What’s eating my berberis leaves? – All about the Berberis sawfly and how to treat it

Last updated on April 27th, 2022

If you have a Berberis (or a Barberry shrub as they are also commonly known) and you have suddenly noticed that the leaves are being eaten away leaving almost nothing in its wake, you might wonder what’s eating leaves on your Berberis. Thankfully, sort of, there is only one culprit: the Berberis sawfly.

The Berberis sawfly made its way to England around the year 2000, and from that time it has spread quickly. It is important to keep your eyes peeled for it because it is the only insect that feeds on the Berberis plant and more importantly, it can lead to severe defoliation in a short amount of time. 

Facts:

• Name: Berberis sawfly
• Plants affected: Berberis, especially the Berberis thunbergii 
• Symptoms: Leaves are eaten by larvae that are caterpillar-like. Plants can quickly become defoliated.
• Cause: Larvae of the sawfly
• Time: Between May and October

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What is the Berberis sawfly?

The sawfly falls under the same group of insects as wasps, bees and ants. They have larvae that are very much like a caterpillar in general size and appearance, as you can see in the picture above. These larvae feed on the plants and once they have eaten everything that your plant has worked so hard to grow the adults turn into winged insects that can fly, like in the picture below.

They have white spotted larvae that have black heads. They will feed on the foliage and cause severe defoliation almost instantly. They only feed on the Mahonia and the Berberis plants, so if you have either of these you really have to be vigilant about finding and treating the problem.

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Symptoms

The symptoms are very easy to spot. Firstly you might notice you can see the branches of your entire plant if you have been particularly unlucky to have it completely defoliated. This is the only insect that will cause severe defoliation on this plant and if you look closely you might notice a black head and creamy white body that looks like a caterpillar but has yellow-orange splotches and black spots.

If you’ve caught one of these on your leaves, you have caught them red-handed. The adults become shiny insects, that are black with greyish-black wings that can reach up to 8mm in length.

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Controlling Sawflies

You can physically check your plants between April and October and remove them by hand if possible, or alternatively, you can opt to replace your Barberry plant with something else that this pest doesn’t eat.

More effective though is using a pesticide control measure. You might have an infestation that is simply too much to pick away by hand, in which case you can spray a pesticide at dusk for the most successful results. Organic insecticides can be very useful although you might need to apply several applications to gain control of the issue.

The main thing to do is check regularly and spray the larvae before they have time to strip the leaves, but you must act quickly.

Last update on 2024-11-22 / Affiliate links / Images from Amazon Product Advertising API