Downy Mildew

[HopGrower]

Is this Downy Mildew? If so, what do you recommend?

[wortly]

Post a pic of the underside of the leaves. That is usually where it starts out.

Looks more like a nutrient deficiency. What are you using for a potassium source?

[HopGrower]

I've just been using 17-17-17 fertilizer.

[mr x]

Could be spidermite damage.

Sent from my Nexus S

[wortly]

You should be good for nutrients if you are using triple 17, but you might be missing some of the micros which would give any number of symptoms.

X is right, that some of those pic do look like mite damage. If you take a hand lens or magnifying glass, you can check to see if you can see the little bastards running around. They have to climb up the plant from the ground, so you tend to see them more on the bottom leaves first.

The second pic of the underside of the leaves actually does look like downy mildew lesions, but it doesn't look like the leaves are cupped. You would normally see downy mildew in the spring rather than right now. To be safe, strip off the leaves with the lesions on the underside. The protocol is to put them in a paper bag and burn them, or submerge them in a bucket of bleach. Flag the plants showing symptoms and keep an eye on them in the spring.

One typical symptom that you would see in the spring is a bunch of basal shoots forming. The disease will proliferate on the tips and spread spores downward, the best way to control it is to aggressively prune the shoots once you start to see the symptoms. Check out http://www.uvm.edu/extension/cropsoil/w ... Mildew.pdf

This late in the season, I wouldn't worry too much about anything other than picking off infected leaves (if it actually is downy mildew).

[MMHoposaurus]

Do you see the leader (growing end) at the bottom of the first shot? If you see those shrivel up and die, that's probably Downy Mildew. As others have said this looks like a nutrient defeciency and it seems to be confined to the lower leaves? Is that right? At this point in the growing season it hardly matters.

[Jayme]

I've had spider mites a few times in the past. It's usually pretty obvious - some small holes in the leaves and small webs built.

[MMHoposaurus]

I've had spider mites a few times in the past. It's usually pretty obvious - some small holes in the leaves and small webs built.

We (Wysmycal farms) just had a hop agronomist come look at the yard yesterday. Unless I am mistaken OPs photos do look like spider mite or aphid damage. Both are very tiny and difficult to see, you would need a lot of spider mites to put visible holes all of the way through the leaf.

The agronomist also mentioned that they aren't really worth worrying about unless you are seeing >10 per leaf on average, especially this late in the season. You could probably lose all of your foliage without any significant side effects at this point as harvest for most varieties should be less than two weeks aways.

edit: apparently I have to select the right language for the spellcheck to work in firefox now

[Jayme]

I've only gotten spider mites indoors when the plants are quite young, making the holes quite obvious in the young leaves - so perhaps it would be less likely for them to chew threw a thicker, mature leave. I was however, able to see them with my naked eye quite easily. Anyhow, I do agree that mites at this point in the season are not a big deal at all.

[mr x]

That pic looked identical to my spidermite attack.

Sent from my Nexus S

[HopGrower]

That pic looked identical to my spidermite attack.

I believe it is spider mites. On second look I found really tiny 'somethings' running around on the underside of the leaf (i don't have a magnifying glass yet) and a fine, fine - what looked like a web. I don't think I need to worry about them this late in the season, as Wortly pointed out.

[MMHoposaurus]

Definitely spidermites. Probably not worth worrying about at this point but if you see this earlier in the season just keep an eye out and if there are less than ~10 per leaf on average don't worry about it too much.

[Jayme]

Seeing small things running around + a fine web seems pretty definitive. Another year you could also try some companion planting to attract some predators that will eat the mites. I've got a lovely flock of lady bugs guarding my bines this year! Although the caterpillars still did some damage early on.

[wortly]

Hi MMHoposaurus, glad to see you on he forum. I was on your farm earlier this summer. JV is here today and tomorrow as part of his East coast tour. Word is you guys have a pretty good crop this year. Any chance you could post some pics?

I've had spider mites a few times in the past. It's usually pretty obvious - some small holes in the leaves and small webs built.

We (Wysmycal farms) just had a hop egronomist come look at the yard yesterday. Unless I am mistaken OPs photos do look like spider mite or aphid damage. Both are very tiny and difficult to see, you would need a lot of spider mites to put visible holes all of the way through the leaf.

The egronomist also mentioned that they aren't really worth worrying about unless you are seeing >10 per leaf on average, especially this late in the season. You could probably lose all of your foiliage without any significant side effects at this point as harvest for most varieties should be less than two weeks aways.

[MMHoposaurus]

Hi MMHoposaurus, glad to see you on he forum. I was on your farm earlier this summer. JV is here today and tomorrow as part of his East coast tour. Word is you guys have a pretty good crop this year. Any chance you could post some pics?

I'm just volunteering there this summer but if everything goes to plan I'll be the primary maintainer of the hop yard next year. I would be happy to post some pics although I'm fairly bad at taking them. I won't be back out there until Friday, we have a second agronomist coming then. Although I'm not sure if he'll be able to tell us much JV didn't already. He really seemed to know his stuff.

I'll try to grab a few pics that aren't terribad while I'm at it. Along with general pics I may start a thread demonstrating as many of the common issues we've identified (caterpillar, mites/aphids Downy mildew, etc) with pics to identify what they look like, if there is some interest.

edit: missed the /quote