How to Spot Heather Beetle Damage on Our Moorlands

A tiny, seemingly unremarkable creature poses a significant and growing threat to our moorlands: the heather beetle (Lochmaea suturalis).

These small, olive-brown beetles are only around 6mm long. Despite their size, when their populations explode, these beetles and their larvae can inflict devastating damage on heather plants. Understanding how to recognize its impact is crucial for protecting our precious moorlands.

The Elusive Culprit

It's often hard to spot the heather beetles themselves because they are small and blend in well with their surroundings. They are well-camouflaged, making direct observation challenging. In fact, you might see extensive damage across the moor without ever seeing a single beetle. This makes recognizing the signs of their activity all the more important.

Key Signs of Heather Beetle Damage

Recognizing heather beetle damage is key to early intervention and understanding the health of our moorlands. The signs left behind by these tiny insects are often quite distinctive, helping you identify their presence even when the beetles themselves are hidden from view.

Here are the visual clues to look for:

• Stripped Stalks and Missing Leaves: One of the most obvious indicators is the appearance of the heather itself. Heather plants that have been targeted by beetles often have their leaves completely eaten away. What's left behind are often bare red or grey stalks. You might only see a few struggling green shoots remaining on these severely affected plants.

• The Distinctive Fox-Red Colour: As early autumn arrives, heather that has suffered from beetle damage frequently takes on a very specific hue. It turns a noticeable fox-red colour, an orangey-brown discoloration. This striking colour change is a clear sign that something is amiss and can be a strong indicator of a heather beetle problem.

• Widespread and Even Damage: When assessing damage, it's helpful to consider its distribution across the landscape. Unlike frost damage, which tends to be more severe in exposed spots, heather beetle outbreaks are typically equally severe. This means you'll see similar damage in both sheltered and shaded areas. Historically, damage caused by heather beetles was often mistakenly thought to be "frosting".

• Loss of Heather Cover and Encroachment of Other Plants: Severe infestations can kill off large patches of heather entirely. This leaves behind bare ground where the vibrant heather once stood. In some cases, less desirable vegetation, such as coarse grasses like molinia, can begin to take over these damaged areas. This change in plant composition is a significant visual cue.

• Increased Wildfire Risk: The decline in heather health caused by grubs feasting on green shoots can have serious long-term consequences. Over several years, this can lead to heather plants dying off. The encroachment of molinia grasses makes moorland areas far more susceptible to large-scale wildfires. Therefore, widespread areas of dead or dying heather should raise concerns about beetle damage.

Understanding the Beetle's Year: When Damage Occurs

Knowing the life cycle of the heather beetle helps us understand when to look for damage and why it appears the way it does. The visible damage primarily occurs during the feeding stages of the beetle.

• Spring Awakening and Egg Laying: Immature adult beetles spend winter hibernating in Sphagnum moss, heather litter, or shallow soil. They emerge in spring as temperatures reach around 9°C to 10°C, ready to feed on fresh heather shoots. Towards the end of April, females begin laying eggs, up to 700 or even 1000 in small clusters. They prefer damp vegetation like Sphagnum moss for egg-laying, and high humidity is vital for the eggs to hatch. This is why outbreaks often start near boggy areas.

• The Hungry Larval Stage (Peak Damage): The most visible damage begins in early July, when eggs hatch within one to four weeks. This period marks the peak emergence of the larvae. These yellow-green larvae climb onto the heather and begin voraciously feeding on the young shoots and leaves. This collective feeding by countless larvae and adults is what strips vast areas of heather foliage.

• Pupation and New Adults: After about six weeks of intensive feeding, usually around mid-August, the fully grown larvae drop off the heather. They then burrow into the soil and litter to pupate. New immature adult beetles start to appear towards the end of August, becoming more common in late September.

• Winter Preparation: As temperatures drop below 9°C, these new adults become less active and seek shelter for hibernation, completing their annual cycle. It's worth noting that normal frost doesn't significantly harm any stage of the beetle's life cycle, meaning mild winters can contribute to their survival.

Why Recognizing Heather Beetle Damage Matters

The consequences of widespread heather beetle damage extend far beyond just the appearance of the landscape. Healthy heather is the foundation of many moorland habitats, providing essential resources and shelter for a diverse range of wildlife.

• Impact on Wildlife: Many animals depend on heather for their survival, including important species like the red grouse and the caterpillar stage of the Emperor moth. When heather declines or is killed off, these species suffer due to loss of food and shelter. A surge in adult heather beetles doesn't bode well for the overall health of moorland areas.

• Ecological and Economic Consequences: Changes in vegetation, such as the loss of heather cover and its replacement by coarse grasses, can alter the entire moorland ecosystem. This can impact vital processes like nutrient cycling. For estates, damage to heather can also negatively affect grouse populations, impacting their economic viability.

• Vulnerability to Wildfires: As mentioned, the shift from healthy heather to less resilient vegetation, especially molinia grasses, makes the moorlands much more prone to large-scale wildfires. This creates a significant risk to the environment and surrounding communities.

Factors Contributing to Outbreaks

While heather beetles are a natural part of the moorland ecosystem, their outbreaks are becoming more frequent and severe. Several factors play a role, making vigilance even more important.

• Climate Change: Warmer and damper springs and early summers can create ideal conditions for a significant build-up in beetle numbers. Conversely, cool, dry springs can slow down their spread. Recent hot weather, droughts, and milder winters have been linked to increased heather beetle damage. Extreme weather events may also contribute to more severe attacks.

• Moorland Management Practices: Historically, large-scale outbreaks have occurred since modern moorland management began. The population dynamics are also influenced by natural enemies like parasitic wasps, ladybirds, spiders, and ants, whose populations can fluctuate. Some also suggest that drainage of wetter areas might reduce the likelihood of outbreaks, as high humidity is important for egg hatching.

Conclusion

The health of our moorlands, with their magnificent heather blooms, is under threat from the small but mighty heather beetle. By learning to identify the distinctive signs of damage - stripped red or grey stalks, the tell-tale fox-red discoloration, and widespread impact - we can become better stewards of these vital habitats.

Understanding the beetle's life cycle and the factors contributing to outbreaks helps us appreciate the urgency of the situation. Your awareness and involvement can contribute to protecting these essential landscapes for future generations and changing national policy.

Further Reading

• What you can do to control heather beetle