Controlling Pesticides

What are the named controls of pesticides?

• Restrictions on use

• Use of non-persistent pesticides

• Use of more specific pesticides

• Use of systemic pesticides

• Application timing

Restrictions on use

Some pesticides have been banned, or their use has been restricted where they could cause problems.

Examples of restricted pesticides

Use of organochlorines is banned in most countries (though DDT can be used in some countries for malaria control)

Use of non-persistent pesticides

Non-persistent pesticides will break down rapidly and won’t become concentrated or travel long distances after application

Example of low persistent pesticides

Organophosphates are less persistent than organochlorine

Use of more specific pesticides

Pyrethroid and organochlorine insecticides are both toxic to insects but pyrethroids are less toxic to mammals

Use of systemic pesticides

They are absorbed by the crop and translocated within it.

They do not need to be sprayed onto all surfaces, are not washed off after they have been absorbed, and will protect new growth.

What is the issue with systemic pesticides?

As the systemic pesticides are present within the plant tissue, they may be eaten by humans if they are still present when the crop is eaten.

Application timing

• Spraying on not windy days results in less spray drifting to surrounding habitats.

• Spraying at night or when crops are not in flower will reduce impact on bees

• Newer spraying techniques use smaller droplets to produce a more even coverage which reduces the amount required

The food samples collected were individually wrapped before being sent for analysis of pesticide levels.

Why is this less important for samples containing systemic pesticides than contact pesticides?

Systemic pesticides will be retained within the food

Suggest why pesticide residue levels in samples of a single type of food may show high variability.

Different amounts of pesticides applied because:

• Types of pest may vary

• Seasonal changes. A species life cycle affect abundance, and therefore different application rates are used

• Different application methods

• Number of predators vary

Variation after application because:

• Rainfall

• Time before harvest

• Storage method

Food items are collected and analysed for pesticide residues throughout the ear.

Suggest other factors that may be considered when selecting food items for testing to ensure that the pesticide residue levels are representative.

• Large sample size

• Random locations

• Samples from different regions

• Large range of food items tested

• Large range of food from different outlets (suppliers, like supermarkets, wholesalers)