Plant Pest Control

August 25, 2025 Tom H

Pest Control

Keeping pests under control is vital if you want healthy plants and maximum yields. Here’s how to identify the most common pests, spot the damage they cause, and take steps to deal with them effectively.

Leaf Miner Larvae

Leaf Miner Larvae live on the leaves. They’re 0.4mm – 1.0mm in size and are off-white or brown in colour.

Look similar to thrips, but move slower, are less colourful, and do less damage.
Usually found on the underside of leaves.
Leave little trails of leaf damage and colour loss on surfaces.
Fast growing plants often outgrow the damage.

Treatment Tips: Unlike thrips, they don’t leave eggs during the larval stage. Damage is slow – a good spray plus manual removal of affected leaves usually solves the problem.

Scariad Fly Larvae

Also known as fungus gnats, these larvae live in the root zone. They’re 0.4mm – 1.0mm and off-white or brown in colour.

Same family as gnats and midges, love low humidity.
Live in the top of the root zone until they grow wings and fly.
Eat roots and spread viruses.
Eggs often laid on media surfaces.
Damage often hidden – usually lots of tiny flies instead.

Treatment Tips: Keep humidity down and water levels lower in substrate. Most larvae won’t survive. Natural predators like nematodes are very effective and safe to use.

Spider Mites

Spider mites live on leaves. They’re 0.4mm – 0.6mm and can be green, straw yellow, brown, or red.

Clusters of white dots on the leaf surface.
Mites and white eggs on the underside of leaves.
Cause general colour loss.
Young mites usually have two dark red eyes.
One adult can lay around 10 eggs a day and over 100 in its lifetime.

Treatment Tips: Remove infected leaves and spray every 4–5 days with a suitable spider mite spray. A final rinse of water clears off residue. Keep temperatures down to slow breeding. Predatory mites (like Phytoseiulus Persimilis) are also effective.

Thrips Larvae

Thrips larvae live on leaves and are 0.4mm – 1.0mm+ in size. They may be yellow, orange, or brick red.

Leave silvery-grey trails and cause colour loss.
Move quickly.
Black dots underneath leaves are their excretions.
During the larval stage they can damage and kill plants fast.

Treatment Tips: Look for developing legs and wings to distinguish them from Leaf Miner Larvae. Remove infected leaves, then spray with Pyrethrum 5 EC – highly effective when applied twice.