Sucking insects are small, but the damage they cause is big. They push their mouthparts into leaves and stems and drink the sap, so the plant weakens and loses colour. Many of them also leave a sticky honeydew that feeds sooty mould, or carry viral diseases that are hard to treat.
This guide covers the main sucking insects on farms and in gardens, how to tell them apart and how to deal with them. Each type has its own detailed article, linked under its name.
Quick overview
- Main pests: whitefly, mealybug, aphids, thrips, scale insects, Asian citrus psyllid, leafhoppers and stink bugs.
- Affected crops: vegetables, fruit trees, citrus, palms, ornamentals and field crops.
- Symptoms: curled leaves, yellowing and stunting, sticky honeydew, black sooty mould, and spots or deformed fruit.
- Most important step: check the underside of leaves early. Small colonies are far easier to control.
What are the types of sucking insects?
They feed in the same way but differ in shape and in the plants they prefer. These are the main ones:
Whitefly
A tiny white-winged insect that gathers under leaves and flies up when the plant is shaken. It transmits serious viruses to vegetables.
Mealybug
An insect covered in white cotton-like wax. It hides in branch joints and leaf bases and produces honeydew.
Aphids
Small soft insects that multiply fast on growing tips and young leaves, causing leaf curl and distortion.
Thrips
Very small insects that scrape the surface of leaves, flowers and fruit, leaving silvery patches and scars.
Scale insects
Insects that attach to branches and leaves under a protective shell, which makes them hard to control if left unchecked.
Asian citrus psyllid
A sucking insect on citrus that carries a dangerous bacterial disease threatening the trees.
Leafhoppers
Agile insects that jump when the plant is disturbed. They cause spotting and drying along leaf edges.
Stink bugs
Bugs with a sharp smell that suck sap from fruit and seeds, leaving spots and deformities that lower crop quality.
How do I recognise a sucking insect infestation?
Check the underside of leaves and the growing tips before doing anything else, and look for these signs:
- Curled, wrinkled or distorted young growth.
- Yellow leaves and a stunted plant despite regular watering and feeding.
- Shiny sticky film on leaves followed by a black layer of sooty mould.
- Ants visiting the plant often. They usually farm the insects for honeydew.
- Silver or brown patches and tiny dots on leaves and fruit.
Turn the leaf over and use a hand lens if needed, because some species can only be seen up close.
What damage do sucking insects cause?
- They drain sap, so growth and yield drop.
- They spread viral and bacterial diseases that are hard to treat.
- Honeydew and sooty mould block sunlight and lower fruit quality.
- Fruit becomes deformed and loses market value.
- Numbers can double within a short time under the right conditions.
How do I tell sucking insects from disease or nutrient deficiency?
- You can see the insect itself on the underside of leaves or in growing tips under a hand lens.
- Shiny sticky film with black mould growing on it points to honeydew.
- Small pale or silver spots with curled, distorted new growth point to insects.
- General yellowing and weak growth that does not improve with feeding may also be insects.
Choosing the right control for the most common species
Aphids, whitefly, thrips, mealybugs and scale insects all behave differently. Aphids and whitefly gather under leaves, thrips hide inside flowers and buds, and mealybugs shelter under a waxy coat. Identifying the insect first saves you from using the wrong product and spraying again and again.
A practical control plan
- Inspect plants weekly, focusing on leaf undersides and growing tips.
- Use yellow sticky traps for early monitoring.
- Start treatment at the first sign, with a product suited to the insect and the crop.
- Cover the plant well when spraying, including the undersides of leaves.
- Repeat on the date written on the label and rotate between active ingredients.
- Control ants and weeds around the plants.
Common mistakes
- Spraying without knowing which insect it is.
- Waiting until the insect multiplies and covers the plant.
- Not covering the underside of leaves.
- Repeating the same product until resistance builds up.
- Over-using nitrogen fertiliser.
How do I get rid of sucking insects?
The plan depends on the insect and the size of the infestation. The key rule is to start early:
- Identify the type first, since each insect has a weak stage and a suitable product.
- Remove heavily infested parts and wash light infestations off with a strong water spray.
- Use agricultural soap or light mineral oil on early infestations.
- When a pesticide is needed, choose one registered for the crop and the pest, contact or systemic, and follow the label and the pre-harvest interval.
- Rotate between different pesticide groups so the insect does not become resistant.
- Check again after about a week and repeat the treatment if needed.
How do I stop them coming back?
- Inspect weekly, especially growing tips and leaf undersides.
- Avoid excess nitrogen, which produces the soft growth these insects prefer.
- Control the ants that protect and farm sucking insects.
- Use yellow sticky traps for early monitoring, especially in greenhouses.
- Isolate and inspect new seedlings before bringing them onto the farm.
- Remove weeds around the field that shelter these insects.
If you are not sure which insect you have, or you need a plan for your crop, message Orkida engineers on WhatsApp with clear photos of the damage, or visit your nearest Orkida branch with a photo or a sample, and we will point you to the right step.
Image source: Shutterstock
Frequently asked questions
How do I know my plant has a sucking insect?
Turn the leaves over and check the underside and growing tips. Tiny insects, sticky honeydew or curled young leaves are clear signs.
Why do the insects come back after spraying?
Usually because the undersides were not covered, new stages hatched after the spray, ants spread them again, or the same product was repeated.
Do sucking insects spread disease?
Yes. Many of them carry plant viruses, so early control matters even for a light infestation.
When should I spray?
When the insect first shows up in inspection or on traps, following the dose and interval on the product label.