Evil weevil...

Answered by Harrod Horticultural Posted in Category Pest Control & Nature

Dear Martin

To my horror I discovered the dreaded vine weevil today in one pot in my greenhouse.  The only indication was that the 'money plant' was leaning to the side of the pot.  It's not a particular favourite of mine but one part of it looked healthy and had roots attached so I decided to replant it, and discovered the vine weevil eggs..... Some 2/3 years ago I found vine weevil in one of my pots outside - so it was easy to recognise.   I managed after a lot of hard work to eradicate it.    I haven't got an enormous greenhouse - standard size - mainly geraniums - all looking healthy.  Kept at 40% by electricity.   

I have placed an order but I was a bit upset to realise that I can't begin to treat the rest of the plants until March!!!   Surely by that time all of my plants could well be infected????  What do you advise?   

Mrs Bailey  

Dear Mrs Bailey

Many thanks for your recent message regarding the nasty surprise you discovered in amongst the roots of your money plant. Unfortunately, as the vast majority of gardeners wish to use the biological vine weevil control Nemasys H in an outdoor environment, we are unable to supply the treatment until soil conditions are favourable – a temperature of 5 degrees C must be maintained before successful applications can be made.  However, there are some cultural methods you can fall back on in the meantime, and of course there are some chemical controls available as a last resort, but we would not advocate this approach due to our firm organic beliefs.  

Removing any adult weevils is the first step, and their presence is far easier to spot than that of the elusive larvae. Small, neat notches are cut out of the leaf edges by the adult weevils, and these nocturnal shenanigans can be severely disrupted by placing a sheet of paper beneath any nibbled plant and shaking. You should find a number of adults come tumbling out of the leaf cover onto the paper, where they can be safely transported away and dealt with. This practice must be carried out under the cover of darkness to be successful.   You can also target the destructive larvae and potentially destructive eggs with a programme of re-potting. As you will no doubt be aware, the eggs and larvae live exclusively amongst the roots of plants and if any are discovered during re-potting, it’s advisable to sterilise or dispose of the infected soil. It’s also good practice to check the roots of any garden centre-purchased plants for evidence of infestations, as this is a common method of introduction.  

Hopefully these solutions will tide you over until your nematodes are despatched and you can mount a sustained attack on any larvae still present – the March and autumn applications cause maximum disruption to the vine weevil’s lifecycle, but you can still apply Nemasys H every 6 weeks throughout the growing season if necessary.