As I was painting the house yesterday, it occurred to me--as the spaciousness of painting allows things to occur--that there was one more tidbit from my visit to the hop fields I failed to mention. Hops have many enemies. Blights of mildew--downy and powdery--can wipe out entire fields. (You know the famous Wisconsin hop fields? No? Right; that's what happened to them over a hundred years ago.) Once a plant is infected, the blight usually recurs. The other problem is creatures, notably spider mites and aphids, which may feast on tasty hops before brewers have a chance to do the same.
As a consequence, controlling these problems without using pesticides is a tricky business, which is why organic hops are still rare. On our tour, we had the good fortune of having the USDA's Dr. David Gent along to discuss some of the challenges, and as it happens, he's working with Gayle Goschie at her farm to test certain theories about natural ways to control pests. These include strategies like planting adjacent fields with flowers to attract pest predators and breeding pest-resistant strains. Below is a visual tour of some of the things Dr. Gent and Gayle Goschie are testing (click to enlarge photos).
Dr. Gent is experimenting with plants where the bottom three feet have all foliage removed as a way of controlling mildew. (Results so far not significant.)
Another strategy is to allow the ground between hop rows grow up with native plants to attract predators to combat mites and aphids.