The HLB vector advances in Portugal and approaches citrus plantations in Huelva

Gregal abril 2021
Fedemco 2021 01
Bioibérica AQ-Flow

The Huanglongbing vector is already present in citrus areas near Lisbon, 190 kilometres away from crops in Huelva


HLB or the Citrus Greening vector continues to press forward in Portugal. / VF

The vector insect of Trioza erytreae, the propagator of the devastating Huanglongbing disease (HLB), is already present in citrus plantations near Lisbon, where it has been rapidly advancing in an irrepressible way, according to La Unió de Llauradors (Farmers Union) of the Portuguese Ministry of Agriculture.

The African psylliod capable of carrying the bacteria that triggers the feared Citrus Greening disease, has been found 220 kilometres south from the last known outbreak in July, located in the areas of Aveiro and Vago (the closest to Oporto) and has moved towards the zone of influence near Lisbon. Specifically, the Trioza erytreae —which is considered in itself a quarantine pest, although secondary compared to the HLB, that is not yet present in Europe—, has recently been confirmed in the municipality of Almada, where the demarcated area around this outbreak point already includes a good part of the first Portuguese commercial citrus plantations in the Tajo Valley area. The aforementioned vector has ceased to be located only in gardens or private properties, as it has occurred until now, and it is currently located within or only a few kilometres away from an area with more than 1,500 hectares that are mainly being cultivated with oranges. This location therefore leaves the closest affected area at a scarce 190 kilometres away from the first Spanish citrus plantations that are located in the province of Huelva (the second most relevant province in Andalucía, with around 19,000 cultivated hectares), and at only 170 kilometres from the main citrus producer in the neighbouring country, the Algarve, with another 14,600 hectares.

Just as threatening as the previous issue, mostly for the neighbouring country, is the fact that further north, the already known infected area of Aveiro has spread, with three new outbreaks detected since July in the area of Oliveira do Barro , Anada and Figuera da Foz, whose respective demarcated areas (where quarantine measures are being applied), are located a few kilometres from Coimbra —in the central region— which is the main nursery area in the country, with a production of 1.2 million plants. The situation in terms of crop protection measures is so critical, that the Portuguese authorities have already regulated the conditions under which their citrus nurseries will have to operate from January 1st, in order to be considered free of this insect and hence, not suffer the restrictions that have been imposed to stop its expansion. These measures go through isolation, by using covers that guarantee the biosecurity throughout the vegetative cycle of all nursery plants of greenhouse citrus plantations.

The infestation is in the process of expanding in the Iberian Peninsula since it was detected in Galicia in 2014 and it is pressing forward with a great invasive potential in the neighbouring country. Before the summer, the insect expanded without any interruption along the Atlantic coast from Galicia to the aforementioned area of influence in Oporto.

Between September and November, up to six new outbreaks were detected: the before mentioned neighbours of the already known areas (Oliveira do Barro, Anada and Figuera da Foz), plus three others —much further south— that have broken the geographical expansion continuity line as known until now (Alcoraca, Sintra /Cascais and Almada). This last fact, inasmuch as the new locations far exceed the ability of flight or propagation of the insect by wind, it encourages the thought that infestation has occurred as a result of the transfer of infected plant material.

In some world leading citrus producing countries such as the United States, Mexico or Brazil, HLB has already caused millionaire losses and is even threatening the very survival of the sector because there is no known cure. All experts in the field warn that the Spanish citrus cultivation faces the greatest threat since citrus Tristeza virus, which devastated a good part of the plantations in the late 50’s and 60’s. In all cases, since the irruption of the vector, the arrival of the disease (of the bacterium, which is not yet present, is reaffirmed) has only been a matter of time.

Huanglongbing causes a rapid weakening of the trees, which ends up causing their death in a few years and it affects the yield potential of plots from the first years of infestation.