The Hoplocampa (Hoplocampa brevis, Klug) is a hymenoptera belonging to the Tenthredinidae family.
From a systematic point of view it belongs to:
H. brevis species.
Geographic Distribution and Habitat –
The pear Hoplocampa is an insect present in some countries of the Mediterranean basin, including Italy, and is a source of significant production damage. The phytophagous that can appear with fluctuating populations in different years preferably attacks plants of the genus Pyrus L., 1753.
Its habitat of diffusion is linked to the aggregate nature of its populations and infestations are usually localized in certain areas and, within the orchard itself, only certain varieties can be attacked. The situations of greatest risk occur in “unloading” years and in the case of poor fruit set.
The Hoplocampa brevis is a small Hymenoptera which, at the adult stage, measures about 3-5 mm of size; it has a brownish color and has yellow legs.
The wings are hyaline.
The larva is a false caterpillar 8-12 mm long. It has a reddish brown head and a grayish yellow body.
The eggs measure one mm in length.
Attitude and Life Cycle –
Hoplocampa brevis is an insect that overwinters in the mature larva stage in the ground.
The appearance of the adults occurs in spring with the beginning in correspondence with the phenological phase of the flower clusters until the beginning of flowering (late March-early April).
The females lay their eggs on the floral structures, at the base of the sepals, up to the beginning of the fruit set; the deposition takes place through an oblique incision towards the center of the glass with the help of their ovipositor; here an egg is laid under the epidermis between the two sepals.
The small larvae that are born enter the fruits, where they lead a more or less solitary endophytic life, the interior of which is destroyed by the larval activity.
The larvae dig a tunnel under the epidermis, on the circumference of the young fruit, and at the base of the sepals which become felted; then they move towards the center of the fruit and gnaw the seeds (called primary attack). Later they come out of the fruit near the sepals and carry on to another fruit (secondary attack), rarely moving to a third. Then they drop to the ground where they sink to build a silky cocoon.
The larvae remain in diapause until the month of February at a few cm in the soil, then pass to nymphosis in spring.
This insect therefore completes one generation per year.
Ecological Role –
The pear Hoplocampa is an insect that has fluctuating population dynamics from year to year. However, as a septum, the situations of greatest risk occur in the “discharge” years or in conditions of poor fruit set.
The presence of the phytophagus takes place on the fruits and can cause very serious damage; this condition is linked to the fact that each small larva can attack, during its development, different fruits by exiting them through a characteristic rounded hole, placed near the cavity of the calyx.
Attached fruits can be identified as they slightly stop the swelling, compared to healthy ones, highlighting a slight deformation; furthermore, signs of rosura are evident, if the larva is still inside, or the characteristic exit hole. In any case, the small fruits are lost with high drops.
Both primary and secondary attacks result in fruit dropping.
The intervention against the Hoplocampa brevis follows the principles of guided struggle and is carried out by monitoring the population, through the use of white color chromotropic traps.
The monitoring must be carried out in the phenological period of the pre-flowering by making a census of the adults that have just emerged from the wintering forms; we operate as follows:
– the traps are installed in the first half of March in number of two per plot;
– the intervention threshold occurs when the catches exceed 10-20 adults per trap.
The treatment against this pest is generally carried out at the end of flowering, excluding the very receptive varieties such as the Abate and the Decana in which one intervenes in pre-flowering if the threshold of 20 adults per trap is exceeded in this phase.
The interventions after flowering are carried out when the threshold of 5-10% of infested bunches is exceeded, or when the threshold of 20 adults captured in chromotropic traps is exceeded if this had not happened in pre-flowering in the receptive varieties.
However, the moment of the intervention must be weighed taking into account the presence of inept pollinators, so as to interfere as little as possible with their activity, and considering that in this period there are also embroiderers, such as Archips and Pandemis, who can create further problems; for this reason the choice of the period and of the products must also take into account the need to carry out cumulative treatments.
It is also interesting to use ground nematodes which, even in open field conditions, have shown a high mortality of the mature larvae of this insect.
Foliar treatments with nematodes can also be carried out, which must be carried out in post flowering when the holes appear in the small fruit, that is when the sawfly larvae make the transition from one small fruit to another.
However, while working with high volumes of wetting, the presence of nematodes inside the fruit was found only in the years in which there was the concomitant presence of rain at the time of the treatments.
In the experimental tests, the nematodes to the ground, on the other hand, were applied under the projection of the crown, wetting the ground before and after the treatment. The tests did not provide any positive response probably because the experimental conditions in which the tests were carried out were not the optimal ones due to the absence of rains in the period following application; despite this, the technique reveals considerable potential and it will be the responsibility of the next observations to verify its feasibility.
In any case, we recommend the assistance of an agronomist, with a specialization in entomology, to intervene and plan the best methods of intervention.
– Wikipedia, the free encyclopedia.
– Russo G., 1976. Agricultural Entomology. Special Part. Liguori Editore, Naples.
– Pollini A., 2002. Manual of applied entomology. Edagricole, Bologna.
– Tremblay E., 1997. Applied entomology. Liguori Editore, Naples.