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Pest control in hops: beneficial insects

Posted by Rebecca Kneen on

Depending on the season, we have two main hops pests in BC: aphids and spider mites. Both thrive on stressed-out plants, exacerbated by excessive heat. Organic growers work systemically to improve the health of our entire ecosystem, as well as using topical treatments. This means feeding the soil, feeding the plants, and feeding natural beneficial insects to do our work for us. Topical treatments are used only as a stop-gap while we are rebalancing the systems or in overwhelming circumstances.

As organic growers, our first resort is always to improve the health of our soil, thereby improving the health of our plants.

Green manures, plenty of compost, reduced tillage, mulching and watering only as needed are all basic ways of improving soil health. At Left Fields we add to that by overwintering sheep or chickens in our hopyards to add animal manure to the soil, giving microbes a more varied diet and adding different nutrients. Kelp meal and blood meal are also useful for adding micronutrients and feeding the whole soil biome. Using drip irrigation for deep watering helps plants grow stronger and deeper root systems, which supports them through drought.

The other principle of organic management, after creating healthy soil, is proactive pest management and healthy above-ground biomes. This means creating optimum conditions for beneficial insects, bees, birds and beetles – all of whom create a viable balance between pest and predator and are part of a healthy ecosystem. While we can bring in species that may not yet exist on our farms, or not in sufficient numbers, it’s expensive to continue buying insects year over year, especially when we can use our buffer zones, field edges and areas between vines to provide habitat so that species thrive on their own.

Spider mites are particularly problematic in hot, dry conditions. Not only does excessive heat stress most hops varieties and make them vulnerable, the mites themselves prefer to live in dry soil. Cover crops and green manures and mulches all help keep soil moist enough to deter spider mites most of the time. The best natural response to an outbreak is predatory mites. There are several species that work at different times of the year, so buy appropriately to your season. Growers should be proactive, bringing in hops predators early in the season if you expect an infestation.

Fortunately for hops growers, aphids are actually easier to deal with through IPM (integrated Pest Management). Because there are dozens of varieties of aphids feeding on different plants all over every farm, there’s often lots of natural predators already present. The trick becomes bringing them over to the hops, and keeping them there. Long-term plantings of insectary beds are a simple and beautiful way to keep them present.

The main predators of aphids are ladybird beetles, lacewings and hoverflieds (aka. Predatory wasps). All have their place, and a balance of all three should keep any yard healthy. All three also, at different times in their lifecycle, feed on the nectar and/or pollen of a lot of native plants, so keeping insectary flower beds keeps them at healthy populations, ready when aphid populations start to rise.

ladybirds at all stages Ladybird beetles are a familiar sight to any gardener, but it’s actually the larvae (pictured here, photo courtesy of the University of California) which are the aphid-eaters. They mow quite a swath through aphids before they cocoon and go to adulthood. Keep an eye peeled for ladybird eggs (also pictured), and move them into your hopyard if you see aphids there. Here’s a free tip: ladybird eggs look almost exactly like potato beetle eggs (a slightly different colour), but potato beetles lay exclusively on members of the nightshade species (potatoes, eggplant, wild nightshade), so anything you see on those plants is ripe for squishing. The same eggs elsewhere are likely ladybird eggs and should be protected. If you want to bring in more ladybirds, buy eggs or larvae, as they not only travel better but adult ladybird beetles have a strong tendency to leave as soon as you open the box, benefiting your neighbours but not you.

Lacewings are the lovely critters that look like the princess version of an aphid. Again, it’s their larvae that are voracious – so much so that lacewings eggs are placed on long stems to keep newly hatched larvae from eating each other. (U of Cal image)

Predatory wasps or hoverflies sound unpleasant, but are a huge boon to growers. They are both excellent eaters of pests and great pollinators of small-flowered plants. They look like the tiniest possible wasp, and are easily identified both by their lack of interest in stinging humans and their distinctive hovering flight. They lay their eggs in aphids, and they find their prey by honing in on the distress signals of stressed plants.

One note: ants actually “farm” aphids, and will also kill aphid predators, so keep an eye on ant colonies in your hopyard – you might have to move them somewhere else.

Once you know what you want to attract and keep, you can start designing your insectary plantings. They should be close to the hops, preferably throughout the yards or along multiple edges so insects don’t have to fly far to find food and shelter. If your plantings can be permanent, use self-seeding annuals and perennial plants. If you will be tilling these areas in with your cover crops, use annuals. Be careful with certain plants, as a species native to one area can be invasive in another. Pay attention to what is already growing in wild areas around you, and bring those species into your plantings if you can – those indigenous plants will already be mutually adapted to your local beneficial insects. Plant in large blocks if at all possible, as individual plants will not be able to attract or sustain insect populations. Finally, try to plant for full-season coverage, with flowers blooming early and late.

The following list is a suggestion only, chosen for the southern interior of BC.

Alyssum – a low-growing self-seeding annual with tiny white to blue flowers. Flowers from early summer to hard frost. Feeds honeybees, solitary bees, many beneficials. Good ground cover.

Calendula – self-seeding annual, long flowering season. Great for lacewings and hoverflies.

Cosmos (sulphur) – annual - the yellow flowering version of cosmos attracts pollinating insects as well as hover flies, parasitic wasps, lacewings and lady bugs. Flowers copiously all summer, tall, delicate plants.

Hyssop, mint, lemon balm catnip, pennyroyal, anise hyssop - Hyssop is one of the best plants for attracting pollinators like butterflies, bees and hover flies. Strong-scented hyssop repels white cabbage butterflies by masking the smell of brassicas nearby with its aroma. Related members of the Labiatae family, including mint, lemon balm, cat nip, pennyroyal are excellent attractors of tachinid flies, hover flies and parasitic wasps.

Dill, Fennel, Parsley, Coriander, lovage, angelica - members of the Apiaceae family are powerful attractors of beneficial lady bugs, parasitic wasps, hover flies, tachinid flies, lacewings.

Yarrow - a good perennial for natural pest protection. The tiny yarrow flowers attract bees, aphid-eating lady bugs, hover flies and parasitic wasps.

The goal is to provide both nectar and pollen for the adult insects to feed on – the bonus is that many of these plants will also help out native bee populations! Add in phacelia, borage, lavender, mints, black-eyed susan or Ratibida, echinacea, clover, alfalfa, vetch and flowering alliums to get good populations of native bees and honey bees as well.


In the end, you will have a more beautiful hopyard, a balance of pests and predators, pollinators and happiness. Only the last is guaranteed.

(pictured is the beneficial insect wildflower blend from WestCoast Seeds)

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