What is this on the bean leaves?

[applestar]

I just recently saw these explained somewhere, but now I can't find the reference and IT IS DRIVING ME CRAZY!

Does anyone know what this is?

Also is it something contagious that the melon can get? -- is that the same thing starting to develop on the melon leaf? (It looks like a light is shining on it but it's not)

...I thought it was a "mosaic virus" but looking up mosaic virus doesn't show any leaves that look like these.

[Lindsaylew82]

Almost looks environmental. Wind damage or sun bleaching...? Some of my beans had some leaf miner damage that looked a little like that. Most leaves had a trail, but some didn't. Mexican bean beetle nymphs can make damage like that too.

The melon leaf looks a bit like downy mildew. I'm not totally convinced of that though. What does the underside look like?

[catgrass]

Could be fertilizer burn (fertilizer spilled on the folage and not rinsed off), wind or sun burn, or maybe someone nearby has sprayed a weed/grass killer and some drift has hit your leaves.

[applestar]

Well... Good guesses but fertilizer burn won't happen here (strictly no chem). And these were too far inside the neighbor boundary to be anything from them unless they shot at them with a water rifle ( I wouldn't entirely put it past them but I'll credit that it's highly unlikely -- ) I would accept environmental possibility if it's happening to more than one or two leaf clusters at a time. But then insect or fungal on one or two leaves could mean beginning of an infestation.

I WISH I could remember where I saw photos of leaves like this.

Look. I found a few more today -- this time on plants in a different bed (last photos were from the Spiral Garden. These are from the Sunflower House -- granted they are next to each other.

Bean leaves with the strange white color loss

Cucumber leaf with similar markings

... ...
Could impact sprinkler hit cause this kind of damage? That would explain targeted damage zone....

[Lindsaylew82]

I'm not a fan of the theory about watering mid day, light refraction, burning leaves, magnifying glass effect... BUT! I think if the water pressure is high enough, it could damage plant cells.

I'd be more concerned with water splashing soil borne pathogens on your plants. Could be fungal.

[catgrass]

Have you checked under the leaves for insects? Possibly spider mites?

[applestar]

Returning to this thread -- I think I figured it out.
It was confusing because the damage was on bean AND cucumber leaves, but I believe the damage was caused by two different but similar species:

The bean leaves were almost certainly chewed up by adult bean beetles that moved on from those particular leaves to lay eggs. Here is a photo collage of similarly damaged leaves and one of their offspring (I have been squishing the rest as I found them):

I think the cucumber leaves were being chewed up at the same time by these:

Squash Beetles

The squash beetle (Epilachna borealis) is one of two species of Coccinellidae known to occur in the United States that eat plant material rather than other insects. The squash beetle feeds upon the leaves of cucurbits. The other species, the Mexican bean beetle (Epilachna varivestis), a close relative of the squash beetle, is a serious bean pest.

The adult of the squash beetle overwinters in crop debris. All other lady beetles are beneficial because they feed on insect pests such as aphids and scale insects.

Adult squash beetle (Epilachna borealis), with spiny larva at left.
Clemson University - USDA Cooperative Extension Slide Series, https://www.insectimages.org

https://www.clemson.edu/extension/hgic/p ... c2207.html

Was it coincidence that these two species were concurrently active in my garden? Not necessarily. I think like other ladybeetle species, these two species might congregate.

[Lindsaylew82]

Squash beetle looks just like Mexican bean beetle! Even the larva!

[applestar]

I know! Maybe they can't tell each other either. I've been having fun imagining the conversation they had if they overwintered together or traveled together in my garden...

(Munch, munch) Hey why are you eating THAT stuff. C'mon try this one, it's delicious!
(Munch, munch) What!? No way! That's not food!
...but... I thought.... You LIED! You're not one of us! You CAN'T be. << >>

...I've been looking around to see if there is any mention of them hibernating together, but haven't seen it mentioned so far. I've also been semi wondering if they can cross species.

I did find this excellent reference on squash beetles, which I suppose could mean that a squash beetle ate the bean leaves too -- the first discovered leaves were Christmas Lima and 2nd were possibly Runner Bean.

However, the pest has also been reported to feed on blossoms and pods of lima beans and cowpeas, and on corn silks.

https://extension.entm.purdue.edu/publications/E-100.pdf

I remember finding a loosely arranged yellow egg cluster like the one shown at that link and destroying it because it didn't quite look right to be ladybug eggs. I also remember killing a dark colored "bean beetle" which could have been the squash beetle. I don't think I've seen any more damage like these in any of the cucurbits.

So the bean beetles could also be a separate influx. My impressions is that summer pest types usually arrive after a serious storm system marches up and through from the south, bringing hotter weather, and possibly the pests themselves caught up in the wind.

[mattie g]

I've noticed similar marks on some of the beans in my oldest bean bed (planted at the beginning of May), but I figured they were from my dog deciding that the beans needed a little extra nitrogen. Now I might have to check into it just to make sure. In nay case, I've already gotten two harvests from those plants, with a third big harvest soon to come, so I'm not terribly worried about it.

My cucumbers were completely devastated by squash beetles last year. I hadn't noticed them in my garden the few years before then, but I had a massive volunteer pumpkin plant that may have attracted them, and when they also saw the cucumbers, they attacked. They did a serious number on the cukes - they wilted and died before I was able to get any harvest from them - but the pumpkin was able to handle the invasion. I haven't seen many of them this year (knock on wood), and my cucumbers have been much better off for it...

[Lindsaylew82]

I did see one on my cucumber plant yesterday, which is 60' away from my beans. I thought it was weird.

I keep finding lots of shell coverings from pink lady beetles which means dead pink lady beetles. Do they compete?

[Lindsaylew82]

Well, funny you should mention....
Found this today, on more than one plant!


Then I looked over and saw this...


So which do you think it is? There's damage to the squash plant AND that volunteer pole bean...
Totally off topic, but I swear every time I read something on here, I see it, next day! Maybe my subconscious gets reminded or awakened when I see these posts, and then I just start noticing them more.

Can we post some pictures of huge praying mantises?!!! Or large toads with squash bugs in their mouths?

[told2b]

Praying mantis

[applestar]

LOLOLOL I had to scroll back through the entire thread to find out WHY you posted the praying mantis pin-up

Well, funny you should mention....
[...]
Totally off topic, but I swear every time I read something on here, I see it, next day! Maybe my subconscious gets reminded or awakened when I see these posts, and then I just start noticing them more.

Can we post some pictures of huge praying mantises?!!! Or large toads with squash bugs in their mouths?

[Lindsaylew82]

Hahahahaha! That bug I posted is a squash Lady beetle. they look exactly like adult mexican bean beetles, but they have 2-4 extra dots on their backs!