Galls: Phytoptus avellanae

20 Monday Feb 2023

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British galls, bud galls, gall mites, gall-causing mites, galls on Hazel, Hazel, mite galls, mites, Phytoptus avellanae

These are my latest gall finds, caused by the mite species Phytoptus avellanae, shown here on Hazel (Corylus avellana) though they can also affect the buds of Filbert (Corylus maxima). The feeding of the mites on the plant cells within the buds causes those buds to swell and multiply. You can see a comparison in my photo below, the mite-infected gall bud on the left, the normal bud on the right.

230220 gall Phytoptus avellanae (1)

The mites that cause these galls are tiny, so rarely seen, but the Dutch Bladmineerders website has some excellent photos showing them in minute detail. As with so many galls, they are thought to be widespread in Britain but are not well recorded. So, if you’re out and about enjoying a spring walk and spot some Hazel, do please cast an eye over the buds, and record any galls you see. Citizen scientists really do make a difference to our knowledge of the natural world around us.

230220 gall Phytoptus avellanae (2)

Holm oak gall mites

09 Wednesday Feb 2022

Posted by sconzani in insects, trees

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Aceria ilicis, British galls, gall mites, galls, galls on oak trees, Holm oak, mite galls, mite galls on Holm oak

During yesterday’s walk, when checking for leaf mines on the leaves of Holm oak (large numbers of Ectoedemia heringella present – you can see one in the photo below), I noticed a huge abundance of small bumps covering many of the leaves.

220209 Aceria ilicis on holm oak (1)

These are the galls caused by the miniscule mite Aceria ilicis. On the underside (though sometimes also on top), the depression in the leaf is filled with tiny brown hairs (an erineum) where the mites make their home. The galls can be seen throughout the year, so next time you spot a Holm oak, check out its leaves.

302/366 Gone galling, again

28 Wednesday Oct 2020

Posted by sconzani in autumn, insects, leaves, trees

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Aceria macrochela, gall mites, gall-causing mites, galls, galls on Field maple, galls on Spindle, mite galls, Stenacis euonymi

October is a good month to check out life on leaves (and I’ll be writing some posts about the various leaf mines I’ve been finding) but today I want to show you a couple of gall species that are new to me. The first is quite common and easy to find, the second perhaps less so.

The first species is Aceria macrochela, a microscopic mite that spends its larval life in these tiny bumps on the leaves of Field maple (Acer campestre). You can read more about them and see more images on the mighty Nature Spot website.

And the second is also a mite, this one called Stenacis euonymi, whose larvae make their homes in the rolled-up edges of leaves on Spindle (Euonymus europaeus). If you have trouble with tree identification, as I often do, this is a good time to look for these as the gloriously obvious fruit of the Spindle are easy to spot.

201028 Stenacis euonymi (1)

Looking on the NBN (Nature Biodiversity Network) Atlas I see there are currently only 112 UK records for this species (113 including mine, which doesn’t show yet) but that’s probably due to it being under-recorded, so if you spot these, please do record your sighting.

174/366 Mitey galls

22 Monday Jun 2020

Posted by sconzani in insects, leaves, nature, trees

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Aceria campestricola, Aceria ulmicola, gall mites, galls, galls on elm, leaf galls

When walking along a narrow path between fields last week, I turned to face into the neighbouring hedgerow so that two other walkers could safely pass behind me. In so doing, I noticed these galls, which I think are Aceria campestricola (also known as Aceria ulmicola).

These growths betray the presence of the hundreds, perhaps thousands of the tiny mites that have caused these galls to form.

These particular galls can only be found on specific elm species, which in Britain include English elm and Small-leaved elm.

161/366 Mite galls on Lime leaves

09 Tuesday Jun 2020

Posted by sconzani in insects, lichen, nature, trees

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Eriophyes mites, gall mites, gall-causing mites, galls on Lime leaves, lime galls, Lime trees, mites

These stopped me in my tracks!

200609 lime gall mites (1)

I’d enjoyed a nice amble around a local park and was on my way home when I spotted these incredible galls and just had to stop for some photos. The galls are caused by tiny mites that spend the cool winter months huddling in cracks on the tree’s bark, then head out on to the leaves when they sprout in the springtime.

200609 lime gall mites (2)

The mites are leaf-sap suckers, and their sap sucking causes a chemical reaction in the leaf, which in turn prompts the leaf to produce these small, conical, hollow growths. The mites are incredibly tiny – less than 0.2mm long apparently – so they’re almost never seen, whereas their cosy gall homes can grow to 8mm long and, when they’re as bright as these ones were, are very obvious on the leaves.

I’m not sure which mites these are as I’m not sure which tree species this is. One mite species, Eriophyes tiliae, is the gall causer on Large-leaved lime trees (Tilia platyphyllos), Common limes (Tilia x europaea) and some hybrid Lime species, and another mite, Eriophyes lateannulatus, causes very similar galls on Small-leaved Limes (Tilia cordata) and hybrid Limes.

200609 lime gall mites (5)