Meet the Squash Vine Borer
Most likely, she has been to your Houston garden and caused destruction.
If you grow squash, zucchini, pumpkins, or other cucurbits, you might someday find your plant wilting mysteriously from the base up. That’s often a tell-tale sign that the squash vine borer (a clear-winged moth in the Sesiidae family) has moved in.
This little pest is sneaky because much of its most destructive work happens inside the stem where it’s hard to see. But if you understand its life cycle, you can time your defenses (or even outsmart it entirely). Let’s walk along its life path—egg to moth—and then talk about what to watch for and what you can do in the garden.
The Life Cycle: From Egg to Moth (and Back Again)
The squash vine borer goes through complete metamorphosis: egg → larva → pupa → adult. Below is a step-by-step journey of its life, and what that means for your squash patch.
1. Egg Stage
• The female moth lays her eggs singly along the squash stem
• The eggs are small—reddish-brown to dull red —and flattened in shape (about 1 mm)
• They hatch in 7 to 10 days
Once the egg hatches, the young larva immediately begins burrowing into the stem (within hours) to avoid exposure.
2. Larval (Feeding) Stage
• The larva (caterpillar stage) tunnels into the interior of the stem and feeds on the vascular tissues (the “plumbing” of the plant), which disrupts the plant’s ability to move water and nutrients.
• As the larva burrows and eats, it leaves behind frass (excrement), which may be pushed out in sawdust-like form around an entry hole at the base of the stem. That is often one of the first visual clues that the plant is under attack.
• At maturity (roughly 1 inch or so long, cream or white body with brown head), the larva will exit the stem to continue its life cycle.
3. Pupation (in Soil)
• After exiting the stem, the larva burrows into the soil near the base of the plant—often a few inches deep, sometimes as shallow as 1 inch.
• Inside a small earthen cell or cocoon, it transforms into the pupal stage.
• In many climates (especially temperate zones), the squash vine borer overwinters as a pupa, emerging as an adult the next season.
• In warmer regions or where seasons are long, there can sometimes be two generations per year (i.e. a second adult flight and egg-laying cycle)
4. Adult Moth Stage
• The adult emerges from the soil when warm weather returns—
• The moth is often mistaken for a wasp or bee because of its clear wings and bright orange-black coloration on parts of its body.
• Once above ground, the adult males and females mate, and females begin laying eggs at the base of susceptible squash plants—thus restarting the cycle.
• A single female can lay 150 to 200 eggs in her lifetime.
There is a lot of information out there for battling SVB using chemicals, pheromone traps, aluminum foil, etc. However, at Learn to Bloom, we believe the most natural defense is to interrupt the cycle. My number one key to keeping my squash plants healthy for longer than my neighbors is to remove the eggs. I find that blue painters' tape works great for this.
A few times a week, inspect your plants for the little brownish red dots and remove them. Now there is nothing to hatch and bore through your stems. Also remove the lower limbs below any flowers or fruit. Now there are fewer places to lay eggs.
It really is that easy. And one roll of tape will last you season after season.
Understanding the life cycle of the squash vine borer gives you power in your garden. Timing is everything—knowing when eggs are laid allows you to place your defenses exactly where they’ll have the most impact. Even though these pests are tricky, gardeners who keep watch, act quickly to remove the eggs often succeed in minimizing damage.
