We had a cracking citrus season this year with an abundance of lemons, limes, grapefruits, oranges, mandarins and cumquats to be seen across the region.
But growing all that fruit has taken its toll on the citrus trees and now they’ll be suffering from what I call ‘general tiredness’, making them susceptible to pests and diseases.
At the moment, it seems that the most common problem is the Bronze Orange Bug, or Stink Bug as it’s also known. And if you haven’t got them, you probably soon will.
Bronze Orange Bug is a native sap-sucking insect which only feeds on citrus family plants. It breeds quickly and the juveniles are small and hard to see in amongst the foliage.
With our citrus feeling a little worn out, their leaves are madly photosynthesising and changing sunlight into high energy sugars which they transport about in their sap stream.
The Bronze Orange Bugs take advantage of this by boring a little hole into the stems and tapping into this sap stream, drinking their fill of the sugary goodness within.
In normal years, this isn’t too much of a problem for citrus trees, as they can produce more sap than they need; and a healthy citrus tree can withstand a few Bronze Orange Bugs stealing their sap.
But at the moment, your trees need all the sap they can muster to recharge their batteries and put the energy into the small developing fruits they are growing.
Bronze Orange Bugs are particularly fond of the new fresh shoots of the citrus, starving them of sap and leading to the shoots wilting and dying, as well as dropping their developing fruits, meaning less for you next year.
This weekend, go out and take a look over your citrus trees. If you see any Bronze Orange Bugs, you’ll need to take action now and then every week or two over the summer months.
The control approach used to be to spray the tree with an insecticide that is absorbed and transported around with the sap stream – called a systemic insecticide. The Bronze Orange Bug would take a drink of sap and receive a tiny yet fatal dose of insecticide as well. This would give the trees protection through the whole summer.
But over time, these insecticides have been restricted in their use for backyard gardeners and so now the options are to use a softer, but less effective spray, on a more frequent rotation; or you resort to doing it by hand.
I’ve found the most effective spray to use is one of the pyrethrum products. These are less-toxic plant-derived contact insecticides that breakdown quickly in sunlight. Because of this, you are best to use them in the evening.
You also need to spray all the leaves – both sides – to ensure you treat all the pests, including the tiny juveniles you can’t easily see. And you’ll need to spray fortnightly. And follow the label safety instructions.
You can also collect them by hand using the ‘knock them into a bucket of hot soapy water’ technique, or – as some people do – using an old vacuum cleaner.
Using this control technique, you generally only remove what you can see – which are the dark adults and the larger almost-adults. The hordes of tiny juveniles will remain to suck sap and grow bigger.
So this technique will need to be repeated weekly or – better still – twice weekly.
But take care, as the adults squirt an unpleasant chemical from their backsides which can be irritating on the skin or damaging to the eyes.
Collected bugs then need to be disposed of appropriately. Don’t feed them to your chooks and they probably won’t like their foul taste and then the bugs just fly back to your citrus.
Keep on top of the Bronze Orange Bugs and your citrus will reward you with juicy fruits come winter.
