My Black Beauty zucchini keeps trying to turn yellow.

Hoping someone can help identify this as I am not quite sure whether I am having a problem with disease or the after-effects of overwatering. Here's the patient:



The zucchini is still a baby, and I was probably overwatering it until recently (I finally got a moisture meter). It's planted in a 2x3 cement mixing tub with plenty of holes in the bottom and is elevated to help with drainage.

The white parts are not powdery mildew - they're the way the leaves are colored. It's *in* the leaf, not on it, if that makes sense.

This happens to the bottom leaves. I've been removing them when they get to about this state. The base of the plant(s - I think there might be two together) is full of new growth.

Any thoughts on whether this is disease or if it's possibly from too much water? There doesn't seem to be anything on the surface of the leaves (like rust spores). The zucchini is in full sun for about 9-10 hours a day right now. I should add that this is not planted in MM - it's a mishmash of leftover, too-sandy MM and a couple of different kinds of compost.

Thanks!

Is there anything on the underside of the leaves?

Your soil may need potassium.

It does look like it's missing something. This may be one of the times when a bit of the oh my gosh Miracle Gro might be needed. Rowena was also posting about using epsom salts on yellow leaves. Hope she sees this.

Kay

elliephant, there's nothing on the underside of the leaves either which is why I'm puzzled at the cause.

Potassium hmm? I will look into that!

I agree with Kay, I do use Miracle Grow and it helps when there are deficencies. I know some people are opposed to it, so it's up to you. You could also try some wood ash. Not too much, or it will sweeten the soil.

In another thread there was talk about that silvering, turned out it is damage from white flys. Those are really tiny and would be sapping the energy of your young plants. A light spray with a couple drops of soap and mineral oil in it should take care of them.

Squash are heavy feeders also. They can live easily and happily in a compost pile. So give it a feeding to help it out grow whatever. It will love some compost/worm/fish/miracle gro tea.

The white parts are normal mottling of some squash. Here is a good link with pictures:

http://forums.gardenweb.com/forums/load/gourds/msg0409541710037.html

In California there is something called the silverleaf white fly. I, also, thought that the silvery color that shows up at vein junctures on zucchini was just normal to that plant. But a thread here showed me other wise. I still wonder if it is not normal for some as well.... but yellowed, stressed leaves with silvering sounds pretty damning evidense of white fly. Next step is to look for them.

Another thread on this~ Silverleaf on squash

I'll keep looking, but I haven't seen any pests really. I did spray the plant down with a neem and soap solution a week or so ago, just in case - it's probably due again, so I'll do it tomorrow.

The nutrient deficiency sounds promising, too. I have some fish emulsion I'll use tomorrow (the tomatoes would probably appreciate it too!).

Turan wrote:In California there is something called the silverleaf white fly. I, also, thought that the silvery color that shows up at vein junctures on zucchini was just normal to that plant. But a thread here showed me other wise. I still wonder if it is not normal for some as well.... but yellowed, stressed leaves with silvering sounds pretty damning evidense of white fly. Next step is to look for them.

Another thread on this~ Silverleaf on squash

Check this link. The mottled pattern caused by the sliverleaf white fly is quite different from the normal mottling:

http://www.ca.uky.edu/entomology/entfacts/ef319.asp

Here is more interesting info on possible causes:

http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/viruses.aspx

Thanks for those links! I am pretty sure that the markings on my zucchini are normal variegations and not disease or pests (all in all it's pretty pest-free). The yellowing however is definitely something else. I'll give it a good boost of fertilizer and see if that helps resolve any deficiencies first, then go from there!

Good infos!
I have been looking at pictures in seed catalogs because I had this sneaky feeling that some varieties intentionally have this.


Patio Star Zuccini


So I think when I see this I will watch for whiteflys and think it pretty.

Coelli, sounds like a good plan.

walshevak wrote:It does look like it's missing something. This may be one of the times when a bit of the oh my gosh Miracle Gro might be needed.

in my opinion, no home gardener should ever feel bad about using a little miracle gro! or for using a little synthetic pesticide if needed. sure, we want to be as organic as possible, but we also want to grow food and no home gardener i know will just indiscriminately use herbicides, pesticides, or synthetic fertilizers in the same careless and liberal way they are used in agriculture. home gardeners use what is needed only when it is needed, in the amounts needed, and they stop using it when it is no longer needed. the food you grow in your own garden will ALWAYS be better, more nutritious, healthier, cheaper, than anything you can buy in any store, even in a farmers market, because unless you truly have to go to the back 40 to harvest your dinner, you are probably not even getting in the car to get it.

Rowena was also posting about using epsom salts on yellow leaves. Hope she sees this.

to my knowledge epsom salts is only indicated for yellowing leaves in tomatoes and peppers. i haven't heard of it being used for squashes but i'll be happy to ask the folks i consult at the ag center in nashville and the TN extension office.

rowena___. wrote:to my knowledge epsom salts is only indicated for yellowing leaves in tomatoes and peppers. i haven't heard of it being used for squashes but i'll be happy to ask the folks i consult at the ag center in nashville and the TN extension office.

ok, i checked my regular sources and they suggest that epsom salts is only indicated for squash if they are experiencing blossom end rot or trouble with fruit set. otherwise, it doesn't have any practical purpose.

Thanks for checking! I worked some organic fertilizer into the soil (this one), and stuck a few Jobe's Organics spikes (half the recommended amount) around it for now. I hesitated to use the fish emulsion yet because I think you need to dilute it in water, and I'm trying to be careful of how much water it's getting. I don't want to drench it on top of what it's getting from the drip irrigation system.

Still no pests on it either, btw - I have been checking. My garden has stayed remarkably pest-free so far (other than a thirsty digging squirrel). I'm a little shocked. Of course, I shouldn't have said that...