Controlling Citrus Gall Wasps in Your Garden

Many garden pests in Australia have come to our yards from overseas, but the citrus gall wasp (bruchophagus fellis) is an Aussie native. Originally sticking to coastal areas in Queensland and New South Wales, the pest has more recently been found to have travelled to South Australia, Victoria, and even suburban parts of Perth.

As its name suggests, these wasps are a rampant destructor of citrus trees, starting with the native finger lime, and now also taking up shelter in orange and lemon trees. If you’re worried about the pests wreaking havoc in your yard, then read on for our top tips on identifying, controlling, and getting rid of citrus gall wasps.

Spotting Citrus Gall Wasps

Citrus gall wasps are meagre 3 millimetres in length and are dark brown or black in colour, making them difficult to see, let alone differentiate from other flies in your yard.

The easiest way to determine if citrus gall wasps are attacking your trees is to check for the galls themselves. These look like swollen nodes or calluses on branches and stems which form when adult females lay their eggs inside. Two telltale symptoms of an affected tree are lower fruit yield with the fruits themselves also being smaller than usual, as well as weakened, dying branches.

Life Cycle

The first thing to do when implementing control measures is to understand the life cycle and active phases of citrus gall wasps.

Adult gall wasps emerge from the gall during spring, typically between mid-October and December, and lay their own eggs within a week. These eggs turn to larvae, then pupae, and stay within the stem throughout their development for 9 to 10 months as the woody gall forms around them. By the end of this period, they are ready to emerge and begin the cycle again, laying up to 100 eggs of their own.

Female Citrus Gall Wasp laying eggs

Wasp larvae growing inside the stem

Citrus Gall Wasp larvae hatching

Getting Rid of Galls

The best time to tackle growing galls is between April and June, as later winter treatment will likely encourage an excess growth of foliage in spring, which will, in turn, attract more wasps to the plant.

There are two main methods that gardeners use to remove galls from their citrus trees; pruning, and paring. Pruning requires the removal of the entire affected branch and its fruit, whereas paring the gall allows gardeners to try and save it, making this the preferred method for most people. If you’re taking citrus gall wasp control into your own hands, then you’ll need a vegetable peeler or a sharp blade which you can carefully control.

With the blade moving away from your body, carefully slice off the top layer of the gall. This will expose the larvae inside to air, which will kill them and prevent them from causing further damage to the plant. The good news is, it won’t cause any harm to the citrus tree itself.

Another way to control citrus gall wasps is to hang sticky yellow traps inside infested trees to trap emerging adult wasps. Be sure to remove these when summertime comes around though, as they can also unintentionally trap beneficial garden insects too.

Disposing of Infested Off-Cuts

When you’ve removed the affected tree parts, they need to be disposed of properly to prevent any pupated wasps from continuing the cycle in your yard. Before placing the prunings in your compost bin or green waste, you’ll need to either leave them in a plastic bag baking in the sun for two weeks, drown them in a bucket with a tightly sealed lid, or burn them. This may seem extreme compared to other disposal methods, but is the only way to ensure that no wasps escape to cause any further damage to your citrus trees.

Get Expert Help

If you want advice or help handling citrus gall wasps or any other nasty garden pests, then get in touch with Jim’s Mowing today to speak with one of our friendly experts!