Hop looper in Ontario hops yards
Hop loopers are actively feeding in many hop yards and, together with earwigs, are likely responsible for much of the feeding damage being observed on hop leaves at this point. The hop looper, Hypena humuli, which gets its name from its distinctive looping gait, is the caterpillar stage of a Noctuid moth. This insect is found in most hop growing regions of the United States and Canada, where it feeds on the leaves and cones.
The hop looper overwinters in the adult stage, at protected sites outside hop yards in the fall. The adult moths have mottled brown wings approximately 26 mm wide, with a dark, W-shaped patch along the margin of each wing that is much more visible on females than males. Adults return to hop yards in early spring to lay eggs, along the veins or leaf margins of leaf undersides. An adult female can lay as many as 600 eggs over several weeks, typically individually rather than in masses or clusters. Hop looper eggs are small, circular and slightly flattened, initially appearing translucent green and eventually becoming white.
The eggs hatch in about three days, depending on temperature. Hop loopers are pale green and slightly flattened, approximately 1-3 cm in length with two thin white stripes running down their backs and another white stripe on each side (Figure 1). They have three pairs of "true" (jointed) legs near the head, and four pairs of "prolegs" (small, fleshy, stubs) on the abdomen - three in the middle of the abdomen and one on the last abdominal segment. This "gap" in the prolegs causes the hop looper to move in its distinct "looping" fashion.
Figure 1 - Hops looper
The caterpillars feed on hop foliage and cones as they develop (Figure 2), and high populations of hops looper can lead to a distinctive, "lacy" appearance of the foliage. Feeding damage to foliage may be worse near the base of bines, however eggs can be laid throughout the canopy. After two to three weeks, mature caterpillars pupate on leaves or in the upper soil and emerge as adults 9 days later. In most hop growing regions of North America, hop loopers have three generations per year and, because these generations overlap, all life stages are typically present in yards at the same time from late May onwards. Feeding on cones by the later generation typically causes the most damage to hops.
Figure 2 - Feeding damage by hops looper. Extensive feeding by high populations can lead to a "lace"-like appearance of the foliage.
Hops looper adults are present in hop yards from April through September, and eggs and larvae from early May through July or August. When monitoring for hop looper, an important consideration is that the insect feeds almost entirely at night. During the day, the larvae seek shelter on leaf undersides or stalks and can be difficult to detect if you are not looking closely for them. When disturbed, larvae may fall away from leaves on a piece of silk, or may move rapidly from side to side. In Ontario, we have noticed that hop loopers are often found under dead foliage on bines killed for other reasons (Figure 3). The dead leaves naturally curl downward, forming a protective shelter for both hop loopers and earwigs. One method to detect caterpillars in a hops canopy is to lay a 3 foot sheet of plastic or tarp along a row of plants and vigorously shake bines. This can dislodge hiding caterpillars from their shelters.
Figure 3 - Hops looper hiding under dead hops leaf.
No management thresholds have been established for hop looper, however large populations after flowering can affect yield. No insecticides, organic or conventional, are currently registered for the control of hop looper in Canada. However, various species of parasitic wasps and flies, as well as a number of predatory insects, will attack hop looper eggs, caterpillars and pupae. To encourage their presence in the yard, avoid the use of broad-spectrum insecticides for other pests which might injure these natural enemies. Dead leaves can serve as shelters for hops looper and other defoliators, so take care to minimize damage to bines and remove dead leaves and bines where possible.
For more information: