Whitefly and Citrus Trees

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With the warm temperatures of the summer comes a rush of new foliage growth, attracting a wide variety of pests not least of which is whitefly, one of the most difficult pests to control, which poses a special challenge to gardeners.

Whitefly numbers grow dramatically in the heat, most strains are resistant to pesticides, and commonly infect citrus trees (you may have noticed these accumulating on the underneath of leaves on your lemon trees).

Here are some natural ways to manage whitefly on citrus trees.

Initially, when purchasing new plants, inspect both the upper & lower surfaces – as preventing white fly infection this way saves problems in the long run. Placing infected plants with plants that aren’t infected can be problematic as the whitefly can easily move from one tree to another.

Encourage natural predators of this pest – ladybirds and lacewing larvae, praying mantis, small spiders and even Cape white-eye all eat whitefly in all its life stages. Introducing an “insect hotel” to your garden to do this is one way, another is a bird feeder or bird bath. Encourage diversity as much as possible.

Interplanting with companions like nasturtium or yarrow around the trees will also contribute to repelling the pest.

Mechanically removing colonies by hand will definitely help to get control of heavily affected trees but this may be impractical if you have many trees to deal with. You should inspect citrus trees for whitefly throughout the spring and summer and look for areas coated with honeydew or sooty mould (sticky black and white under leaf). You can also prune off and discard severely infested leaves.

By far our favourite method to control this resilient pest is a vinegar dilution.  Mix 1 cup of malt vinegar (5% acidity) with 10L water and spray directly onto the pests and all over the tree on top of and underneath the affected leaves (we like to use the Mathabi range of sprayers for this). Apply this solution once a week for a month. Best time to spray would be early morning. We have seen the best results with this solution and the trees don’t seem to mind the slight increase in acidity over this period.

With a little effort you can eradicate your whitefly infestation naturally – good luck and enjoy eating your lemons!