The Easiest Methods for Organic Grub Control
Here's the deal:
White grubs -the larval stage of beetles -eat roots. In the vegetable and flower garden, they are not usually a major pest because flower roots are too far apart and annual flower beds are repeatedly dug up.
In lawns, where roots are conveniently close together, the grass is easily pulled away from the soil because the white grubs have eaten off the roots. Dead or yellow dying grass is a primary symptom.
The shape of the grub damage is usually irregular (when compared to the damage caused by dogs which is usually a regularly-shaped circle with strong growth at the edges.)
Cornell University found that, even in a very bad year for grubs, only 18% of the tested lawns needed organic grub control treatment (or any treatment at all) because they were heavily infested. In the majority of cases, it would have been a waste of money to spray. (This is not the message that lawn companies tell you.)
When To Use Organic Grub Control
Peel back a square foot of your lawn turf. The threshold is 5-7 grubs in this square foot of ground.
If there are over 7 grubs, then use a control. If there are 5 or less, don't do anything
If there are between 5 and 7? Do multiple squares and average the results to get an overall number.
Easiest Grub Control
The easiest organic grub control is predator nematodes and if you don't want to be bothered digging and counting, simply apply them every two to three years.
Another option is Milky Spore Disease - a disease that kills grubs and establishes itself in your soil after applying it.
Note the instructions on the label and you'll definitely see the area should be well watered before during and after the application. These tiny creatures swim on the water between soil particles so you have to wash them down into the soil so they can find and attack the grubs.
The Same Treatment For...
These grub control instructions are essentially the same for Black Turfgrass Ataenius (Ataenium spretulus), Asiatic Garden Beetle (Maladera castanea), European Chafer (Rhizotrogus majalis), Green June Beetle (Cotinus nitida), Northern Masked Chafer (Cyclocephala borealis), Southern Masked Chafer (Cyclocephala lurida), Oriental Beetle (Anomala orientalis) and June Beetles (Phyllophaga sp).
Image of European Chafer courtesy Wikimedia
Shopping Resources for this Page
Milky Spore for organic grub control purposes