These are the long Sicilian zucchini and this year the leaves are turning yellow on a few plants. This is the first year I observed this. Does anyone have any idea if its a disease? Or something else. It has been very hot (South Ontario Canada) but it doesn't look like damage caused by heat. In my experience I never really seen these affected too much by strong sun, except a bit of wilting in the day which goes away in the evening. I've also never seen any insects attack these plants. The only other thing I can think of that has been different from previous years is the fertilizer, my father has been adding chicken manure pellets to the soil (mixed with water) Could this be causing an imbalance in the soil nutrients and damaging the plant?
Good morning sjs, mine have had this problem in the past when it has been very hot and I thought I had watered enough but I hadn't. You should consider twice a day watering for Zucchini during hot weather as they are very very thirsty indeed. Your dads use of chicken pellets should not affect your plant. I fed in early Spring with a general purpose growmore and then when closer to flowering with Tomatoe feed. (High nitrogen). IMO I would increase your watering regime and water thoroughly. It may not help the lower leaves at this time of the season, but will help it when fruiting. Hope that's of a little help to you.
I was doing some more research and I found that this resembles a lot the symptom of a virus such as cucumber mosaic virus or zucchini yellow mosaic virus. Could that be it? If it is I'm worried about it spreading to other plants.
Hmmm you said you had seen no insects Aphids etc. Mosaic is often caused by Aphids. If it is this you do need to remove and dispose of the plant fairly quickly and also watch for other signs on other Zucchini if you have them. There is no treatment as far as I'm aware as it is a virus. The only way to stop this is to replace your crop next season with a resistant seed. Do check under the leaves for aphids and especially the healthy looking ones.
I'll have to check, I haven't looked for insects, I have noticed a few ladybugs hanging around. Also maybe 5 meters away we have roses which are being ruined by pests, I also haven't looked closely at them but in the past they have always had aphids. Not sure if the proximity is close enough for them to make their way to the vegetables. Although this and two other zucchini plants are having the same problem, this one in the picture the worst and it was like that from very young, so it could have been diseased from the seed.
Hi @sjs, you have hit the nail on the head so to speak, aphids travel !! If you had this from very young then the virus would have been there already in the seed, coupled with aphids that you say are close on your roses, then the answer is there. IMO I would remove all of your Zucchini and replant next season with a confirmed resistant seed. Not what you wanted to hear, but others might have a different opinion. Good luck.
@sjs Hi! I think there were aphids because I seem to have noticed exuvies. They may still be in business.
@sjs Good morning! Exuvia is a term used to describe the remains of an exoskeleton after the moult of an arthropod. In practice, it's the "stopped dress" from the insect after the wetsuit! The exuvia of an animal can be very important because it can often be used to identify the species of an animal and also its sex as well as for us "gardeners" the sign that even if the aphids, for example, are not present at the moment on the plant show that there have been and certainly have produced damage to investigate.
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