Citrus Gall Wasp causes lumps in the lemon tree.

by Dennis Ting

It is common these days for people to come into the garden centre either describing or bringing in branches of Citrus trees (commonly lemons) which have thick knobbly sections or rounded bumps on them wondering what it is and how to treat it. 

 These galls or cankers are caused by a native pest called the citrus gall wasp which usually parasites native plants in its home areas of northern NSW or southern Queensland.  It has unfortunately taken a liking to introduced citrus especially lemons and grapefruit but also oranges and other citrus to a limited extent. 

Its natural distribution is far north of here around the NSW and Queensland border.  Unfortunately over the last decade or so it has become more and more common in the gardens around Victoria and Melbourne. 

The adult gall wasp lays eggs on the stems of the host citrus plant from late spring on new young stems.  The eggs hatch and the larvae burrow into the stems and cause the plant to form cankers around them as they develop inside.  When they are mature in late spring they come out of the gall by burrowing leaving pin sized holes. 

A severe infestation can lead to a loss of vigour and dieback of the tree.  Therefore it is essential to reduce the infestation by treating the tree as in a couple of years it can lead to very reduced vigour and cropping of the tree. 

There is no recommended insecticide or similar treatment for this pest and the recommended treatment is to remove the galls with larvae in early spring before the next generation of wasps appears.

 Another treatment is the use of Sticky Traps which we stock in the nursery hung in the plants from early spring onwards.  These long yellow tubes attract the emerging adult wasps and they get stuck on the exposed glue.

 
I used one in my small "Lot's A Lemon" Dwarf Meyer from September onwards and I can report that I had

My suggestion for treatment is to remove as many galls as possible around August and hang the sticky traps in the tree around this time too.  Feed generously in spring to ensure that good growth develops to replace the one year old growth that has been removed and the tree remains in good health.

 

Comments

[Suelle]

Thankyou!
I just moved into my new house and was so excited about having a lemon and lime tree and thought it had some kind of disease.
Now I know what it is i can tackle it!

You're awesome :)

[buy kamas]

I used one in my small "Lot's A Lemon" Dwarf Meyer from September onwards and I can report that I had

[Shona Beagley]

Thanks for the information on Gall Wasp... Have had this problem for a few years and kept cutting the infected pieces out then feeding with worm juice regularly... I didn't know if I was doing the right thing but didn't want to destroy the plant... I'm so glad I won't have to destroy my citrus tree...

Shona...

[Jamie Pearce]

Apart from the suggestions for traps and a difficult to source spray made up of different chemicals plus urine, it would appear that cutting out the galls is the only solution. But in our heavily infected tree ( I think I must have missed the first infection two seasons back) this will mean reducing the tree by half. I have heard it recommended that wrapping some sort of tape around the 'warts' now will prevent the emergence of the maturing wasps. This sounds plausible but i would appreciate advice in dealing with a major problem.

[Helen]

I have just come inside from cutting a few branches off our 50 yr old lemon tree. There it was the dreaded gall wasp swellings. Im not sure how long they have been there as the tree doesnt get what some would call T.L.C. There is very healthy new growth and the fruit is as good as ever, too much if anything. This year it will have its usual once every decade cutback. Im not going to worry about the swellings. Who knows they couldve been there for a long time. When i cut it back ill try to take as much of the swellings off as possible [ the tree is huge ] and thats about all im going to do. If its lucky i might even feed it. Will let you know what happens.

[kerry]

I was given a young Lisbon Lemon that was already infected. The tree struggled for about two years before I discovered how to treat it. I pruned harshly and now two years later I have some young buds and lemons forming.The tree will come back once you free it of the infestation.

[margaret]

A neighbour had a young lemon tree about 2 metres high, infested with gall wasp. He cut off ALL the affected branches, leaving NO foliage, in early Spring, and hung a sticky trap in the branches. I thought the tree would not re-grow, but 6 or so weeks later it started to sprout new shoots. Four months later, it looks brilliant. I am going to risk the radical cut back on my 30 year-old tree in August. It looks too ugly to put up with as it is, but I'm really hoping it will do the Lazarus trick that my neighbour's much younger tree accomplished!

[Armil of Wasps]

Thank you for your informative post with an image that made your discussion clear.

I can now connect my previous experience regarding the causes of some trees in our neighbor hood especially coconut trees slowly decaying itself and died.

The reason behind this tragedy of plans are the wasps. Thanks!

[Patrick D]

I have just discovered that my lemon tree has been infected quite severly. We have removed all the infected branches, giving quite a heavy prune. We are lucky that we have been able to retain most of the fruit and it has opened the tree quite well, enabling the rain to penetrate the root area.

[nethmi]

Thanks for sending us your website for us. :] :]:]:]:]:}:]:]:]