This year's spring temperatures are bringing forward the olive tree's vegetative phases. In many olive-growing areas, advanced bud development is already observed, and in some areas, the beginning of flower bud development.
In parallel with the vegetative recovery, in several olive groves the first signs of the presence of olive margaronia (Palpita unionalis). In these days, in fact, it is not uncommon to observe larvae on the vegetative apices that feed on the most tender tissues, causing the first erosions on the shootsIn this phenological context, it therefore becomes important to pay attention to this lepidopteran, which finds favorable conditions precisely when the plant produces new vegetation and temperatures remain mild.
The biology of margarine
The margaronia is a lepidopteran belonging to the family Crambidae, widespread throughout much of the Mediterranean basin. Its growth is favored by temperatures between approximately 16 and 30°C, conditions that frequently occur during spring and summer.
The insect generally overwinters in the larval stage of various ages, sheltered among the vegetation of the olive tree or on other plants of the olive family. Oleaceae present in the surrounding environment. With the rise in spring temperatures, feeding activity resumes, and then it transforms into a chrysalis.
Adult butterflies are easily recognizable by their pearly white color with silver highlights and a wingspan of up to 25–30 millimeters. They are active mainly in the evening and at night. After mating, females lay their eggs on the leaves or young shoots of the olive tree.
The eggs hatch into light green larvae with brownish heads, responsible for damaging vegetation. The margaronia moth can produce multiple generations throughout the year, with its presence generally most evident between late spring and summer.
Damage to vegetation
La margaronia attacks mainly young leaves and tender shoots, that is, the tissues richest in nutrients and most easily degraded by the larvae. In these weeks, with the vegetative recovery of the olive tree, the first damages on the vegetative apices are starting to be observed, where the larvae feed, compromising the development of new shoots.
The most characteristic symptoms are:
• leaf rot, often reduced to just the central rib;
• eroded or damaged vegetative tips;
• leaves folded and tied with thin silky threads, inside which the larvae find refuge and continue to feed.
In young olive groves or nurseries, these attacks may be more evident, as damage to the apices can interfere with proper canopy formation. In mature olive groves, however, the impact on production is generally limited and rarely causes significant losses. Attacks have also been reported on drupes during the stone hardening phase, which, if left unchecked, can lead to significant yield losses (see attached photos).
The importance of monitoring
Monitoring is the main tool for evaluating the presence of margaronia in the olive grove. At this stage of the season, it is useful carry out periodic checks on the vegetation, noting in particular:
• damaged or eroded shoots;
• skeletonized leaves;
• folded leaves that can host larvae.
Careful and constant observation allows for the timely identification of any outbreaks and the assessment of whether intervention is necessary.
defense strategies
Balanced vegetation management – It is important to avoid excess nitrogen and manage irrigation correctly, since overly tender and vigorous vegetation can encourage larvae attack.
Constant monitoring – Particularly useful in young plants, where damage to the apices can have a greater impact on the structure of the plant.
Conservation of beneficial insects – Maintaining the biodiversity of the agroecosystem promotes the presence of natural antagonists that contribute to the containment of margaronia.
Targeted interventions only when necessary – In case of significant infestations, especially in young olive groves or nurseries, it is possible to evaluate interventions with products permitted for integrated or organic pest management, preferably when the larvae are in the early stages of development, the phase in which they are most sensitive to treatments.
In years characterized by mild springs and early vegetative development, margarine can find favorable conditions and show the first damage already in the early stages of the season, such as that observed in recent days on the vegetative tips.
In this scenario, careful and timely monitoring remains the most effective tool for assessing the true extent of the problem and adopting, if necessary, appropriate management strategies, while preserving the biological balance of the olive grove.
