I have a terrible problem with weevils in my front garden and need help. So far I have done 2 applications of nematodes last spring and fall and it doesn't seem to have made a dent. Already this spring I'm seeing signs of their damage. I've also tried looking at night with a flashlight and haven't found anything. I have read of a weevil barrier, can anone tell me where to get it in the lower mainland?
I'm surprised...I've had excellent results with nematodes. When did you apply them exactly...timing is pretty critical. Also watering them in sufficiently, also I like to apply in the evening to give them all night to wander down into the rootzone before the sun can get to them. Tanglefoot type barriers could stop the adults from notching leaves, but wouldn't do much to slow down the root damage which is the real problem.
I did one application in late April/May once the soil had warmed up and a second in September I think. I mixed them in water and applied while it was raining so I didn't have to water too much. I will be trying another round again in a month or so. Where can you buy tanglefoot wraps?
Is it adults or grubs that you are finding? I have seen only grubs this year so far; I don't think any adults have hatched yet. That would be why you didn't find anything on the plants at night. So I'm curious how you know you have weevils. If it is foliage damage you are seeing, perhaps you have cutworms or slugs. I actually don't think I have ever lost a plant to weevil root damage; but I have had them eaten virtually to the ground by the adults. My methods of control are all manual, and I have been able to fight back from significant infestation years. I think I've posted most of my weevil info on previous threads; a search might bring them up. But basically, I am always alert for grubs when digging and when emptying pots, and of course squish them, and I do night hunts on foliage of notched plants in spring when damage first starts. Where you find one grub in the ground or in a pot you will almost always find a group. Also, certain environments make such good habitats that you are, I think, doomed to have an endemic population at least.
The leaves are all quite chewed with a C shaped pattern, I took a few to a garden center and they confirmed it to be weevils. I've gone as far to dig up one recently planted Rhodo and did find quite a few of the grubs but can't do that with all of them. I think I probably have a great environment for them, they sure seem to love it here.g
Like Karin, I was beginning to wonder if it was something other than weevils. Any currently nibbling adults will be those overwintering adults, a small % of the population compared to all the larvae around the roots right now. Tanglefoot is available from most nurseries, but I've never tried it...always seemed to be too many low branches and walls for the weevils to sneak up other than the main trunks, a lotta work and still only treating the "effect" more than the "root cause". Again, I'm surprised that the nematodes didn't give good control...esp. now that you confirm your application method sounds similar to mine. Did you get your nematodes from a garden centre...I wonder if they might have been "stored" too long or poorly...being alive there are other possibilities between the lab and our gardens to consider, hmmm. I've gotten mine direct from Koppert and they are obviously fresh and "wrigglin'"... Maybe someone else can confirm the best time to apply, I've only done them in the fall, aiming for Labor Day or whenever it first gets cooler sometime during Sept. I know there can be a spring window as well...just don't want to time it for the pupating/adult hatching window. Sept. seems easier as pretty well everything is vulnerable larvae then.
Again the timing of this is mystifying me. Are you looking at new foliage or old, new damage or old? As far as I can tell the adults are just not out chewing right now in this area. If you found quite a few of the grubs then you might well be best off with nematodes, and might just need repeated applications (and better batches?) to ultimately triumph. But as for digging up every plant... you may not need to do that if you do some digging near each plant. I'm so often planting and transplanting at this time of year that I seem to find and destroy several caches - if your garden is established you may not be in the ground so much. It might be worth it - for every grub you get at this time of year I think you prevent the genesis of many adults later. Follow that up with night hunts as the real munching starts. Or give the tanglefoot a try, and do report! I too find this option hard to implement, having had a patch of iris one year be the favoured food (and thus my trap plant!) but if your targets have just a couple of trunks and no branches on the ground (or touching other plants) you might manage it. Also, I pretty much rip apart or cut well into the root balls of plants I purchase before I plant them, and have found grubs in plants coming even from some excellent nurseries. Gateway vigilance is an important part of the package.
There is a little new and a lot of old damage. I'm picking off some of the worst leaves so I have a new view and will hopefully notice new damage easier. I am not ready to give up on the nematodes, I'll try again when it warms up a bit. The ones I got before were from a local nursery, they were refridgerated and packed in a little bit of sand. I can't say I noticed them moving once I added them to water.
Applying nematodes in April/May may be too soon. The soil temperature needs to be at least 55degreesF for them to survive, and 60 is better. For us, just to the south, July seems to be the best month to apply them. An the soil needs to be quite moist, not just surface moist, for them to "swim" to their grub food. We have had good success with them. Another method of control that seems to have some success for us is a soil drench in April/May of diluted neem oil. Not toxic to earthworms, toxic to weevil larvae.
That sounds interesting, I'll give that a try. Do you purchase neem oil at garden centers? Can you tell me how you dilute it, what ratio?
I don't know if it is available in Canada- it is a botanical insecticide. We diluted it at the rate suggested on on the lable.
QD--neem should still be available in 1 litre jugs from most or all hydroponic stores, the brand name is Grotek. It's a bit tough to get it to emulsify, so I would mix it up in hot water along with some basicH or safer's type soap to get it to stay in suspension...and apply on the hottest part of the day possible (the oil tends to solidify at lower temps, and I can visualize it just forming a sludge on top of cold soil without really penetrating). ("Regular" garden centres rarely if ever carry that format, but all seem to have a dilute neem, sold as leaf shine for legal reasons. Don't buy this pre-diluted stuff in spray bottles, you would pay more than the plants are worth trying to treat soil with that!) Neem is one plant growing tool I would hate to be without (with some hort. soap it is the spider mite control that actually works in my experience).
This month's newsletter from The Natural Gardener on West 10th in Vancouver talks about a nematode product that can be used at fairly cool temps - it is not yet archived on the website (http://www.thenatural-gardener.com/) but if you go to the site and sign up for the newsletter you might receive the current one.
