Crop Report - Powdery Mildew Update
By Ralph Olson, as seen in Southern Draft Brew News
It is now the middle of October and all the hops have been harvested and put into storage. It has been quite a season.
My last article discussed the new disease that hit the U.S. hop industry "powdery mildew." This is really not a new
disease but one that has been in many parts of the world for many years. In the Yakima Valley, where most of the U.S.
grown hops come from, this was the first outbreak and it took the growers quite by surprise. Growers were not even
aware that a problem existed until a meeting was called towards the end of June by Washington Hop Commission. An
announcement was made that this disease had accidentally gotten out from a greenhouse that was being used to
propagate a new variety called "Symphony." This variety had been planted throughout the valley in early Spring and with
it spread the powdery mildew. While no one really knows how the disease got into the greenhouse it was quickly found
that this new variety was extremely susceptible to downey mildew. During this first meeting there was some cause for
concern but the growers didn't really know what damage this disease could do. At the time it had only started to infect
some of the leaves and looked like some fuzzy patches. The hops were still in their growth stage and no cones had
developed yet. Most growers had not yet even seen any in their fields or so they thought. It can very hard to detect even
if you are looking for it and most growers didn't know what to look for.
We unfortunately also didn't have much in the way to fight this disease. The first thing everyone used was sulfur and we
quickly got on emergency "Section 18" use from the government to use a chemical called "Rubigan." While both help to
control the disease they are considered not very strong ways to fight this disease. The biggest problem with both products
was that they are only topographical and this disease is most interested in attacking new growth. Because these chemicals
had no systemic powers, the spores that were not killed outright, quickly would attack the new growth. In the beginning
this new growth would only be new leaves but soon cones started to develop on the plants. The powdery mildew quickly
attacked these new cones causing death and abnormal formations. Some fields got bad enough that they were destroyed
by cutting them down and then burning the piles. In my twenty years in the industry, I have never seen such a thing.
While the numbers are sketchy, it is felt that at least 2,000 to 2,500 acres were destroyed in this manner. During the
month of August one could see huge columns of smoke rising from different parts of the valley and know more fields
were falling victim to this disease. It was hard to realize that only two months before, this disease was just being discussed
as even being in the valley. Many fields that were picked had greatly reduced yields and were not the best quality. This
has lead to many gloom and doom reports in newspapers around the country and has caused moderate amounts of panic
with brewers who felt there would be no hops this year. Well I'm happy to say that we do have plenty of hops available
for the consumer and the majority don't look too bad.
First, many different varieties did show moderate to heavy amounts of resistance. Most aroma hops got through in pretty
good shape. The hops that appeared to have the least resistance were the Symphony, Cluster and Galena. I personally
inspected all the lots of hops we get into our facility. My general conclusion was that while we saw some higher than
normal amount of spray burn from trying to keep this disease at bay, the aromas coming from the hops were quite nice.
Growers who started a spray program immediately after the announcement was made and were lucky enough to not be
by the worst infected sites, did by and large all right. It has been said that if you see just one postule of this disease in a
field you had better start spraying and if you see two it is probably already to late to combat it. I saw some growers who
probably lost 1/3 to 1/2 of their crop to this disease while others had virtually no problems.
No one knows if this disease is here to stay but the odds are that it will be here in the future. Much research and field
work has been done and efforts are already underway to get better chemicals to fight this disease. Europe has regular
programs in place since this disease is common in most of their hops growing areas. The U.S. grower will need to also
develop these programs. We will also need to find out which varieties show resistance and which do not and react
accordingly. Already it has been announced that the variety "Symphony" will be pulled out and destroyed. This is a very
costly measure and therefore a hard decision to make. My hat is off to the growers/dealers going ahead with it. While the
cost of growing hops has just gone up, the growers determination has gone up as well. The Yakima Valley will continue
to be the hop capital of the United States and will still grow some of the best hops in the world.
Return to Top