stem rot and powdery mildew issues

jensunAugust 10, 2010

Hi all :)

I'm having a load of trouble with my jack b. little's this week. The past three days have brought high temperatures and evening thundershowers, perfect conditions for the dreaded powdery mildew. So with extreme trepidation I went out in to the garden this morning armed with a pair of shears, rubbing alcohol and hacked away at the spotty leaves.

I know from past experience that it's best to get them as soon as the spots form and be vicious about it. If you've got a generally healthy plant it will survive and continue to grow, if not more vigorously to replace the leaf loss.

But here's what I wasn't expecting- stem rot. The mildew was centered around one area that due to the fence gets hit by the sun last.

Here's a photo to show the area I mean:

I still have a few leaves to thin out but I wanted to get some advice before I continue to hack away.Has the mildew reached the stem? Is it another issue? No bugs from what I can tell...oh and I water daily in the early morning with an every other week fertilizing, good soil- little bit of compost at the beginning of the growing season but none since. Here is a shot of the rot (not the most in focus srry):

What do I do? I don't want to lose the 7-8 fertilized pumpkins on this vine!!

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Powdery mildew always hits and if it is late season once fruit have set I normally do just as you did and remove the first infected leaves until I can't keep up with it. Not that big of a deal if it is late in the season in my opinion.

The 'stem rot' on the other hand is actually cause by the squash vine borer. There is one or more grubs tunneling through your plant that need to be killed. I just get a pin and scrape away the frass and rotted part see if I can see the grub if not I stab the vine a bunch of times and inch or two above and below where the 'rotting' is to ensure a good kill. Some people slit the vine lengthwise to remove the grub but I find the pin works fine. Also burying the base of the plant isn't a horrible idea after you kill the grub(s).

    Bookmark   August 11, 2010 at 9:27AM
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So I went at it with a pin. Cleared most of the debris left by the bugs, but it wasnt a grub that did the damage- it was baby potato bugs! I stabbed as many as I could find and pulled the vine apart higher up where it looked to be healthy- no debris and no grub. I'm thinking these little guys are the culprit, unless the grub has already moved on?

    Bookmark   August 14, 2010 at 11:07AM
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susancol(7 Atlanta)


That picture is classic SVB damage, as WeirdTrev said. I'm interested in the pin technique, as I have always done the slit thing. It is likely that the grub is just farther up in the vine than you can see. If you take a knife and slit up or down the stem from the damage, you will likely find him. White with a red head. Gross. You might have gotten him already with the pin. It is possible that it has progressed to the pupae stage and has left the plant to burrow in the soil and form the pupa.

But while the potato bugs may have been taking advantage of the situation, they are not to be directly blamed. They should get a lawyer! They've been framed by the SVB!

Bury the stem to cover the damage and up a ways so that additional roots might form above the damaged area. That is what causes the plant to die, failure to get water to the plant around the damage.

Best of luck on your pumpkins. SVB killed most of my plants this year.


    Bookmark   August 18, 2010 at 9:40AM
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The grub might already be underground. I really like the pin technique. I wasn't happy slitting the vines plus the grubs aren't very aesthetically pleasing as you mentioned! I find the pin is faster, less disastrous to the plant, and less grotesque! I have a little bit of a technique but it is mostly just stabbing the vine. I try to find any openings or soft spots in the vine and push the pin in all directions in the opening especially up the hollow center of the vine where the grub is. Then for good measure I poke the vine 5 or 6 times above and below the damages part focusing on going to the center of the vine as that is where the grub is not really along the edges.

    Bookmark   August 18, 2010 at 8:42PM
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