser competitors. This is particularly true of the introduction of fungicides that were able to
move within plants and throughout crops, the so-called systemic or mobile materials,
which captured a significant part of the market previously held by surface-bound
non-systemic (immobile) products such as sulfur and copper-based materials.
Fungi infect plants through wounds or directly via stomata or penetration of the
surface layers. In leaves this barrier is further enhanced by the presence of a sometimes
thick and waxy cuticle. Before the development of systemics in the late 1960s, all fungicide compounds were non-systemic protectants, effecting disease control only
through their activity on the plant surface. Characteristically, after application to
foliage these compounds control disease either by killing superficial mycelium, as for
example in the powdery mildews that penetrate only the topmost cellular layer, or
more commonly by preventing the germination of fungal spores already present on the
leaf or impacting on the leaf after application. Non-systemics cannot penetrate the leaf
and hence cannot control pathogens already established within the plant tissue.
Therefore foliage must be treated before the pathogen has colonized the plant.
Subsequent development of the plant exposes new tissues to fungal attack and may
rupture protective fungicide deposits. Hence, such products have to be applied frequently during the growing season to maintain acceptable disease control levels.
Although the lack of mobility of early fungicides limited their flexibility of use, their
inability to penetrate plant tissue allowed them to exploit the control spectrum
inherent in their non-specific biochemical mode of action (MOA). This remains a valuable feature in their current uses against minor pathogens and in strategies to control
resistance to systemic fungicides.
The introduction of systemic compounds caused a revolution in farmer practice
and in fungicide discovery and development. New opportunities for fungicides were
immediately identified, as in intensive cereal production in Western Europe. Fungal
diseases of wheat and barley had been a disturbing feature of cereal production for
at least 2000 years but the use of resistant varieties, stimulated in part by the failure
of early products to control pathogens such as mildew and rust, enabled infection to
remain at what was considered to be an acceptable level. The associated yield losses
were estimated to be insignificant until systemic fungicides were discovered and
tested, beginning with ethirimol and tridemorph.
Field trials demonstrated that the yield benefits that could be achieved using the
new fungicides were on average about 10%. Yields increased further as the limits of
varietal potential were explored using combinations of higher fertilizer inputs and fungicides. European Community legislation encouraged high-output production systems,
and inputs such as the use of high levels of fertilizers and pest control chemicals
increased to maximize yields. The rate of discovery of new and more effective fungicides also increased and in 20 years the range of foliar and ear diseases for which some
control could be claimed had expanded from a few seed-borne pathogens and mildews
to include PUCCRT, LEPTNO, SEPTRI, Fusarium, Pyrenophora, Pseudocercosporella,
Cochliobolus and Rhynchosporium.
The new products afforded better levels and duration of control and allowed the
grower more flexibility in application. However, even they failed to provide complete
disease control, and the search for more effective materials and technology continues.
The appearance of systemic fungicides and the increasing variety of products
available to the grower corresponded with the requirement of the fungicides industry
to adopt new and higher standards of performance. The most important was, and
remains, safety to the manufacturer, the user, the consumer of treated crops and all
aspects of the environment. The industry and government registration authorities
became responsible for the development of only those materials proven to be safe and
environmentally acceptable. In addition, in order to compete successfully, product
attributes other than biological activity assumed major roles (Table 1.4).
The number of products and mixtures grew to meet the new market standards of
disease control. In the triazole family alone there are on average about ten products
(different formulations of solo active ingredients and mixtures) per compound. Many
fungicides appear to increase yield beyond that attributable to the reduction of disease. Late-season treatment with benomyl, an early systemic fungicide, was shown to
delay senescence and increase yield by up to 10% through a combination of fungicidal action and plant growth regulator effects. Similar activity is reported for QoI
Table 1.4. General targets for new fungicidal products.
Type of product improvement
Safe to users
Safe to consumers of the treated product
Broader disease-control spectrum
Extended control period
Improved crop safety
Compatibility with other products
Lower cost per treatment through the use of:
lower use rates
fewer treatments per season
lower application costs
and succinate dehydrogenase inhibitor (SDHI) fungicides and is associated with the
control of phylloplane organisms and, more likely, a direct effect on the maintenance
of photosynthetic ability.
Devastating crop diseases and their social impact can now be avoided by the
careful use of fungicides. Yet, as in any living system, the threat posed by fungal disease is dynamic and we cannot afford to be complacent. If any one crop can be identified as having stimulated the growth of the fungicide business and been the subject
of intensive fungicide use, then it must grapevine. But it appears that even in vines
new problems can emerge. In 1977, Eutypa armeniacae was identified in France and
by 1996 an estimated 50% of all vines in the Cognac region were infected, causing a
total loss of about 10%. Once again, the official advice is to destroy affected vines
while waiting for new fungicidal treatments to be developed or for the arrival of genetically engineered resistant varieties.
There is little doubt that the intensive agricultural systems that are needed to
provide the growing population with food also encourage fungal disease epidemics,
and the removal of fungicides from agriculture does not appear to be a realistic
option. The emergence of fungicide resistance and the need for more cost-effective
products encourage the search for better remedies, whether they be synthetic products
or materials derived from natural sources or through the introduction of genetic
modification of target crops.
The Growth of the Agrochemicals Industry
Pesticides, synonymous with agrochemicals or crop protection agents, comprise
mainly herbicides, insecticides, fungicides and plant growth regulators. Further definition can be confusing. A pesticide is strictly an agent that kills a pest and it can be
either synthetic or natural. However, the definition omits plant growth regulators,
which are designed to enhance the growth and development of crops directly. In addition, the term pesticide is often applied only to insecticides. Pesticides are better
classified as agents that maintain the yield potential of crops under adverse growing
conditions, most commonly caused by the presence of weeds, fungi or insects. In other
words, pesticides combat biotic stresses.
Agrochemicals companies developed as a diversification of those chemical industries specializing in the manufacture of organic dyestuffs. Originally including the
fertilizer industry, the agrochemicals business is now distinct and comprises a large,
high-value, high-technology industry that survives upon innovation and the discovery
and development of synthetic and natural pesticidal products. Despite the success of
the pesticides business, the industry is shrinking. The conflicting forces of price competition, affecting margins and profitability, and the increasing costs of discovery and
development of potential products and the maintenance of established pesticides have
resulted in a phase of consolidation. The situation was made more acute through the
increased political and social recognition of the environmental issues associated with
pesticide use and the subsequent demand for more extensive product examination.
This led to spiralling increases in the costs of safety testing, the prolongation of development time and a subsequent reduction in effective patent life. A shorter product
lifespan and the need to generate a return on a rapidly increasing research and development investment have stimulated the search for economies of scale such that the
Author H.G. Hewitt and Richard P. Oliver Isbn 1780641664 File size 4MB Year 2014 Pages 192 Language English File format PDF Category Biology Book Description: FacebookTwitterGoogle+TumblrDiggMySpaceShare Plant pathogenic fungi cause devastating damage to crop production worldwide. The growing global population necessitates reduced crop losses to improve food security, and the control of fungal plant pathogens is vital to help maintain food production. Providing a concise and balanced review of fungicides used in crop protection, this book describes the science of fungicide use, selection and resistance within the context of farming situations. Major updates and additions reflecting the emergence of two new classes of fungicides (strobilurins and SDHI) and the increased incidence of fungicide resistance are included in this new edition, which also discusses legislative requirements to reduce fungicide applications, and current trends in fungicide use. Download (4MB) Plant Breeding Reviews, Volume 40 Silicon in Plants: Advances and Future Prospects Growth And Mineral Nutrition Of Field Crops, Third Edition World Economic Plants: A Standard Reference, Second Edition Nitrogen Management in Crop Production Load more posts