The three common species of white grub worms are Japanese beetle grub worms, June beetle grub worms, and European chafer beetle grub worms. The worst are the invasive species female Japanese beetles. This is because they mate in the summer and lay one to five eggs at a time. They continue to do this every two or three days through July and August until they have lain between 40 and 60 eggs. Grub worm damage can be noticed by patches of dead or dying grass in the lawn. Affected grass is brown and wilted, looks burned, and rolls easily away from the soil. Grub worm damage is usually worst in April and May when grubs move up to the soil’s surface, and then again in September and October before they head back down. The worst thing about lawn damage from grub worms is that the grass rarely recovers and the lawn will have to get treated to get these pesky grub worms under control.
Controlling Grub Worms
Figure out if grub treatment is necessary. To do this, grab a shovel, pick a spot within the yard where brown grass meets green, and cut three sides of a 1 sq ft chunk of sod. Half of the square should be in the green grass, half in the brown grass, and cut down about 4 inches. Cut one line in the brown grass, the two side lines, and leave the line in the green grass attached. Once the three parts of the square are cut, try to peel the sod back. If the brown grass rolls back easily, the roots have been eaten by lawn grub worms. If there are 6 or more grub worms per square foot well, this is a major problem!
Kill grubs with Milky Spore
This is the most recommended product for grub worm control. Milky Spore is the commercial name for the bacteria Bacillus Popillae. Once spread on a lawn, this bacterium enters grub worms and only grub worms, and starts killing them. Beneficial critters are safe. In climates where the soil is moist and at least 70°F, Milky Spore Grub Control can work its magic in as little as two weeks. If you don’t have those soil parameters, it will still work for you, but may take a little longer. Once Milky Spore is established in your soil, it can provide you with season-long grub worm control.
Control grub worms with beneficial Nematodes. Right up there with Milky Spore is an awesome thing called Nematodes. They’re perfectly safe for homeowners, pets, earthworms, and most beneficial insects. These are microscopic worms that get sprayed onto your lawn and they find their way into white grub worms. Once inside, they emit a bacterium that liquefies the grub worms’ innards so that the Nematodes can devour them more easily.
Kill grub worms with grub insecticides. There are numerous commercial grub worm pesticides available that rely on various chemicals for killing grub worms. Some of the most effective are Merit 75 (uses Imidacloprid), Dylox (uses Trichlorfon), Sevin (uses Carbaryl), Mach 2 (uses Halofenozide), and Scott’s GrubEx (uses Chlorantraniliprole). Most of them can be applied as powders, dusts, granules, and/or liquids. Read the directions any purchase of a grub control product and keep in mind that every grub worm pesticide has the potential to be harmful.
Keep grass thick, medium to long in height, and dryer is best for grub worm control during the beetles mating season of July and August. The beetles that lay the grub worm eggs prefer laying those eggs in areas with short, sparse grass. Keep grass at least two inches long. Also, grub worm eggs need plenty of moisture in order to hatch. Start doing a few deep watering instead of lots of light watering. Not only will this cause eggs to be exposed to water less frequently, it also forces grass to grow longer roots which will enable it to withstand more grub damage before dying.