Ask a Question forum: Rapidly spreading brown spots on vegetable leaves

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Austin, TX (Zone 8b)
Apr 11, 2015 9:18 AM CST
I'm panicking. I have two raised garden beds with green beans, bell peppers, jalapeños, cucumber, yellow summer squash, and tomatoes. A week ago I fertalized with miracle grow and left for three days. I came back to wonderful new growth and LOTS OF PROBLEMS. The leaves on my cucumber sprouts began accumulating yellow/tan spots, and a few holes. Then it went to the green bean sprouts, which started to pucker as well. My bell pepper plants are getting curled and puckered leaves. My squash sprouts are getting the brown spots. My tomatoes and jalapeños are the only things that seem unaffected. I did find aphids and quickly sprayed-they have been gone for a while now, but the symptoms persist. I found teeny tiny black bugs on the undersides of the leaves, I think they are mites. I have sprayed for those twice (two days apart) but the brown spots are still spreading QUICKLY. My cukes are deffidently stunted, and I fear they are going to die. I'm desperate for a solution.
Thumb of 2015-04-11/visitor/cc3123

My sad cucumber two days ago, which now has even more brown spots.
Name: Michele Roth
N.E. Indiana - Zone 5b
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Apr 11, 2015 10:48 AM CST
Chemical burn from the synthetic fertilizer is possible, as well as too rapid and succulent growth. The latter is very attractive to many types of sap-feeding insects. Using an organic balanced fertilizer usually produces slower, but healthier results.

It looks like your cucumber has a new healthy leaf coming on though, so it may be okay once it has time to recover.
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Name: Sandy B.
Ford River, Michigan UP (Zone 4b)
(Zone 4b-maybe 5a)
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Apr 11, 2015 8:54 PM CST
Hi ako0396 -- welcome to ATP !

How exactly did you fertilize with MG? sprayed the plants? drenched the root zone? The spots on the leaves could be a combination of the fertilizer and sunburn on the leaves -- I don't think it's really anything to panic over... maybe just a lesson to learn from Smiling

From your post, I think you may be over-reacting a bit to every bug and spot that you see... nature has a way of correcting itself, although sometimes we do need to step in for major issues. A few holes in the leaves won't hurt the final result -- you might want to just try using a brisk spraying of water to remove some bugs. I'm not an "organic gardener," although I aspire to be... but my motto is to use the least poisonous tactic first and proceed from there.
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Name: greene
Savannah, GA (Sunset 28) (Zone 8b)
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Apr 11, 2015 9:11 PM CST
Welcome! ako0396,
Can you post a photo of your entire garden? What type of soil mix or planting medium are you using? Did someone water the plants while you were away for the three days?

I agree with chelle that it could be a chemical burn from the fertilizer. Miracle Grow is supposed to be a 'foliar' type fertilizer but I find that the sun can quickly harm the plant if the solution is not rinsed from the leaves.

I agree that you should not have to spray for every insect the minute you see it. Either pick off the bugs if possible or use a spray of water from the hose to knock them down as Weedwhacker suggested.

Maybe using a lightweight fabric floating row cover would help to keep the insects off the plants. Since you are working with a raising bed that could be an option.
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[Last edited by greene - Apr 11, 2015 9:11 PM (+)]
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Name: Sue
Ontario, Canada (Zone 4a)
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Apr 12, 2015 7:39 AM CST
There is a pale "halo" around the spots which may indicate a disease but I'm not sure what, or whether fungal or bacterial. Can you see any ooze from the spots on the undersides of the leaves? This page may help, since you have the patients there to compare:

If you see the black "mites" again can you try and post a picture?
Name: Elaine
Sarasota, Fl
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Apr 12, 2015 8:53 AM CST
I agree If there were droplets of fertilizer/water left on the leaves, that could have caused those little burnt marks. Are they still appearing?

Two things to consider: First always water in the early morning so the leaves have a chance to dry off during the day. If you are using the MG as a foliar spray, rinse it off with the hose before the sun hits the leaves. Again do this in the morning ALWAYS! Second, water the ground under the plants, and try not to wet the leaves. If you're using a sprinkler, consider going to a soaker hose system or something that keeps the water low down, under the plants. Wet leaves are an invitation to fungus infection. I really like micro-irrigation, and it's pretty cheap and fun to install too.

I also agree that you must not expect perfection in plants, and not worry about every little spot or bug. As long as you have lots of healthy green leaf tissue, the plant is still making food for itself. If you do see a lot of aphids or other bugs, don't resort to a spray right away, try the hose-em-off method first. (but don't do it at night!!) Especially with edibles you must be so careful what you use.

I keep a spray bottle of soapy water for insects, one of baking soda and water for fungus prevention, and one of Bt in case of caterpillars. Those are the extent of my "sprays" that I'm willing to use on my edibles. I'm not a strict organic gardener either, but I do want to harvest healthy (to eat) veggies - that's the whole reason I grow my own.

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