The olive fly, as is known, is one of the main parasites that compromise the quantity and quality of olives and their oil (sensory and nutraceutical properties)The increasing restrictions on the use of insecticides—such as dimethoate, revoked in 2020—require alternative, sustainable, and preventative solutions.
Insect nets are a physical defense strategy, already well-established in fruit growing, but still in the experimental phase in olive growing. These nets—based on experimental evidence—not only hinder adult egg-laying, but can also improve the microclimate, reducing environmental stressors such as excessive summer sunlight. Additionally, it can also help in managing other adversities such as hail, wind or heavy rainfall.
Experimental studies and results
As already mentioned in a previous article of ours, in July 2021 the Polytechnic University of Marche started a experimentation on adult plants (~15 years) grown in polyconic pots, 6 x 6 m spacings, using “Monotex 50” nets (15% shading, 0,97 × 1,54 mm). The installed nets (especially after the core hardening) have reduced fly attacks at extremely low levels (less than 1-2%). THE fruits are results larger and longer shoots of almost half a node during the growing months (July-August). No significant changes were observed in October photosynthesis between protected and control plants.
However, i labor costs and material prices are results high, making the technique economically sustainable especially for table olives and organic cultivation.
Between 2015 and 2016, again in the Marche region – precisely in Mogliano – a survey was conducted Experiment in an integrated olive grove on the Piantone di Mogliano cultivar, with HD polyethylene net, using two mesh variants.
The results on the microclimate were: light reduction 33% (with a 0,8 × 0,3 mm mesh) and 27% (with a 1,0 × 1,6 mm mesh); reduced internal temperature on average 1,21 °C, down to –1,56 °C in July, increase in humidity internal relative (+4,1-4,6% in the summer months; attenuation in autumn).
Practical experiences
In the area of San Casciano in Val di Pesa (Florence), insect nets have been implemented on a super-intensive system (Tuscan cultivars on rows, spacing 4,5 × 1,3 m): the nets (70 g/m²) have effectively blocked adults e prevented egg laying. No appearance of fungal diseases was recorded, nor any drop in production (about 80 q/ha). The coverage also had the sun has mitigated, favoring the microclimate and limiting vigor and the development of suckers, useful for adapting more vigorous varieties to super-intensive systems.
Despite thehigh purchase and labor costs this solution appeared anyway sustainable in super-intensive systems.
Economic considerations and applicability
I high costs – both of the material and of the labor – represent themain obstacle to the large-scale adoption of insect nets. They are advantageous in cases where: the focus is on table olives (fruit valorization), it works in organic farms (where the use of chemical insecticides is not permitted), super-intensive systems are available (easier installation, better yields). Optimal canopy management and more efficient installation techniques could lead to cost reductions in the medium term.
Conclusions and perspectives
Insect nets represent a promising strategy for the integrated management of the olive fruit fly, with tangible benefits in terms of protection, fruit quality, and microclimate. Studies show a significant reduction in attacks and improved plant physiology, without compromising photosynthesis. However, to make them economically viable on a larger scale, it is necessary to reduce installation and removal costs, enhance quality (e.g., table olives), and expand trials to include different varieties and environmental conditions.
In the future, it was assessed, a synergy with other technologies – such as the use of drones for monitoring or localized “attract-and-kill” treatments – could create even more effective and sustainable integrated strategies.
