22 The Global Food System
started subsidizing pesticides and in 1977 over 1 million tonnes of rice were lost,
enough to feed some 2.5 million people (Kenmore, 1991). In 1979, 750,000ha
were infested, followed by lower, but not insignificant, levels of infestation of
between 20–150,000ha per year during the 1980s. During this period, BPH was
only really checked with the release of rice varieties containing genes that confer
resistance, though even some of these have been attacked by new biotypes of the
pest (Khush, 1990).
Studies in the Philippines and Indonesia have clearly shown that outbreaks
occurred after increases in insecticide use (Kenmore et al, 1984; Winarto, 1993).
BPH is kept under complete biological control in intensified rice fields that are not
treated by insecticides. Even with over 1000 reproducing adults per square metre,
the natural enemies exert such massive mortality that rice yields are unaffected. As
Peter Kenmore (1991) describes ‘insecticide applications disrupt that natural con-
trol, survival increases by more than ten times, and compound interest expansion
then leads to hundreds of times higher densities within the duration of one rice
crop. Trying to control such a population outbreak with insecticides is like pouring
kerosene on a house fire.’ Other countries in South-East Asia still, however, suffer
significant losses to BPH. In central Thailand, some 250,000ha were infested in
1990, the worst year on record.
Pesticides and Human Health Impacts
Mortality and morbidity from pesticides
There is no doubt that pesticides are hazardous. At very high dosages many are
lethal both to laboratory animals and people, and can cause severe illness at suble-
thal levels. But just how serious is the hazard from medium to low dosages is open
to question (Conway and Pretty, 1991; IARC, 1991). In the 1950s, 1960s and
1970s organochlorine insecticides were in widespread use in the industrialized
countries and high levels of exposure were common in those engaged in their
manufacture, in agricultural workers and, because of the presence of residues in
foods, among the general public. Nevertheless, there is little evidence of serious ill
health, other than as a result of accidental exposure to high dosages. The herbicides
2,4,5-T and 2,4-D were also commonly used in that period, and were originally
thought to be a cause of miscarriages. Subsequent, more thorough, studies suggest
a link with increased incidence of a certain rare cancer, non-Hodgkin’s lymphoma,
but not with miscarriages or other reproductive effects (Hoar et al, 1986, 1988;
Witt, 1980; Agresti, 1979; Conway and Pretty, 1991).
Other pesticides appear to be intrinsically less hazardous, although the organo-
phosphates, in particular, can cause severe poisoning. These are more acutely toxic
than organochlorines but since they are not stored in body tissues are probably less
hazardous over the long term. Two highly hazardous pesticides are the nematocide,