Protecting Plants From Pest Attacks

‘Hello Garden Doctor!

Two weeks ago, a couple of our little white flower bushes by our swimming pool which are in raised circular potters started yellowing and slowly wilting/dying. We fertilized thinking it would help but instead they appear dead. We noticed ants going to and from forming a highway between two potters in front of our big bale. This afternoon I removed a small bromeliad looking plant growing underneath one of the flower bushes thinking the ants could be attracted to the sap of the non-flower bush. To our surprise we revealed a heap of little mini 1.5cm snails with a long skinny yellowish-brown cone shell! I think perhaps the ants are loving the snail poo because I found that the only 2 planters that had ants going in them had the snails in. One planter more than the other.

Being unfamiliar with Indonesia’s little critters and land compositions I need some guidance for the best step forward to keep my garden thriving. The issue has just begun to show itself to be severe and deadly to our plant family! HOW DO WE GET RID OF THESE SNAILS/ANTS AND SAVE OUR GARDEN FROM A MASS INFESTATION!? Attached is some evidence of the suspects and the crime scene. Thank you so much for your time! Looking forward to your reply! Jet from Seminyak’

Thanks for the interesting question – I think you have two separate unrelated issues going on with the ants and the snails. Ants go after anything sweet. Whenever you see a large population of ants in and around your plants its usually an indication that you have an aphid or scale insect infestation. So whilst it’s not the ants that are causing the initial problem, they can exacerbate it, which I will get to a bit later.

Aphids and scale insects are tiny bugs usually only a few mm in size. Aphids are commonly green to brown and camouflage themselves very well, whereas scale insects generally will show up as white, beige to brown in colour. These bugs cleverly reside on the undersides of the leaves so they can go about their business of sucking out the fresh sap from the leaves in secret, placing the plant under severe stress – essentially they are stealing the plants nutrition. By the time that you’ve realised this, the plants could be dead and the bugs already moved onto the next victim. Aphids and scales can rapidly decimate plants and their populations can explode into plague like proportions in just a matter of a few days.

As the bugs consume the sap, the excrete a sweet ‘honeydew’ waste by-product, and ants absolutely love it. So of course, they move in to consume it – for them it’s like the sugar pot has been left out in the garden. From here a symbiotic relationship develops between the bugs and the ants, whereby the ants protect the sap sucking bugs and even transport them around to other sites to send the honeydew production into overdrive – it’s an ant farm of a different type that you won’t like!

If you ever see ants crawling up and down stems and across leaves alarm bells should be ringing as it’s the first sign that you have a problem. Ants are typically found on the ground and will only inhabit plants if there is a honeydew source, which means either aphids or other types of scale insects have moved in. A quick check of the growing tips and the undersides of foliage will likely reveal the bugs. They say where there’s smoke there’s fire, well where there’s ants on your plants you probably have a sap sucking insect problem.

So first, to get to the aphids and scales you will need to check the undersides of the leaves. In the initial stages hosing with a fast jet of water underneath the leaves could be enough to rid a small infestation, but as your plants are dying and the infestation is severe its probably best to spray with an organic pesticide such as white oil or neem oil that is available at hardware and garden centres.

As the ants may be in on the deal, protecting, transporting and farming the bugs around you should probably deter them also. Ants generally don’t like moist conditions, keep the soil around your plants well-watered directly to the root-zone so you don’t wash off the pesticide.

Here’s another tip. Plain old chalk used to write on chalkboards is all that’s needed to keep the ants away. Ants will not walk through a line of powdery material such as chalk dust or talcum powder. Test it and see!

Anywhere you have ant problems get some chalk and start drawing barriers to the ants. Draw a circle around an ant and watch what happens! I’m suggestion that you draw chalk lines around your pots to stop the ants migrating back and forth, draw chalk barriers wherever you don’t want them. Of course, after rain or every few days you may need to re-apply.

It’s kind of amusing when you first start experimenting with this. The chalk deterrent is also useful in the home as a good way to stop them entering the house for example through a crack in the wall. Just draw a circle around the crack or a barrier line wherever they are entering.

As for the snails, well it makes sense that they would be hiding around bromeliads or strappy type leafed plants. Snails are molluscs and like a dark moist environment for protection and to avoid drying out. They will hide under leaf litter, dark places and cover that keeps them moist.

The snails in the pictures you have sent look like decollate snail (Rumina decollata) with the conical shell. They are omnivores, so they will eat plants and other snails. If there are no brown garden snails to eat or other alternatives this snail is going to eat your plants and they can cause serious damage quickly. The easy fix is snail pellets, though not my preferred choice, especially if you have children and pets to consider. Laying down a dry rough mulch such as jagged bark mulch is one way to deter snails or even crushed eggshells or shell grit mulch, as they don’t like to crawl across the sharp jagged edges which probably feels like razor blades to them and their delicate slimy exterior.

Snails prefer cool, dark, moist places to hide out, so by creating these locations in the garden you can locate the snails and dispose of them. Upturned terracotta pots are a good snail trap, check every few days and you’ll find them congregating inside. Orange or any other citrus halves with the pulp scooped out is another known trap method. Leave them face down in the garden bed slightly propped up with a small gap for the snails to enter. Finally, the snail beer trap is the easiest way to take them out. A container, jar or a plastic bottle cut in half and then placed in the garden filled with a cup of beer is irresistible to snails and slugs. Dig it in level with the soil so they can easily enter – they love the yeast.

Snails can easily be removed using the combination of methods – hand picking, trapping, barriers, and bait/pellets. Modifying habitats can help prevent snail plagues by removal of hiding places such as thick clumps of vegetation, empty pots lying around and by using a rough dry mulch.


Dr. Kris

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