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White Grubs

By Debbie Roland, Master Gardener

 

If you have ever had grubs in your yard or flowerbeds you know that they can cause quite a bit of damage.  White grubs, sometimes referred to as grub worms, are the larval stage of Junebugs or June beetles. Grubs have four life stages:  Egg, larvae, pupae and adult.   There are over 100 species and only a few causes damage.  However, a few species damage turfgrass and other cultivated plants.

 

White grubs feed on roots and other underground plant parts.  They can cause lawns to first turn yellow and then brown.  As damage progresses the turf can be lifted and rolled like flooring or carpet.  Warm season grasses such as St. Augustine, buffalograss and Bermuda are susceptible with damage occurring in summer and fall months.  Some lawns never suffer from grubs and others seem to suffer year after year.

 

White grub damage looks like irregular shaped areas of weakened and dying grass.  The damage usually appears between June and October.  If you suspect you have grubs dig down in the first few inches of your turf.  Do this several times at different locations in your yard.  They should readily be found.  Finding more than five white grubs per square foot can justify treatment.  You will want to be certain of an infestation before you use an unnecessary pesticide and spend money on grub control. 

 

Oddly, spiked sandals which are sold for aerating turf show some success in treating grubs.  If you decide to use this method walk repeatedly over heavily infested turf.  This can reduce the population up to 50%.  They are available through garden supply catalogs.

 

If you decide to go the chemical route proper timing is critical. Be aware that pesticides can have detrimental effects on organisms like earth worms and can be toxic to birds and other wildlife.  Because of this it is not recommended that a chemical treatment be used as a preventative measure.  A grub treatment must be applied when the larvae are less than ½” long.  If they reach the third life stage, pupae, they are more difficult to control.  The best time to apply in West Texas is mid-July.  AgriLife suggests watering ¼” to ½” the day before treatment is applied.  Use a rain gauge or a straight sided can (like a tuna can) to judge when you have watered enough.  After you have treated irrigation is essential to be sure that the chemical reaches the root zone. If your soil is very dry it may take two waterings to reach the root zone. 

 

 

If you have questions, call the AgriLife office in Odessa at 498-4071 or in Midland at 686-4700.   Additional information, and our blog for access to past articles, is available at westtexasgardening.org.  Click on “Resources”.


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