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Zucchini Stem Rot – Identification, Control, Prevention

Zucchini Stem Rot – Identification, Control, Prevention

Growing your own zucchinis amongst other fruits and vegetables but experiencing problems with the stems rotting? You are not alone – zucchini stem rot is a common problem. 

Luckily however for you there are a couple of easy fixes you can try in order to nurse your crop back to full health.

Read on for the things you need to do to prevent this issue and repair your plant. 


What is causing Zucchini stem rot?

Caused by larvae from the squash vine borer moth, stem rot can quickly destroy an otherwise healthy zucchini plant. Keep the moth away as best you can by covering the stems, applying moth traps or even growing your zucchini earlier in the season. As soon as you see any eggs remove them immediately, and cut out any young larvae from the stems with a sharp knife. 


What exactly is zucchini stem rot?

This unfortunate condition is usually caused by the presence of an uninvited visitor. The squash vine borer (usually shortened by gardeners to SVB) to be precise. 

This is a moth that just loves laying eggs at the bottom of plants such as pumpkins, squash and zucchinis. 

Once the eggs hatch, the larvae head down into the stems of the affected crop, introducing infection and causing it to rot. 

Unfortunately, once the eggs have hatched it is usually difficult to recover the plant.

So, the best way is to be prepared, try to minimize the chances of a batch being laid on your crop, and removing eggs at the very first sign. 


When should you suspect zucchini stem rot?

If you are inspecting your fruit and vegetable patch regularly you may have developed a keen eye for what is normal and what isn’t. 

And certainly, the base of your zucchini rotting is not normal. You may notice a mushy skin, or even a white substance appearing along the base. 

If you spot this unpleasant sign then know that you must act quickly in order to save the crop. 


When is your zucchini plant most at risk of SVB attack?

The end of spring through to mid-summer is the prime season for the moth to lay its eggs. It is key that you take preventative measures before this time in order to minimize the chance of an infestation. 


How to identify intruders on your zucchini plant 

Keep an eye out for uninvited visitors to your plants. If you see the moth itself, try to get rid of it – although of course, you cannot sit around all day waiting for one to fly on to your plant. 

It has orange or red markings on its body and its wings are usually a shiny green color.

Around the base, check regularly in the spring and summer for any signs of eggs. 

These usually look like little brown circles or oval shapes. At least if you see these you know they haven’t hatched yet.

Worse is if you find the hatched larvae – you will instantly recognize these guys.

But that is only if they haven’t yet bored into the stem. Usually, you will need to actually cut open the stem in order to catch them, at which point it is generally too late to save the plant. 


First symptoms of zucchini stem rot

Aside from the presence of unwanted visitors, there are other signs that you can watch out for that are typical of a stem rot infection. 

Firstly, you may notice that the leaves of your Zucchini plant are beginning to wilt despite the fact that you have made no changes to your watering regimen or soil upkeep. 

You may also be able to see the residue of what the larvae have chewed up as they tunnel into the stems.

This usually looks like orange mush, and is a true telltale sign that something is eating up your zucchini! 

Finally – mushy bases of zucchini plants should never be ignored and need immediate attention. 


How to protect zucchini plants from stem rot

The good news is that, although zucchini stem rot can be fatal to the plant, it is actually quite easy to prevent if you take the right measures at the beginning of the season. 

Read on for these key tips on how to stop your zucchini plant from being targeted by the squash vine borer and its offspring. 


Top methods for prevention of stem rot in zucchini plants


Cover your stems to prevent infestation

Covering up the base of the plant can help to prevent the moth landing or laying its eggs. This can be useful – if you create an environment that makes it impossible for any eggs to thrive then even better. Tinfoil is a good idea, or old tights! 


Avoid it altogether

Since the squash vine borer starts to lay its eggs only as spring turns into summer, you could avoid the problem altogether by planting your zucchini plants before this time. 

Of course, you would need to take measures to protect the plant from spring frosts and cold temperatures, as well as excessive rain. 

This would mean that by the time any moths are looking to lay the eggs the plant is very well developed and may actually be ready for a harvest. 

At this point the stems will be much harder and the larvae will not be able to enter the base of the plant. You could also try to grow zucchini indoors or in a closed greenhouse for even more protection.


Promote wasps

Yes, you heard it right. The squash vine borer hates wasps, so if you are able to introduce or attract these to the area then it will likely keep them away. 

However, if you are planning to dine in your garden beside your vegetable patch then this might not be the nicest experience and leaves you with a different problem altogether. 


Top methods for removing an infestation of squash vine borers

So you tried everything to prevent eggs being laid in your zucchini crop but it happened anyway? That’s too bad, but the game is not over yet. Act quick and you could still save your plant. 


Remove them yourself

This trick works only very early on – just after the larvae have made their journey into the stem, but not for too long after. You may notice the telltale residue of chewed-up zucchini around the base – this is usually a first sign that something is amiss. 

Cut into the stem with a sharp knife and remove the larvae – there could be more than one in there. Then, close the cut over and cover it with aluminum foil or even soil. 

This will stop the plant forming new roots. If you don’t fancy coming face to face with one of these pests, some prefer to poke some chicken wire into the stem around the entry point. But that’s not likely to catch them all. 


Add a dash of pepper

This one is nearly as weird as the wasps – but some claim it works. Add a bunch of pepper around the soil! Apparently, the squash vine borer does NOT like pepper! 


Come out at night

Creep out at night and you may catch the wasps taking a rest on the plant. This would be a pretty tiresome task and has no guarantee of success, but may be satisfying for some!


Buy fly traps

You know those yellow sticky strips that you can get to catch flies in the kitchen? Well turns out they work pretty well on moths too. You could try hanging them above and around your zucchini crop in a bid to stop them getting to the base of the plant. 


Trap moths in a sweet drink

Another tip is to create a sweet drink – in a yellow bowl. The moths are attracted to this and hopefully will stop for a drink. 



Frequently Asked Questions related to Zucchini Stem Rot


What causes stem rot in zucchini?

Stem rot is a condition that affects zucchini and other squash-like plant systems. It is caused by the larvae from the squash vine borer and can be fatal to the plant. 


Is stem rot the same as root rot?

Stem rot affects the stems of the zucchini plant, whereas root rot is a condition caused by too much water in the soil, which in turn leads to the decay of the root system.