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MockY
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Joined: Wed May 06, 2015 5:30 pm
Location: Sacramento, Zone 9b

Zucchini keeps dying off. Help identify the issue

I built a new raised bed garden earlier this year and bought 7 yards of 50/50 from a local company to fill the beds with. This soil is definitely void of nutrients even though it consists of 50% compost. I've amended it with additional store bought compost and peat moss and organic fertilizer (the latter not so much). While most things grow, a lot is not performing as it should. The tomatoes got to 8 feet before I topped them off and the cucumbers were spewing out fruit until downy mildew get a foothold. But pretty much everything as a whole has various issues. This is something I'm working on as I have compost in the works and worm bins. I know it takes some time to build up proper soil in other words. But the reason why I bring this up is I'd like to determine if this is the reason why I simply can't grow Zucchini.

I started seedlings in pots this year (it was warm out so no need to be indoors) and planted them in the beds as soon as I had the beds ready (I was a little late). They took off and grew rapidly. But both plants eventually had their outer/bigger/older leaves brown up and finally died off. Over the course of a few weeks, I had to rip the plants out and replace them with some other crop.

Fast forward a few months, and since I live in zone 9, I direct sowed another zucchini in a different bed. It germinated quickly but as soon as the first true leaves got to the size of 3 quarters, the same thing started to happen to it. The outer edge of the leaf browned up and eventually the entire leaf died. Simply put, I can't currently grow ZXucchini, even though it's one of the easiest plants to grow..or so I've heard.

So before posting pictures, I'd like to share my theories. I first thought downy mildew was the cause since all my cucumber plants eventually succumbed to it. But when I look at the young seedling, it is obvious that downy mildew is not the cause as it starts along the edge. I believe it may be Fusarium wilt. This nasty stuff winterize in the soil and I may have to deal with this until I replace the soil.

Enough of my babbling...

Here is a picture of the first plants:
2015-06-24 17.40.23.jpg
2015-06-24 17.40.08.jpg
2015-06-24 17.39.57.jpg
And this is how the seedling now looks like
2015-09-14 16.21.17.jpg
Any help is much appreciated.

catgrass
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Location: Southwest Louisiana

Looks like Mosaic virus. Not sure-I just read something about this a few days ago.

imafan26
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Location: Hawaii, zone 12a 587 ft elev.

You say you are in zone 9, Florida? It helps if you edit your profile and add your zone and location.

It does not look like a virus to me.

With that much compost, how often are you watering and is your soil drying before you water again?

It looks like there could be multiple problems going on. Fungal problems on the older plant and possibly a nutrient deficiency. The younger plant looks like something is sucking on it aphids, mites or thrips from the scars and frass.

If plants are overwatered they cannot take up nutrients very well and they get weaker and become targets of pests and disease.

Pests and disease further weaken the plants.

If the plants look good before you put them in the ground, then I don't think it is the fault of the plant.

If you are planting in the same spot over and over again, it is not a good place for the zucchini, try a different place or put it in a pot with MG potting soil (different soil) in a different place.

Other things grew well and produced but I still would get a soil test especially if this is a new garden to see if your nutrient levels are balanced. I do not like so much compost. It holds a lot of water and for me raises the soil pH higher than I would like making micronutrients less available and also consuming a great deal of the nitrogen. Your other plants grew vigorously so that may not be a problem. When I add compost and only try to fertilize organically with organic lawn fertilizer or blood meal, my plants will grow but be much smaller than they would have been with synthetic nitrogen.

Check under the leaves of the young zucchini, I suspect you will find that something is sucking on the leaves and you need to do use use some insecticidal soap or oil or water to blast them off. If you have diverse plantings, especially nectar and insectary plants, aphids are much less of a problem. Planting in the same spot is not a good idea, they will hang around for the buffet.

I have been having problems growing zucchini myself the last few years. I used to get so much zucchini I could not give them away, or they would become bats before I got around to picking them. Now, I am lucky to get couple of zucchini from a plant since the male and female flowers can't seem to get their act together and bloom at the same time. Eventually the plant does die of fungal disease but for me that is a normal part of their life cycle.

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MockY
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Joined: Wed May 06, 2015 5:30 pm
Location: Sacramento, Zone 9b

I've added my location to my profile.

The 50/50 compost/topsoil is garbage. Repels water, does not hold water, high PH, low nutrient levels. Probably void of everything. When I filled the boxes with this mix, I also added a 2-3 inches of peat moss in each bed, that I mixed into the soil for the top 6 inches. I then added a layer of potting soil that I did not incorporate into the soil. With the help of mother nature, all the boxes were thoroughly watered and I started planting just days after the rain.
This was the base of the soil. Throughout the season I have been keeping a layer of straw in each box to retain as much moisture as possible, and along with sporadically adding small amounts of dry organic fertilizer, I've also done a lot of chop-n-drop and used seaweed fertilizer.

When the growing season for the warm weather crops is over, I'm planning on building a large keyhole bed and take the bottom half layer of most beds and use that as base for the new bed. As a result, the older beds now have the top layer as their base. I will then top them all off with my homemade compost, vermicompost, and substitute what I'm lacking with store bought compost. I'm hoping this will make things a bit more balanced.

Back to the topic at hand.
The watering schedule was controlled as far as I could see. I monitored it daily and at first the plants thrived. My first hinch was that the roots now had reached the bottom layer which is just the original 50/50 and either got herbicide poisoning (the compost was mainly based on cow manure, and the herbicide could have been in the feed) or simply was fed nothing and therefore got much weaker and eventually died due to disease. I could not at this point find a single bug in the garden. Not even Aphids, so I ruled out insects as a cause. The latter did eventually come in droves but only attacked radishes, lettuce, and Kale.

As for the zucchini seedling, the plant is so small that keeping the soil evenly moist is fairly easy. I've given it liquid fertilizer as well with no effect. I did notice today that there were a couple, maybe 4, whitefly-like creatures on it. I also noticed some more on my hops plant that is somewhat nearby. But I believe these whiteflies came later when they spotted a weak plant.

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applestar
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Hmm... The damaged leaves REALLY look like they have been infested by sucking insects. Since you are not actually seeing any, could it be possible that the culprits are spider mites which are microscopic?

With all the yellowing and lack of chlorophyl, sucking insects are likeliest unless it was nutrient deficiency, but all the organic fertilizer you have been adding should have taken care of their nutrient needs, and you said other plants grew well.

imafan26
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Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

The fact that you said your bottom layer of soil was not the greatest and you had overlaid it with potting soil does explain why the plants did well in the beginning and only ran into trouble when they hit the layer of junk.



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