Leopard Moth is a wood parasite that affects fruit and forest trees. Its scientific name is Zeuzera pyrina, but it’s also commonly known as the wood leopard moth due to the beautiful markings on the adult butterfly. It’s an insect with a very long biological cycle, causing damage to tree crops in its larval stage. Eliminating the Leopard Moth requires careful monitoring and interventions involving the use of sexual confusion traps and other organic farming remedies.
Let’s explore everything you need to know about the Zeuzera pyrina, the damage it causes to crops, and how to eradicate it.
Which plants are affected by the Leopard Moth
The Zeuzera pyrina is an insect of the Lepidoptera order, Cossidae family. We’ve already discussed a similar species (but with significant biological differences), the Cossus Cossus, also known as the red leopard moth. The Leopard Moth is highly polyphagous, attacking numerous tree species.
Here’s a list of the main ones:
- Pome fruits (apple, pear, quince, common medlar, Japanese medlar, azerole);
- Stone fruits (peach, plum, apricot, almond, and cherry);
- Walnut and hazelnut;
- Deciduous forest and ornamental trees.
Recognizing the adult Leopard Moth
The Leopard Moth is easily recognizable in its adult stage:
- It appears as a medium-sized butterfly with a wingspan of almost 70 mm.
- Its forewings are white with distinctive blackish-blue spots.
- The thorax is also white, downy, with 6 large bluish spots.
Recognizing the larvae of the Leopard Moth
However, it’s important to recognize the larvae of the Leopard Moth. They are the ones that cause damage to fruit trees.
- At full maturity, the larva can be up to 60 mm long;
- It has a dark-colored head and prothorax.
- The body is yellow (hence the common name), covered with numerous black tubercles arranged in longitudinal rows.
- The eggs laid by the adult Leopard Moth butterfly are pink.
Damage to crops by the larvae of the Leopard Moth
The larvae of the Leopard Moth cause the most damage to plants and are therefore a major concern for tree growers.
Through their trophic activity, they create galleries on the tree’s apexes. They are genuine wood-boring insects. When the larvae are in their early stages, they primarily attack young branches and shoots. In later larval stages, the Zeuzera pyrina moves to older and tougher branches before eventually reaching the tree trunk.
The larvae create these long galleries, often targeting the center of a branch or shoot. One of their characteristics is repeatedly entering and exiting the wood. The affected parts of the plant show significant wilting, particularly in young shoots. In harder wood, it starts losing strength as it’s eroded from the inside. After a strong windstorm following rain, it’s common for branches attacked by the Leopard Moth to break, unable to support the weight of the vegetation. Overall, when a plant is infested by the Leopard Moth, it undergoes visible deterioration, especially in the case of young trees. Another risk factor resulting from the insect’s galleries is that they can become entry points for fungal diseases or wood cankers.
Biological cycle of the Leopard Moth
The Leopard Moth has a very long biological cycle, which completes in one or two years. The larvae overwinter within the galleries they’ve created. This can occur in either the first or second year. In spring, emergence begins, taking place from May to September, with peaks in July. During this period, mating and egg-laying occur. This can take place within old galleries or in other types of tree lesions. The newly hatched larvae of this pest immediately start attacking shoots or young branches. As mentioned, they expand their range as they grow, moving from tender to tougher parts of the tree.
In this phase, the damage caused by the Leopard Moth is observable and evident. Attention should be paid to exit holes and the accumulation of frass at the base of the plant or around the holes. These larvae overwinter before the cold sets in, and in the following year, two situations can occur: spring emergence, resulting in one generation per year, or they remain in the larval stage into the second year. In the latter case, they spend the winter as larvae and then emerge in the spring of the third year, completing a single generation in two solar years.
How to eliminate the Leopard Moth
Controlling the Leopard Moth is challenging because the larvae operate within the woody tissues of trees, making their presence difficult to detect. Therefore, it’s essential to conduct spring monitoring using pheromone traps that intercept males during emergence.
Sexual confusion traps
While a few traps can be used for simple monitoring, sexual confusion traps allow for a mass capture of Leopard Moths. When using these traps, a minimum of 10 traps per hectare should be used.
This solution is simple, effective, and environmentally friendly.
Sex pheromone traps intercept only the target species, leaving beneficial insects unharmed.
For the Leopard Moth, using sexual traps prevents the females from mating, leading them to lay sterile eggs. Over time, this significantly reduces the parasite’s population. We’ve also discussed this technique in relation to the tomato leafminer. The application challenge lies in the costs and availability of pheromones, which are only found in highly specialized agricultural stores. However, for professional fruit growers, it’s a necessary choice.
As we know, bacillus thuringiensis is an effective biological insecticide against lepidopteran larvae. Therefore, it could also be effective in eliminating young Leopard Moth larvae. However, Bacillus thuringiensis acts on contact. Unfortunately, the Zeuzera pyrina larvae operate within shoots, branches, and stems, making it challenging to target them using this natural soil bacterium. It’s important to be vigilant regarding monitoring trap indications and to treat as soon as the eggs hatch.
A highly artisanal method to eliminate the Leopard Moth is the wire technique. This involves identifying holes on the tree left by the larvae. Then, a wire is inserted to try to impale the larva. The practical difficulty arises from the larva’s high mobility, meaning it might not be in the hole being observed. Additionally, the Zeuzera pyrina larvae attack young shoots and small branches, making it challenging to insert a wire. This is more of an emergency solution, recommended only for a few trees already attacked on the trunk, indicating an ongoing infestation.
Lastly, biological defense against the Leopard Moth has proven very effective through the use of microorganisms, in a technique known as microbiological control. This involves the use of Beauveria bassiana, which is also effective in combatting the Colorado potato beetle and entomopathogenic nematodes, which we’ve discussed in relation to the black vine weevil. For more information on these biological methods, please refer to the respective articles.