Outsmart Squash Vine Borers This Season – Featured Video

Do your squash plants look wilted in the summer? There could be an invisible enemy larva eating your plant stems from the inside out. And worse yet, typically there is more than one miner inside!

This troubling pest, squash vine borer, seems to hit everyone’s garden in the eastern United States! The borer pest is very hard to control since targeting the egg-laying clearwing moth is like throwing darts in the night. Honestly, it is best to plant squash plants at different time intervals to increase your chance of missing the egg-laying time. Early transplant squash can beat out the egg layers and then late season squash can miss them.

Plan your garden accordingly this year, and you may be able to avoid most of the vine borer problems!

HGIC Website: Squash Vine Borers

Joyce Browning Horticulturist, Master Gardener Coordinator Video credit: Bethany Evans Longwood Gardens Professional Gardener Program Alumni; CPH

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

Intermediate Gardener – Growing Season 2021

Hello again! Last year, I published a series of blogs chronicling my 2020 growing season from the perspective of a “semi-novice gardener.” Some things went well, some things did not, and I learned a lot in the process, thus I am upgrading my gardener status to “intermediate!”

This year, I will share my work with the class again, but with a focus on certain challenges I encountered last year and what I am doing to do better this time.

Seed starting

For starters, my wife Krysten decided to try seed-starting this year. We set up a grow station on a shelf in the basement with a grow light. I used a smart outlet to power the lights and programmed it to turn on at sunrise and off at sunset. Krysten even pointed a fan at the seedlings, as she read that it simulates a breeze and helps them grow stronger than if they grew without any breeze pushing on them. We started Tomatoes and squash. This was Krysten’s department, so I don’t have a ton of details to share, but we got a ton of tomato, cucumber, and squash seedlings out of it.

Seedlings growing stronger in the indoor breeze.

We had a cubic yard of compost delivered (along with mulch and soil for other projects) and added that to the previous year’s soil in the raised beds.

Our overall plans and goals

Like last year, we are growing:

  • Tomatoes
  • Squash
  • Cucumbers
  • Green beans
  • Corn

Unlike last year, we are attempting strawberries and tromboncino squash. Tromboncinos are purportedly squash vine-borer resistant (a big issue for our squash in the past), easy to grow, and I thought it would be fun to have high-hanging vegetables.

Like last year, we have several pollinator-attracting plants in the garden, but this time, we are keeping them in pots and not planted in the raised beds with the vegetables since we had issues with overcrowding last year. We’ve got cone flowers, milkweed, marigold, lilac, zinnia, and dahlias around the perimeter.

We are upping our security from munching mammals such as deer and rabbits. Pictured at the top of this page, we still have the low rabbit fence as last year, but we are going to build a high fence to keep out deer JUST around the bed with the corn. I thought this would be much easier than creating a high fence around the whole garden area like in this video.

We are taking steps to stop squash vine borers from killing our squash plants mid-season, and that will be detailed in a future blog post.

I’ve built a big support structure for the tromboncino squash; it is the big triangular ladder structure you see in the photo. I am planning on some different structures to support tomatoes as well, and I will detail my construction projects in a future post.

One notable item

Before I sign off, I thought I’d share one interesting issue I discovered with my tomatoes:

White growths on tomato stems
Adventitious roots on tomato stems

I found these weird white growths on the stems of my tomatoes last week. I sent in this picture in to the horticultural consultants at Ask Extension (you can too!) for identification. They answered:

Those are adventitious roots along the stems. See this page on the HGIC website. Some heirloom varieties of tomato tend to produce these roots, which would grow into normal roots if placed in contact with the soil. In some cases, adventitious roots are a reaction to a stressor (too much water/poor drainage, high nitrogen, even exposure to herbicides). There is nothing you need to do other than consider if the plant was under a period of stress and then improve the conditions, if possible. For example, if the plant was growing in a pot with poor drainage, if you move that plant into the ground with good soil conditions, those roots will develop into normal ones to support the plant (assuming the plant is otherwise healthy, no disease issues).

This particular tomato plant is in a pot. It may have been over-watered, and it had also been humid and rainy in the last few days. It’s good to know it isn’t a big deal. We’ll just watch out how much we water that one.

Stay tuned! My next update will likely be about all the construction projects I’m wrapping up as I write this post. I’ve got the big triangle trellis, tomato suspension supports, row cover support, a new garden gate, and deer fencing around one bed.

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

Dan Adler
Web Support and Video Production

Semi-novice Gardener – Raised Bed Vegetable Garden Adventure (vol. 3)

Hi all!  It’s time for check-in #3 on my summer gardening efforts.  Overall, things are going well, but there have been big ups and downs.

The new raised bed we built is doing well.  Krysten planted corn in the center one, and a couple cucumber seedlings in the rightmost one.  The cucumbers have been slow to develop and grow.  I think this is because of the extreme heat.  In the last week or two, one’s growth has accelerated and it’s finally growing one nice cucumber.  I may harvest it and slice it up to use as an ingredient in a nice summer cocktail drink tonight (It’s Friday as I write this draft!). Do a web search for “porch swing” cocktail recipes.

Since we got the fencing up that encloses the whole space, we have had 0 evidence of animals munching our crops!  Huzzah!  However, we DID see one deer in our yard and it was eating our hostas elsewhere on our property (and has continued to; the hostas are mostly gone now).  So, we DO have deer, but they haven’t been interested in our vegetables (yet).  I wonder if they don’t like walking on the gravel we have down?


We have been harvesting a lot of tomatoes! One of our plants grew very large and tall and ended up flopping over the tomato cages we built in the last update.  We needed something taller!  We were worried that the tropical storm in the first week of August was about to topple the biggest one completely, so we hurriedly built an extension.  We found some scrap wood in the garage, attached it vertically to the sides of the raised bed, and strung twine around nails in the boards back and forth from board to board.  This seems to hold it up well and while the tropical storm wasn’t too bad here, there was no damage afterward.  We need to do the same for our second largest one this weekend.

Taller tomato support
Taller tomato support

The early blight issue I spoke about in the last update has seemed to be controlled by pruning more heavily and keeping air flowing.  However, our smaller tomato plant has been slow to fruit and has some holes/spots on the leaves.  After perusing the HGIC site, my guess was that it was Septoria leaf spot which is a fungal disease, however as a couple knowledgeable HGIC coworkers proof-read this post, they said it was actually most likely from flea beetles. It may sound like I’ve got the inside connection with experts, but everyone can send in questions to our Certified Professional Horticulturists for help like this!

Septoria leaf spot on my tomato plant
Flea beetle damage on my tomato plant

There are prevention and control directions on the HGIC page for flea beetles, but since the damage isn’t large at the moment, I think we’ll leave it as-is now, and plan to clean up and remove garden debris to reduce overwintering sites for the beetles when we wind down the growing season this year.

Overall though, we’ve been harvesting more tomatoes than we know what to do with, so we’re happy with our tomato efforts here! I’m considering making a whole lot of sauce.

Tomato harvest
Tomato harvest

Squash and zucchini

In the last update, I mentioned I suspected squash vine borer larvae to be killing my zucchini plant from the inside.  I did the surgery and discovered I was right.

Squash vine borer larvae in zucchini plant
See the white larvae in the center, lower third of the image?

I remember reading on the HGIC site at some point that in general with cucurbits, you can cover parts of the plant that grow above the soil with soil, and they will begin to root.  I cut the plant to disconnect the borer-infested segment (which was pretty much down into the roots) from the good parts.  I ripped out the roots and infested stuff, then planted the remaining stuff back in, mounding soil over it.

For a few weeks, things seemed promising.  Most of the large leaves did not make it, but some younger and new leaf sprouts were growing strong, and a small fruit started growing.  This suggested to me that after some time, we’d likely have this zucchini plant back from the dead and producing again.  However, that little fruit died and rotted, and the leaves and stems suddenly showed damage.

Our squash had been doing great.  It kept producing great fruit at a rapid pace, and kept expanding.  It was healthy; not showing damage from squash vine borers or cucumber beetles like the zucchini had.  It expanded outside of the raised bed and sometimes those leaves would appear wilted.  We assumed it was because of the extra heat from the gravel and the hot sun.

All was going well until a few days ago – it began wilting everywhere and wasn’t recovering.  Fruit production stopped.  We took a closer look, and we’re seeing the same squash vine borer type damage we saw with the zucchini!  Noooo!  It looked pervasive.  I wasn’t about to do more larvae extraction (it was gross, and squash isn’t my favorite vegetable).

So, we called it on both the zucchini and the squash plants.  2:35 pm, Friday, August 10th, 2020.  We ripped them out and tossed them far from the garden.  We’re making space for some sort of cooler season crops (the planning hasn’t started yet).

Next year, we are absolutely taking the following prevention steps (taken from the HGIC page on squash vine borers):

  • To prevent egg-laying, wrap a collar of aluminum foil around lower stems or dust or spray lower stems with spinosad or pyrethrum.
  • Cover plants with floating row cover until flowering.
  • Plant early to lessen injury. Use transplants instead of seeds. Or, plant squash seed mid-June.
  • Butternut and cushaw are resistant; yellow crookneck less susceptible than zucchini.

Green beans

We’ve been harvesting a few green beans from the mature plants that survived the rodent massacres that happened before we got the fence up, but it wasn’t enough to make a meal out of.  Several weeks ago, I planted more seeds to replace the eaten ones and those have grown and should be fruiting soon.  I hope that we can have some dinners with roasted green beans soon; they are my favorite of our garden veggies after tomatoes (and since tomatoes are fruit, I could say that green beans are my favorite veggies).

The zinnia we planted in the center of the green beans has gotten large and is crowding them.  We will likely try to tie it up to keep it more vertical than horizontal.

There are a couple bean leaves with holes munched out of them from some insect, but nothing to be too concerned about yet.

Moving forward

We’re still having fun with the garden.  It’s great to be done building for the most part.  Krysten has been adding a few pots on the outskirts with flowers in them which makes the space look nice.  I think in the next season, we’ll probably add more flowers in pots and save the beds for the vegetables.  The flowers have overcrowded vegetables in some instances in the raised beds, and we should be able to attract pollinators close enough to the vegetables via potted flowers.

I’m looking forward to more tomatoes and our first meal with green beans.  Perhaps in the next update, I may present our plan for cool-season crops.

View previous updates:

Dan Adler
HGIC Web and Communications Manager

Squash Vine Borers Collapse Plants

Gardeners are made of tough stuff. We manage a brave smile when our seedlings get nibbled, our leaves go spotty and the blessed groundhogs help themselves to our harvest.  

But there is one affliction that bring tears to our eyes: squash vine borers. I just felt the shudders from those of you who’ve had a close encounter. It’s awful.  

wilted squash plant
Squash vine borers cause the collapse of squash plants.

Picture if you will a robust squash plant, deep green, full of flowers and fruit, tall enough to shade several small children. The next morning as you sip your coffee, you spy it out your kitchen window, wilted, flattened, gone.

Yes, your neighbors heard you wail.  

What happened? Squash vine borers. These insidious insects tunnel inside squash as larvae, happily munching away as they fatten. Finally they hollow out enough of the plant that it collapses, its vascular system vanquished.

Squash vine borers most often hit summer and winter squash and pumpkins. But they can go after cucumbers, gourds and melons, too.  

So how do you prevent this tragedy? There are several good preventive measures and treatments.  

One trick is to plant early. Every insect has a prime time and simply planting earlier helps you avoid squash vine borers’ window of activity. It pays to know the enemy. 

Use established transplants instead of seeds or plant squash seeds mid-June. Again, it’s all about timing.  

You can prevent flying adults from laying eggs on your plants in May and June one of three ways. Wrap a collar of aluminum foil around the lower stems. Dust or spray with spinosad or pyrethrum. Or, cover your plants with floating row covers until they flower.  

Check your squash plants daily for signs of larval feeding. If a runner suddenly wilts, there’s probably a borer in there doing its worst.  

Also look at the base of your plants for holes and tan, sawdust-like bits. As borer larva feed, they push out frass, a fancy word for insect poop. If you find any, the game’s afoot.

squash vine damage from borer larvae
Squash vine borer larvae tunnel out the inside of squash plants.

Use a knife to make a slit upward from where you see frass. Cut halfway through the stem and remove and kill the larva, a white caterpillar with a dark head. Mound soil over the cut to promote healing. 

If you’re squeamish about squishing, inject Bt – a naturally occurring soil bacteria and organic insecticide – into the wound to kill the borer.  

If you remove an infested vine, seal it in a plastic bag and put it in the trash. This prevents the larva from dropping to the ground to pupate and return to infest your plants next year. 

I just heard Arnold say, “I’ll be back.”  

It also helps to know which squash the vine borers prefer. Butternut and cushaw squash are resistant to borers. Yellow crookneck squash is less likely to get borers than zucchini.  

Don’t give up on squash. I for one will not be without butternut squash soup. And Halloween without pumpkins is unthinkable. So prepare, prevent, and treat wisely to keep enjoying squash.

By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension. This article was previously published by Herald-Mail Media. Read more by Annette.

Squash Family Pest Problem Tips

CucumberThe squash plant family (Cucurbitaceae) includes many garden favorites- cucumber, summer and winter squash, pumpkin, muskmelon, and watermelon. Unfortunately, it’s a family vulnerable to some of the most consequential insect pest and disease problems. The names squash bug, cucumber beetle, squash vine borer, downy mildew, and bacterial wilt strike fear in a gardener’s heart. And those just represent the starting team. The legion of potential pest problems is sufficient to bring the toughest gardener to his knees sobbing in anguish.

But there’s hope for the human animals competing against insects, mites, and pathogens for these valued food resources. There are many ways to prevent and manage these problems and these are covered in detail on the HGIC website. Here are a few strategies that I think are less widely used. Give them a try in your pursuit of higher yields with fewer tears!

  1. Select disease resistant cultivars. Cornell University’s Vegetable MD Online website has a matrix for each vegetable crop that lists all major diseases and cultivars with resistance claims. They even include seed companies that sell the seeds! Special note: ‘County Fair’ cucumber is resistant to bacterial wilt; butternut and ‘Tromboncino’ squash are fairly resistant to squash vine borer.
  2. Apply floating row covers when seedlings emerge or transplants go in. The material excludes all critters. Remove the cover when plants start to bloom.
  3. Plant around insect pests by planting healthy transplants as soon as conditions allow or waiting until mid-June to plant seeds. Plant pumpkin and winter squash from late June to July 4th.
  4. Keep planting. Cucumber and summer squash can be sown several times, 2-3 weeks apart.
  5. Scout your plants for signs and symptoms of problems and take action early!

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