Discoloring on leaves... ?

[MHam2019]

This is one of my watermelon plants, this discoloration is happening currently on the bottom leaves. Its been very hot and humid this past week and they do have a few watermelons growing on it at the moment.
Is this a nutrient deficiency? A hot/humid issue? Water? Bugs?
Thanks!

 

[DirtMechanic]

How far along are your fruits toward ripeness? WM grows so fast it is hard to consider decline is as fast.

 

[MHam2019]

How far along are your fruits toward ripeness? WM grows so fast it is hard to consider decline is as fast.

They are sugar baby watermelons- One is probably about 6lb now, starting to lighten on the bottom so I assume it's fairly close to ripe. The others are still fairly small, baseball to softball sizes.

 

[Chuck]

Is the new growth affected at all or is it just the older leaves?

 

[MHam2019]

Is the new growth affected at all or is it just the older leaves?

It's hard to tell, really, because they're all so twisted together but it looks like it's all of them.
I should have mentioned in the originally post, they are growing up a trellis because they started reaching too far to the neighbors lawn; I had to reign them in. So it's probably about the first 12"-18" from the ground, the leaves are doing this.

 

[Chuck]

It's hard to tell, really, because they're all so twisted together but it looks like it's all of them.
I should have mentioned in the originally post, they are growing up a trellis because they started reaching too far to the neighbors lawn; I had to reign them in. So it's probably about the first 12"-18" from the ground, the leaves are doing this.

Usually a nutrient deficiency shows mostly on the new growth. I am sure, at least from the single picture, that it isn't insect damage. Too much water will show browning of the leaves and too little water will show wilting and browning. Heat and humidity will also show afternoon wilting. IMO it is a nutrient deficiency

 

[DirtMechanic]

Mine have done that, but it appears to be older leaves mainly, so I would expect senescense at some point since fruit have ripened on mine.

 

[MHam2019]

Its been a few weeks, I fertilized with blood meal and bone meal. Initially, right after, the plants began growing new blooms, a few were pollinated and started growing but shriveled and died (I'm fine with it, the other watermelons are still growing). The problem is, the leaves have gotten worse. Many dried up and crumbled. One plant is looking very scarce of leaves
.
I took a few photos... First photo is how to seems to start...
1- what's happening??
2- should I somehow shade the watermelons that are still growing to prevent sunscald?
3- How likely is it that these plants are just going to die and the watermelons (and my time and effort) are going to be a waste?

 

[Chuck]

Its been a few weeks, I fertilized with blood meal and bone meal. Initially, right after, the plants began growing new blooms, a few were pollinated and started growing but shriveled and died (I'm fine with it, the other watermelons are still growing). The problem is, the leaves have gotten worse. Many dried up and crumbled. One plant is looking very scarce of leaves
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I took a few photos... First photo is how to seems to start...
1- what's happening??
2- should I somehow shade the watermelons that are still growing to prevent sunscald?
3- How likely is it that these plants are just going to die and the watermelons (and my time and effort) are going to be a waste?

It sure looks like Downy Mildew, especially the first and last pictures. I have never seen watermelons shaded and Texas is a big watermelon growing state. What I would do at this late date is try to control the mildew until harvest. I would spray Neem Oil or a copper spray either in the morning or late afternoon hours when the sun isn't so hot.

 

[MHam2019]

It sure looks like Downy Mildew, especially the first and last pictures. I have never seen watermelons shaded and Texas is a big watermelon growing state. What I would do at this late date is try to control the mildew until harvest. I would spray Neem Oil or a copper spray either in the morning or late afternoon hours when the sun isn't so hot.

I thought it may be downy mildew, thank you for confirming. The only neem oil I've been able to find in store is the Bonide brand which is premixed. No concentrate anywhere, despite stores websites stating they have in stock... should the premix be enough to keep this from progressing?

 

[Chuck]

I thought it may be downy mildew, thank you for confirming. The only neem oil I've been able to find in store is the Bonide brand which is premixed. No concentrate anywhere, despite stores websites stating they have in stock... should the premix be enough to keep this from progressing?

I don't know how big your plants are so it's impossible to say but, I just checked Amazon and Neem concentrate is all over the place and from many different sellers.

 

[MHam2019]

I don't know how big your plants are so it's impossible to say but, I just checked Amazon and Neem concentrate is all over the place and from many different sellers.

I'm sure it is online to order but I went to three different stores to purchase after their sites said they had in stock. In frustration, and hours of driving, that's what I bought a while back when some kind of bug was taking a liking to my pepper leaves.