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Pine Tortoise Scale (Toumeyella parvicornis): A Serious Threat to Italian Pines

The pine tortoise scale is a highly damaging alien insect for Italian pines. Explore how to control it using the right agronomic practices.

by BioGrow

The pine tortoise scale (Toumeyella parvicornis) is an insect belonging to the Arthropod phylum, Emitters order, Coccidae family. It’s also known as the pine scale insect, being a specific parasite of trees in the Pinus genus. The name pine tortoise scale is due to its distinctive morphology, which in adult females resembles the back of a tortoise. This parasite is an alien species in our country, originating from the American continent. It first appeared in Italy in 2014, near Naples. To date, it has also spread to Lazio, especially in the urban area of Rome, putting the survival of the city’s pine trees to a severe test.

In this article, we’ll explore the characteristics of this pine parasite, the damages it causes to the trees, and the containment techniques being developed.

What Does the Pine Tortoise Scale Look Like?

Pine tortoise scale
Toumeyella parvicornis is a scale insect that, in its adult forms, resembles a small reddish shield, attaching itself to the buds of pine trees. The visible ones on the vegetation are the adult females, ranging in size from 3.9 to 4.4 mm. Morphologically, two types of adult females can be distinguished, their shape varying depending on the attachment point on the shoot. Some, the predominant ones, are semi-spherical when attached and feeding along the shoot axis (bark form). The others have an elongated form, adapting to their direct presence on the pine needles (needle form). If the infestation is severe, numerous overlapping adult females can be observed, forming dense concentrations resembling a “sleeve” with dozens of individuals.

Eggs

The eggs of the pine tortoise scale are oval-shaped, measuring about 0.4 mm, and have a shiny reddish color.

Females

The Toumeyella parvicornis females go through 3 nymphal stages before becoming adults. Those in the first stage are oval, reddish, and have 6 short legs. They represent the mobile stage of the parasite, which, once attached to the tree, does not move. Then there are the second and third nymphal stages, which are oval-convex in shape, light green turning reddish, with reduced and useless legs. Upon maturation, they become darker and show small blackish spots on their backs.

Males

Males of this species have two nymphal stages, followed by prepupal and pupal stages, and then winged adults. The male follicles are oval, white, and translucent, measuring about 3 mm. From small oval pupae, they evolve into winged adults in about 1-2 weeks. Adult males have wings and are present on the trees for a limited time in each generation. They mate and fertilize females just after the final molt.

Life Cycle

Observation of the Toumeyella parvicornis life cycle in our latitudes has shown that the parasite completes 3-4 generations in a year. Overwintering occurs in the form of fertile females, with rare presence of male pupal stages. In April, the first egg laying by fertile females takes place, with a generation completing in spring or summer in 9-10 weeks. Each female lays an average of 500 eggs during her life (10-30 per day), with peaks that can even reach 1,000. The egg hatches quickly, in just 1 or 2 hours. Mobile nymphs are distinctly present in May, July, September, and November, indicating that there are 3 + 1 partial generations.

Spread of the Pine Tortoise Scale in Italy

The pine tortoise scale was reported in Italy in 2014. Today, its major spread is in Campania, where it affects Naples, the coastal area from upper Caserta to Salerno, and some inland areas of Benevento and Avellino. In Lazio, infestations started in 2018 in Rome’s public parks and have now spread throughout the territory enclosed by the GRA (Grande Raccordo Anulare). We do not know how the insect arrived in Italy, perhaps through the trade of plants with foreign countries, as happened with the Asian bug and the red palm weevil. However, its spread is judged by expert entomologists to be exponentially increasing, not so much due to the insect’s ability to move over long distances but because of its presence along roads and highways, where the air movement from large trucks allows the parasite to easily move elsewhere. Let’s not forget the normal contact that occurs between the tree canopies.

Host Plants

In Italy, at the moment, the domestic pine (Pinus pinea) is the most affected by the pine tortoise scale. The maritime pine (Pinus pinaster), although very common on the Lazio coast, has proven to be less susceptible to attack.

Damages Caused by the Pine Tortoise Scale

Pine tortoise scale sooty mold on a pine branch
Serious damages have been recorded on domestic pines due to the pine tortoise scale. For many trees, these damages have led to severe decline or even death. This parasite essentially drains sap from the trees and compromises their photosynthetic capacity, causing phylloptosis (abnormal defoliation due to pathological causes). Abundant honeydew production and the formation of sooty mold with consequent blackening of vegetation are abundant on infested trees. The symptoms of an attack primarily include the reduced development of shoots in the upper part of the canopy. Then the lower part is affected, with wilting of shoots, arrested development, and drying of individual branches or entire limbs. As indirect damages, the pine tortoise scale causes soiling of the area beneath the pines (ruining, for example, car paint). Furthermore, dead plants must be removed by local authorities to prevent damage from falling during periods of strong winds.

Difficulty in Recognizing Symptoms

Only a close observation of the tree’s apices can allow the detection of a pine tortoise scale infestation (ongoing or just started). Pines, however, are tall trees, so a ground-level glance is entirely insufficient. For accurate analysis, periodic samples of vegetation parts, especially in high-risk or neighboring areas, must be taken. This careful monitoring is the first step in limiting the parasite’s spread.

Natural Enemies of the Pine Tortoise Scale

Parasitoid of the pine tortoise scale
Although it’s an alien insect, effective natural enemies of the pine tortoise scale are already present in our latitudes. In particular, we have the Cryptolaemus, which is the coccinellid predator Cryptolaemus montrouzieri. Another useful insect is the entomophagous and polyphagous parasitoid hymenopteran Metaphycus flavus. Unfortunately, these antagonists have not been able to adequately control the parasite on their own. Research on their use must be further explored and stabilized over time.

Preventing Pine Tortoise Scale Infestation

As one can imagine, eliminating the pine tortoise scale from pines is not at all simple. This is because we are dealing with tall trees distributed over a wide geographic area. From an agronomic point of view, the first thing public authorities should do in parks and roadside trees is constant monitoring, allowing for timely interventions and containment of infestations. Periodic and rational pruning is also recommended to remove dry parts of the canopy, ventilating it. We know that the pine tortoise scale thrives in humid environments where air circulation is limited. Of course, pruning waste, especially if infected, must be immediately destroyed through chipping. When planting new trees, favor more resistant species, such as the maritime pine.

Biological Defense Against Pine Tortoise Scale

For adequate biological defense against the pine tortoise scale, we hope that natural enemies do their job and effectively control the pest. Realistically, however, this is very difficult, especially in a suburban context. Interventions that humans can make, in addition to the aforementioned agronomic ones, include washing the tree canopy using potassium soaps and high-pressure water jets. This treatment is desirable in spring when the trees have the first-stage nymphs, the mobile forms of the insect. Another effective strategy, although not yet fully developed, is the creation of mass-trapping devices activated with pheromones, intercepting pine tortoise scale males before infestations explode.

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