The species of lisso which we commonly call chard awl they are more than one. These are insects belonging to the order Coleopterafamily Curculionidae. Among all, the most harmful species, however, is the common lisso (Lixus junci). The blood smooth (Lixus sanguineus) and the lisso scabricolle (Lixus scabricollis). These pests of chard they are able to cause significant damage to plants, both in the home garden and in specialized crops.
It is therefore important to understand how to recognize them, what are the problems they cause to crops and what biological defense techniques we can use to combat them.
Description of the common lip
The Lixus junci or common lisso is present mainly in the central-southern regions. It is a small, elongated beetle that measures 8-13 mm in length when ripe. It has a black body, covered with yellow-orange bloom. On the sides of the thorax and on the edge of the elytra there is a white band of pubescence.
The eggs are oval, with a smooth pale yellow chorion.
The larvae of the common lysus are apod, white with a darker head, when ripe they measure 12-14 mm in length.
Finally, the pupa, of a narrow and elongated shape with the last 5 uritri curved in an arc, measuring 10-13 mm in length.
Description of the blood lip
The Lixus sanguineus it is also present in a particular way in the Center and in the South. The adult is oblong in shape with black integument, covered in the individuals recently shrouded in rusty dust, with the sides of the prothorax, the elytra, the antennae and the reddish tarsi. The head is densely dotted with a pubescent rostrum. Measures 7-8.5mm in length.
Description of the Lisso scabricolle
The Lixus scabricollis in Italy it is present everywhere. The adult of this lysus also has an oblong shape, with a black integument, covered in the recently shivering individuals with reddish or yellowish dust. The head is dotted with a slightly arched rostrum. It is the smallest lysus, its dimensions do not exceed 4-6 mm in length.
What plants does the chard weevil attack?
The Lixus junci it is the most polyphagous species of lysus. Lives and develops mainly on chardsugar beet, seed chard e beetrootbut it does not disdain other plants, spontaneous and cultivated, for example spinach, cabbages And Fava beans.
The other two awls (Lixus sanguineus And Lixus scabricollis) are more specific parasites than chard.
Damage caused to crops by the common lysus
The adults of the chard weevil Lixus junci they perform typical semicircular leaf erosions. However, it is the larvae that cause the most significant damage, digging 6-7 cm long descending tunnels on the coasts, on the collar and in the swollen roots of beets and beets. Infested plants dry out early. On adult beet plants, development is blocked and rot processes are easily triggered. The larvae of the weevil also undermine the leaf petioles, compromising the normal physiology of the leaf which ends up turning yellow and then drying.
In seed chard, the tunnels dug in the flower stem weaken it, exposing it to the harmful action of atmospheric agents. The beet seed yields from a field attacked by the weevil drop significantly.
Damage of other species of lysus
The damage of other chard weevils, Lixus sanguineus And Lixus scabricollis, are related. The larvae burrow into the tissues of the basal part of the leaf petioles until they reach the collar. In correspondence with the oviposition lesions, small enlargements are formed, called cicatricial circles, with subsequent appearance of cracks in the tissues.
Life cycle of a chard awl
Here we take into consideration the life cycle of Lixus junci, the weevil of the chard of the most important economic importance. As for the other two, the following description is comparable.
Adult individuals appear in the fields as early as the end of winter, feeding on host plants. In April they are taken to the chard fields and begin to mate. The females leave immediately with the deposition of the eggs, on average 30-40, laid within incisions made with the rostrum in the petioles of the leaves or in the collar. After about a week of incubation, the larvae are born. These complete their development in 30-40 days, then pupate to give birth to new adults after 10-12 days. The new adults emerge from the infested plants by making circular holes. They stay in the chard fields until autumn, moving from one field to another in the warm hours of the day.
With the arrival of the first cold they hide in the ground to survive the winter.
How to prevent chard weevil
To keep the populations of the different chard weevil species under control, it is first of all necessary to act with agronomic prevention. Fundamentals are the crop rotations, i.e. do not plant susceptible crops on the same plot all the time. Without crop rotation, all crop pests have an easy life.
Then, since the lisso winters in the adult stage sheltered in the ground, the winter tillage of the soil, for example with the subsoiler or the tillerallow the wintering beetles to emerge and thus eliminate them in large numbers.
This kind of choices are obligatory in a field of beet previously infested by the weevil.
How to get rid of the chard awl
The defense with products allowed in organic farming is very complex on the larvae, as they live and feed inside the tissues of the host plants. It is therefore necessary to hit the adult weevils in spring, when they show up on the fields. In this phase there are two organic products that can be used with appreciable results, namely the natural pyrethrum And azadirachtin (the active ingredient of neem). In a home garden, the option of manual removal of adults should not be underestimated, shaking the plants early in the morning or during weeding operations. Cleaning weeds in the rows is positive, as is the maintenance of uncultivated areas adjacent to the field, with the function of trap plants. Furthermore, if you notice leaves with circular holes, therefore probably attacked by the larvae of the lysus, it is good to pick them, get the healthy part and destroy the rest.
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