La asian bug is a very invasive species which, despite having preferences for some crops, such as the cherry, apple and pear trees, also feeds on other plants, including the olive tree. Individuals of this species have a high reproductive capacity, I am very mobile, can travel a few kilometers a day in flight, while the young, without wings, can only move a few tens of metres. Furthermore, they have a long lifespan, living up to a year. The presence of wintering sites such as houses, buildings and piles of material represent a favorable factor for their proliferation, offering an ideal refuge for reproduction.
La proliferation of the Asian bedbug is also favored in fragmented terrain, where the presence of different crops reduces the defense capacity of plants against attacks by this harmful insect. In such situations, Asian stink bugs can easily move from one crop to another, especially when one of them is treated with plant protection products or concludes the production of fruits desired by the insect.
From observations, it emerged that some varieties such as Frantoio, Leccino, Pendolino, Casaliva, Moraiolo, although to a lesser extent, are particularly susceptible to attacks by Asian bedbugs.
The Asian bedbug begins to cause damage to the olives shortly after their fruit setting. Thanks to its stinging and sucking mouthparts, the insect pierces the small drupe, penetrating inside the pulp and feeding on the sap present and the integumental tissues still in the milky phase, which will then form the seed.
The lesions caused by these suctions deprive the olives of both essential nutrients and parts constituting its drupe structure, thus becoming one of the main causes of its early fall or abscission, a phenomenon known as “anomalous green drop”.
In case of attack, the growing olives lose their grip on the branch, being weakened and deprived of one of their constituent parts, begin to necrotize the underlying part of the olives and fall.
The damage can be identified by dissecting the small olives and observing the presence of necrosis of the seed and the almost total absence of its internal part, which has been sucked by the insect.
For control the Asian bedbug it is essential to adopt a approach based on visual observation in order to collect information on all stages of development of the insect. This process allows you to evaluate the extent of the infestation and identify any changes in its life cycle. Furthermore, it is important to place monitoring traps in strategic points of the olive grove to capture and monitor the activity of adult insects.
Il visual inspection must be carried out in the early hours of the morning, when the bedbugs are less active, also using, if necessary, an entomological net which is a thin net or sheet, similar to a mosquito net, mounted on a light and easy to handle frame. This tool is used to vigorously pass it over the foliage of the plants in order to capture the insects present and quantify their population.
Le traps, which can be containers or adhesive sheets and come activated with pheromones, should be placed outside the olive grove to avoid attracting insects inside, which could increase damage to the surrounding area. These traps should be set at the beginning of the season and checked weekly until the end of October. Monitoring allows the population size of the phytophagous to be assessed.
Even if there are no established intervention thresholds, to contain the anomalous green drop it can be hypothesized that, in a visual check lasting 15 minutes, the presence of 2 adults, in years of low fruit setting, or of 5 adults, in years of high fruit setting, you already represent a significant index to implement counteractions.
The containment of the bedbug can be implemented with the use of rock powders, kaolin and zeolite, already when the olives have the size of peppercorns and until the stone hardens. The intervention shifts depend on the formulation used and on the arrival of heavy rain, in which case the coverage must be restored.
To contain the anomalous green drop, the defense with Insecticidal products authorized for the Asian bug are based on Deltamethrin and must be used at the doses and in the manner indicated in the various commercial products; they must be applied when the olives are the size of a peppercorn and before the stone hardens. It is preferable to intervene in the cooler hours of the day, since at that time the bugs are less mobile and therefore more vulnerable to the agrochemical.
Other effective products, although not specifically registered for the Asian bedbug, are Neonicotinoids containing acetamiprid. Two commercial formulations, Kestrel and Epik SL, registered for the control of the olive fly and the olive moth, have demonstrated good knockdown power against adults and greater effectiveness on juvenile forms. Even the natural pyrethrum, registered for use in organic farming against the olive fly, although not specifically targeted at the Asian stink bug, has proven to be effective especially against juvenile forms. In this case it is important to apply it in the evening, to limit degradation due to the sun's UV rays and increase the persistence of the product on the crop.
With these phytosanitary interventions, the use of a wetter can improve the distribution of the product drops on the plant surface and therefore the effectiveness of the treatment. For large plots, it is preferable to concentrate treatments on the edges or along the perimeters, because these are the areas most susceptible to attacks by the Asian bug.
AIPO Director
Interregional Association
Olive producers
