Potato Issue #2: Grubs

In previous posts I’ve mentioned grubs but I’ve never really discussed them.

The grubs we have in our garden are the larva of either the June Beetle or Chafer Beetle.  They are white or yellowish and have fleshy, wrinkled, C-shaped bodies with a darker head and six spiny legs close to their head.  They vary in size with the mature grubs being about the size of a quarter.  They are a gross little bug; Steve says they look like aliens.  We hate grubs.

Grubs feed on the roots of plants and are more known for causing severe lawn damage.  They can also cause serve crop damage to home gardeners and farmers.  This year I think it was grubs that were eating the roots of my young beets, spinach and swiss chard.  Last year they only noticeable grub damage was in the potatoes.  Grubs can be devastating to your crops; they don’t just nibble on the potato, they actually eat part of the potato leaving the rest to rot in the ground.

So far this year they don’t seem to be much of a concern in the potatoes.  Out of the two plants we’ve pulled we’ve only see one grub and only one small potato showed damaged.  Hopefully this is an indication of things to come.

Grub damage in last years harvest, see the holes?
(bottom left & top right)

Like every other pest in the garden, grubs are next to impossible to get rid of without using harsh chemicals.   I think like any other bug, they have their cycles and some years will be worse than others.   I’m hoping they didn’t like all the rain at the beginning of the year and either drowned or went deeper into the soil to escape the moisture.

The preferred method of getting rid of grubs organically is to use beneficial nematodes.  Nematodes are small microscopic worms that will seek out grubs and other soil born pests and kill them.  They infect the grubs, using them as a host for their young, eventually killing them.  Unfortunately nematodes are quite temperamental.  They are sensitive to temperature, your soil temp needs to be consistently above 15C, and the soil needs to be damp, the wetter the better.  A dry, cold soil means dead nematodes.  We tried using them last year without much success.  (It was too hot & dry and we didn’t have the water to keep the soil consistently wet.)

Another method is to trap the beetles before they burrow into the dirt to lay their eggs: there are scent traps you can buy to attract and trap the beetle.  We’re not too sure of this because it has the potential to make the issue worse by attracting more beetles.

This year we planted the potatoes in a different part of the garden in attempt to “hide” from last years grub infested soil.  We’re also hoping that if we can get the pH of the soil down the dirt will become less hospitable to them and the will go away. 

One can always hope.