What's That Bug? does not endorse extermination

Great Golden Digger Wasps
Location: Eugene, Oregon
August 17, 2011 7:33 pm
Hi this is my first year seeing these bugs and they have taken over a corner of my sand riding arena. I was weed wacking around the edge of the arena and at least 40 of them came out of their little burrows and just sat on the top of the sand (probably trying to figure out what that noisy irritating thing was doing and whether it was going to attack them). They never made any aggressive movements towards me so I wasn’t concerned about their presence (I am however intensely allergic to wasps so once I saw them so I kept my distance for my own safety)
My problem is, I need to be able to ride in this arena and I’m afraid if my horses big hooves stomp on a bug or onto one of their burrows they might feel the need to get aggressive. Is there a way to gently encourage them to find another home? preferably before they take over the entire arena? I have no idea how many larvae they lay each year but I would assume it could get out of hand with 40 or so adults in one spot this summer.
I’d prefer not to use pesticides, as much for the bug’s benefit as for the horse’s (horses can metabolize insecticides through the sole of the hoof and cause irreversible damage to the internal structure of the hooves and liver).
Any advice would be appreciated. I was thinking maybe dragging the arena more often with a tractor might encourage them to find another home. do you think that would work?
Signature: Teresa Hetu

Great Golden Digger Wasp

Hi Teresa,
Alas, we have no suggestions on how to solve your dilemma.  It seems you have too many restrictions (your allergies, horses reactions to insecticides, need to use corner) to make any decision that will meets all your qualifications.  Insects are like any other living creature.  They nest where conditions are suited to their needs, like food and shelter.  Once humans begin to alter the landscape, things change.  Creating a sandy arena for riding has produced conditions that made that specific area attractive to a large number of wasps.  Dragging the area with a tractor will not encourage them to find another home, but if you dig deep enough, you may destroy the broods that are there.  A female Great Golden Digger Wasp
Sphex ichneumoneus, expends a great deal of energy hunting and paralyzing a single cricket or katydid that will provide the necessary food for a single egg.  She will provision each chamber of her nest with enough food to sustain a single offspring and her instincts tell her when to plan for another offspring.  If she is lucky enough to survive predation herself, she may produce several offspring.  For some reason, the conditions in your area supported a large population this year.  You cannot expect that to keep happening because the habitat would not sustain ever growing populations of predators.  Nature seeks balance.  Good luck with your quandary.

It is odd that so many showed up this year when we have never had any before. or at least never saw any. We’ve had the arena for 10 years now and this is the first time I’ve seen anything like this. I have a tiller that I can use on their area perhaps that would work. How deep do they usually dig their nests? I suppose if all else fails I can just block off about a 20 foot diameter location and they can do their thing and hopefully move on next year.
Thanks for your help
Teresa

Perhaps weather conditions produced more Katydids than normal last season.  Did you place new sandy substrate recently?  That might attract them. 

nope, same thing it’s been for 10 years. would watering down the area make a difference? (I’m thinking soaking it?)

We love that idea.  Try it.

I’ll let you know the results… I have to daisy chain like 8 hoses to get all the way out into the corner but it’s sure worth a shot.
Teresa

We have never heard that term used with hoses.  We believe that hosing down the area will not make any difference to the developing larvae, but it may discourage the mothers from remaining and continuing to provision the nests for additional offspring.

Update:  September 26, 2011
Daniel, just wanted to let you know how the “experiment” went with the wasps. I’m sad to say it was a miss. they just relocated all over the arena rather than one corner after I soaked it.
Teresa

What's That Bug? does not endorse extermination
Location: Oregon

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