As the year draws towards a close and darker nights arrive, there’s doom and gloom in the campo; the terrible trio are with us and sending shivers down the spine! I’ve written before individually on them but some of these articles were some time back and the threats are so great that I think an update would be useful to us all.
THE TERRIBLE TRIO: the ‘ebola’ of the olive trees; the black weevil/picudo negro of agaves and red weevil/picudo rojo of palms.
Xylella fastidiosa, known as the ebola of the olives, is the most recent and its effects have not yet been seen here but we all have good reason to be terrified of it. It is a bacteria that, at the moment, has no cure and can affect over 300 species, some of the most important being olive, orange, lemon, almond, grapevine, avocado, peach, nectarine, plum, pear, blueberry and ornamentals such as oaks, elms, sycamores, plane trees, oleander and rosemary. Some will simply be carriers of the bacteria and show no signs of the plague but they are a great threat to important crop trees. Insects as varied as scale insects, aphids, mosquitos and cicadas are all thought to be vectors, passing the bacteria from one plant to another. But, as usual, it is man (and woman!) that is doing and has done the main damage. The transport of live plants worldwide is a huge and profitable business; some of this plant material is infected.
In Spain there are some 2.5 million hectares of olives; 60% of those are in Andalucía. Málaga province alone has 130,000 hectares of olives; 16,000 of almonds, 6,000 of avocado, 4,000 of grapevines. Now you can see why Andalucía – and Spain as a whole – is trembling. The olive harvest alone, within Spain, is worth 1,800 million euro annually; the almond harvest is worth 60 million euro and citrus over 2000 million euro.
The bacteria works by blocking water flow from the roots to the plant; strangulation is slow and inevitable. First symptoms show as drying leaves and a general sickening of the plant. Later stages will show dry twigs and branches, increasing until the tree dies. Unfortunately, the earlier stages can easily go undetected or be confused with other more minor problems; it is often mistaken for stress because of the long hot summer, wind damage, or because of salinity in the water – all will produce a similar pattern of damage. A certain sign is when branches are cut, they display a blackness of the internal wood.
When I last wrote about xylella (in March), it was restricted to the Spanish Islands but it has now been detected in Valencia province where there are 26 distinct outbreaks. The Junta de Andalucía are taking it very seriously. More agricultural technicians have been employed to give advice and make inspections. They have a ‘hot-line’ (tel. 955059898) and are available on
info.xylella@juntadeandaluciia.es
The Red de Alerta de Información Fitosanitaria (RAIF) have an app to install on your mobile which uses GPS to track possible outbreaks and also enables photos to be sent for immediate analysis by experts.
The picudo negro or scyphophorus acupunctatus is not being taken as seriously but it is certainly causing havoc amongst our agaves and, to a lesser degree, aloes, yuccas and dracaenas. Again, when I last wrote about this evil weevil, it was still far from Andalucía but it has certainly landed here now. It arrived from Mexico and is devastating those plants that are such a distinctive part of our landscape and are so incredibly useful in dry gardens and parks. It loves elevated temperatures, so this long hot summer has suited it well and especially the warmer southern areas of Spain. At 2.8 cm long, it is smaller than the palm weevil but still very distinctive. The female can lay up to 500 eggs at a time and the beetles and grubs carry a bacteria called erwina carotovora. As they eat, the bacteria is released into the plant tissues where it multiplies rapidly causing rotting and the collapse of the plant. If you want to try and save infected agaves, spraying with systemic insecticides containing imidacloprid or clorpirifos seems to have some success but they are very damaging to our environment. The weevils seem to go for the largest and lushest agaves; youngsters are often left alone so maybe, once the invaders have moved on, you can replant the ‘pups’.
Because the plant is not a native of Spain (it was introduced by the conquistadores from the ‘New World’) and has, in some areas, become rather a pest (it is on the register of invasive plants and can be a nightmare to get rid of!) the authorities have decided to take no action against the weevil using it, instead, as a form of biological control. Let’s just hope that it doesn´t entirely wipe out these majestic giants. Friend or foe, they have had a worthy past used for fibre extraction and building materials. Our skylines will certainly look very different without them.
And to round up the terrible trio, I must update you on the picudo rojo or red weevil of the palms. This one has been in Spain for some 30 years now and was even detected in the United Kingdom last year. We may have become rather complacent about it, but it is still very much around and in full destruction mode. In Spain alone, it is reckoned that some 100,000 palms have been lost.
But technology has come to the rescue, firstly by detecting infected palms both by smell and the sound of the grubs chewing and forming a nationwide network of the spread. And now, the saviour from the skies! Drones can be loaded with a fungi called beauveria bassiana and inject it with great precision into the crown of infected palms. The palms react by activating their natural defence systems to high levels, making them unpalatable to the weevil grubs. The drones can reach palms up to 15m or more high and even on windy days; they are capable of injecting 140 palms daily. Tests have been carried out in Abanilla in Murcia, which has the second most important palm plantation in Spain with some 25,000 specimens, and results were excellent. The use of drones in urban areas, of course, is strictly prohibited but a special EU ruling is expected shortly which would give special permission for the palm drones.
It’s a great biological solution, but before you go calling up your drone, there is a downside to this tale. Each application costs between €7,000 and €10,000 so you’ve got to love your palm a lot!
Viveros Florena – Probably the best little garden centre in Andalucía!
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Viveros Florena, Ctra.Algarrobo/Cómpeta km 2, Cómpeta 29754,Málaga
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A DATE FOR YOUR DIARY:
6th December 2017
Our Christmas Crafts and Food Market. If you enjoyed the last one, you ain’t seen nothing yet! And, if you missed it, well, what can I say!
We only hold these Markets twice yearly & they are very special days!
