Grass Grubs and Porina

Gardeners that have problems in the lawn with either of these two pests should take note that both are coming up towards maturity at this time and will do the maximum amount of damage.

With porina caterpillars, they live in the soil and come out after dusk to feed at the base of your grasses.

They are fairly easy to control with a spray of Neem Tree Oil. This should be applied late in the day to the lawn after it has been recently mowed. Repeat again about 4 weeks later.

Grass grubs on the other hand are much more difficult to control and dependant on the size of your lawn a more expensive job. Likely there is little need to treat the whole lawn with a control as the biggest number of the grubs will be where there has been problems in the past. This is also true in areas where they are lite after dark, by street lights or security lighting. In my book, Wally’s Down to Earth Gardening Guide I give an excellent way to control the pest in early summer when the adults are on the wing.

Before you start to spend your money to treat the lawn you should check to see how many grubs are in the lawn. This is done by cutting several small squares with the spade and lifting the turf. Examine both the hole and lifted section for the number of grubs. If there are none or only a few then it is not worth worrying about. (Use the summer control of the beetles) But if a good number is found then that area should be treated.

There are two treatments that you can use and the first of these is Neem Tree Granules sprinkled on the lawn and lightly watered in. The granules break down and release the Neem properties which are taken up by the roots. When a treated root is chewed on by a grub, that will be the last bite it ever takes.

Safe for pets and wildlife including birds as Neem only harms insect pests.

For those gardeners that like to use a strong chemical then use Pyrifos G. It too is a granule that is spread at the rate of 2 grams per square metre. (Needs to be applied with a spreader).

It is a strong poison and you need to take great care in handling and prevent pets and children from using the target area till it is well absorbed into the soil.
Diazinon is another chemical treatment but does not work well in all soil types (best used only in light, sandy or volcanic soils) otherwise it can be a costly exercise for no advantage.

The utmost care must be taken if using either of these two chemical products.

8 comments on “Grass Grubs and Porina

  1. allan mcdonald on said:

    have many hectares severly infected 3o plus grubs under a single rye grass plant Any suggestions of an economical control method

  2. Helen on said:

    Hi Wally

    We have a lot of grass grubs in our raised vegetable bed – what is the best way to get rid of them here, please?


  3. we have a grass grub problum how can i get a price on nematodes to control them per ha price please

  4. John Ross on said:

    Could you tell where I can purchase Neem Tree Oil.

  5. Hi John,

    you can contact Wally direct 0800 466464 (Palmerston North 3570606)
    Web site



  6. Marilyn on said:

    Hi there, my lawn looks like a bird has been scratching and ripping up tufts of grass by the roots, Is that what grass grub looks like? It started off as a small patch and after about two weeks it is now about ten times the size. Haven’t seen any grubs so far.
    Regards, Marilyn.

  7. bill parlane on said:

    wally my lawn looks like birds have scratched all the top of it could this be grass grub.realey apreciat your opinion thanking you
    Yours Bill

  8. Jase temel on said:

    look for green caterpillars in the soil (porina) they come out of soil at night and feed on the blades of grass causing die back. The birds are after the bugs. You will have to re-sow patches otherwise to kill the buggers use diazanon or pyraphos G this will also work on other soil pests eg grass grub

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