Is it too late to apply Beneficial Nematodes & Rose Chafers

I almost forgot I wanted to apply them this year
and does anybody know what they are effective against?
I get European Rose Chafers on my roses really bad
and they should be emerging in June.
I'm hoping they are still in their grub stage.
Any ideas what i can use if I'm already to late

C_R, I just applied beneficial nematodes last week. I stood out in the rain with my watering can, and then it rained for the next two days, too. Weather jackpot. The little buggers can't survive dry soil.

There are so many confusing details about nematodes - which species to use, soil temperature, soil moisture (too dry and they die; too wet and they drown) - I got confused and frustrated and put it all off. Bad mistake, because my problem with rose slugs only got worse.

So I bought a mix of two types of nematodes to avoid puzzling over which ones to get: http://www.naturescontrol.com/predatornematodes.html I rushed to apply them, because I read somewhere that sawfly have two generations a season. I was too late for the first one.

I would go ahead and apply them now if I were you. Good luck!

C_R, read this, especially the last sentence: "This fawn-coloured, long-legged beetle usually appears in late May or early June. There is one generation per year. Winters are spent in the larval or grub stage in light, sandy soil. In the spring, the larvae come to the surface and pupate. The pupal stage takes place in May and lasts about 2 weeks. Adults emerge and feed on flowers, buds, and foliage for 3-6 weeks. They have chewing mouthparts and damaged leaves appear skeletonized. After the feeding period, eggs are laid into the soil where they will hatch in late summer."
from http://www.uoguelph.ca/pdc/Factsheets/Insect/Rose_Pests.htm#Chafer

Because of the late summer hatch, you may be better off waiting until then to apply the nematodes, when they can attack the larvae. The company that sells them would be able to advise you on timing.
(This is one of the things that drives me NUTS about nematodes.....too many conditions to consider!)

WR thank you MUCH for that very important info!

This is all very new to me, and fascinating. I an wondering how you know that the nematodes will only affect the pest? Does it have any affect on ladybugs or other beneficial insects?

Nematodes work against things that have a larval/grub form living in the soil as part of their lifecycle, and typically it's just nasty things like Japanese beetles that have forms like that living in the soil. Most of the beneficial insects I can think of don't have a stage where they are a grub living in the ground, so the nematodes can't affect them. That's what's nice about biological controls, they are typically very specific about the type of things they work against, so you minimize the chances that it's going to harm a good bug along with the bad ones. Here's some info on how they work http://www.gardeninsects.com/beneficialNematodes.asp

Thank you for the link ecrane3. Does that mean that the nematodes will also attack slugs?

The ones you get for Japanese beetles and rose chafers won't deal with slugs. I have seen some UK-based sites mentioning one that they have there that will work on slugs, but I don't think that one is available in the US at this point (the tradename I saw was Nemaslug if you want to do some googling)