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This Spring there seem to be grubs all over my garden, in just about any handful of dirt you flip over. There are lots of articles about how to handle grubs in your lawn, but I don't have a lawn, just a vegetable garden.

Reference Grub WormMy insect
(Left image is public domain from Wikipedia. Right is from my garden.)

I have a couple of raised beds, currently empty, where I'm planning on planting tomatoes and artichokes. Are grubs damaging to those plants? If so, what can I do about them?

I also have a half-barrel with a Valencia orange tree in it. The soil seems to be full of grubs. If I turn over a handful with a small trowel I find a grub about 1 in 3 tries. I don't want to dig down and risk harming the roots, so I can only see the grubs near the top. They never come above the soil, and I haven't seen any beetles on or near the tree. The tree seems to be doing fine, but I'm concerned. Will the grubs be a problem? What can I do about them without harming the tree?

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Grubs like the one you've pictured feed on plant roots. If there are a lot of them, then yes, they are doing damage. You may just not be noticing it yet. The worst part is they will eventually pupate into adult beetles, and those will work on damaging the above-ground parts of your plants. If they are Japanese Beetles (hard to say without more info but the grub you pictured looks like one) then they can really devastate certain plants.

Here is an article on Japanese Beetle control from Organic Gardening. Basically, control of Japanese and similar beetles is a three-fold fight - you need to try to reduce the numbers of grubs in your soil by using some sort of grub killing control measure (some organic options are listed in the linked article) eliminating as many adult beetles as you can during the year and then blocking them from your plants so they do not lay more eggs into the soil to bother your garden next year.

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That picture shows what looks remarkably like a chafer grub, commonest in lawns, but also found in borders and vegetable beds, where it particularly likes root crops. Japanese beetle grubs are similar, but have, if you look closely, a sort of hairy spine - small, fine hairs that stick up, which I cannot see in the picture, so closer examination would be good to make sure exactly what it is.

Given you've used the term 'dirt' and not soil, I assume you're in the USA and not the UK, so I can't recommend a treatment if it is chafer, but you need to look for something which will treat for chafers (sometimes called cockchafers) but which will still enable you to grow edible crops. There are nematode solutions which can be used, but as I said, I'm not sure what's available where you are.

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  • Thanks for your answer. The image you were referring to is just one I pulled from Wikipedia (identified by the USDA as Japanese beetle larva). I edited to add a photo of one of my grubs... looks the same to me. I am indeed in the US, although "dirt" and "soil" are not quite synonyms here (and my question uses both). – Robert Apr 9 '14 at 18:59
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    @Robert - I can't see hairs on the spine of that one from your garden either - also seems to have bent up or missing legs at the front. Yours looks fatter, which might point to chafer rather than japanese beetle, not sure. My remark about 'dirt' was not a criticism, by the way - because most people don't say where they are, any clue in the text of their question is useful! – Bamboo Apr 10 '14 at 11:14
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In my experience, the grubs will not be a problem in the veggie garden. That said, once they go through metamorphosis, they very well may damage your plants. So, when I loosen the soil in my veggie garden in the spring, I leave the grubs on the surface for the birds to get.

As for your potted orange, what do you mean when you say it is totally infested? How are you seeing them? (Are they on the surface? Are you digging and finding them?) If it truly is infested, I'd be inclined to repot it with new soil, removing as many of the grubs as I could in the process.

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    I edited my question to clarify. No grubs on the surface but there are a lot of them just underneath if I dig or rake the soil with a cultivator. – Robert Apr 8 '14 at 19:41
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I apply predatory nematodes every year for these and wireworm.

Do it while the soil is still slightly damp so the nematodes can work their way down into the soil.

Treat both your lawns and garden area as you don't want any sort of "reservoir" that allows them to transfer back into either area.

They tend to go after carrots, I can tell how effective the treatment is by checking in spring for munched trails. I missed application one year, the nematodes definitely help quell the population.

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Milky spore will help get rid of the grubs, though it may take a little while to work.

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I had 6 potted artichokes (small pots), one of which suddenly died, I waited a while to see if the artichoke would stem flowers, but it did not. When I investigated I could not see any reminisce of the artichoke bud. I found two fat grubs like your picture in the pot, I assume they ate the whole plant.

What I did, is submerged the small pots in a bath of water and plugged the large pots and filled with water, The grubs came up to the surface in no time. (unfortunately, so did my worms), But I think they are more comfortable in the soggy soil and seemed to be ok.

I find that the main source of grubs in my garden is from my compost heap, where grass cuttings are constantly fed, and then I re-distribute the compost to all areas of the garden.. pretty bad mistake!

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  • If your compost is harboring critters then you aren't composting properly. It should be hot inside the pile. Are you watering your compost? Maybe it's just too dry. Grass clippings should produce a really hot compost heap, though too many grass clippings doesn't produce the best compost...It should however still produce a LOT of heat. – Escoce Feb 23 '15 at 18:28
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I found that I had these in my container cherry tree.

The interesting thing that I accidentally discovered is that they did not like a solution of CalMg which I mixed 15ml to 1quart of water.

After 5 minutes of application they came crawling to the surface.

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