Steinernema kraussei, the nematode used against Vine Weevils, can be applied at any time when there are likely to be larvae present, being most effective when the temperature is 5 degrees C or more.
The compost must be kept moist at all times to enable the nematodes to swim (they live in the moisture that surrounds soil particles).
The nematodes enter the weevil larvae via body openings; once inside they release fatal bacteria that kills the larva within 48 hours. The nematodes reproduce within the dead grub and the new generation are released back to the compost as it decomposes.
If no more larvae are in the vicinity, the nematodes will die out after a few weeks.
Seeing as how your plants are in a protected environment, if we should get a milder spell at all , you may be able to apply nematodes.
Generally, if the larvae are in an active state, nematodes will be too (vine weevil larvae enter diapause when it grows very cold).
Generally, the best results are reported where application is timed to the pest's life-cycle and so an application in March-May and another in August-November is recommended.
However, in protected environments, the larvae may be present all year round...
Philippa - at least you're aware of the dangers of the stuff, and anyway, as co-founder of the Snail Lover's Society you must like wildlife in general, so we'll let you off!
Carried on examining other plants in the tunnel. Grubs in Astilbe pumila and tiny newly hatched ones in Salvia turkestanica. Never seen them in Salvias before.
Dianthus, various bulbs, Cyclamen, lots of different Saxifrages all clear for the moment. Will go through them all again before the New Year, just in case.
Just thrown away 30 or so Primula allionii babies. Not going to grow them after we move, they need a humongous amount of coddling. Not a single weevil grub in any of them. Weird! Yet in the P. sieboldii there were newly hatched ones.
Absolutely no point in using GH smokes on vine weevil, the adults will be dead now and the grubs in the soil will emerge as adults in the Spring.
The adults do not live in pairs, they are all females and all lay eggs.
next year take precautions earlier, apply nematodes at the end of March and again in October, that will kill the grubs that would normally do the damage over winter.
They do work, I have used them and just one application did the trick, but it’s probably best to apply another lot to see you through the winter.
Expensive, but probably no more that the bottles of provado, which you need to apply in quite large amounts to thoroughly drench the pots. And of course safer.
As to the above post, I don’t think ‘most’ gardeners spray their plants and I wouldn’t use smokes anyway.
Gardening on the wild, windy west side of Dartmoor.
Smokes would not be much use in a poly tunnel in any case, especially as it is wide open at one end. The compost is peat free stuff mixed with sterilised top soil and gritty sharp sand. The pots were all brand new (bought 7,000 of them a couple of years ago.)
No amateur spray will kill adult vine weevils. I dropped one in pure bleach one time, it swam around for 24 hours.
As I said hopefully we will be moving in the new year. I will take my Auriculas as bare unrooted cuttings.
I have used Nematodes with success before but obviously we are not on the scale you are on Berghill. I was going to suggest sterilising your soil / potting compost but it sounds as though you are already doing this. There must be a reservoir of infection (? unhatched eggs) in your system. The only problem with any biological control is that it will never eliminate the host completely. Your solution to take cuttings into sterilised compost in clean pots sounds like the only way forward. There used to be soil sterilising fumigants available but I doubt they are still available- maybe commercially.
This is a large area surrounded by fields. When we did a sweep of the garden a few years back we caught over 100 adults. No way of clearing the garden completely. Not found any more larva for a few days, but I will soon have to start going through the plants in the frames. Lot of susceptible things in there. That is over 1,000 plants to unpot and examine.
Posts
Steinernema kraussei, the nematode used against Vine Weevils, can be applied at any time when there are likely to be larvae present, being most effective when the temperature is 5 degrees C or more.
The compost must be kept moist at all times to enable the nematodes to swim (they live in the moisture that surrounds soil particles).
The nematodes enter the weevil larvae via body openings; once inside they release fatal bacteria that kills the larva within 48 hours. The nematodes reproduce within the dead grub and the new generation are released back to the compost as it decomposes.
If no more larvae are in the vicinity, the nematodes will die out after a few weeks.
Seeing as how your plants are in a protected environment, if we should get a milder spell at all
, you may be able to apply nematodes.
Generally, if the larvae are in an active state, nematodes will be too (vine weevil larvae enter diapause when it grows very cold).
Generally, the best results are reported where application is timed to the pest's life-cycle and so an application in March-May and another in August-November is recommended.
However, in protected environments, the larvae may be present all year round...
Philippa - at least you're aware of the dangers of the stuff, and anyway, as co-founder of the Snail Lover's Society you must like wildlife in general, so we'll let you off!
Carried on examining other plants in the tunnel. Grubs in Astilbe pumila and tiny newly hatched ones in Salvia turkestanica. Never seen them in Salvias before.
Dianthus, various bulbs, Cyclamen, lots of different Saxifrages all clear for the moment. Will go through them all again before the New Year, just in case.
Sorry to hear that Berghill.
I've never heard of them in Salvias before either - they're obviously not fussy.
Worried about my new Salvias now....
They were only in the one S. turkestanica. The S. hians and various other slightly tender ones were clear.
Just thrown away 30 or so Primula allionii babies. Not going to grow them after we move, they need a humongous amount of coddling. Not a single weevil grub in any of them. Weird! Yet in the P. sieboldii there were newly hatched ones.
Absolutely no point in using GH smokes on vine weevil, the adults will be dead now and the grubs in the soil will emerge as adults in the Spring.
The adults do not live in pairs, they are all females and all lay eggs.
next year take precautions earlier, apply nematodes at the end of March and again in October, that will kill the grubs that would normally do the damage over winter.
They do work, I have used them and just one application did the trick, but it’s probably best to apply another lot to see you through the winter.
Expensive, but probably no more that the bottles of provado, which you need to apply in quite large amounts to thoroughly drench the pots. And of course safer.
As to the above post, I don’t think ‘most’ gardeners spray their plants and I wouldn’t use smokes anyway.
Smokes would not be much use in a poly tunnel in any case, especially as it is wide open at one end. The compost is peat free stuff mixed with sterilised top soil and gritty sharp sand. The pots were all brand new (bought 7,000 of them a couple of years ago.)
No amateur spray will kill adult vine weevils. I dropped one in pure bleach one time, it swam around for 24 hours.
As I said hopefully we will be moving in the new year. I will take my Auriculas as bare unrooted cuttings.
I pleased to hear that you know that Berghill, as my OH always says, the wrong information is worse than no information at all.
I have used Nematodes with success before but obviously we are not on the scale you are on Berghill. I was going to suggest sterilising your soil / potting compost but it sounds as though you are already doing this. There must be a reservoir of infection (? unhatched eggs) in your system. The only problem with any biological control is that it will never eliminate the host completely. Your solution to take cuttings into sterilised compost in clean pots sounds like the only way forward. There used to be soil sterilising fumigants available but I doubt they are still available- maybe commercially.
This is a large area surrounded by fields. When we did a sweep of the garden a few years back we caught over 100 adults. No way of clearing the garden completely. Not found any more larva for a few days, but I will soon have to start going through the plants in the frames. Lot of susceptible things in there. That is over 1,000 plants to unpot and examine.