Grub Worms

Grub Worms

Grubs are a root-feeding headache for the turf pro.  Short curative treatments used to be our only weapon against these destructive pests, but new preventative products have given us more tools to help in the battle.  To understand today's products we must first look at the biology of grubs.

Grubs are the immature (larval) stage of beetles, which include the following: Japanese beetle, European chafer, masked chafer, Oriental beetle, green June beetle and the Asiatic garden beetle.  They have a one year life cycle and the beetle it self is most active from June through mid August. 

The beetles lay their eggs 1 to 2 inches deep in the soil and the eggs hatch in 2 to 4 weeks.  The young grubs begin feeding on grass roots immediately.  They grow to full size within 3 to 4 weeks.  This is their most daming time to the turf.  The grubs move deep in the soil for hibernation just before winter arrives.  They come back to the root zone and start eating again in the spring.

Around May, depending on your location, the grub transforms into pupae and a few weeks later they emerge as adult beetles.
Their most visible damage can be seen in the late summer months when the turf is most stressed.  Severe infestations may see numbers of up to 50 grubs per square foot.

Easy to see signs:
1. The turf rolls back like carpet.  This is because there are no roots left to anchor the turf.  For this reason, there is no way for the turf to extract water.   The turf will yellow and die quickly.
2. Digging holes may appear over night.  This is from skunks, raccoons, armadillos, moles, birds and other varmints.  They all love the taste of the juicy little guys.
There are over 60 varieties of white grubs in Texas. The Phyllophaga Crinita is the dominant species in Texas turfgrasses.

To check a lawn before damage is visible, cut a square foot block out of the lawn. It needs to be at least 4" deep. Remember that it takes 4 to 7 per square foot to cause damage. If only 1 or 2 can be found, there is no need for panic or treatment.

Adults are better known as the "June Beetle". They are about a half inch in length and brown. The flight period last between 1 to 2 weeks. This is the time where males look for females to mate with.

The egg laying period last 30 days and a female can lay 30 to 40 eggs.  They will generally avoid heavily watered sod.

Insecticides such as organophospates or carbamates have been the most common treatment of the past.  Their weakness is that they only last 2 to 3 weeks and that gives you a very narrow window for effective control of the grubs.  You must time your application accurately or you still stand a chance of a grub infestation and possible turf loss.

The value of using a preventative grub control product is, you apply the product before you have a grub problem.  Timing is no longer an issue and guess work is totally illuminated.  The down side is you don't know if you are going to have grubs or not.   It's very similar to insurance.  If you have it, you won't need it.  If you don't have it, you will need it.  Bottom line is,  preventative protection is much cheaper then replacing the turf.
If you see damage, use a curative insecticide.  If there is no visible damage then use a preventative program.