The hop looper, Hypena humuli, is a native noctuid moth widely distributed across the continental USA and Canada (Holland, 1905). The larvae usually feed only on hops, although they have occasionally been found on stinging nettle (Urtica sp.) (Grimble et al., 1992). The hop looper was first recorded as a pest of hops in the eastern US in the mid-1800s, but until recently has only been regarded as an occasional, or relatively minor, problem. However, hop looper is now beginning to re-emerge as a more frequent and damaging pest of Washington hops, probably as a result of the replacement of broad-spectrum organophosphate compounds for aphid and mite control by more selective products that provide little incidental control of loopers.
Biology and life history
Hop loopers overwinter in the adult stage. Both sexes of the adult have a distinctive, elongated snout that gave this species its original common name of “hop- vine snout moth.” The females have a distinctive W-shaped dark patch along the leading edge of each forewing (Fig. 1), while in males this mark is generally obscured by the darker and more uniform color of their wings (Fig. 2). As the males age, however, some of the surface scales on their wings may be lost, making them appear more like the females. The overall wingspan of both sexes is approximately 26 mm (1 inch).
The adults leave the hop yards in autumn (late September/October) to seek shelter elsewhere. They have been found overwintering in caves (Kikukawa, 1982; Godwin, 1987) and probably also use other protected sites such as cracks and crevices in tree trunks, fallen logs, fence posts, etc. The adults are thought to be capable of dispersing several miles to and from their overwintering sites, but the maximum extent of their migratory flight is not yet known. They return to the hop yards in early spring (late March/early April) and typically remain concealed within the hop foliage during the day, flying only at night or when disturbed.
Looper eggs may be found on hop foliage from mid- April onwards. The eggs are slightly flattened and are approximately circular when viewed from above, with an average diameter of 0.5 to 0.6 mm (about 1/5 inch) (Fig. 3). They are translucent and, when first deposited, have a faint greenish tinge which gradually disappears as the eggs mature and turn white. In general, just a single egg is found on each leaf, although it is not unusual to find two or three on the same leaf, and very occasionally as many as eleven have been found; in such cases,