Report from the Sub-comittee on the environment and health

Prevention of disease in
cereal crops through <strong>the</strong>
use of resistant plants
Prevention and regulation
of problems with seedborne
diseases in cereals
168
already made of undersown and second crops. Consideration could also
be given to <strong>the</strong> use of “undersown crops” in <strong>the</strong> form of low-growing
herbaceous plants, such as white clover, but o<strong>the</strong>r plant species could
also be grown. Leguminous plants are an obvious choice with respect to
nitrogen fixation, but species that are good “catch crops” could also be
used and would be advantageous with respect to holding on to <strong>the</strong>
nitrogen until <strong>the</strong> crop can absorb most of <strong>the</strong> amount available. In
addition, undersown crops would give more varied cover, <strong>the</strong>reby
promoting part of <strong>the</strong> fauna – particularly earthworms and surface
predators. Lastly, a cover of undersown crop would reduce <strong>the</strong> weed’s
possibility of germinating both in <strong>the</strong> crop and after harvesting.
On <strong>the</strong> health side, <strong>the</strong> main change in connection with <strong>the</strong> prevention of
weed problems and <strong>the</strong> use of mechanical control methods instead of
pesticides would be reduced exposure of agricultural workers and less
pesticide residue in <strong>the</strong> crops. Potential problems with physical loading
in connection with increased mechanical or manual weed control are
discussed in section 6.1.
9.3 Prevention and control of diseases
In a scenario without pesticides it would be important to use crop species
with good resistance to diseases in order to reduce <strong>the</strong> loss <strong>from</strong> infection
by leaf diseases. The biggest losses <strong>from</strong> diseases occur in potatoes,
wheat and winter barley. There are at present no varieties with sufficient
resistance to all leaf diseases in <strong>the</strong>se crops.
There is a big potential for improving <strong>the</strong> resistance of <strong>the</strong> varieties both
by traditional breeding and by genetic modification, but it is difficult to
breed, at one and <strong>the</strong> same time, resistance to leaf diseases and seedborne
diseases, better weed competition, stem strength, winter resistance,
a high yield and high quality.
The environmental benefit of developing and using resistant varieties is
<strong>the</strong> obviously reduced consumption of pesticides, with consequently
reduced risk of pollution of <strong>the</strong> groundwater and <strong>the</strong> surroundings. The
health benefit would be less exposure of farm workers and less pesticide
residue in crops.
In Denmark today, 85-90 % of all cereal seed is dressed today, as is a
large proportion of o<strong>the</strong>r crops in Denmark. It is believed that generally
omitting such treatment would lead to a rapid spread of many of <strong>the</strong>
seed-borne diseases that cause heavy losses.
It would be possible to reduce <strong>the</strong> consumption of pesticides by
continuing to dress <strong>the</strong> first generations of cereal and <strong>the</strong>n assessing <strong>the</strong>
need to dress <strong>the</strong> subsequent seed batches. However, this practice would
first have to be more thoroughly analysed and tested. An assessment of
<strong>the</strong> need for dressing would require fast and reliable methods of analysis,
separation of seed batches and presumably rejection of substantial
quantities of grain for multiplication. In beets, too, <strong>the</strong>re could be
considerably losses owing to uncertain establishment if dressing products
were prohibited. In this case, however, <strong>the</strong> losses would be due to a