Downy mildew, something else, or both?

[PhillyGardener]

A few weeks ago, I noticed some white spots on some of my young plants; before long it was on all of them. At first I chalked this up to a botched Murphy Oil Soap aphid spraying (I didn't wash the soap solution off, which I later learned will burn leaves) and hardening them off too quickly. I've also been treating with diluted Neem oil so figured maybe the oil was just drying up on the leaves, discoloring them--especially since the spots appeared on plants I just bought last weekend, including the oregano pictured blow. However, now I'm really worried that I've got downy mildew on my cucurbits and something else on my other plants.

My cucumbers and zucchini are growing very well and actually producing some flowers, so I'm really hopeful that this is just leaf burn, but looking at photos online I'm afraid it may be the dreaded mildew.

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-19130153.jpg[/img]
National Pickling cucumber

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-19130345.jpg[/img]
National Pickling Cucumber

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-19130222.jpg[/img]
Thai basil

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-19130312.jpg[/img]
Bush beans

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-19130238.jpg[/img]
Oregano

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-19130230.jpg[/img]
Sage

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-191304161.jpg[/img]
Catnip

[PhillyGardener]

One other idea: spider mites. I've seen them around, occasionally on my plants (especially the cilantro). The spots on the herbs especially look like photos of spider mite damage I found online. If that's the case, could the damage to the cucumber plants be from the same thing, or do I have downy mildew AND spider mites?

In either case, hopefully my Neem applications will keep these issues in check. Is there anything else I should be doing?

[rainbowgardener]

You can worry too much about every tiny speck! Nature is pretty random and there's always something. I think mostly your plants are looking pretty nice and healthy.

I'm not thinking downy mildew
[img]https://vegetablemdonline.ppath.cornell.edu/Images/Cucurbits/Downy/SmSq_DM02.jpg[/img]

The exception to mostly looking healthy is the Thai basil, which is looking pale and more significantly blotchy. That could be spider mites or some sucking kind of pest.

The rest look quite happy and can easily live with a little damage like that and not be slowed down as long as it doesn't keep getting worse.

[jal_ut]

Were these plants started indoors or in a greenhouse then moved outside into direct sun? It is quite common for plants to get some spots on the leaves when moved out into the harsh world. It has nothing to do with fungi. When it is shock from being moved out, the new growth is usually nice without the spots.

I live in a dry climate and don't have problems with some of the plant pests that plague gardeners in more humid areas. I have never seen downy mildew.

I have plenty of little insect critters that like to punch holes in leaves though.

Hope someone who is familiar with downy mildew will post on this.

[PhillyGardener]

Whew, OK! Thanks for your responses. I will trust your judgment, since you both have a lot more experience than I do. Everything was started inside except for the oregano, which I bought from an organic nursery last weekend. It likely came from a greenhouse grower, though, and I don't know how long it had been outside in the sun before I bought it. So far the newer growth on most things looks normal (except for some deformity caused by a now-minor aphid problem), but some of the leaves that are spotted (cucumbers, beans, peppers, and herbs) are new. I'll keep an eye on it. From what I've read, downy mildew wipes out plants in a matter of days, and this has been going on for a week or two at least, so hopefully that's not what it is.

Thanks for your help!

[PhillyGardener]

The cucumbers look amazing now (I was definitely overreacting), and the aphids are fewer in number thanks to some newly hatched ladybugs, Neem treatments, and plenty of squishing. Yay!

But the weird white patterned specks on the Thai basil, basil, other herbs, and bush beans continues. It almost looks like leaf miner damage, but it's not as distinct. Almost every leaf of my two Thai basil plants has these specks, many of my Italian basil plant leaves, and maybe 1/4 of the leaves on some of my bush beans too. I don't see any obvious damage under the leaves. I did find a couple of tiny "inch worm" like caterpillars near the bush beans this morning, but nothing else but aphids. The odd thing is that the aphids have mostly left my basil and herbs alone. I also haven't seen more than one or two spider mites around the basil and bush beans. Any ideas as to what it could be?

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/Square%20Foot%20Garden/2012-05-19130222.jpg[/img]

[PhillyGardener]

After doing some research, I think I may have found the culprit of the leaf-spotting damage: leafhoppers. I've definitely seen these little 1/4" long light green bugs around and didn't know if they were beneficial or not, so I left them alone. They move very quickly when disturbed. Googling "leafhopper herb damage" I get photos almost exactly like mine. Now I just need to figure out how to get rid of them. I'd imagine ladybugs don't move quickly enough to snag these suckers...

[applestar]

Keep your eye out for spittle bugs which are leafhopper larvae. They are easier to "catch" Encourage spiders -- I.e. don't get rid of them.

Best protection is to encourage beneficial insects. There's a sticky I think in Diseases and pests forum with lists of plants that attract them.

It's powdery mildew season with all the rains we're having plus the heat, so start spraying with 10~20% milk solution.

[PhillyGardener]

Thanks Applestar. I haven't seen any larvae but haven't been looking for them either, so I'm sure they're around. I always leave spiders alone because they freak me out, so no problems there

I released 1,500 (mostly dead, ordered online) ladybugs a few weeks ago and saw one juvenile cruising my zucchini plant the other day, and I just called my local nursery and asked them to set aside a 1,500 box for me.

[mattie g]

Thanks Applestar. I haven't seen any larvae but haven't been looking for them either, so I'm sure they're around. I always leave spiders alone because they freak me out, so no problems there

I released 1,500 (mostly dead, ordered online) ladybugs a few weeks ago and saw one juvenile cruising my zucchini plant the other day, and I just called my local nursery and asked them to set aside a 1,500 box for me.

The ladybugs are a good idea. I bought some from a local nursery about 10 days ago, and released them the other night (stored them in the fridge for about a week). I was lucky that all but one were alive - and that one was accidentally squished. I now have a *ton* of ladybugs making their homes in my vegetable garden, as well as in our flowers/bushes out front. I'm hoping they take care of any aphid problems for the season!

[PhillyGardener]

Yep, ladybugs and Neem oil seem to be the solution to everything that ails my garden! I thought the leafhoppers must be too quick for ladybugs, but of course the ladybugs can eat their larvae/nymphs. Duh I hope the new ladybugs set up shop quickly.

Let me tell you, there is nothing more depressing than opening a bag of ladybugs and having 3/4 of it pour out dead. Ugh!! Thankfully I think a few who lived stuck around. I haven't seen any eggs, but I did squeal with joy a little when I saw that one juvenile! I figure if I see one, there must be more around. And with the number of aphids I have still hanging around, plus some spider mites and leafhoppers, I'm sure they have plenty to eat.

[Patrol_4x4]

Hey!!this post has been super helpful for me, I kinda have the same problems with the same plants. This is my thread:

https://www.helpfulgardener.com/forum/viewtopic.php?t=46169

So, the whitey spots are likely to be grasshoppers... Hmmm
And neem oil is the only thing to get rid of them? Is that easy to find in a shop or nursery?

Thanks!

[PhillyGardener]

Hey!!this post has been super helpful for me, I kinda have the same problems with the same plants. This is my thread:

https://www.helpfulgardener.com/forum/viewtopic.php?t=46169

So, the whitey spots are likely to be grasshoppers... Hmmm
And neem oil is the only thing to get rid of them? Is that easy to find in a shop or nursery?

Thanks!

The spots on your basil leaves look like leafhopper damage, but could also be spider mites or something else. They seem to love my herbs. The rest of the damage (brown leaf edges, bites out of leaves, etc) don't look like leafhoppers to me. But it could be a combination of things. I found Neem oil extract at Lowe's, of all places. Good luck!

[Patrol_4x4]

I found Neem oil extract at Lowe's, of all places. Good luck!

I don't know what that is, hehehe, I'm in Australia, but will have a look! Thanks!!

[PhillyGardener]

I found Neem oil extract at Lowe's, of all places. Good luck!

I don't know what that is, hehehe, I'm in Australia, but will have a look! Thanks!!

Ah OK! It's a "big box" chain home improvement store. Neem is a kind of plant, and the oil is an extract made from its leaves. It is all natural (though not without any risks, of course) and organic. It acts as both an insecticide and a fungicide. Good luck!!

[rainbowgardener]

Neem oil comes from the neem tree, which is native to India and widely grown in the tropics and subtropical areas.

[!potatoes!]

So, the whitey spots are likely to be grasshoppers... Hmmm

note: the spot are likely to be leafhoppers, not grasshoppers. very different insects with very similar common names.

[PhillyGardener]

OK, now I'm fairly certain I really *do* have downy mildew or some other kind of fungus. I let my guard down for a week and didn't spray with neem oil because everything looked good--and also because it was raining almost every day for a little while. This morning I noticed discolored leaves on one of my 7 cucumber plants. All of the older leaves look dappled like this, but so far no other symptoms. The spots don't have sharp edges like other photos of downy mildew I've seen. (The small holes/tears are from a hail storm.) You can see two healthy leaves from neighboring plants compared with the sick looking one. Any ideas?

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/2012-06-10114155.jpg[/img]

[applestar]

You keep saying downy mildew, but downy mildew s a more serious fungal disease and I tend to think powdery mildew before downy. Not even sure if I would recognize downy mildew.

Anyway, I like spraying with milk and water. 10~25% I,m too cheap to mix it any stronger. Usually old or leftover milk. And some lquid from cultured product -- yogurt, sour cream, cottage cheese, etc. The spray encourages lactobacillus colonies on foliage surface that competes with pathogenic fungi and acts as preventive. Bacteria stick to the leaf surfaces on their own so they are not easily washed off by rain, unlike non-biolgoical sprays -- another plus.

Those marks could also be from sucking insects underneath the leaves.

[rainbowgardener]

It's not looking like powdery mildew to me, because it doesn't have that distinctive gray powdery appearance. I'm not so familiar with downy mildew, but it isn't really looking like that to me either, still. Sucking insects sounds like a good theory.

Downy mildew is virulent. Since you first wrote in about this May 23, I'm thinking if you really had downy mildew, your plants would be clearly dying by now.

[PhillyGardener]

Well, a similar discoloration is spreading to one of my zucchini plants--that one might be powdery mildew, I'm not sure. The cucumber plant continues to look dappled and the leaves are starting to look slightly curled. All of the other 7 cucumber plants (including 3 more of the same variety) remain just fine, so while I know I have some leafhoppers and thrips hanging around and see some minor damage from them, it seems weird that just this one cucumber plant would react so poorly. At any rate, I agree it's not downy mildew--I didn't know when I first posted here that it's so rare. I do think it may be some kind of mildew or fungal disease though. I sprayed Neem on Wednesday morning and will spray milk this weekend. I don't drink cow's milk and don't keep it on hand, or I would have already

Thanks for the replies and suggestions!

[rainbowgardener]

Applestar suggested damage from sucking insects. You say you have leafhoppers and thrips. Here's one image of what leafhopper damage can look like:

[img]https://utahpests.usu.edu/admin/images/uploads/UtahPests/small-fruit-advisory/2008/08-01/grape-leafhopper-damage.jpg[/img]

Here's a similar image of thrip damage:

[img]https://www.ipm.msu.edu/perennials/images/ThripsDamage.jpg[/img]