Squash vine borers and squash bugs: two garden villains!

My squash and zucchini have been breeding grounds for these two garden pests in past years. They also have confused me because I tend to conflate the two or have mixed up which one I’m searching for information on online. This year, despite taking more steps to combat both of these evil-doers, my garden still took major hits from this duo.

In anticipation of this insect onslaught, I took the following extra steps:

  • I kept the young squash and zucchini plants under floating row cover until they flowered. I uncovered then so that pollinators could get in and do their thing. I potentially could have kept them under cover longer if I manually pollinated, but the plants were growing beyond the cover structure I made, so it was time.
  • I wrapped foil around the lower stems of the plants as HGIC suggests to prevent egg-laying.
  • I searched for and removed more regularly squash bug eggs found under the leaves.
  • I planted these crops in a bed that had NOT yet been used for squash or zucchini and therefore hopefully would not contain overwintering vine borers in the soil.
  • I planted yellow squash, zucchini, and, HERE COMES A NEW CHALLENGER: TROMBONCINO SQUASH! The tromboncino variety is supposed to be vine-borer resistant.

The following is my garden’s tale of woe, and my future plans for growing a squash bug and squash vine borer-free garden.

Let’s start with the one that has been the most visible to me, the squash bug.

Squash bug

For the past few years, I’ve been seeing these guys’ eggs on the undersides of my squash, zucchini, and cucumber plants. When I find them, I tear off the small section of the leaf, smash ’em between my fingers, and chuck them away. I kept doing this, but kept finding more this year. I’m sure tons of the eggs got past me.

Confirming that notion, I did later catch these nymphs having a party on my plants.

Squash bug nymphs
Squash bug and eggs

In my garden at least, I don’t believe the squash bugs are the main villain destroying my squash and zucchini crop. I saw some stippling on the leaves here and there, but nothing that seemed to do severe damage.

Squash bug and stippling on leaf
Squash bug and stippling on leaf – this was about the worst damage I saw like this.

One of my later tromboncino fruits had a ton of superficial damage on it. My guess it is from the squash bugs. They didn’t touch any other tromboncino fruits, and this particular one was closer to ground level, while most of the rest of my tromboncino crop was high in the trellis. Are these guys afraid of heights?

Squash Vine Borer

Previously, in my gardening efforts, I’ve had zucchini and squash plants succumb to the squash vine borer, and I took several steps to avoid them again this year, but to no avail. I’m sorry to say, both our zucchini and squash plants grew large and healthy, produced a round of solid fruits, then quickly wilted and died within a couple weeks of each other.

Tromboncino squash on trellis
Tromboncino squash climbing up it’s trellis, making fruit, and not worrying about any bugs.

I did not see any adult vine borer moths, but I found a big fat larva in the dead plant’s stem. I tore out the dead/dying plants.

While yellow squash and zucchini were out for the count, the tromboncino kept on truckin’ and had no issues so far with either of the nasty bugs other than the one damaged fruit.

What else can I do?

There are more means of combating these bugs if I decide to do battle with these villains again:

For squash vine borers (info mainly from the HGIC page):

  • Adjust the timing of planting. Planting early or late in the season to attempt to avoid the life cycle of the vine borer. Or, plant in succession; stagger when we plant so if some crops get taken out, you still have another coming along with more fruit and another chance at success.
  • Do surgery on the stems of the plant you fear is infested, rip out any larva, and mound up dirt over wounded stems to induce supplemental rooting.
  • Spray lower stems with spinosad or pyrethrum.
  • Spray lower plants stems and base of plant with pyrethrins when adults are flying (mid-late May). Repeat 14 days later. Or sprinkle diatomaceous earth on lower stems. 
  • Bt (Bacillus thuringiensis) or beneficial nematode Stinernema carpocapsae can be injected into wound to kill borers.
  • Seal up infested vines in plastic bag before larvae pupate (break life cycle).
  • Plant resistant crops: Butternut and cushaw are resistant; yellow crookneck is less susceptible than zucchini. (I went for the tromboninos).

For Squash bugs (info mainly from the HGIC page):

  • Neem, horticultural oil, and insecticidal soap are effective when sprayed directly on nymphs. Adults are very difficult to kill with the insecticides available to home gardeners.
  • Trap adults and nymphs by placing boards near host plants under which they will hide. Lift boards and destroy bugs in the morning.
  • Bugs also hide under mulch. When numbers are high, mulch may need to be removed.
  • Removing all plant debris at the end of the growing season is essential.
  • Check seed catalogs for cultivars of summer and winter squash that are resistant to squash bugs.

What will I actually do?

I’m gonna give up!

This is at least the third year in a row with a similar story for the yellow squash and zucchini in my garden, and I think I’m done with regular yellow squash and zucchini for a bit. There are more things I could do to mitigate the problem, but I’m tired of providing food for these buggers, and I’m not into high-maintenance gardening, so I’m gonna call it quits on those crops for now.

Besides, the vine-borer-resistant tromboncino squash crop I tried this year has excelled, and it cooks and eats pretty much like its susceptible cousin crops. I plan to keep going with tromboncino. Maybe a year or two without fodder for these bugs will break the cycle and allow them time to die off or move elsewhere.

Here are two great videos on both of these problem bugs:

Feel free to take a look at my posts from last year’s growing season.

Dan Adler
HGIC Web Support and Video Production

2 thoughts on “Squash vine borers and squash bugs: two garden villains!

  1. George Lambert August 18, 2021 / 10:16 pm

    Did you extend the foil below the soil surface? I too was overwhelmed by squash bugs; it is impossible to effectively spray the bottom of leaves and the eggs are too hard to squash and impossible to scrape off. They won, so I have given up too.

  2. Denee November 18, 2023 / 2:14 pm

    hey there…so the viscious vine borer…I grew tromboncino and it did perform well, ate it all summer with 5 left on the vine for long term storage as winter squash…wonderful!…I also find that the Waltham butternut is somewhat resistant…I add soil over the vine as it grows throughout the length of it. The plant continues to root and stay alive….also the Tatume squash, Zucca Lunga Di Napoli, and Seminole pumpkin squash all do well resisting the vine borer…Good Luck!!! and enjoy!

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