Insecticides - Best Practice to Minimise the Environmental Impact in Arable Crops

Safe application


Choice of product

Correct choice of pesticide treatments is crucial not only to control the pest effectively but also to protect non-target species.

Always explore the alternatives and determine the best choice on the basis of the strengths and weaknesses of each aspect, such as persistence versus short-term action.

As far as possible, choose products which are specific to the problem and are not harmful to predators and other non-target species. Where a choice exists, choose the product with the least indirect effect on wildlife, for example destruction of food sources (See list of useful contacts for advice on page 17).

The risks to wildlife are greatest where broad-spectrum insecticides are used in late spring/early summer when the young of such birds as grey partridge and corn bunting are dependent on insects for food. Where their use is unavoidable, they must not be used on crops in flower (unless there is a specific statement on the label which allows this) or when bees are actively foraging.

Always check the label to make sure that the chemical you are about to use is approved for the pest you are targeting. Ask your agronomist to recommend a product that will have the smallest impact on beneficial non-target species.

Applying insecticides
  • Before applying a pesticide always check that the sprayer is in good working order and the correct nozzles are fitted for the job ahead;
  • Be aware of the latest technology, such as low-drift nozzles, to help reduce the chance of spray drift, especially when applying next to headlands and watercourses;
  • Comply with any buffer-zone or LERAP requirements;
  • Listen to the weather forecast to help you decide when to spray;
  • Avoid spraying in wind speeds over Force 3 where possible, as this can lead to unacceptable levels of drift. Wind conditions in the early morning or the evening are often more suitable than during the day;
  • Always remember to read the label and act on the instructions given.
Preventative spraying
  • Avoid adding a little insecticide, into a tank mix just in case. Remember, insecticides may affect beneficial insects as well. Work to action threshold levels.
  • Always check each field and treat accordingly.
  • Do not blanket-spray all fields just because one has reached a threshold level.
  • Some pests occur in patches in a field and can be spot-treated following field sampling, such potato cyst nematode and slugs on some headlands.
  • Slug pellets can harm beneficial ground beetles, earthworms and, in some cases, small mammals. Remember too that some ground beetles predate slugs. If there is a strong likelihood of slug attack, consider placing some slug pellets in with seed. Mixing pellets with seed is possible if conditions are dry; if it is wet it is usually better to broadcast them.
Spray timing

For some pest species it is vitally important to apply the insecticide at exactly the correct time so that the target pest is controlled before potential yield loss is suffered. For some pests there is a well-defined window of opportunity, such as pollen beetle on oilseed rape when applications should go on as soon as flower buds open. Dont spray, though, if a crop has passed the damage-susceptible growth stages.

Some treatments need to go on as quickly as possible, for example where there is a threat of virus spread.

Insecticide treatments during winter months appear to have far less of an effect than breeding season applications on skylarks, yellowhammers and probably to other farmland bird species with similar ecologies. Wherever possible, avoid applying insecticides during the breeding season.

Application rates

When any chemical is used, the policy should be to use as little as possible but as much as necessary to do an effective job. Follow the manufacturers label and use the recommended rates of products. On occasion reduced rates may be used but advice should always be taken from a trained agronomist as under-dosing may lead to resistance problems. Adjuvants can also be used to reduce dose.

Lower rates of slug pellets may be used in Integrated Crop Management regimes, although some damage may still result.

Protecting bees

Insecticides should not be used in such a way that endangers bees. As a general rule, honeybees are best safeguarded by avoiding the use of insecticides when crops and weeds are in flower. If this is unavoidable, choice should be made from products that present a low risk.

Insecticides that present a special risk to bees have been classed as high risk to bees, harmful, dangerous or extremely dangerous to bees and they carry specific label warnings that must be followed. Normally this requires users to avoid treatment of crops in flower or when bees are actively foraging, or when flowering weeds are present.

Try to spray in the evening once bees have stopped flying.

Before spraying any flowering crop such as oilseed rape or beans (even weedy fields with bee activity), always contact  your local beekeepers spray liaison officer, who will in turn contact all local beekeepers on your behalf, so that they can lock their bees away. It is important to give 48 hours prior-notice of spraying. 

Never spray a conservation headland with any insecticide.

Water protection

Even greater care should be taken when applying insecticides indeed, all pesticides next to water courses as many aquatic species are particularly vulnerable to insecticide pollution. Legal requirements, in the form of local environmental risk assessments for pesticides (LERAPS), should always be adhered to where appropriate. Use of  permanent buffer strips next to water are ideal for protecting all kinds of waterways i.e. 10m set-aside or 6m Countryside Stewardship grass margins.

ADLib logo Content provided by the Agricultural Document Library
© University of Hertfordshire, 2011