ADLib Glossary (A)

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Adjuvants have an important role to play in improving pesticide product efficacy.

Chemical pesticides are often applied to the crop by mixing them with water. However, in many instances this can be very inefficient as water droplets are reluctant to stick to any thing but themselves - i.e. they globularise and run-off of the crop foliage with very little product actually adhering. If pesticides are used at reduced application rates it is quite important that the application is spread evenly across the crop. Surfactants added to the mix can help ensure that this is achieved. Many formulations already contain surfactants but in an attempt to cut spray costs and to improve efficiency many growers add more to the mix. In order to get the best from the many available products now available it is important to understand what they do and it should be remembered that these products are classified as pesticides and can do environmental damage if they are misused.


These products act by reducing the surface tension of the water. When a droplet hits foliage it tends to drain from the crop and the chemical is lost. Wetters help the chemical stick to the foliage, improve efficiency and cut costs.

Adjuvant oils

There are three main types, mineral oils, vegetable oils and methylated seed oils. These are widely used to improve the activity of graminicides. Oils soften the plant cuticle making it more vulnerable to attack from the herbicide. They are very important when treating blackgrass. However, mineral oils are derived from the petrochemical industry and are not environmentally acceptable for use in food crops. Vegetable oils are better but not as efficient as the methylated seed oils. These are derived from rapeseed and are used at a lower rate than mineral oils.

Penetrating agents

These tend to be based on lecithin and do a similar job to adjuvant oils in that they help the pesticide penetrate the waxy cuticle of the leaf. They also help to transport the pesticide around the plant cells.


These products help to stick the spray droplet to the crop foliage. They tend to contain gums or resins and some require sunlight to help them set. Stickers help make pesticides rainfast.

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