Healthy acorn squash on a vine
Organic Gardening Pest Control

Organic Gardening: How to Prevent & Control Vine Borers

Your squash plants look withered and lifeless, are shriveling, and there’s a strange substance coming out of the stem. What’s causing your plant to die?

My Experience with Vine Borers

My experience with vine borers started about 2 or 3 years ago. Before that, I had never had any issues with them until we moved to our new home. It took a little bit of time for me to finally realize what exactly was affecting my plants. One minute they were looking lively and great, then one day they weren’t. It wasn’t until I heard other gardeners and homesteaders talking about vine borers that I started to investigate my plants.  They fit all of the characteristics for vine borers – wilting leaves, pulp coming out of the stem of the plant, and the stem has a pale appearance. The plant eventually dies from a lack of nutrients.

They are truly my worst enemy in the garden and for the past 2 years, I haven’t been able to grow squash. This year things are being handled differently. Here’s what I’ve learned along the way and the steps I’m taking to protect my plants.

What are Vine Borers?

The squash vine borer is a type of moth that sort of resembles a wasp. A good idea is to wait for it to land to identify it (they fly really fast!). The moth is black and orange in color with one pair of metallic green wings and another pair that’s clear. They love to lay their eggs on all kinds of squash – zucchini, yellow squash, pumpkins, spaghetti squash, acorn squash – any type of squash. In small crops, like in a home garden, entire crops can be lost in a year because of vine borers (like what happened in our garden). 

The moth typically lays its eggs from mid-June to July. Once the month has laid its eggs on a plant, it takes one week for them to hatch. At this point, the destruction of the plant begins. The larva makes its way to the stem of the plant and bores into it, leaving a clumpy greenish or orange “sawdust” known as “frass”. The “frass” is a great way to identify if you have vine borers.

The larva looks like a grub or maggot. It has an off white color with a brown head.

***An important thing to keep in mind is that these moths do not come out at night, like most moths. Instead they are out during the daytime, and I’ve noticed they tend to be out in the middle of the day. I thought it was interesting that they were out during the hottest points of the day.

Damage to the Squash Plant

Once inside the stem, the larva eats its way throughout the stem/vine of the plant. The plant starts to wilt and may look like it needs water. However, there’s a lot of damage happening to the plant. As the larva moves throughout the vine, it’s eating the inner pulp of the plant and cutting off its ability to absorb nutrients and water.

Preventative Measures Against Vine Borers

For the past two years, we didn’t have any squash. It was unnerving not to have a big yummy zucchini during the summer months. Last summer, I think we were only able to grow 1 zucchini before they died from the vine borers taking over. Preventative measures are the most effective means to reduce or eliminate vine borer damage and the eventual death of your plants. Once the vine borer larvae have damaged the plant,

Preventative Care I Took This Year

Here’s what I did differently this year:

  1. When the plants were set outside and big enough, I wrapped the stems in tinfoil. The tinfoil is supposed to protect the bottom of the stem to prevent the larva from drilling into it. If you’re opposed to using tinfoil, there are other types of barriers that can be used like:
    1. Row covers (need to be removed for pollination)
    2. Nylon stockings
    3. Mound soil and mulch around the bottom of the stem
  1. Plants were treated proactively with a homemade concoction of water, non-toxic dish soap, and 3 essential oils. I used rosemary, cedarwood, and peppermint.
  1. Daily inspections of the plants. Inspecting the plants took up a good amount of time. However, by being diligent, I was able to either chase away or destroy the moths. I was also able to get rid of the small eggs that were left behind, which can be confused with a speck of dirt. The eggs are either dark brown or a dark red. They weren’t found on any of the stems but rather on the top and the bottom of the leaves. I make it a point to always inspect underneath the leaves since that is a very common hiding spot for many insects.

Other Preventative Measures

There are several other ways to take preventative measures in order to either reduce or eliminate vine borer larvae damage.

Here are some additional tips:

  1. Plant vine borer resistant varieties. Try varieties like  ‘Cocozella Di Napoli‘ and ‘Costata Romanesco‘.
  2. Plant either early or late. There are a couple of suggestions with when to plant your squash. If you start early enough in the season (weather permitting), squash plants can grow big enough with thick stems to prevent the larvae from boring into it. Other squash growers plant after the threat of vine borers has passed. Vine borer moths only lay their eggs for 6 to 8 weeks during the summer. So planting or sowing after that timeframe is a great idea.
  3. Remove vine borer larvae. I have not found this option to work very well, but it’s something worth trying if you can catch the larvae in the process early enough. Cut into the stem length-wise to extract the larvae. A word of caution is that you may wind up causing too much damage to the stem and ultimately lose the plant anyway.
  4. After the growing season, clean up debris and dispose. Vine borer moths overwinter in cocoons in the soil.
  5. Sprinkle diatomaceous earth (DE) or black pepper around the stems of the plants. Use DE with caution as it can harm beneficial insects. Do not sprinkle on any of the flowers.
  6. Add in beneficial insects (like parasitic wasps) and nematodes. Parasitic wasps are natural enemies to vine borers. Beneficial nematodes parasitize insect pests that have soil dwelling larval or pupal stages and can take care of certain pests above ground.

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