Report from the Sub-comittee on the environment and health

Leaf beetles
Direct effects of spray drift
on arthropods in areas close
to fields
Waysides
Direct effects on higher
fauna
insects in a field depends on <strong>the</strong> amount of weed and <strong>the</strong>refore decreases
where <strong>the</strong> weed is controlled (Wardle 1995).
There are insecticides, fungicides and herbicides that are poisonous to
earthworms, but very few of <strong>the</strong>m are sold in Denmark today. The
carbamates are <strong>the</strong> only group of substances that is generally assumed to
be poisonous to earthworms (Edwards, Bohlen 1992). Some of <strong>the</strong>se
substances are on <strong>the</strong> Danish market.
The knotgrass leaf beetle is a source of food for field birds. It is estimated
that when a cereal is treated with <strong>the</strong> insecticide dimethoate, 7-40% of
<strong>the</strong> population is exposed to a directly fatal dose of <strong>the</strong> insecticide (Kjær,
Jepson 1995; Kjær et al. 1998). Practically no leaf beetles survive
treatment with insecticides because <strong>the</strong> survivors eat leaves containing
dimethoate (Elmegaard et al. 1998).
When a field is sprayed, drift can occur to areas in <strong>the</strong> immediate vicinity
of <strong>the</strong> sprayed area. The extent of this drift depends on both <strong>the</strong> spraying
equipment and <strong>the</strong> climatic conditions – primarily <strong>the</strong> wind velocity (see
section 4.1.6.2). A number of studies have been carried out of <strong>the</strong> effect
of spray drift on <strong>the</strong> large cabbage white butterfly. These studies showed
that <strong>the</strong> butterfly was affected by insecticides right up to 24 metres <strong>from</strong>
<strong>the</strong> edge of <strong>the</strong> field. The effect naturally depended on <strong>the</strong> spray product
used and varied between 2 and 24 metres (Davis et al. 1991, 1993, 1994;
Sinha et al. 1990; de Jong, van der Nagel 1994). The long-term effect can
be expected to be greater since <strong>the</strong> studies mentioned only monitored <strong>the</strong>
butterflies for a short time after <strong>the</strong>y had been exposed. Cilgi and Jepson
(1995) thus found, for <strong>the</strong> same species, that exposed larvae continued to
have excessive mortality 10 days after <strong>the</strong>y had been removed <strong>from</strong> plant
surfaces treated with <strong>the</strong> spray product deltamethrin.
Waysides, like o<strong>the</strong>r small biotopes, have important ecological functions
for plants’ and animals’ survival in <strong>the</strong> landscape. Wayside flora in
Denmark comprises several hundred species and many different plant
societies, ranging <strong>from</strong> totally dry to distinctly wet and <strong>from</strong> completely
light and open to very shady. Studies of waysides at <strong>the</strong> end of <strong>the</strong> 1960s
showed that perennial species covered about 90% of <strong>the</strong> wayside area,
biennials 2%, and annuals 9%. Of <strong>the</strong>se species, only <strong>the</strong> dandelion
spreads seeds to annual crops. The dandelion is also favoured by <strong>the</strong>
widespread mowing of waysides. Some local and county authorities still
use chemical weed control in many places, over a width of about 30 cm
along roads and under and around crash barriers and road signs
(Bisschop-Larsen 1995). In addition, damage is often seen after herbicide
treatment of fields, and in some cases <strong>the</strong> herbicide is sprayed directly
out onto waysides. There is no systematic Danish registration of <strong>the</strong>
effect of pesticides on wayside flora and fauna.
Direct poisoning of birds and mammals has been reported many times –
also in Denmark. However, cases of individuals found dead after normal
agricultural use of pesticides are rare. Many of <strong>the</strong> cases of poisoning
observed and described are due to dressed seed or granulates that tempt
mammals and birds. Dressed seed and granulate, lying accessible, make
it possible for <strong>the</strong> animals to consume large quantities of pesticide in a
short space of time. Since it can be difficult to find carrion after a case of
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