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Jul 28, 2014

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Home-grown hops: Diseases and pests
Second of three parts

By Alan Moen

Homebrewers who grow hops for the first time are not unlike gardeners who try zucchini: the vigorous nature of the plant will convince anyone they've got a green thumb. But prolific as they are, hops can still be easily devastated by diseases or pests, which can turn a healthy, flowering vine into a withered weed in a few weeks or even less. Home hop growers need to recognize the signs of problems in the early stages to correct them . Here are some things to look for:

Downy Mildew - this disease is the bane of hops worldwide, and has contributed to the decline of more than one major hop-growing area. It is typically caused by too much moisture in the soil or on the plants themselves, either from frequent rain or overhead watering ( a good argument for drip irrigation.) Usually the first signs for this are on the leaves, which curl and become brittle - silvery on the upper surface and dark, even black, beneath. Since mildew typically begins at the bottom or shaded part of the vine, it's a good idea to keep this area well weeded and prune back the hop leaves for the first three feet or so. There are also fungicide sprays that can be quite effective for mildew control ,such as Ridomal, and others that are systemic poisons, but these are usually not available to the home grower.

Verticillum Wilt - another hop disease caused by excessive moisture on the plants. I once had three healthy vines growing in my backyard in the Seattle area that were nearly ten feet tall by the end of April; thanks to incessant rainfall in May, they were a total loss to wilt in the ensuing months. Again, pruning and fungicides can help, but you can't always fight Mother Nature very effectively.

Wet, cool weather can also help spread another threat to the health of your vines: aphids. These insects are typically white and can quickly cover the underside of leaves with their sticky goo. Depending on how your hops are trellised (hopefully not against a wall, ) aphids can be destroyed by the use of insecticidal soaps such as Safer or oil sprays. A hop expert once recommended a mixture of sugar and diatomaceous earth as a spray, which literally cuts the bodies of the nasty beasts as they crawl over the leaves (sorry to say, I've never tried this.) Ladybugs provide a good natural solution, since they are a very voracious aphid predator, but it may be hard to obtain enough of them to be effective. They also have a nagging tendency to fly away just when they are most needed. Organic gardeners who buy ladybugs usually keep them cool (even refrigerated) before releasing them on the plants. which should be done at night or very early in the morning. I have used them on spider mites with some success. Lacewing larvae also kill aphids and have the additional advantage of staying put on the hop leaves. Once again, you may need quite a few of these, which can be expensive.

Another hop pest actually proliferates in hot, dry weather: red spider mites. Look for brownish or rusty spots on the upper parts of leaves and the thin white webs they make beneath. It's best to remove any infected leaves immediately to keep mites from spreading. Natural soaps and garden sprays work quite well against mites, including Diazinon, but sure not to spray within a couple of weeks before harvest.

With proper planting, hop maintenance, pest control, and some important help from Mother Nature, you're set for a good hop harvest in the fall, which I'll discuss in the next installment.

© 1997 Alan Moen

STORIES BY
ALAN MOEN