While there are many chemicals that keep hop pests in check, there are also multiple arthropods throughout the hop yard that can help control pest populations. For all of the predators listed in this fact sheet, it is important to consider the effect of pesticides. Using broad-spectrum pesticides can be damaging to natural enemies and will decrease their ability to control pests.
Some of the predators described in this fact sheet—such as predatory mites, minute pirate bugs and lacewings—can be purchased online. Suppliers can be found at anbp.org/wp-content/uploads/2021/11/Guidelines_for_Natural_Enemies_2021.pdf. Growers should not purchase lady beetles (specifically, Hippodamia convergens) for release, as they are collected while overwintering and will disperse away from the release site. Released lady beetles can also spread diseases to native populations.
Predatory Mites (Acari)
|Left: Two-spotted spider mite (pest). Right: Predatory mite. Courtesy of University of California.
Predatory mites are active, eight-legged hunters that move quickly in search of prey. They feed using needle-like mouthparts, and there are many species, which range from yellow to red in color. Their rapid movement and coloration distinguishes them from spider mites.
Size: 1/50 to 1/25 inch
Prey: Predatory mites feed on spider mites, aphids and caterpillar eggs.
Monitoring and Enhancement: These mites can be monitored while scouting for two-spotted spider mites (see the OSU Extension fact sheet Hops in Ohio: Pests). By July, numbers can reach a level where predatory mites can provide control of spider mites. A predator to prey ratio of 1:20 indicates that sufficient control can be provided. Typically, biological control is not obtained without the presence of other spider mite predators such as those described below. Providing refugia for overwintering populations such as border plantings, hedgerows and ground covers can help conserve predatory mite populations. If mites are purchased for release, it is important to inspect shipments by sprinkling a small amount onto white paper to confirm they are alive, active and ready to start hunting!
Lacewings are efficient and voracious predators. Both adults and larvae consume pests.
Eggs: Eggs are stalked and can often be found on leaves.
Larvae: Larvae are brown with long bodies and sickle-shaped mouthparts for sucking fluids from their prey.
Pupae: Pupae are silken and spherical.
Adults: Adults are green, with two pairs of lacy wings.
Size: 3/5 to 9/10 inch long
|Larva. Courtesy of Whitney Cranshaw.
|Pupa. Courtesy of Whitney Cranshaw.
|Adult. Courtesy of Whitney Cranshaw.
Prey: Lacewings feed on mites, aphids and other soft-bodied insects.
Monitoring and Enhancement: Lacewings can be monitored with yellow sticky card traps placed throughout the field, or by shaking hop bines over a large tray.
Lady beetles (Coccinellidae)
In Ohio, many species of lady beetles contribute to biological control in hop yards, but only a few are described here. For more information on lady beetles, consult the Buckeye Lady Beetle Blitz Identification Guide at beht.osu.edu/sites/ubeht/files/imce/Non%20Native%20Lady%20Beetles.pdf.
|Lady beetle eggs are bright orange, oval-shaped and often laid in clusters. Courtesy of Joseph Berger.
|Lady beetle larvae are usually dark in color with bright orange markings. The body is elongated with long legs. Courtesy of Clemson University.
|Lady beetle pupae are round in shape and usually have orange and black spots. They are often found attached to leaves. Courtesy of Russ Ottens.
Prey: Both adults and larvae feed on spider mites, aphids, thrips and other small, soft-bodied insects.
Monitoring and Enhancement: Monitoring lady beetle populations can be done by walking through the hop yard and inspecting the leaves. If there is an average of one adult lady beetle per every two or three hop plants, the beetles may be able to prevent an aphid outbreak. Conservation and attraction of lady beetles with alternative prey and floral resources are more effective than purchasing and releasing lady beetles into the hop yard.
|Adult 14-spotted lady beetles are round and 1/7 to 1/5 inch long. They are yellow, with approximately 14 square-shaped spots, which are sometimes connected. Courtesy of Graham Montgomery.
|Adult multi-colored Asian lady beetles are round and 1/5 to 1/3 inch long. They range in color from yellow to red, with many to no spots. Courtesy of Jon Yuschock.
|Adult pink lady beetles are oval-shaped and 1/5 inch long. They are bright red to pink, with six black spots on each wing cover. Courtesy of David Cappaert.
|Adult mite destroyer lady beetles are round, tiny (1/16 inch) and black. They are important predators of spider mites. Courtesy of F.C. Schweissing.
Spiders are among the most abundant predators found in hop yards. Some common types are jumping spiders, wolf spiders and crab spiders.
|Wolf spider. Courtesy of Joseph Berger.
|Jumping spider. Courtesy of Merle Shepard.
|Crab spider. Courtesy of Frank Peairs.
Prey: Spiders are generalist predators that feed on many types of arthropods. They can serve as buffers that limit initial exponential growth of pest populations.
Monitoring and Enhancement: Spiders can be monitored by shaking bines over a large tray or inspecting the ground surrounding the plants for their presence. Wolf spiders are commonly found moving quickly near the bases of plants. There are many local factors such as availability of overwintering habitat, vegetation in the hop yard margins and tillage practices that can influence the abundance of spiders. Spiders do best in hop yards where pesticide usage is limited.
Minute Pirate Bug (Orius spp.)
These tiny true bugs are voracious predators with piercing, sucking mouthparts and a wide host range. Adults and immatures can consume up to 40 spider mites or aphids per day.
Nymphs: Nymphs are yellow-orange to brown in color and teardrop-shaped.
Adults: Adults are black with white and brown markings and are oval-shaped.
Size: 1/12 to 1/5 inch
|Minute pirate bug nymph. Courtesy of Adam Sisson.
|Minute pirate bug adult. Courtesy of Ted Kropiewnicki.
Prey: Minute pirate bugs feed on aphids, mites, thrips, caterpillars and other soft-bodied insects.
Monitoring and Enhancement: Minute pirate bugs can persist in the hop yard by feeding on pollen and nectar. Providing these resources via flowering plants can enhance their populations.
Gent, D., J.D. Barbour, A.J. Dreves, D.G. James, R. Parker, and D.B. Walsh, eds. 2009. Field Guide for Integrated Pest Management in Hops. Washington Hop Commission.