planting grapes and grubs

[harrybrew69]

We have had a "black hamburg" grape in a pot outside the back door for three years. We have never had a good crop of grapes, the first year I removed all the fruit so the vine could build up some strength for the coming years. The second year there were around seven or eight bunches on it which i thinned out, and they were coming along nicely, until, we come home one night to find that the birds had helped themselves. so, year three we used the same procedure as before by thinning etc, and we covered the vine with netting (take that birds) but we waited and waited, the weather started to turn but the berries were all still small and mostly just a seed with a skin. I put this down to the fact that it was in a pot and maybe didn't have enough room or food. So this morning I put the pot (that weighed a ton) and vine in the van, and of up to the Lotty with it. I Had made a eight foot by five foot frame with wires for it at the side of the shed, so the roots would be in shade but the rest would get full sun all day. After wrestling to get it out of the pot I made a disappointing discovery. The root ball was infested with small white grubs with brown heads and mean looking jaws. I don't know what they are (of to google it in a min) but I imagine that they've been gorging themselves on the roots thus preventing a good crop.

Any advice would be very helpful I still put the vine in after removing as many as i could, just wondered if there was a drench or similar to treat with.
cheers
Harry

[realfood]

They are almost certainly the grubs of vine weevils, a well known pest of potted vines and they eat the roots. As far as I know there are no authorized treatments against vine weevils for edible crops.
The good news is that once the vine grows deep roots in the ground, the roots seem to be too deep for the grubs to reach.

[harrybrew69]

definitely vine weevil I looked it up on the web and there's no doubt.
I think in gonna try the nematodes you can get but you've got to wait for the soil temp to rise above 5 or 6 degrees Celsius.
thanks for the heads up realfood much appreciated

[selfraising]

Yep definitely vine weevil. I had a pot grown vine and lo and behold found them in the bottom of the pot! Picked off all the ones I could see and left them out for the birds, then planted the vine straight into the soil. Not had any problems since. There is a product called Nemasys vine weevil killer which is a biological control but more a preventative I think.

[gojiberry]

There is Provado vine weevil control but is not for edible plants. You could however decide to forgo grapes this year and concentrate on getting rid of the pests. Provado is systemic and lasts for approx 4 months. I have used it successfully on strawberry plants in late summer after fruiting.

Ian

[FB.]

Yup.
As above.

Grapes like to send down a large and deep tap root, to provide water and nutrients. A pot prevents them from growing how they would like. The grubs in the roots won't be helping.
Plant it outdoors against a sunny, south-facing wall and it'll be much happier.
Black Hamburgh is marginal for ripening in the UK, so the sunny wall really helps. I grow a BH up the SW side of my house.
Fruits can be a little small, but are pleasant enough to eat. Lots of large pips though; 2, 3 or 4 grain-of-wheat sized pips per grape.

[harrybrew69]

Thanks everyone! Its defo vine weevil, ive put the vine up at the lotty now so i might just let it fight its own battle. Its got a full barrow load of premium rotted horse and cow muck to its self. on the plus side the way ive planted it i will get some privacy and a sort of foilage screen this year. If it looks to be struggling i'll cut of all the friut and consider treatment, but, nature probably knows best eh?