Battling the Evil Weevil!
It has been a long time since my last post. Almost 4 months in fact and what a lot has happened since then, most of it unthinkable. Next week I should have been heading for the US to visit to my son, instead of which we are in global lock-down against the dreaded Corona virus. Here we are 2 weeks in and I've done almost everything in the garden I can except defeating the Evil Weevil.
Vine weevil is the bane of Heuchera growers, they love them. I had a few last year but was able to defeat them with nematodes, a natural predator which you water in and it destroys the weevil larvae. Unfortunately although the winter has been too warm (and wet) to kill the weevils, it still isn't warm enough for nematodes to work. My heuchera collection has been devastated but I am fighting back however I am running out of hospital space. The number of plants now runs to over 200!
What is the problem? Vine weevils themselves don't do much harm - chew a few leaves but that's all except for laying eggs of course!. It's the larvae that are the problem. They eat the roots of the plants leaving a drooping top behind. If a plant looks suspiciously droopy, give it a gentle tug. If it comes away easily look for the white larvae in the soil. If you catch it in time there maybe some roots left. Sometimes the first thing you know is that a gust of wind has blown the plant out its pot.
The larvae are white, about 1/2cm long and are often curled in a C-shape as can be seen in the image above. They eat the fine roots - which is when the plant starts to droop - then burrow into the thick chunky roots from which they have to be winkled out leaving a hole. Squashing them is a bit like squeezing a spot (sorry!), revolting but very satisfying!
So your heuchera has been attacked by Vine Weevil, what can you do? The best solution is douse them in Nematodes which you can buy from various places online but they will only work when the soil is above a certain temperature. There is a Bug Killer aimed at weevils (Bug Clear Ultra Vine Weevil) but I haven't tried it and you can't use it on edible plants (weevils like strawberries too apparently). The third option is to carefully remove the plant from its pot (not a problem if there are no roots left). Take care not to scatter larvae around and destroy any you can find. Carefully wash the soil and larvae off the plant, winkling out any that had burrowed in - you can tell if there is a dusty patch on the root which has passed through the larva. I sometimes cut a chunk off the root to check inside, it doesn't seem to harm the plant. Throw away the infested soil - in your waste bin not compost or green waste bin - and check around carefully to make sure you haven't missed any of the little so-and-so's. I use a mixture of potting compost and grit and it can be hard to tell whether you are trying squash grit or weevil larvae! Wash and disinfect the pot.
Once what is left of the roots are clean and bug free, you can split and replant them in fresh soil. Heucheras are tough and will often regrow from almost nothing.
These are the plantlets I got from this particular specimen. Two had a chunk of root left but the remainder are little more than leaves and the crown. Be careful not to bury the crown or it will rot. As these have so little root I will keep them in the greenhouse. I date them and should be able to tell in 3-4 weeks if they have survived. Below are some successes. The top two are recent but have strong sprouts coming, the bottom two were repotted in November last year and are growing strongly. As you can see, you can end up with a lot of plants!
