I have received many e-mails in the last couple of weeks by homeowners that cannot believe the amount of water it is taking to get their grass to maintain the correct moisture and not exhibit drought stress conditions.  If you’re following all of the cultural practices necessary to maintain a healthy lawn and you are still seeing signs of trouble you may need to take a look under the turf for grubs. 

While most of us are lucky enough to rarely get hit with an insect infestation in our lawn there are several others who are unlucky.  There is not a single condition that determines why you may have grubs in your lawn, or why your next door neighbor has none.  Some possible causes are infertile soil, no organic matter, compacted or poorly drained soil, or yards that use preventative insecticides for years and have killed off all the beneficial insects.  

When going about looking for and treating grubs one needs to take the integrated management approach to control.  By definition “IPM is a long standing, science based, decision making process that identifies and reduces the risks from pests, and pest management strategies.”  In general terms this is the process by which a turf manager or homeowner determines what the threshold is for a grub population before treatment is necessary.  Many insects and insect related problems can easily be controlled without the use of pesticides and most are not harmful at all to your turfgrass. 

I am going to discuss in general terms the signs of white grub damage and without getting into extensive detail on each type of insect give you some various control techniques.  The easiest ways to tell if you have grubs are if your grass pulls up like carpet, shows signs of continual drought stress, or if you spot the c-shaped grubs underneath the sod layer in your turf.  You will have to dig up the lawn in a few areas to see them, but if they are the problem you will not miss them.

One of the largest insect populations we see in the southwest is the masked chafer beetle.  It is a C-shaped white grub with 6 legs and is a root feeding insect.  The masked chafer beetles fly around in June and July laying eggs that hatch about 4-5 weeks after they emerge.  Research at several of the universities has told us that they typically fly around and emerge right around May 25^th-June 5^th.  After they have laid their eggs one of two scenarios happen.  The young larvae hatch, pupate over winter and emerge reading to chomp at your lawn next season, while the older large larvae begin to feast on your root system.  One of the obvious signs of grubs in your lawns in several birds pecking at the lawn, continual dry areas even though they are being well watered, and even the sign of some animals such as Javelina that are in search of a nice feast.  Most of us are not going to see Javelina roll up into our backyard for a feast, but I have seen firsthand the amount of damage those guys have done to golf courses that I have worked on.  They have the noses that can sniff out the grubs and then they begin to dig into the turf for a nice feast.  So if you ever go out into your yard and it looks like your dog has dug up patches all over your yard, you may want to take a look underneath your turf to see if any grubs are present.  If you have a large population of grubs your lawn will pull right up like a piece of carpet since the root system has been severely damaged.  

Having a few grubs in your lawn is not going to hurt anything and there is no need to run out and buy an insecticide the minute you see some unless the damage is severe or deemed above your threshold.  I would say that if you see more than 10 grubs in a 1ft x 1ft area.  Even the most expensive golf courses and athletic fields determine what an appropriate amount is before they treat for them.  The life cycle of the grub is the most important part of control and it will determine how successful you are at treating them.  If you catch adult larvae late in the season they are very difficult to control and you may have recurring damage next year.  The best approach is to get them while they are young. 

As I previously said most of the eggs are hatched 30 days after they are laid and this is the perfect time to get them.  Most entomologists will tell you that when they start catching a high amount of beetles in their black light traps in the spring it is time to apply your insecticide for the best control.  You can apply products such as Mach-2 and Merit in areas that have been hit hard in past years and get control for up to 90-120 days so you don’t have trouble in the fall.  Before applying these products water your lawn deep and flood out the area bringing the harmful insects closer to the surface so they can be treated early in their life cycle.  There is no need to spray your entire lawn, nor is there a need to spray preventatively if you have not had an infestation in the past.  This is where the key principles of IPM come into play and you need to decide how much damage is too much damage.  

I talked previously about areas that grubs tend to call home and often times you can alleviate an insect problem by just providing your lawn with the appropriate cultural practices.   If aerifying your turf, or reducing the thatch layer has not helped you in years past and you are seeing significant damage then you have no choice but to eliminate them with an insecticide.   If you are now seeing damage to your turf and you have several large c-shaped grubs feeding at your root system you will have no choice but to apply a quick acting product such as Dylox or Carbaryl (Sevin).  These should be used in limited quantities and do not exceed the recommended rate.  If you exceed the rate all you are doing is killing beneficial insects and increasing your chances of having an insect problem the next year.

As with any turf problem the best approach is to have a healthy lawn that fights off insects, diseased, and weeds that try to emerge through the ground, but even the best management strategies don’t always work.  If you have tried reducing the compaction, increasing the organic matter in the soil, and watering your lawn correctly then you may need to consider an insecticide if you see several grubs present.  Remember to practice IPM strategies and use chemicals only if necessary.

Check out my past blogs for lots of useful tips on how to have the best lawn on the block!

Jay