When at rest, the wings are held almost vertically against the body with two buff areas at the front of the thorax and at the tips of the forewings which look very like the pale wood of the birch. The rest of the wings are the same mottled grey colour of the birch bark.

Occasionally the adults can be found resting in the day on a twig or the ground. They fly at night and comes to light, usually after midnight.

The yellow and black caterpillars can be seen from July to early October before they overwinter as pupae under the ground.

Size and Family

  • Family – Phalerinae (Notodontidae)
  • Large Sized
  • Wingspan Range – 44-68mm

Conservation Status

  • UK BAP: Not listed
  • Common

Caterpillar Food Plants

Deciduous trees; most frequently on sallows, birches, oaks and Hazel (Corylus avellana) but also Alder (Alnus glutinosa), limes, elms, Beech (Fagus sylvatica), Rowan (Sorbus aucuparia), Hornbeam (Carpinus betulus) and Sycamore (Acer pseudoplatanus), preferring those in sunny locations.

Habitat

Open woodland, scrub, hedgerows and gardens.

Distribution

  • Countries – England, Wales, Scotland and Ireland
  • Well distributed and frequent throughout England, Wales, the Isle of Man and the Channel Islands. More local in mainland Scotland.

Name: Box tree caterpillar.

Age: About four weeks as a caterpillar, then a few weeks more as a moth.

Appearance: Beautiful long green-and-black stripes dotted with black circles and yellow hairs.

Habitat: Your hedge.

Diet: Your hedge.

Argh! I’m afraid so. In fact, these pests can quickly defoliate an entire box hedge, and are now doing so all over the south of England.

Is a box hedge a hedge in the shape of a box? Often, although box (or buxus) is really the name of the type of shrub that is frequently clipped into formal squares, topiary animals, mazes and so on.

Yes, my garden in the south of England has several of those. So, how come they’re only being chomped by these caterpillars now? Well, the box tree caterpillar is an invasive species. It only arrived in Europe from east Asia in the last 10 years, and the first caterpillars were reported in Britain in 2011.

It’s a Chinese invasion! Probably. Last year, the Royal Horticultural Society, which is like the AA for plants, received more inquiries about these caterpillars than any other pest; there were 122 inquiries about slugs and snails, which came second, compared with 433 about the box tree caterpillars.

Won’t that just reflect the fact that gardeners already know about slugs and snails and don’t need advice, whereas these caterpillars are new to them? Shush. The point is that the box tree caterpillar is a major problem, and it’s on the march.

But how can we stop them? Er … Don’t know. There are things to try, but they all have drawbacks. In east Asia, their population is regulated by predators that we don’t have here.

Let’s import some, then! I wouldn’t recommend it. The main one is the Asian predatory wasp, which has a very nasty sting and is itself an invasive species in south-west France, where it is a threat to bees.

Curse these marauding foreign hordes! Yeah, maybe. Sometimes it’s a matter of getting used to things. Remember that, in Britain, we are an invasive species. It was all Neanderthals round here until Homo sapiens came along and eventuallly drove them to extinction.

At least we didn’t eat their hedges. No. There is that.

Do say: “They come over here … devouring our topiary …”

Don’t say: “We must take back control of our herbaceous borders.”

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This is a guest post by PhD student Adam Dale.

Dusky birch sawfly larvae feeding on river birch. Photo: A.G. Dale

This weekend as I was walking my dog down the greenway I noticed several heavily defoliated river birch branches overhanging the trail. Upon closer examination I saw several groups of a dozen or so yellow-green bodies with black spots and black heads chomping away at the leaves. When I reached up to grab a branch and take an even closer look, almost in unison they all swung their rear ends away from the leaf margin forming little S-shapes. This is the dusky birch sawfly, Croesus latitarsus.

Sawflies are relatively common leaf-eating pests of many landscape trees and shrubs. Different species usually specialize on one plant species or group of plants. Although easily confused with Lepidopteran (butterflies and moths) caterpillars, sawflies are actually Hymenopteran (bees and wasps) pests. The larvae are the damaging stage, which pupate in the soil after getting their fill of leaves, and turn into a winged, wasp-like adult. Don’t worry, though. It can’t sting you.

Typically, sawflies are shinier than caterpillars. However, the best way to distinguish between sawfly larvae and caterpillars is by counting the number of prolegs (the suction cup-like nubs along the rear underside of the body). Caterpillars always have five pairs of prolegs or less, while sawflies have six or more. As you can see in the photo, dusky birch sawflies have six.

As its name suggests, the dusky birch sawfly feeds primarily on birch trees, most commonly river birch in North Carolina landscapes. It is found throughout the United States and has two generations per year in NC. Right now they are in the larval stage of their second generation. Since these pests feed in groups, they tend to defoliate entire portions of a canopy and can clean the foliage off of an entire small tree. Despite this, they seldom reach high enough numbers to cause any lasting damage to a tree and rarely require intervention.

Defoliation by dusky birch sawfly larvae. Photo: A.G. Dale

If you’re concerned about them damaging your trees and you can reach them, just pluck them off and toss them into some soapy water or prune the whole branch. If you can’t reach them, you probably didn’t see them until they were pretty far along. Therefore, they’ll be gone soon and killing them now won’t prevent much damage. If you catch them early, good coverage with horticultural oil is effective and populations of larger individuals can be controlled with reduced-risk insecticides like spinosad. Products like Bacillus thuringiensis (Bt) will not work on them since they’re not caterpillars.

One interesting note is that I only saw clusters of these leaf-eaters on branches overhanging the paved greenway trail. When I ventured off trail into the forest they were nowhere to be found. It appears that they prefer the trees along the edges of the forest over the trail, perhaps because it’s sunnier, warmer, easier to find, less dangerous, or tastier. Edge effects like this aren’t unusual and can be caused by various factors. Remember that when scouting for pests like this and look at the prolegs if you’re not sure what it is.

Buff-tip moth (Phalera bucephala)

Buff-tip moth and caterpillar, Phalera bucephala

The Buff-tip is one of the most instantly recognisable moth species in the British Isles.

A common species throughout most of the British Isles, it is more numerous in the south.

Found in most habitats containing some deciduous trees including urban gardens, woodland and more open countryside.

The caterpillars feed on a wide range of deciduous trees including Oak, Sallows, Hawthorn and Blackthorn.

For help with caterpillar identification

Identification of the Buff-tip moth

Length of forewing is variable, ranging between 22-34mm with the male being smaller than the female.

It is an unmistakably distinctive moth, cryptically marked to resemble a broken twig.

Similar species – none, it is unlikely to be confused with any other moth in the British Isles.

Life-cycle of Buff-tip moths

The adult moth flies at night in a single generation from May to early August and is attracted to light.

Eggs are laid in clusters on the underside of the caterpillar food plant and hatch in 14-21 days.

The caterpillars feed gregariously and can cause quite severe defoliation. They grow rapidly, having 4 instars and are fully grown in about 30 days.

Once fully grown they leave the food plant to pupate in the soil and over winter.

Buff-tip caterpillar identification

The Buff-tip caterpillar is easily recognised from other species found in the British Isles.

The fully grown caterpillar is up to 75mm in length and has a distinctive trellised yellow and black patterning with a covering of fine pale hairs.

The face is black with an inverted yellow V. Identification of early instar caterpillars is also possible from their yellow and black colouring.

Other caterpillars

Hairy caterpillars

Rearing Buff-tip moths

Rearing of the Buff-tip is easy. Eggs and caterpillars may be found in the wild and females lay freely in captivity.

Caterpillars can be located by the defoliation caused by their feeding and, when fully grown,on the ground as they search for a place to pupate.

The caterpillars require a thin bed of soil in which to pupate and overwinter.

Pest status of Buff-tip Moth caterpillars

The caterpillars feed gregariously and can cause the significant defoliation of small trees, although not normally causing any permanent damage.

Prevention of defoliation

The most environmentally friendly way for gardeners to prevent caterpillars of the Buff-tip from stripping trees of leaves is to remove them either as eggs or when small and clustered together. The parts of the plant holding them can then be gently cut off and transferred to another larval food source. When larger they may have to be picked off individually wearing gloves.

Health warning

Please note the hairs of the some caterpillar can cause skin irritation so care should be taken if moving them.

Recommended Moth reference books

Buff Tip Moth bucephala pupae

Buff Tip Moth Phalera bucephala

The Buff Tip, once very common, is remarkable and a must for the enthusiast. The eggs are laid in a tight cluster on a leaf underside of the foodplant. A hatched group of eggs is illustrated and you can see the skeletonised leaf left by the tiny larvae as they progress feeding across the leaf. The larvae are gregarious and quite conspicuous by the trail of eaten leaves, and the fact that they form quite a lumpy cluster!

They are coloured with a netted pattern of yellow and black, warning colours that ward off predators, and larger larvae have a covering of long, fine white silky hairs. The group does not disperse until pupation when they descend to burrow quite deep into the soil.

The moth is a master of deception, rolling its wings to form a silvery tube with extraordinary likeness at either end to a broken branch. If it flies up on being disturbed, it is hard to spot on landing, unless you know what you are looking for, because it so closely resembles a piece of branch. The larvae feed Maple, Birch, Hazel, Laburnham, Poplar, Prunus (Plums and Blackthorn), Oak, False Acacia Robinia, Hazel, Rose, Willows, Sallows, Lime, Elm, Viburnums.

We recommend Buff Tips as a great experience of nature.

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