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I salvaged and planted three watermelon seedlings a few weeks ago after my, somewhat flimsy, greenhouse blew over in a wind storm. The seedlings seemed to be thriving in their new homes, but this past week they have taken a turn for the worse. As can be seen in the following two photos.

Watermelon plant with black and brown leaf discoloration as well as holes in leaves. Watermelon plant with black and brown leaf discoloration as well as a white soil fungus circled in red.

tl;dr;

Do the two photos of the watermelon plants show signs of either tobacco mosaic virus or cucumber mosaic virus?

Note that the second photo has a red circle around what appears to be a white soil fungus. This fungus was not present before this morning but is now at the base of two of the three watermelon plants. I'm not sure what this fungus is, but I did notice it on some of my other transplant's peat pots.

But back to the mosaic virus, I've noticed and removed winged aphids and ants carrying aphids on the watermelon plants. I've read that aphids and thrips are big spreaders of mosaic virus. Which is why I have been spraying a watery mixture of Dyna-Gro neem oil and Dr. Bronner's unscented pure-castille liquid soap every seven days, since before the seedlings were transplanted. I've also occasionally used food grade diatomaceous earth to try and curb the ants, I don't want to kill the good insects though.

Also, one of the watermelon plants has a fissure in the stem running from just above the soil to the first set of leaves. As seen in the following photo, which also shows a closer view of the white soil fungus mentioned earlier.

Photo of a watermelon plant with a fissure in the stem running from just above the soil to the first set of leaves.

I think this was caused by a pest, either below ground or above it, but I was wondering if this kind of fissure could be caused by a period of under or over watering?

My main question is, do the first two photos of the watermelon plants show signs of either tobacco mosaic virus or cucumber mosaic virus?

Note: I'm not familiar with the proper tags to use, or if you think I rambled too much, please feel free to edit my question.

  • I do see the mold, don't worry about it. Can you explain the white powder? – Rob May 17 '19 at 19:12
  • The white powder is DE that fell out of my hand/blew off the plant in a previous application. – Jonny Henly May 17 '19 at 19:16
  • Have the aphids been heavy this year? Despite your attempts at prevention? – Rob May 17 '19 at 19:22
  • Yes they have been on other plants, like tomatoes, but not on the watermelon - just a few here and there. – Jonny Henly May 17 '19 at 20:24
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    It definitely looks like it could have symptoms of a mosaic virus (and I don't know what else it would be offhand), but I'm not sure. – Brōtsyorfuzthrāx May 23 '19 at 8:55

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