Mildew alert!

[Jagdad]

With all the rain and humidity we've had in the midwest, mildew is making an early appearance. Any time the leaves are wet or humidity is above 80% for an 8 hour period with temps above 60; conditions are right for disease formation. Spores overwinter in old plant debris/ mulch and are carried on the wind. Watch for random white flecking that starts in the lower leaves. The flecks will coalesce into dead tan areas, eventually killing the entire leaf. You can see tiny black specs on the leaf bottom side (you might need a hand lense for this, if you eyes are as bad as mine) The infection typically moves up the plant, and cause a complete crop loss if not controlled. Older, non-hybrid varieties such as fuggle, hallertau show little resistance- even centennial and galena are susceptible.
If you don't have access to mildew preventatives like mancozeb, etc., some control is possible with safer soap and/or baking soda sprays. These work by preventing spore germination and/or creating a pH level on the leaf surface that is unfavorable for mildew. On plants with infections, remove the bottom2-3 ft. of leaves and any mulch that can harbor the spores. If you catch it early, you can manage it.

 

[Jagdad]

An effective downy mildew control is Bordeaux mix. You can usually find it at your local gardening center. If you have a history of downy mildew problems, integrate Bordeaux into your control program. Use it as a spring and fall dormant application. It will clean up the crowns and surrounding mulch. It has activity against fungal diseases and some bacterial blights ( a side effect is reduced fungus gnat populations). It is a combo of copper sulfate and hydrated lime so I hesitate to classify it the same as other fungicides for those who are concerned about pesticide apps and such. You can make your own as you need it - don't try to store it. Here's a recipe:
For 1 gallon -

• dissolve 6 .5 teaspoons copper sulfate in one pint hot water
• dissolve 3 tablespoons hydrated lime in another pint water
• mix the 2 pints togather,add water to get 1 gallon finished
• add a drop or 2 of dish soap as a surfactant.

They have used this mixture for control of downy in grapes for decades.

 

[Jagdad]

Scenario: you just checked on your beautiful hop plant a found it covered with mildew! Now what?!! Freak out!!
You want to stop it in its tracks to halt even more damage, right ?
Grower tip: You need a contact killer. (contact killer not contract killer)
Professionals use a product called Zerotol - a combination of hydrogen peroxide and peracetic acid. It is a "super disenfectant" used by everyone from hospitals to dairy farmers. It literally fries fungus and bacteria. And you can easily make your own homemade version. Mix 1 pint peroxide in 1 gallon of water and add 1 drop dish soap & 1 tablespoon white vinegar. (The vinegar reacts with the peroxide to make peracetic acid) Spray all surfaces of the plant. Let it dry.
How does it work? The peroxide oxidizes or "roughs up" the cell walls of the fungus allowing the peracetic acid to penetrate and fry it.
Now that you have stopped the active phase follow up with a protectant spray of safer soap at a reduced rate. Remember, the peroxide also scrubbed the leaf surface also, so it will be more sensitive to this spray.