Hello, Fellow Wrigglers!
Welcome back to another one of our pest management articles. And today, we will be exploring whiteflies:
What are Whiteflies
What impact do they have on our poor plants
Identification of Whiteflies
How to control the Whitefly population in our urban garden
1) What are Whiteflies
Whiteflies are soft-bodied, winged insects closely related to aphids. The adult female can produce up to 100 eggs in her lifetime. These eggs take approximately 6 days to hatch into "crawlers" that walk a short distance before settling at a feeding location. Here, the "crawlers" lose their ability to move and become "nymphs" that continue feeding on plant sap and mature into adult whiteflies in 2 - 3 weeks.
The entire life whitefly life cycle takes about 3 - 4 weeks under favourable conditions allowing for populations to build up quickly.
If not carefully managed, these would be detrimental to our plants (speaking from our own real-life experience!).
2) What impact do they have on our plants
Whiteflies feed using their needle-like stylets to ingest nutrient-filled sap from our plants depriving them of the nutrients they need to remain healthy.
Similar to aphids, whitefly also produces sticky, sugary honeydew that attracts ants. In return for their honeydew-producing service, the ants protect whiteflies from their natural predators such as ladybugs. This makes it harder to naturally control the infestation
As the infestation becomes more severe, the plants would begin to yellow, lose their leaves and eventually die.
To make matters worse, whiteflies are excellent vectors for over a hundred different plant viruses. The viruses are taken up by whiteflies when they feed on an infected plant. The viruses are introduced into the new plants during feeding and the new infection cycle begins. Depending on the strain of virus introduced as well as the type of plant infected, symptoms displayed by your plant may vary; from being asymptomatic to suffering a slow and painful death.
Therefore, we always recommend controlling whitefly infestation early. To do so, we'd first need to be able to recognise them.
3) Identification of whiteflies
The adult whitefly is quite easy to spot. They are normally found on the underside of the leaves and they will disperse and fly away when disturbed. Once adult whitefly is spotted, it is normally a matter of time before we find eggs and nymphs on the underside of our leaves.
The eggs and nymphs are harder to spot due to their small size. It doesn't help that the eggs and nymphs are translucent. But don't worry, there are clues that will suggest the presence of these elusive eggs and nymphs.
As the nymph feeds and produces honeydew that results in mould and attracts ants. Therefore, seeing ants or mould on the underside of your leaves are distinct clues that you should look out for when investigating for whiteflies festering in the vicinity. The amount of mould found on the underside of the leaves corresponds directly to the density of the nymph population. We'll show you how we use this as a gauge to decide when to do a full plant wipe-down using rubbing alcohol.
4) How we control whitefly population
Even though we are unable to see the nymphs, we know that they do not have the ability to walk. Hence whitefly population growth can be controlled using the following means:
High-pressured spraying of water to blast off the eggs and nymphs from the underside of your leaves
Insecticidal (sulphur) detergent mix applied via a spray mist bottle
Manual wiping of the underside of the leaves using rubbing alcohol
Chemical pesticides that are guaranteed to rid your plants off whiteflies
From our own experience, methods (1) and (2) are only semi-effective. Whilst good at controlling the whitefly population to a certain extent, we have to (3) manually wipe the underside of the leaves using rubbing alcohol from time to time once the infestation becomes too severe.
We normally measure the severity of the infestation by the amount of sooty mould on the underside of the leaves as this directly corresponds to the number of nymph feeding on our poor plant's sap. Once the amount of mould collected under the leaves grows over a certain amount, we proceed with the full plant wipe-down and this method is super effective (although very laborious and time-consuming).
We have read many reviews on the usage of chemical pesticides and this would be the preferred approach for larger-scale farms as they are unable to wipe the underside of every single plant leaf. However, as always, we do our best to keep it organic :D!
Best of luck in fighting the war against the whiteflies, and may the odds be ever in your favour.
The Wriggley Farm