We have a number of citrus and other trees which are subject to infestation with scale. Scale are small sucking insects (2-3mm) which grow beneath a waxy cover and infest the leaves of the plants they attack. They can only move around under their own steam in their younger stages with the adults tending to remain in the one spot once they become attached. The scale is a sucking insect and enough of them can affect the plant adversely, they also pump out a sugary liquid called honeydew. Honeydew on the leaves of the plant attracts a fungus called sooty mould, due to the sooty look which the leaves take on, but is a cosmetic effect more than anything.
Scale is usually dealt with by an application of white oil (early in the morning or later in the afternoon to prevent the sun burning the host plant) which blocks the scale’s breathing holes, suffocating it. Unfortunately for us, the scale’s best friend is the ant. The ants can “farm” them, moving them from one plant to another or from one area of the same plant to another area. They harvest the sugary honeydew which the scales secrete and in return protect and move them around.
I have recently noticed that out Tahitian lime tree was not looking happy and it was covered in ants and the scale was starting to take hold. So I needed to deal with the ants before I could sort out the scale, otherwise a re-infestation was highly likely.
To fix the ants’ little red wagon I applied a homemade sticky strip to the trunk of the lime tree. I made the strip as follows –
- I first measured the trunk circumference using Linda’s sewing tape measure, and it came out at 16cm.
- I got hold of some cardboard from the recycling, in this case it was the outer packaging of some catfood which we had bought.
- I cut the cardboard to 19cm long (to allow overlap) and 6cm wide to allow a deep enough barrier.
- I then smeared a goodly layer of Vaseline over the surface of the cardboard to act as the sticky layer, but I have heard of molasses or automotive grease being used instead.
- I checked that there were no alternative routes on and off the tree like errant twigs or branches touching the ground or contact with other trees or fittings.
- I then applied the band to the base of the trunk of the lime tree.
That was no mean feat! By the time I had the cardboard in place and wired on I was covered in Vaseline, well it was all over my hands anyway. I used two wires to ensure that the barrier was flat against the trunk and the ants couldn’t sneak their way underneath and tightened them up pretty tight. To replace the Vaseline now on me I applied a liberal smear all around the cardboard to ensure a good barrier.
I then sat down to watch what happened. There were copious ants on both sides of the barrier, but the ones still on the tree (above the barrier) seemed to be more determined to get across it. I don’t know if it was because the higher ants had gravity on their side or because they were not on the nest side of the barrier. I expected the little buggers to move onto the cardboard and then get stuck, slowing covering the surface of the Vaseline, but that is not what happened.
They could walk right across the band of Vaseline without getting stuck if they wanted, but seemed to be extremely reluctant to do so. I saw a few very courageous ants above the barrier walk down across it and escape but none from below tried to climb up onto it, they seemed totally put off by the barrier. The application of the barrier did cause extreme consternation within the ranks of the ants who were, only a moment before, passing up and down the trunk unmolested. They just milled around but, with the exception of the previously mentioned hardy individuals, didn’t achieve much.
If they do manage to find a way through under the barrier, wiping some more Vaseline over the breach in your defences will fix the problem.
Two Weeks Later
Two weeks after I wrote this I decided to check back and see if my handywork was still effecting, and sure enough there were no ants on either side of the barrier or anywhere near it, the mission was clearly a success! Ahhh, if that were truly so, where were all the ants on the limbs and leaves above the barrier coming from?
OK, maybe not such a success (cue frustrated screams). So I went back into surveillance mode and watched where the little buggers were coming from/going to and sure enough one of the limbs of the lime tree came very close to the leaves of the macadamia tree next door to it which I had missed on my initial survey. I removed the offending twig from the macadamia and all of a sudden there was a traffic pile-up on the leaves of the lime tree near where the twig had been. That should hold ém!
This only emphasises the importance of my earlier comments about the intial look over to identify alternative pathways which will allow the ants to bypass your barrier. If they exist, the ants will find and exploit them.
