Squash & Why My Neighbours Can Leave Their Car Doors Unlocked – Part 1

This year I am growing 5 types of squash – 4 summer squash and 1 winter.  In terms of bush summer squash, I have “Dark Green” & “Sure Thing Hybrid” (both are zucchini) as well as “Early Prolific” which is a yellow straightneck.  I am also trying a vining variety - “Zucchetta Tromboncino”.  This one is supposed to be a dual purpose squash in that you can eat it young as zucchini or it can be left to mature on the vine for a winter squash.  I will be growing Tromboncino on a trellis, alongside my cucumbers.  And lastly, I am trying a winter squash for the first time – “Gold Nugget”.  It is a buttercup type that produces small (1-2 lb.) fruits.

This Year's Squash Seeds
The bush summer squash are from seeds purchased & grown last year.  I was able to get a few squash from them, but not a lot.  Let’s put it this way, my neighbours have no issues leaving their car doors unlocked ;) **

I have never had luck with squash – if I get a dozen or so zucchini, I’m tickled pink.  There are 3 main issues that I have when growing squash.

Squash Issue #1 – Squash Vine Borer

First and foremost is the squash vine borer (SVB) – sneaky little bugger.  Half the time I didn’t even know he was there until after my plant keeled over.  So last year I tried a new approach.  I learned that there might be a way of preventing the plants from getting infected if they were covered until the SVB moths had finished laying their eggs.  This magical date is about 3 weeks after the moths have emerged.  And that is where Growing Degree Days come into play.
Squash Vine Borer Moths
I've actually never seen one of these in person (didn't I say they were sneaky?),
so the above photo is from the University of Minnesota Extension Offices
Very, very simply, Growing Degree Days (GDD) is a measure of the daily accumulation of heat.  Plants & insects rely heavy on temperature and heat accumulation to develop.  You can easily see how this works in the garden – when days warm up, plants grow much more quickly & conversely, when temperatures cool down, plant growth slows down.  The same is true for insect development.  That is why GDD - and not a calendar - is the best predictor of such things as plant budding, flowering and fruiting, as well as insect life cycles.

Back to my squash plants.  My online research indicated that the SVB emerges from the ground in June around the 900 - 1000 GDD (F) mark.  Then it lays its eggs over a 2-3 week period, after which, the plants should be safe.  So my plan was to keep the plants covered with netting during this time.
Here in Canada, I use a site provided by The Weather Network called “The Farm Zone” to determine growing degree days for my area.  As far as I know, this is the only website in Canada that provides this kind of information.  If you live in the United States, weather.com has a GDD calculator HERE.
The only problem I had with The Farm Zone calculator was that the GDD listed on this site was in Celsius and all the online information on GDD and the squash vine borer was in Fahrenheit.  To convert Fahrenheit GDD to Celsius GDD you must divide GDD (F) by 9 and then multiply by 5.

So this means that 900 GDD (F) is 500 GDD (C).  I decided to use this number to start.  If I still had issues, then I would go up to try 1000 GDD (F).

So back to what I did last year.  I transplanted my baby squash plants outside, covered them with netting, and then checked the Farm Zone site each week.  When 500 GDD (C) was reached, I started my 3 week countdown.

2013 - Squash Plants Covered with Netting

Just over 3 weeks later I removed the netting.  Lo & behold no borers!!

Insert happy dance here

I do have one little caution.  In my northern garden, we only have one generation of SVB to worry about, so once their egg laying time has passed, we are home free so to speak.  But my understanding is that in the South, there can be 2 or 3 generations – just something to consider if you live in a warm climate.

There is one problem with covering the plants, of course, and that is lack of pollination.
Initially I thought I had a great idea to deal with this.  Since the SVB is the larva of a moth, I would uncover the plants during the day and replace the netting at night.  Then I find out that this particular moth is one of the few that flies around during the day – figures!  So that idea was out the window.
I resorted to hand pollinating any female blossoms that opened but I was only successful a few times.  Of course, once the netting comes off in July, this is no longer an issue.

Unfortunately, the SVB was only one of the problems that I had with squash last year – but more on that in Part 2.

Till next time…

** I’m assuming that everyone has heard the infamous zucchini joke, but just in case you haven't, it goes something like this – Why do folks lock their cars in the summer?  They fear that their neighbors will fill them with zucchini....hehehe....

This post was shared on Green Thumb Thursdays.


  1. I use the GDD too, but my husband gave me a weather station for Christmas one year. So I get to use the real temperature that I have here to do the calculation. Right now we are at 730F GDD (base 50F). So in about a week I need to make sure the edges are battened down well. Though I have the cover on already. I did it last year too and they still got to the zucchini. Sigh. I know from past years they are usually out around the beginning to mid July. I so hate the SVB. I only grow butternuts for winter squash because they are resistant.

    1. I had no idea that the weather stations you buy actually had GDD on them - I MUST look into that - it would be so incredibly useful!

  2. I've never heard of GDD. Where have I been??? Must do some googling now. That's a lot of squash. You will be drowning in them by August.

    1. Me? Drowning in squash? Now THAT would definitely be a change!

  3. That was some great info about the SVB and the GDD. I will be using that! Though I'm not a HUGE fan of the squash-I would like a few. Thanks!

    1. Thanks Sue! I'm telling myself this will be the year when I actually get a good amount of squash - knock on wood, fingers crossed, etc., etc. :)

  4. This is great information. The SVB isn't usually a big problem in my garden. We usually get to 900 GDD pretty early here, which may help. The calculator has us reaching it on June 1st. I don't know if we have a second generation or not. But squash bugs and cucumber beetles are a big problem for me. I spray neem oil on stems and leaves and it seems to keep them away.

    1. The SVB is such a menace, you are so fortunate not to have to deal with it! So far, I haven't had any issues with squash bugs or cucumber beetles - I'm just hoping that it's not because they just haven't found my garden yet.

  5. I feel so lucky to not have SVBs. I deal mostly with squash bugs and stink bugs and eventually powdery mildew. A second planting of squash usually gets me through to fall when the early plants give in to the abuse. Thanks for sharing at Green Thumb Thursday!

    1. You ARE lucky! I actually made a note recently about possibly doing a 2nd planting of squash next year, depending on how things go this summer.


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