Another Evil Weevil!!
Written in April 2013 by Lorraine Cavanagh
We are passionate about plants!
We are still reeling from the attacks of the palm weevil or picudo rojo and we now need to square up to another attacker – the agave weevil or picudo negro, scyphophorus acupunctatus. It doesn’t yet seem to be in our area of
the Costa del Sol but, make no mistake, it’s on its way!
The huge and seemingly invincible agave Americana that we see growing wild and in so many public gardens and parks and private gardens is its preferred host. Incredible as it seems, this little bug can topple those giants and in a very short time too.
A native of the Southern states of U.S. and, in particular, Mexico, its favourite food source is the agave, though it will also attack aloes, yuccas and dragon trees. The bigger, chunkier and more fibrous the plant, the more they seem to like it so large specimens are really under threat.
It was first detected in 2007 in Barcelona area and, although this weevil cannot fly, it has now spread to the Southern part of Alicante province.
Alarm bells are ringing all over the Costa Blanca since it was first detected there some 18 months ago and several hundred agaves have already been destroyed.
Know your enemy! The adult weevil is about 2 cm long, black and wingless with the typical weevil snout that bores holes deep into the base of the succulent plants to lay eggs – up to 500 of them. But worse still, when the female bores into the plant, her saliva introduces a bacterium called erwina carotovora which causes a fast developing rotting of the plant, making the flesh easier for the grubs to digest. So the attack is two-pronged. The voracious tunnelling of the grubs destroys the water-transporting tissues of the plant and, by tunnelling their way down to ground level, they sever
the plant from its roots. Collapse is very quick.
Up until now, the response by authorities has been to throw away affected examples in an attempt to stop the spread, but spreading it is and it seems like more desperate measures will be needed but little investigative work has been carried out as yet. The use of triazine granules, applied monthly around the base of agaves seems to kill the beetles and grubs as will consistent use of either imidacloprid or clorpirifos but all are very aggressive to the environment and can enter the water table. Regular spraying with neem oil would seem to be the best bio solution at the moment.
The picudo rojo and the negro seem to have a lot in common. Both live inside the plant, eating away and causing collapse. The damage is often not detected until it is too late for effective treatment and both are resistant to many of our ‘milder’ insecticides. Deep inside the plant, the micro-climate created means that they are impervious to freezing temperatures in winter and, although they are dormant then, they are pupating to rise like a phoenix when warmer weather returns.
The first agaves were probably introduced into Spain during the 1570’s by the Toledan botanical doctor, Francisco Hernandez. Now, like our palms, they are being massacred.
Throughout the centuries, the hefty flower spikes were traditionally used for steps and stairs because of their
enormous strength. The name agave signifies, in Greek, marvellous. It will indeed be sad if this marvellous dinosaur of a plant is wiped out by such a tiny attacker.
There is one other way to beat these baddies. You know the typical grub found in the bottom of Tequila bottles? Well, it is the grub of the agave weevil – after all, the Mexicans, too, had to find some way to control it. So, if we all promise to drink a bottle of Tequila a day, we could probably wipe out this latest scourge. Anyone game?