THE LITTLE BLACK ANT, SCALE INSECT, MEALY BUG, APHID ALLIANCE
by Ben Wallace
* A contribution to the Australian Orchid Foundation Awareness Campaign.
These four groups of insects can work hand-in-glove to make a living at the expense of your orchids. The last three literally suck sap from your plants for their own needs, and produce sugary exudates that ants then feed on. In turn the ants carry the sapsuckers to the choicest localities, such as young emerging leaves, expanding buds or active root tips, where the orchid's nutrient content is at its greatest. Loss of these nutrients from the plant can seriously affect its ability to grow and flower. Worse still, the insects may inject pathogenic viruses into the plant, thereby spelling its doom.
To deal with such a conspiracy requires a multi-pronged response from the grower. First you need to watch where the ants are running to and fro, so that you can discover where their nest is located. If it's in a pot, the nest is easily destroyed. Simply tip the plant and mix onto the soil outside your green house, remove the plant, spread the mix and spray both mix and plant with a mixture of Pest Oil® and pyrethrum. If the ant nest is beneath a concrete slab or in a brick wall, you'll need to use more guile and lay a bait of ant poison. Mortein Ant Sand® is an effective one that has been introduced recently but other types are also available.
Having dealt with the ringleaders, next get the subordinates. Close examination of all plants is important to locate infestations of scale, aphids and mealy bugs. Remember that they often hide in obscure places, such as down in leaf sheath bases, on buried roots and in other hidden spots. Remove all infested plants individually, and spray them with the above-mentioned mix, or use a soft toothbrush to apply it, mixed with detergent. It's important to use some sort of surface-tension breaker (such as a soluble oil, detergent or methylated spirit) to penetrate the waxy coat of some insects. Don't apply more of these chemicals than necessary, as they may damage the plant's softer tissues.
Remember that it's important to deal with all the culprits, not just the sapsuckers doing the immediate damage.
Illustration courtesy of Rex Johnson