1
Entomology and the World Food Situation
By M. J. WAy2
Imperial College, University of London, England
I start from the premise that adequate nourishment is
an essential prerequisite for self control of reproduction
and hence that any humane solution of the world's
population problems depends fundamentally on greatly
accelerated food production. This is the philosophy of
the United Nations Food and Agriculture Organisation
and of the International Institute such as IRRI (rice),
CYMMYT
(wheat and corn), ICRISAT
(sorghum
and other dry tropics food crops) and !ITA (humid
tropics food crops), a1\ of which are dedicated to the
improvement of food production in less developed countries where food supply is inadequate or critically low.
tion was due solely to increased yield per unit area of
land, and the cropped area even declined.
Using rice as an example, Fig. 2 shows the striking
discrepancies between yields in developed and less developed countries, mostly due to comparative stagnation
in food production technology, including pest control, in
the latter. An encouraging feature, however, is that
despite relatively poor yields, food production has so far
kept ahead of the population increase of 2*% per annum
in less developed countries and, for the future, the opportunity still remains for striking yield increases per
unit area from a low base-line, in contrast to what is
now possible in developed countries, where crop yields
are seemingly coming relatively close to their potentials.
For example, if the Indian rice yield per unit are of
land was increased progressively to reach the present
Japanese yield in 26 yr time, the yield increment during
the intervening period in India alone would satisfy the
increased needs of all developing countries in South-East
Asia, based on the present 2*% population increase per
annum. Put another way, the land devoted to rice in
India, yielding at the present Japanese level, would
satisfy current rice needs for about twice the present
human population of all South-East Asia. The dilemma,
of course, lies in how to realize some of this tremendous
potential. Pests in general are one of the several constraints to be overcome.
Emphasis on the predominant need to increase food
production in less developed countries should not detract
from the continuing importance of some developed countries as world food suppliers. The USA, in particular,
is the only country which, at present, can provide the
food surpluses that are vitally needed to buffer periodic
crop failures in some drought-prone countries. However,
for less developed countries, where up to 70% of the
population may be in farming families, it is now widely
recognized that the only durable solution is to increase
local farm output and farm income, and so provide more
food in a way which simultaneously
invigorates the
economy and life-style of the rural communities (Bunting 1970, 1974). I therefore propose to focus attention
mostly on basic food crops in the less developed countries.
First, I will remind you of the contrasting nature of
crop production in developed and less developed countries
which influences the role of pests and the kinds of pest
control practices that are feasible and desirable in developing countries. Secondly, I will refer briefly to estimates of world-wide losses by pests. I wi1\ then use
one major food crop, rice, to exemplify present-day developments towards increasing crop yields through pest
control. This wi1\ lead on to some special problems and
possibilities for pest control in small farmer less developed country conditions. Finally, I will mention the
Sudan, one of several less developed countries where
vast areas of good agricultural land remain unexploited,
where pests, notably insects, are a key problem in future
exploitation of such areas and where there are radical
and cha1\enging possibilities for pest control.
Estimates of Crop Losses Caused by Pests
Estimates of worldwide losses are given by Cramer
(1967), and while these can be criticised as being outof-date guesses, they are the best we have (Table 1).
It is noteworthy that even for developed countries,
Cramer's figures and also recent USDA data for certain
States in the USA (Anon. 1974b) indicate large losses
from insects in spite of pest control measures. The 1973
USDA estimate of 17.5% crop losses by insects to corn
in certain States of the USA is remarkably high. This
is perhaps salutory evidence of possibly large uncontro1\able losses from insects even in sophisticated conditions. USDA data for 1973 (Anon. 1974b) also indicate
that the cost of the chemical controls used against insect
pests of corn was greater than the cost of the uncontrolled and uncontrollable losses caused by insects. So
insects alone seemingly caused an overa1\ loss in farmer
profit of about 30% which would have been even greater
had insecticides not been used. This touches on a critically important constraint to pest control in less developed
countries, namely, a capital-scarce sma1\ farmer's very
limited ability to risk or justify the cost of insecticides
on his relatively very poorly priced food crop.
Fig. 1 gives estimated annual world agricultural production from 1956-73 in developed and less developed
countries based on an average production of 100 for the
5-yr period 1961-<15 (Poleman 1975). The rates of increase in total production are similar for developed and
less developed countries, but, calculated on a basis of
production per person, food production rose by an average of about 30% in developed countries but only just
kept ahead in less developed countries. Furthermore, in
less developed countries an increase in area cultivated
accounted for more than half of the increased production, whereas in developed countries, increased produc1Text of an invited address given at the Annual Meeting of
the Pacific Branch of the Entomological Society of America at
Portland, Oregon, June 24th, 1975.
• Currently Visiting Professor, Department of Entomological
Sciences, University of California, Berkeley.
Another disturbing prospect for less developed countries is their tropical environment where, in equivalent
agronomic conditions, insects are likely to cause more
damage than in temperate countries. Data in Table 2
no doubt partly reflect poorer insect control but it is
a disturbing feature that this loss is occurring in conditions of low crop fertility where most pests would be
expected to be less damaging than in more intensive
125
130
DEVELOPED
DEVELOPING
COUNTRIES
COUNTRIES
120
........
.
....
• •• •••.PER
.
110
PERSON
PER
....
.......
..
.......
..... ........
100
...
PERSON
........
...) ..
-..
.....
90
80
1960
1965
FIG. I.-World
1970
agricultural
cropping systems which the less developed countries must
now have as their objective.
Pests of Rice
Some of these problems and their possible solutions are
exemplified by rice in Asia. This crop, together with
other cereals, notably wheat and corn, supplies about
% of human food calorie needs and substantial protein
(Anon. 1974c). In Asia almost
of the world's human
population depends on rice for about 80% of its food.
India and Bangladesh are outstandingly important because, excluding China, they cultivate more than :If.! of
the land devoted to rice in Asia. Moreover, nearly %
of the malnourished people of the world are in India
and Bangladesh (Anon. 1974c, Poleman 1975) where
8 yr ago it was estimated that more of the rice yield
is lost from pests than is left for the human population-
*
1000' s kg/ha
•..
1960
1965
production for 1959-73. Based on years 1961-65
N
JAPA.'J
U~ITED STATES Of AMERICA
57%, including 36% by insects (Cramer 1967). Recent
'maximum protection' experiments in India have borne
out these estimates by showing an average increase of
35% from insect control. Perhaps the most careful recent studies on losses in small farmer conditions have
been made by IRRI in the Philippines. Their surveys
in the early 1970s (Anon. 1974c) indicated that pests,
especially insects and their transmitted diseases, are the
main limitation to increased rice production.
For example, it was concluded that, according to season, there
was a 1~24% greater loss from pests in farmers' fields,
where some pest control is practiced, than when IRRI
recommendations
are correctly followed-which
would
still not fully protect the crop. It is therefore not unreasonable to conclude that, in the Philippines, insects
were seemingly causing at least 20-30% crop .\oss of
rice in the early 1970s. By this time the early weaknesses
of the so-called Green Revolution were being severely
criticised (Anon. 1974f). Epidemics of insect pests and
of transmitted diseases occurred because uniform plantings of new and potentially high yielding Green Revolution rice varieties, such as IR8, were intrinsically more
pest- and disease-susceptible
than traditional varieties,
and they were also made more susceptible by other
agronomic changes that formed part of the Green Revolution 'package of technology' (Pradhan 1971, Smith 1972).
Table I.-Estimates
of World Losses of Major
stuffs Caused by Pests (Cramer 1967).
MALAYSIA
%
INDIA
Insects
Cereals
Major tuber/root crops
vegetables
Oil-protein crops
BA~GLADESH
+
FIG. 2.-Rice
1970
= 100.
Yields, annual averages for 1971-73.
126
Food-
losses caused by :
Diseases
Weeds
Total
15
9
11
35
10
12
15
)0
8
11
33
33
Table 2.-Estimated
from Pests (Cramer
Regional Percentage
1967).
Region
Crop Losses
Insects
Diseases
Weeds
Total
5
9
10
13
21
13
11
15
13
11
7
8
8
16
11
25
28
33
42
43
Europe
N. & Central America
S. America
Africa
Asia
However, the plant breeders were undoubtedly correct in
first seeking basically high-yielding attributes to which
other attributes can later be added according to the different constraints and needs of particular countries or
cropping conditions (Jennings 1974). This is precisely
what is now being done, with the high-yielding but
otherwise unsuitable IR8 proving an invaluable parent
(Anon. 1975a).
Table 3 shows how resistance to hopper pests and
their transmitted viruses, which severely damaged early
rice varieties in the Philippines, has been successfully
incorporated in the three high-yielding varieties IR28,
29, 30 released in 1974 which also, unlike IR8, have good
eating qualities. Furthermore, they are quick maturing
and, for the 1st time, satisfy Filipino multiple cropping
requirements-a
major advance because, hitherto, the
official recommendations were for insecticide-dependent
non-resistant varieties in preference to the slower growing varieties that were relatively pest-resistant.
This is
a promising beginning for the Philippines, but not necessarily elsewhere. For example, strains of rice resistant
to brown plant hopper in the Philippines remain susceptible to the same species in India. It is perhaps encouraging that many genes for resistance to insects and their
transmitted viruses seem to exist in rice (e.g., Shastry
et at. 1972). Plant breeders should therefore be able to
construct varieties appropriate to different countries' pest
problems as well as introduce other relevant modifications, for example, to produce varieties that are not
heavily dependent on energy demanding, expensive artificial fertilizers.
The currently expanding development
of breeding programmes within different Asian countries
will, no doubt, greatly facilitate the production of such
rices.
Enthusiasm for host plant resistance as a means of
preventing insect damage to rice must unfortunately be
tempered by heavy doses of caution. The apparently
Table 3.-Resistance
rather specific host plant resistance mechanisms, potentially very susceptible to resistance-breaking
biotypes of
the pest, point to the fallacy of undue reliance on one
method· of control. It also seems unlikely that the most
consistently severe pests of rice, various species of
lepidopterous stem borer, will be adequately controlled
by host plant resistance. It is now recognized that the
future of control of insect pests of rice in less developed
countries depends on appropriate combinations of host
plant resistance, cultural controls, maintenance of important natural enemy action and essential use of insecticides. Nowhere, however, is there an adequate concentration of either research or development effort on
such integrated control practices. The urgent need for
integrated control practices that are appropriate to less
developed countries has long been protagonised
and
recognized by authorities (e.g., Smith, 1972, 1973) and
by organizations such as FAa, whose Panel of Experts
on Integrated Control has recently detailed a framework
for a global programme of research and development of
integrated pest control on major crops, amongst which
rice is highlighted.
Insect Pest Problems in Small Farmer
Cropping Systems
The small scale, labor intensive, capital scarce agriculture characteristic
of less developed countries contrasts strikingly with the large scale, labor scarce,
capital intensive agriculture in most developed countries.
This creates opportunities, particularly for cultural controls, that are impossible in developed country agriculture. In other respects, however, opportunities are restricted, for example by the cost of chemical insecticides
which severely limits their use particularly
on basic
food crops for which the farmer gets a poor price
compared with his developed country counterpart.
In the developing countries about a thousand million
people are in peasant farmer families. FAa
(Anon.
1970) calculates that this agricultural community will
have increased by at least 400 million by the year 1985.
Bunting (1972) also quotes a probable 175 million
agriculturally based people in West Africa by the year
2000 compared with only 105 million in 1972, and he
points to a continued increase of this order for another
SO years. The emphasis must therefore be on improved
small scale, labor intensive farming rather than on
dramatic changes towards labor saving developed-country technology. Strategies of pest control for small scale
peasant farmers therefore demand priority attention by
research workers
(Way 1973). At present we are
abysmally ignorant of essential details of causes of pest
incidence and of possible controls in such conditions,
Ratings of IRRI Rice Varieties
(Anon. 1975a).
Insect-transmitted
viruses
Insects
Year of
'release'
Variety
Green
leaf
hopper
1966
IR8
R
S
S
S
S
R
R
R
R
R
R
MR
MR
MR
R
R
R
R
R
R
1974
{ IR28
IR29
IR30
R
= Resistant
Brown
plant
hopper
MR
Stem
borer
+ Mod. resistant
127
Grassy
stunt
Tungro
S
=
Susceptible
Other diseases
Blast
Bacterial
blight
MR
R
R
S
R
R
R
S
which involve systems of multiple cropping (Anon.
1971) and also complex forms of strip and mixed cropping that are uniquely different from developed country
conditions.
A major cause of ignorance is that experts from the
Western World have only recently accepted these farming systems as respectable, partly through evidence of
their success in China (Anon. 1975b) and partly as a
result of pioneer studies in Nigeria (Norman
1972,
1973) and at IRRI and IIT A. In present conditions
such methods, developed empirically by African farmers,
often give higher and more dependable returns than
monoculture cropping partly because they involve important elements of insect pest control. For example, in
Northern Nigeria the invaluable protein legume crop,
cowpeas, grown as a monoculture, may suffer more than
900/0 crop loss unless protected from flower and fruit
feeding insect pests by insecticides (Becker 1965, Raheja
1974), whereas, in mixed cropping systems, unprotected
cowpeas produce acceptable yields. Until the mechanisms which decrease pest damage in mixed or inter-
important in these circumstances, in contrast to the traditional system whereby the borers survive in stalks that
are stacked or left standing. What effect these new
monoculture practices will have, or are having, on other
pests is still undetermined.
The borers are among a complex of insect pests that
cause severe losses to corn, sorghum and millet in
virtually all developing countries-for
example, an estimated 38% loss of corn in Kenya (Walker 1967). They
are a major problem in The Sahel where the latest
severe drought-induced famine occurred, and ironically
the drought seems to have subsequently exacerbated stalk
borer and grasshopper damage (Smith & Schlegel 1975).
While rainfall is periodically a crisis factor throughout
much of the dry tropics, insects and other pests undoubtedly cause consistently much larger losses and are
also a major limiting factor in the savannah areas of
the Sudan, where rainfall is more dependable than in
The Sahel. The Sudan is one of the few countries in
the world where there are large areas of good unexploited agricultural land, probably about 100 million
cropped systems are elucidated, it will not be possible
hectares (Anon. 1973). Its agricultural potential can be
to manipulate the agro-ecosystem to improve pest control or to translate the useful components of such systems into more productive forms of cropping.
The
current need for such work in the tropics provides a
reminder of pioneer work in Tennessee by Marcovitch
(1935) with 'tropical' crops such as corn, okra and
legumes strip cropped to control insect pests, and of more
recent studies on strip cropping of alfalfa in cotton in
California (Stern 1969) which has, however, proved
unacceptably complex for the Californian farmer but
would be the epitome of simplicity for the Nigerian.
gauged by comparison with the USA where nearly half
of the world's corn crop is grown on less than 25
million hectares.
In many countries the improvement of small farmer
cropping systems may be more hampered by pests indirectly acting on man and domestic animals than by
those which directly attack the crop. For example, in
much of Africa, insect transmitted diseases deprive the
farmer of so-called intermediate technology in the form
of draught animals. Unlike his Far East counterpart,
he cannot use bullocks or other animals for ploughing
or cultivating because they are debilitated by trypanosomiasis transmitted by the tse-tse fly. This means a
huge jump from hand cultivation to mechanisation which
is becoming increasingly more expensive and probably
also less feasible as a long-term solution.
Insect Pests in Tropical Dry-land
Cereal Monocultures
The savannah region of the Sudan seems well suited
for large scale cereal cropping and parts are already
being used for mechanised monoculture sorghum production. Apart from general organisational :~nd transport
problems, the main problem at present seems to be damage by pests, notably insects (Way & Gonzalez 1974).
These comprise a complex of at least 5 kinds of insects
which must all breed initially on wild sorghum and
other grasses before moving onto the sorghum. Some,
such as the sorghum bug, only attack sorghum as adults.
The situation is reminiscent of the early exploitation of
the United States prairies, where pests such as the
Rocky Mountain locust, breeding on wild grasses, caused
severe damage to arable crops, until cereal crops or
changed grazing systems largely replaced the unexploited
grasses in the breeding areas (Uvarov
1928). The
Sudanese problem may eventually be resolved in the
same way, or by replacing the grass fallows by non-host
crops. The solution will depend on much greater understanding of how to use chemicals in an integrated control
system, but, no relevant research is now being done
despite the importance of the region as a food source
for Africa, particularly for the adjoining drought-prone
Sahel and over-populated land-scarce Egypt.
While the bulk of food grown in less developed
countries must continue to come from improved small
farmer, diverse cropping systems, a strong case can be
made for more radical approaches to production of basic
cereal foodstuffs by methods analogous to those that
have proved so successful for wheat and corn in developed
countries. Many mechanised schemes are being introduced throughout
the tropics-frequently
without an
adequate knowledge and appreciation of economic and
agronomic problems, including pest control. A seemingly
more rational approach is exemplified by schemes such
as those in Southern Nigeria for the community production of monoculture corn and other food crops. The
key to apparent success is minimum tillage plus use of
corn crop residues as surface mulch. Besides maintaining fertility, the surface mulching causes high mortality
of a major pest, corn borers, which spend the dry season
in the old stalks. Consequently, corn borers seem un-
Summary
To sum up, there is no excuse for peSSImism in the
struggle to increase food production in developing countries. Yields can be greatly increased even in countries
like India and Bangladesh which are already exploiting
virtually all the land that can be cultivated. Furthermore, countries such as the Sudan have large areas of
exploitable virgin land. Yet, some of us have been
disillusioned by the prophets of doom and most remain
dissatisfied by setbacks and by apparent slow progress,
for example of the Green Revolution.
But, we have
recently been reminded by a USDA Report (Anon.
1974g) that the USA took more than 20 yr to accept
hybrid corn technology, whereas India adopted Green
Revolution wheat in less than half the time. Without
doubt, many people in developed countries have suffered
from the illusion that there were quick, cheap solutions-
128
cheap, anyway, to judge from the meagre support for
international research and development work on insect
pest control in less developed countries.
A humane
solution will be neither quick nor cheap. Developed
country biologists with experience in pest control can
make a major contribution by giving greater support to
national and international organizations involved in this
work. Their expertise is needed, not just as ephemeral
purveyors of advice but, now, much more importantly,
as on-the-spot collaborators,
staying long enough to
make a real contribution to the programmes of research
and extension on integrated pest control that are so
urgently needed. The emphasis must be on close collaboration, blending the special skills of the visiting
worker with the wisdom and experience of local scientists.
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129