Squash Vine Borer Life Cycle – and Control Methods

Anyone interested in the life cycle of the squash vine borer or how to recognize it at each stage?  It’s probably not quite what you think.  I am including a photo library below for your visual pleasure.

The squash vine borer (Melittia cucurbitae) is a moth.  The most surprising thing is that it looks nothing like a moth, it looks more like a fly and it’s far more attractive than you’d expect for such a malicious monster.  It’s like a wolf in sheep’s clothing.

The fly lays it’s eggs on the squash plant itself, usually on the stem but can be on a leaf, within a couple of inches of the soil.  After the eggs hatch, the “caterpillars” (maggots!!!) burrow into the stalk of the squash plant.  The only evidence of this happening is a patch of yellowish brownish fine sawdust looking stuff that gathers below the hole in the stalk made by the squash vine borer “caterpillar”.  Once inside, the squash vine borer eats the stalk from the inside out.  Most gardeners discover the invader when leaves turn brown, shrivel up, and fall off.  It’s almost 100% too late at that point.

Once the borer has had it’s fill, it burrows into the ground and cocoons for the winter.  Guess what happens in the spring?  shiver.

So what can be done?  Well, I’ve tried a few methods and know of a lot more.  After about 3 years of battle, I haven’t beat it yet.  Here are some combat methods:

– pesticides – useless to the borer once inside the plant.  also pesticides must not contaminate the flowers or all pollinators will be killed.

– wrap the based of the plant in nylons, tinfoil, plastic, etc etc to block the moth from laying its eggs at the base of the plant.  I tried this and it didn’t work for me but I know it worked for other gardeners

– row covers so the fly cannot land on the plant – must get the cover off in time for pollination of flowers so it’s all a timing issue, you may need to hand-pollinate flowers if they are early in the season (oh, and what if that cocoon hatches and the fly is INSIDE the row cover?  whaaat!)

– bury multiple points along the stalk so that your plant puts out roots in multiple places.  this allows for nutrients to flow to unaffected parts of the plant and the original portion of the stalk can be cut away if it becomes infect (my favoured option so far)

– cut away the “old” leaves that may have seeds on them during egg laying time. the problem is that eggs are often laid directly on the stalk and it’s a timing issue again

– plant your squashes later in the year past egg laying time – can anyone tell me when, precisely, that is?

– harvest your squash early, before the plant is killed – in my experience not many squash are produced that early on

– slice open the effected stalk and kill those life-suckers one by one – good luck. it’s gross. it’s difficult. usually results in the loss of the plant anyway or at least results in a non-productive plant.

– locate the eggs on the plant and scrape them off – you might not get them all but worth a try

– plant your squash in a different location every year since the moth arises from the earth directly under last year’s infected plant.  problem is my property is way too small for this to be effective

2 Responses to Squash Vine Borer Life Cycle – and Control Methods

  1. joann murnane says:

    Didyou try neem oil ??

  2. Richard says:

    I sliced open the vines and fed the grubs to my chickens; they love them.

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