Tuesday, March 17, 2020

June Beetles by Numbers this Spring

The weather is starting to remain warm and the insects are responding!  Every spring, when things warm up, insect populations rise.  It is not different this year than in previous years, but when we've gone months in cooler weather and haven't seen much insect activity, the emergence of June Bugs by large numbers can seem worrisome.
June Bug Adult - photo by G. McIlveen Jr.

June Bug adults are emerging now from the soil and mating.  As adults they do feed on foliage, but for the most part, are not considered a pest in this life stage.  They are highly attracted to lights, so you'll find them all over your porches in the evenings. 

I keep hearing concerns about the adults eating up the landscape.  If you are seeing damage to new growth, I would consider other culprits not the June Bugs.  The June Bugs are just prevalent and noticeable, so they are an easy blame, but likely you have beetles or caterpillars or maybe even pill bugs if the plants are seedlings.

After mating, June Bugs will lay their eggs in the soil of turf and those eggs will hatch into C shaped, creamy, larvae.  Those larvae feed on the roots of turf.  They can damage turf, but just because you see the adults doesn't necessarily mean they will be laying all their eggs in your lawn!  In addition, it takes through about end of July in our area of Texas (South Central Texas) for the numbers to be high enough to see damage.

For the San Antonio area, the best time to treat is around mid July, but you can probably give yourself a range of mid June through mid July and still be effective.  There are plenty of granular formulations for grub management on the shelves.  Be sure to water very well before you apply and water in after you apply.  Saturating the soil will push the grubs up higher and allow them to come into contact with the pesticide.
White Grub Larva - Photo by M. Merchant

Now remember, grub is a term we use for any scarab beetle larva and there are hundreds of species!  My rule of thumbs to know if you should be concerned are:

  • Is it late spring or summer months?  Yes - continue down, No - stop!  Not time of year to worry about grubs
  • Are you finding grubs in the turf - Yes - continue, No - stop!  White grubs that damage turf only feed on turf, if you find them elsewhere, they could be predatory or composters.
  • Are they are 1/2 inch or less (curled up)?  Yes - continue, No - stop!  Larger grubs are composters or predatory.
  • Do you see signs of damage or stress to your turf?  Dead patches? Yes - treatment is warranted, No - treatment isn't warranted, there probably aren't enough grubs to be causing damage.

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