olive butterfly

The olive moth is an insect present in all regions of the Mediterranean. Along with the olive fly and the cochineal, half a peppercorn represents one of the main phytophagous of the olive tree, so it is important to learn to recognize it and defend our plants against this annoying parasite.

These Lepidoptera do more damage to the olive groves present in the maritime areas of southern Italy, due to the mild temperatures and the high percentage of relative humidity, which favors their spread. However, phytophagous population density rarely exceeds the damage threshold that economically justifies defense interventions.

Let’s try to learn more about the moth and, above all, how to fight and prevent it with specific organic farming methods.

Contents [Ocultar]

• Characteristics of the moth

• Damage to the olive grove

  • Olive Moth Damage

  • Moth damage on leaves and flowers

• How to Defend Against Olive Moth

  • Natural Moth Antagonists

  • Prevent moths with traps

  • Treatments: how and when to defend yourself

Characteristics of the moth

Olive moth ( Pray oleae ) is a small insect belonging to the Lepidoptera family. It is a butterfly with silvery gray wings, with blackish spots on the forewings and a wingspan of about 12 mm. The size of the mature larva is about 7 mm. The insect has a greenish or hazelnut coloration, with olive bands on the dorsal side and two yellow bands on the sides. The butterfly develops around 3 generations each year, the damage it causes are respectively the flowers (antiphage generation), the fruits (carpophagus) and the leaves (phyllophage). They hibernate in the leaf mines, on the upper side of the midrib. The larva follows its development on the leaf through five stages, during which it makes characteristic erosions.

Damage to the olive grove

The alterations caused by these Lepidoptera are made by flowers, fruits and leaves, as mentioned above.

Moth damage on olives

The carpophagous generation of the butterfly drops the fruit at two different times of the year (July and October), i.e. when it enters the fruit and when it emerges to crack.

Since the olive tree has a natural thinning or cascade, in the beginning, when the olives are still in the early stages of development, the fall of the olives due to moth attack might be underestimated. The second fall due to the attack of insects occurs right next to the ripening of the olives, when it is no longer possible to intervene with the defense.

The first drop of olives affects the small fruits that are still developing and if the percentage of damage caused by the insect is not too high, it can even lead to an increase in the weight and size of the olives that remain on the tree, with the consequent increase in oil yield. Moth damage, on the other hand, results in a significant decrease in production and when it occurs, it is too late for any treatment.

Moth damage on leaves and flowers

Leaf damage is mainly due to erosion of the leaf parenchyma by the larvae, with possible loss of shoots in the spring following the attack, and by malformations to varying degrees of the leaf mines. The antiphagic generation, on the other hand, causes the flowers to drop, which results in a decrease in production.

How to Defend Against Olive Moth

The olive moth is a very common insect throughout the Mediterranean region, although it can cause damage to olive crops, and often the presence of this insect is insignificant, so it is not necessary to intervene to defend it. A natural environment with good biodiversity has a series of natural antagonists capable of limiting the presence of the insect. However, if necessary, we can put in place a biological defense against this pest of the olive tree.

Natural Moth Antagonists

The density of the moth population barely causes enough damage to require treatment, so in many cases no intervention is necessary. In general, environmental conditions, such as temperatures above 30° and low relative humidity, naturally limit the population density, causing the mortality of eggs and newly hatched larvae, as well as the presence of various antagonists and natural predators. In the literature, more than forty antagonistic species of the olive fruit moth are reported, of these only about ten constitute a permanent parasitic complex and only two are specific to the Prays genus, the braconidia Clelonus elaphilus SILV. and the encirtide Ageniaspis fuscicollis DALM. they are able to parasitize the larvae of three generations of the butterfly. T. embryophagum can parasitize even large numbers of eggs and is able to help keep moth population density below the damage threshold.

Among the predators, the lacewing Chrysoperla carnea and the antocorid hemittero A. nemoralis are of some importance.

Prevent moths with traps

If the biodiversity of the environment and the natural predators are already a method of spontaneous defense of the olive tree, we can also decide to set up a very simple and inexpensive prevention, by inserting food traps like the Tap Trap between the plants. They are simple water bottles with a “welcome” bait for Lepidoptera, with a lid capable of letting insects in while keeping them inside. The bait can only be made with wine, sugar, cinnamon and cloves macerated for 15 days.

The traps are obviously intended to attract adult insects and thus reduce the population of olive moths.

Treatments: how and when to defend yourself

The use of defensive interventions may be necessary against the carpophagous generation, which is the one that causes the most damage in terms of reduced production, and very occasionally against the anophagous generation. However, the damage threshold must also be assessed of the anophagous generation, fixed in 10 to 20% of the attacked inflorescences . From observations made in southern Italy, it appears that even in the case of 32% of the inflorescences affected, the economic repercussions of the infestation do not require defensive measures.

If the damage threshold is exceeded, it is appropriate to intervene in the generation of the carpophagus with Bacillus thuringiensis, when the eggs hatch, when the larvae are about to penetrate inside the fruit and are therefore more exposed to the action of Bacillus. It should be remembered that in organic farming the use of synthetic pesticides for treatments is not allowed.