It looks like that is probably the cause. Thanks!

I take an exact knife or utility knife And make a vertical slit and dig that larva out then I mix some mud in a bowl and plaster it on the cut, making a mound of mud over the base . Hopefully the plant will make roots in the cut. When I plant the squash , I should put a floating cover over the plant to keep the Squash Vine bore moth from laying her head. When the plant starts to flower I normally take the cover off because I need the flowers to be fertilized. There was a tube on another thread here that shows how to operate on the stem.

To me, SVBs are the single most devastating garden pest. One strategy is to cut them out, but then you have to regularly inspect what can seem like miles of vines regularly to look for the frass they leave. Another is to cover with netting, but that too can be a major job for a big vine, and you'll likely have to do hand pollination. What I've been doing lately is spraying weekly with BT. So far so good. Be aware that moschata-type squash (butternut, etc.) are more "resistant" to SVBs that pepo-types (zucchini, etc). No, SVBs can still decimate moschata, but they'll decimate them less. Cukes and melons are not immune to them either.
Many parts of the country don't have them. Notably the Pacific coast. So if your vegetable gardening experience is based in those parts of the country, you'll be unaware of and unprepared for them. Been there, done that.

The gardener at the Natural Gardens in Austin covers them until they blossom and then he uncovers them and let the bees pollenate under the theory that then will get a crop before the laid eggs mature enough to cause major damage. I have not tested this out yet. I have heard that putting tinfoil around the base f the vine is a deterrent Most of these do not work with long squash vines. I have never had them on my cucumbers

If you have the time and patience you can go out and inspect the vines for the SVBs tiny eggs. It's a lot of work as the vines grow but you can do it. If you notice any frass, cut those fat white little worms out. I'm not sure it's a deterrent but I leave their dead bodies on the vine (as a warning not to lay eggs and because they make me mad). I've been able to manage my yellow squash well just by checking for eggs but my spaghetti squash will likely produce much less than its potential. Another method I have tried is to take the garden hose and spray into the hole left by the svb for a good minute. I know they drown but I'm not 100% sure it's worked yet. Would love it if it's that easy! I haven't had any problems with SVBs on my butternut or crookneck but as soon as I saw some getting through my spaghetti squash I mounded dirt over the nodes of my other squash. I've seen them lay eggs on the leaves and squash fruit though so I don't know how well it'll work. I think the SVBs stop laying eggs around July if I remember correctly. I might try a net next year until I see flowers (as other posters have said) and then I'll start checking the vines every other day or as I have time. I think it takes a little over a week for the eggs to hatch so if I check often, even if I miss some, I should catch them on my next go round. Has anyone had success with a trap crop or is there an SVB predator I can attract? I have a friend who uses Sevin dust and never gets SVBs but I wouldn't want to kill all the beneficial bugs in my garden.

check out my blog. http://cabalgarlandtxgarden.blogspot.com

I have many posts regarding growing squash/pumpkins here in the Metroplex, and also about SVB and other pests. I try not to use pesticides.

I think the best advice for now is to get familiar with the eggs. Remove them from the vines. They are mostly laid at the bottom side of the vines. Then bury or mound dirt over the vines. That encourages more root formations, which lets the plant survive longer. But the best advice in general is to start them real early. I started mine in March and have had a great harvest. The SVB and Squash bugs have mostly killed my vines now but they were too late... I got my harvest already ;)

Also try a late crop. If you can time it to have squash ready by early November you avoid much of the SVB too. That usually means planting early September,and protecting the young plants with netting. Tulle netting works great and is cheap.

sustainabee,

You can also get a syringe (get them cheap on Amazon, the ones for refilling ink catridges or other purposes, not the medical ones) and inject either a mixed BT solution, or just soapy water into the holes with frass. I have done this and a few minutes later the grubs back out of the vine trying to escape and I kill them.

Again, for long vines, inspecting them for frass is a load of bending-over type work. If you're looking for eggs, it's even harder. Not fun, and takes a while. It has been reported that weekly spraying of vines with BT will do the job, and that's vastly easier. I'm trying that this year. FWIW, BT is cheap and entirely organic.

If after spraying, you see damage, injections are a good way to go, and do minimal damage to the stem. I want to emphasize the good point about syringe needles. The medical ones are too fine, and when you stick them in the stem, they will immediately clog with stem material. The ones for refilling ink cartridges (14 or smaller gauge) really are best.

I get Plastic syringes , (that I use with glue) from Woodcraft that might be good. Also the vet has some Big ass syringes that I use for injecting animal skin glue into bubbled veneer that is metal tipped exchangeable tips of different sizes.

Hey Jessica, I'm the one who posted that first link (http://forums.gardenweb.com/discussions/3957069/squash-vine-borer-warning-gross?n=1) and I just updated it - long story short I can't guarantee they'll survive the season but cutting them out with a knife seemed to work for me even though the vines looked pretty bad once I was done. I agree that it's tough and unpleasant, and I plan to be much more diligent about looking for and removing the eggs BEFORE they hatch next year.