186
(f. R. POTTS AND Q. P. VICKERMAN
in prep.). The adoption of varieties with reduced tillering capacity
may mean that one should consider pest populations which are at
present unimportant. The introduction of the new semi-dwarf cereals
should be considered. Not only do these have higher nitrogen requirements but the weed control has to be more efficient.
It appears that even with pesticides, cereal crops must, in the long
term, be grown in a rotation of one kind or another to maintain high
yields. All the arable break crops (except grass as currently grown)
require relatively high pesticide inputs; this is also true of the expanding
semi-break crop, maize. Overall it appears that the present trend of
increasing pesticide applications will be maintained.
Therefore we ought to be able to predict the indirect effects of this
increasing use of pesticides on the cereal ecosystem and on other
affected ecosystems. The first generation of pesticides such as the
organochlorines DDT and dieldrin could be monitored in the biosphere
(Coulson et al., 1972) and lethal and sub-lethal effects on wildlife were
eventually quantified (Ratcliffe, 1970; Blus et al., 1972; Cooke, 1973).
By contrast the newer pesticides are specific and less persistent so that
their indirect effects are less tangible. Side-effects will be in the form of
abnormalities in the population dynamics and energy flows of the
system rather than in the physiology of contaminated individuals. The
grey partridge is an example of a species which has been affected
indirectly by pesticides, by agrochemicals generally and by changes in
agricultural cropping systems. All this happened before its “natural”
biology was fully understood-we believe this must be typical of most
species in the farmland fauna. Abnormal perturbations can only be
quantified if the normal state is fully understood.
It is surprising that such a high proportion of the field layer fauna
is so directly dependent on the fungi. The most recent and widespread
change in the cereal ecosystem has been the application of fungicides,
new systemic seed dressings such as ethirimol and foliar sprays such as
tridemorph. We cannot even guess the ultimate ecological repercussions
on the fungus-feeding fauna, nor indeed do we know if there will be any
long-term effects.
It is essential that the fundamental reason for the application of
pesticides, i.e. the cause of the breakdown in natural control, is fully
understood. But the natural control mechanisms have not been fully
explored or evaluated (and this is likely to prove difficult).
Predation clearly seems to be an extremely important form of
natural control and yet at the same time is extraordinarily difficult to
quantify. The processes of predation are often at the heart of heated
debates in applied ecology-a clear reflection of the lack of real knowledge on the subject a t the system level. Given proper attention in the
(f. R. POTTS AND Q. P. VICKERMAN
in prep.). The adoption of varieties with reduced tillering capacity
may mean that one should consider pest populations which are at
present unimportant. The introduction of the new semi-dwarf cereals
should be considered. Not only do these have higher nitrogen requirements but the weed control has to be more efficient.
It appears that even with pesticides, cereal crops must, in the long
term, be grown in a rotation of one kind or another to maintain high
yields. All the arable break crops (except grass as currently grown)
require relatively high pesticide inputs; this is also true of the expanding
semi-break crop, maize. Overall it appears that the present trend of
increasing pesticide applications will be maintained.
Therefore we ought to be able to predict the indirect effects of this
increasing use of pesticides on the cereal ecosystem and on other
affected ecosystems. The first generation of pesticides such as the
organochlorines DDT and dieldrin could be monitored in the biosphere
(Coulson et al., 1972) and lethal and sub-lethal effects on wildlife were
eventually quantified (Ratcliffe, 1970; Blus et al., 1972; Cooke, 1973).
By contrast the newer pesticides are specific and less persistent so that
their indirect effects are less tangible. Side-effects will be in the form of
abnormalities in the population dynamics and energy flows of the
system rather than in the physiology of contaminated individuals. The
grey partridge is an example of a species which has been affected
indirectly by pesticides, by agrochemicals generally and by changes in
agricultural cropping systems. All this happened before its “natural”
biology was fully understood-we believe this must be typical of most
species in the farmland fauna. Abnormal perturbations can only be
quantified if the normal state is fully understood.
It is surprising that such a high proportion of the field layer fauna
is so directly dependent on the fungi. The most recent and widespread
change in the cereal ecosystem has been the application of fungicides,
new systemic seed dressings such as ethirimol and foliar sprays such as
tridemorph. We cannot even guess the ultimate ecological repercussions
on the fungus-feeding fauna, nor indeed do we know if there will be any
long-term effects.
It is essential that the fundamental reason for the application of
pesticides, i.e. the cause of the breakdown in natural control, is fully
understood. But the natural control mechanisms have not been fully
explored or evaluated (and this is likely to prove difficult).
Predation clearly seems to be an extremely important form of
natural control and yet at the same time is extraordinarily difficult to
quantify. The processes of predation are often at the heart of heated
debates in applied ecology-a clear reflection of the lack of real knowledge on the subject a t the system level. Given proper attention in the