Thrips sap sucking insects under microscope

This is a thrips under a microscope about 60x magnification.

What are sap sucking insects?

Sap sucking insects are common in nature and our gardens. Sap sucking insects are herbivores. They eat or consume the sap of a plant. The sap of a plant is the liquid that maintains hydration and transports vital nutrients through the plants body.

Therefore, sap sucking insects can severely detriment a plant by reducing its hydration and vital life giving nutrients. It is uncommon for sap sucking insects kill a plant.

Plants can and most often do recover from an infestation of sap sucking insects and this largely depends on factors including: soil quality and access to nutrients, the microbes in the soil, the age of the plant, the resilience of the plant, other environmental factors such as rain or drought, and/or the presence of predators.

Sap sucking insects can transfer bacteria and viruses between plants. Therefore, plants can be negatively affected and die from secondary issues related to sap sucking insects.

Examples of sap sucking insects include: plant scale insects, mealy bugs, aphids, white fly, thrips and mites etc. Some are easily seen with the naked eye and others are only visible with a microscope.

Signs and symptoms of sap sucking insects includes the presence of ants, black sooty mould, leaf stippling and small spots on the leaf, leaf curling, leaf yellowing and/or galls.


What might we do about sap sucking insects on our plants?

Sometimes when we see sap sucking insects on our plants we just want to know how to kill them. We might reach for the horticultural oil, the neem oil, the pyrethrum or a toxic systemic insecticide. I read about such things in the gardening group on Reddit all the time.

First, we should know that many of the chemicals we reach for are unlawful to use on the insects we’re dealing with. I’ve seen people advise others to use neem oil on aphids. However, I am yet to see a neem oil registered for that use. Therefore, using a product in that way breaks the law in most countries including Australia and the USA.

Second, we should realise that when we seek to kill sap sucking insects we are taking away food for our predator insects. Predators are the only effective way to deal with most sap sucking insects. However, if we use insecticides then we kill not only the sap suckers but also non-target species such as lady beetles and their larvae, hover flies and their larvae, parasitic wasps and their larvae and the list goes on.

Most contemporary research shows us this fact: when we kill pest insects with insecticides we increase the numbers of those pests in the medium and long term. We do this by eliminating predator insects when we use the insecticide. We also do this by taking away a key food source for those predator insects to increase in numbers.

When we kill or reduce predators the ‘pests’ prevail, despite short term indications to the contrary. Predator insects reproduce at a much slower rate than our pest insects. Therefore by using insecticides and pesticides we “select for the pests“.

I’m sure pesticide producing multi-national corporations would love you to continue to do this because the more you use their product… the more you need their product.

I’ve seen predator insects deal with problems in my gardens over and again. We just need to stop and wait. Watch and learn. It would be helpful to all of us if more of use were mindful.

I’ve also seen gardens become devoid of predatory insects for up to 12 months after the use of insecticides. The predators may or may not have learnt that pesticides were used in that garden causing mass killings. They may or may not have passed that vital knowledge onto their offspring.

The effect is the same: insecticides (even natural ones) encourage pests and reduce and/or deter predators.


Cost – benefit analysis of killing sap sucking insects

If we want to kill the sap sucking insects on our plants using synthetic insecticides, we should also know that we are contributing to global insecticide resistance. This is happening at a global scale at alarming rates.

However, even if we use organic and natural insecticides we’re causing an effect.

Plants have the capacity to ward off insects and disease if they are healthy and if they have the conditions necessary to thrive. They may release metabolites to encourage predators to help clean up a sap sucking invasion. This is a natural evolutionary process.

When we use synthetic chemicals in particular we are shortcutting the evolutionary process and co-creating super bugs.

One question I would ask you is this: How important is this plant to you? If we let those sap sucking insects persist, what will be the real consequence? What does it really matter if we leave them be?

If we’re a farmer than our answer will be different from someone with a few tomatoes or zucchini growing in their back yard. Read my blog on trusting nature to see how predatory insects took care of a massive colony of aphids on my fennel flowers. I rely on my garden to survive yet, I didn’t kill any aphids on my edible plants.

If we’re going to play or work in the garden then we have a responsibility to continue to learn and evolve. We might learn what predatory insects look like. What do all the different species of lady beetles look like? What do their larvae look like? What do spiders and preying mantis do in our gardens?

Predatory insects hunting sap sucking insects
Juvenile preying mantis searching for sap sucking insects on native Australian mulberry shrub.

Juvenile preying mantis hunting for thrips (sap sucking insects) on Pipturus argenteus (Native Australian Mulberry).











Small spider hunting sap sucking insect on a leaf

Small spider hunting for thrips that are visible on the leaf just to the right of the spider.










Mealy bug lady beetle larvae hunting mealy bugs

Mealy bugs have consumed a lot of vital nutrients from this plant. It is wilting as a result of that and as a result of a general lack of hydration and care. Which comes first: chicken or the egg? We can see many predator insects: mealy bug lady beetle larvae. They look like mealy bugs but in this photo they are quite distinct as they have consumed nearly all the sap sucking mealy bugs.




















Anonymous · October 17, 2020 at 8:45 am

I found this article while searching for a “safe” pesticide to rid a few of my balcony plants of a small but noticeable sap sucking infestation. I will let nature take care of it’s self. No intervention from me. Thank you!

Anthony Mendes · October 12, 2020 at 5:48 pm

awesome article to enrich the knowledge of the sap sucking insects in the garden. well it would be great help if more knowledge about the predatory insects. In this way we who have little knowledge about them will think twice to reach out for pesticides

Henry · September 10, 2020 at 12:51 pm

Awesome article that make any domestic plant lover think twice before using any insecticide. Tks!

What do you think? Leave a comment :)

This site uses Akismet to reduce spam. Learn how your comment data is processed.