Major grub attack

Asked March 1, 2013, 6:49 PM EST

Dear Experts, Can you make some helpful suggestions about our Grub problem. We noticed that as we put down more wood chip and leaves mulch in our yard as we add more plants in, we have more and more Grubs which are killing the trees and plants. We no longer have grass, although it was here 5 years ago. They seem to love the wood chips, leaves and grass clippings. We found hundreds of Grubs last fall – always under the mulch. Not under rocks or plastic it seems. Since we don’t like the rocks and plastic , what other ideas do you have? I am wondering if landscape fabric between the soil and mulch would keep the Grubs out While allowing water to enter? Plastic maybe? We have used nematodes, but this is expensive and seems less effective. We also understand that Milky Spore is not effective on our NM Grubs. We have many birds, not many Robins, but they do not know Grubs lie down under. We have set trays of Grubs out and some of the birds finally seem to be catching on to that, but they wont dig for the Grubs. Not much room for poisons, as we have fruit trees, and vegy gardens growing. Any ideas of what to try will be appreciated. Thanks, Ross

Bernalillo County New Mexico

1 Response

I generally am a big supporter of the kind of mulch that you have used, and of using such a mulch without a fabric barrier - the decaying organic matter can get into the soil which really helps plant growth. The plastic is not recommended, as it will prevent water getting into the soil should it rain again, and it prevents gas exchange between soil and air and that can lead to a buildup of CO2 in the soil, harming root function. Have you seen any of the grubs this year? Do you recall seeing any large, green beetles last year?
In your case it might make sense to pull of the organic mulch, lay down a fabric weed barrier, and then replace the mulch. The fabric will likely keep the grubs from getting down into the soil where they can feed on roots.
I would not recommend insecticides, in part because of your food plants, but also because the successful use of those chemicals depends on a lot of factors which might be hard to meet in this setting.
Since you are into growing food, would you consider obtaining a few chickens, and allowing them to periodically scratch through the mulched areas? They can be hard on small plants and certainly on veggies, but under perennial woody plants, they may do a real good job of hunting down the grubs and turning them into eggs for your breakfast.