Adjuvants: When and How to Use Them

What Are Adjuvants?

Adjuvants are additives mixed with pesticides in the spray tank to improve performance. They do not have pesticidal activity themselves — they help the pesticide work better.

Types of Adjuvants

Spreader-stickers (surfactants) Reduce surface tension so spray droplets spread and stick to waxy leaf surfaces. Essential when spraying tough-to-wet crops like maize, brassicas, and grasses.

• •Use rate: 0.1–0.25% (1–2.5ml per litre of spray)

Penetrants / Penetrating oils Help systemic herbicides and fungicides enter the plant more quickly. Particularly valuable in hot, dry conditions when leaf cuticles are thick.

• •Use rate: 0.25–0.5% (2.5–5ml per litre)

Drift control agents Increase droplet size to reduce off-target movement. Use near sensitive crops, water bodies, or in windy conditions.

When Adjuvants Add Value

✓ Herbicides on grass weeds (waxy surfaces) ✓ Systemic products in hot or dry weather ✓ Post-emergence applications where rapid uptake is needed ✓ Tank mixes where compatibility is a concern

When to Avoid Them

✗ Contact fungicides like Mancozeb (can cause phytotoxicity) ✗ Products that already contain built-in surfactants (check label) ✗ When applying near water — may increase runoff

Correct Dosage

Always use the minimum effective rate. More is not better — excess surfactant can cause leaf burn (phytotoxicity). Always add adjuvant LAST to the spray tank after the pesticide.