The Dirt on Texas Grub Worms

Background: During a garden community gathering on Saturday morning, September 7^th, several members were involved in shoveling out all the soil from Garden Bed 1 as the first phase to install an experimental water wicking system. During this effort, a large “grub worm” was discovered deep in the north-west corner of the bed. Out of concern for the worm and future plants, my son, Evan, removed the worm and transplanted it outside the garden (near the chimney swift habitat across the park).  See below for images of the grub worm.

Evan holding a Grub Worm found at RWCEG

Close up of the Grub Worm

Identification: As the so-called “garden entomologist”, I was asked to identify the worm and determine if they are a potential threat to the garden. Per my research to date, I believe the grub worm to be the larvae stage of a scarab class beetle commonly known as the May Beetle or June Bug (most common is Phyllophaga crinit).  I base this on positive image identification from several websites. Furthermore, back in June, Evan and I discovered a few adult June Bug beetles caught and strangled in the bird netting that covered that garden bed at the time. Below is a picture of one such tangled beetle in the netting. Also included is a clear picture of a June Bug beetle.

June Bug beetle found caught in netting at RWCEG back in June.

 

June Bug (Scarab) Beetle

Are they harmful?  Unfortunately, grub worms can be harmful to lawns and gardens. They eat the roots of grass and vegetable plants (up to 200 times their body weight!). They have been known to destroy lawns if there is a large number of them. However, since the grubs cannot bite or sting, they are benign to people. Since we only found one grub in the garden bed, I doubt it would have been a serious threat, but it is good it was removed.  Since the other garden beds have had all or most plants removed, it would probably be a good idea to sift through the soil of these beds to clear them out if found.

Organic Control:  Of course there are several chemical pesticides on the market used to control grub worms, but according to a “fortworthtexas.gov” website, “non-chemical controls include applying beneficial nematodes. These are microscopic round worms that attack white grubs and other soil inhabiting insects. Nematodes need damp soil to travel down into soil where the grubs are feeding. Apply at least ¼-inch of water before and another ¼-inch after spraying the nematodes on the lawn or garden soil. These worms are available in stores or through garden supply catalogs.”  But of course, the best way to remove a grub worm is to find it and then have Evan humanely remove it. Like his garden pest pet, Big Green (a tomato hormworm caterpillar), he actually thinks grub worms are “cute” and has great respect for them.

Further Information:  As gross as it may seem to many of us, several cultures eat Grub Worms indigenous to their areas. For those interested in knowing more details about the life cycle of these creatures and control methods, I encourage you to check out the following websites:

https://insects.tamu.edu/fieldguide/bimg141.html

http://fortworthtexas.gov/water/info/default.aspx?id=6034

http://www.youtube.com/watch?v=B86lSXKp5iA

      - Glenn & Evan Starnes