Are these grubs decomposers or root eaters?

We get these grubs in our soil and in our manure piles. They don't seem to be harming plants, and they make copious castings that are like little mouse turds and seem like good compost. But there are blob-shaped blackish june-bug or chafer-beetle type things that fly around in the summer, and I'm pretty sure these grubs are their children. I thought June-bug or chafer-beetle grubs are considered harmful to plant roots.

When I come across them in the soil where I'm about to plant something, should I remove them or encourage them?

We have tons of those too. They're in yard, gardens and open compost pile. I've read that they grow into Japanese beetles. They may be helpful in my compost but I'm thinking that they're destructive everywhere else. I think they are the reason I have so many moles and voles.

Bump. Anybody in the " amen corner "?

I find them in some of my sweet potatos and they have eaten the roots on a few of my small fig trees. I think the larger fig trees outpace the speed that they eat the roots. From what I understand they have a 2 year cycle, so you may have one year heavy with them and the next year lighter. Supposedly the beetles also mate in the trees and lay the eggs beneath said tree. They tend to come out all at once for a short period. I need to set my sweet potato bins on logs next year and cover them with netting or something when they come out to mate. I don't know of any other methods of control, but they don't seem to attack most of my other plants. Then again with delicious sweet potatos around they can afford to be picky I guess.

Many beetle grubs look the same, and the most common in my area are June Bugs, which are mostly harmless. We also have huge grubs who turn into the Ox Beetle http://aggie-horticulture.tamu.edu/galveston/beneficials/beneficial-44_ox_or_elephant_beetle.htm

June bug grubs are root eaters. It's one of the areas where people use a lot of heavy chemicals to kill them when they infest a lawn.

My parents always had a big patch of dead grass in the front yard because my dad didn't want to accidentally poison the armadillos who would come and dig the grubs out of our lawn. I don't see much of them any more, since the same nematodes we use for fire ants will also attack these grubs.

The root eaters will follow the roots, so if I found it where there where no roots I would assume it was a decomposer. There are grubs (like the Rhino grub) which are great additions to a compost pile.

If I found it in the soil by growing roots I would toss it to an area where I wouldn't care about the roots being eaten, and hope a bird ate it while it was above ground. I had one pleasant afternoon where I dug more than 100 grubs out of a new bed (just after we moved here) and tossed them into the street. Then I spent a pleasant afternoon watching several mocking birds and bluejays go back and forth grabbing food for their young.

They look very much like the grubs I regularly find in mulch. I get them from those bright metallic green fig beetles that are common here.

I find them occasionally munching on my sweet potatoes, nom, nom, nom. I get thousands of them, however (both grubs and almost invasive sweet potatoes), so the bigger issue for me are the raccoons and possums that love to dig through the mulch to find them.

Thank you, everyone! Though not conclusive, your replies are very informative!

I had one pleasant afternoon where I dug more than 100 grubs out of a new bed (just after we moved here) and tossed them into the street. Then I spent a pleasant afternoon watching several mocking birds and bluejays go back and forth grabbing food for their young.

Haha, I did this too! I was flinging them on the bare desert soil, and two magpie hung around and nabbed them each, one by one.

junebug grubs will kill parts of your lawn and weaken your shrubs in large numbers. luckily i have a family of skunks that happily remove them for me. its a pain to put the divets of grass back in place but at least they control these bugs and i don't need to spend a small fortune on poison to kill them , risking killing the pollinators visiting my fruit and berry bushes. everyones happy this way!

I thought it was skunks making all those holes. Keep on eating skunks, y'all have many more to devour.
Also saw a brown thrasher eating one the other day.

i also like to play baseball with the junebugs flying around my porch light. the more adults you kill the less eggs get laid in the grass.

This is actually probably a good time of year to set up one of those junebug traps in my area.

Hang a bucket of water (doesn't have to be very deep) just under an exterior light. Apparently these things are so clumsy that they will ricochet off the light and fall into the water where they'll drown. Dump that bucket to your chickens (or other insectivores) each morning and you can capitalize on that free protein source. Actually, as I think on it, I wonder if doing this each morning and leaving the remains near my peach trees might distract the local birds from my ripening fruits.

Those we call gallina ciega-blind chickens. They are the larvae of large beetles. They will eat roots if there normal food supply is depleted. They eat low quality organics. I suffer damage from them when if have dug compost , or not completely done compost into the ground during the rainy season. Dont dig, they will proliferate on the undone compost then  they eat your roots when they have exhausted there food supply. Another good and bad depending on the balance.

Marco Banks wrote:They look very much like the grubs I regularly find in mulch.  I get them from those bright metallic green fig beetles that are common here.  

I find them occasionally munching on my sweet potatoes, nom, nom, nom.  I get thousands of them, however (both grubs and almost invasive sweet potatoes), so the bigger issue for me are the raccoons and possums that love to dig through the mulch to find them.

We have those here too, and I am wondering, if their grubs are edible? People who ate wood eating grubs said they tasted very good sauteed, and because they are so fat, no additional fat is needed.