Phenology and impact of natural enemies associated with the hop looper (Hypena humuli) in Washington State, USA

Abstract

The hop looper, Hypena humuli Harris (Lepidoptera: Noctuidae), is becoming an increasingly important pest of hops (Humulus lupulus L.) (Rosales: Cannabaceae) in western USA. Currently, control of this pest usually involves broadspectrum pesticides that kill natural enemies and disrupt biological control of other hop pests. In order to develop better management strategies for H. humuli, field and laboratory studies were conducted over a four-year period to identify the pest's natural enemies and to investigate their phenologies and to assess their impact. Nine parasitoid species and assorted species of invertebrate predator were found to attack different life-stages of H. humuli. Levels of parasitism were consistently low throughout the study period and none of the parasitoids found was a specialist natural enemy of the pests. Exclusion cage studies showed, however, that the complex of natural enemies as a whole can significantly reduce larval densities of the pest, and laboratory studies confirmed successful predation of H. humuli larvae by several generalist predators including the European earwig (Forficula auricularia L.), the damsel bug Nabis alternatus Parshley and two species of the geocorid bug genus Geocoris.

Suppression of Hop Looper (Lepidoptera: Noctuidae) by the Fungicide Pyraclostrobin

“…Complete reliance on biological control of hop looper has not been a viable management approach, even though numerous natural enemies of hop looper have been identiÞed (Grasswitz 2009, Grasswitz andJames 2011). Commercial management of hop looper often includes the use of pyrethroid insecticides (Grasswitz andJames 2008, Grasswitz 2009).…”

“…Documented to be a pest species on hop in the eastern United States in the late 19th and early 20th centuries, hop looper likely diminished in pest status during the mid-and late 20th century owing to the application of broad-spectrum organophosphate pesticides for control of hop aphid (Phorodon humuli Schrank) and twospotted spider mite (Tetranychus urticae Koch;Howard 1897;Holland 1905;Hawley 1918;Grasswitz andJames 2008, 2011). With use of more selective pesticides, hop looper has reemerged as a pest that routinely requires applications of insecticides to mitigate crop damage (Grasswitz 2009, Grasswitz andJames 2011).…”