Hello everyone,

I am a novice gardener, this is the first time I've tried to grow vegetables. I had bought a small zucchini plant from my hardware store and planted it last December. I had planted it in full sun in a raised garden bed, I watered it every few/couple of days, placed compost around the base, and picked slugs off the leaves at night. It seemed to be growing very well, yesterday it looked quite robust and vigorous. I checked the zucchini last night to pick off any slugs, I could not find any, and it looked perfectly well to me. However, this afternoon I found that the zucchini had dried up dramatically. The leaves had turned light green, were shrivelled up and felt crispy to touch. Some of the stems were completely limp and they were tapered off to the base of the leaf. I don't know what has happened.

I am based in Sydney, Australia






I have a second zucchini plant which is not as affected. However, the tips of some of the leaves are beginning to shrivel up.




Any advice would be very much appreciated. I want to keep trying to grow vegetables.

That's Phythophtora, and pretty much a textbook case of it.

Pull the plant from the ground as quickly as possible and treat the remaining ones with a fungicide. I don't know what you have available in Australia but generally Bayer Aliette is the easiest to obtain product and most effective to boot against Phythophtora.

I have other plants in the garden bed - Cherry tomato, Basil, Chrysocephalum, an Australian daisy (Brachyscome Multifida), and the other zucchini plant. Should I treat them all with fungicide?

Is there anything else I should do?

I just looked it up and it seems quite destructive.

I had uploaded the same post on reddit's r/plantclinic and one member has suggested that it could be Verticillium wilt.

There are several species of Phytophtora, and each tend to affect plants for certain families.

Usually vegetable crops (be them industrial, garden or whatever) are infected by P. capsici, which affects a wide range of species including peppers, tomatoes, beans and all commercially significant cucurbits. So, yeah I would definetely treat at very least the tomatoes and cucurbits.
Without expensive testing (which unfortunately far too many laboratories consider nothing more than a nuisance) there's no way to say if Phytophtora was present in your garden in dormant form (spores) or if it originated from the plants you bought so in the future you should favor Phytophtora-resistant cultivars. For example all purple-colored tomatoes are known to be resistant to some degree, a trait most likely inherited from the original ancestor(s). Also consider switching to a different seedling supplier.

Other good practices are to avoid overwatering (read: soaking the soil) and to reduce the amount of nitrogen available to the plant: the latter can be achieved by using nitrogen-free fertilizers during the growing season.
As far as fungicides go, P. capsici is well known to be highly resistant to copper-based fungicides, ruling out that cheap road unfortunately. Bayer Aliette is the only product I can recommend that can be easily obtained: most other stuff is restricted so unless you have a mate with a permit willing to help there's no point in recommending it.
Please note that Neem oil is not a fungicide: sadly I've seen it advertised and sold as such several times despite this being a classic case of false advertising.

cooldog94 said:I had uploaded the same post on reddit's r/plantclinic and one member has suggested that it could be Verticillium wilt.

Saw this just now: the chief difference between Verticillium and Phytophtora is how quickly the latter spread. That's why I spoke about a "textbook case".
Verticillium is quite hard to diagnose in cucurbits as it often doesn't result in wilting and the leaf lesions look very similar to those caused by many other causes (not just diseases).

Thank you so much for all your help, El Pollo.
So far, I've only been able to find Bayer Aliette online and I would prefer to get a fungicide asap. I am planning on getting Yates anti rot fungicide, its active ingredient being phosphorous acid.

I was reading a pamphlet by the Royal Botanic Gardens Sydney on Phytophtora and it had recommended treating Phytophtora with phosphonate.

Thanks again.

I would cut all those leaves and throw them away. Last year I had mildew, not the same problem, but that's what I did and then sprayed them with milk and water,1:8 ratio.

I pulled the whole plant out.
Do you think I'd need to cut the leaves of the second plant? It has only been affected a little bit, and I've already sprayed it with the phosphorous acid.

I would cut and throw away all the bad leaves just to be sure.

ok will do. thank you!

cooldog94 said:I pulled the whole plant out.
Do you think I'd need to cut the leaves of the second plant? It has only been affected a little bit, and I've already sprayed it with the phosphorous acid.

If it's already wilting the plant is a goner and needs to be removed. Squashes/zucchini and pumpkins are the cucurbits most affected by P. capsici.

Phosphorous acid is only used as a preventive against P. capsici, meaning it should applied (as a drench) on squashes/zucchini and pumpkins at regular intervals to lessen symptoms. It will not act as a curative.

@ElPolloDiablo Ah ok, thanks for the heads up.

I think I'll try my luck and keep the second zucchini plant (I did remove the first zucchini plant) it has bounced back well and I can't see anymore signs of wilting.



However, not long after I sprayed the phosphorous acid solution onto my plants light brown spots began to appear on the leaves of my tomato plant. Do you think this could be related to the potential Phytophtora in the roots, or could it be related to the phosphorous acid? I've also realised that I have been overwatering my tomato plant... So that might have something to do with the spots as well.