Getting rid of aphids and whiteflies
Updated: Mar 13, 2019
The most commonly encountered insect pests in urban gardens (at least in Klang Valley) are probably aphids & whiteflies. These two types of insects are often found on the underside of leaves. They depend on plant sap to survive. They can transmit diseases to the host plants and can potentially cause extensive damage if not controlled.
Here are some of the methods that can be implemented in an urban setting:
1. Physical Removal
Aphids and whiteflies can be dislodged by spraying water on them. They can also be removed by wiping the underside of the leaf with alcohol swab or soapy water. Adult aphids and whiteflies can be eliminated by using yellow sticky trap.
2. The Good Bugs
In urban gardens, we have ladybirds, long legged fly, robber flies, hoverflies and lacewings among others to take care of the bad bugs for us.
When the ladybirds arrive, aphids are typically wiped out within a week or two. Ladybirds are one of the most effective biocontrol agents of aphids by far. While the ladybirds are doing their work, you can help to maintain the vigor and health of the plants by feeding them seaweed extract (Algae). Long legged flies are known to feed on aphids and whiteflies, so be happy when you see them in your garden.
You can grow flowers and herbs to attract beneficial bugs to your garden. Plants like marigold, cosmos, dill and coriander are able to attract ladybugs.
3. Organic Pesticides
If the situation is dire, I would spot spray the pests using a concoction made with the formula provided on this website -http://www.rnzih.org.nz/pages/Aphids.htm - with slight modification.
50mL Hui (palm ash, vinegar extract with near neutral pH)
1 tsp dishwashing detergent
2 tbsp baking soda
The first ingredient can be swapped with any other types of liquid fertilisers. I use Hui (vinegar extract) instead of seaweed extract as I want to feed more potassium to the infested plants (which are usually fruiting crops e.g. chilli). Aphids, whiteflies and even ants die within minutes with a single spray application. Beware of leaf burns when use in excess (further dilution may be required).
When you use pesticides, you will run a risk of killing the good bugs. Thus, it is wise to use pesticides only when absolutely necessary. Also, leaving a few pests behind can help to sustain the population of beneficial bugs in your garden.