Submitted to: The Canadian Entomologist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/22/2013
Publication Date: 1/27/2014
Citation: Miliczky, E., Horton, D.R., Lagasa, E. 2014. Arthropod fauna of rolled alder leaves in Washington State, United States of America (Insecta: Arachnida). The Canadian Entomologist. DOI:10.4039/tce.2013.84. Interpretive Summary: Native trees and shrubs growing adjacent to the fruit-growing regions of Washington State may be a source of pest and beneficial arthropods that colonize orchards from those native habitats. Scientists with USDA-ARS, Yakima Agricultural Research Laboratory, Wapato, WA in cooperation with a scientist at the Washington Department of Agriculture, Olympia, WA determined the numbers and types of arthropods associated with caterpillar-produced leaf-shelters and leaf-rolls on alders common west of the fruit growing region of central Washington State. Our results showed that these caterpillar-built leaf-rolls are secondarily colonized by a large diversity of arthropods, including species that are important in orchards. These results will allow scientists and fruit growers to better predict what types of both pest and beneficial arthropods are likely to be present in orchards located near habitats that support large stands of native alders.
Technical Abstract: Alders, Alnus spp., growing on the eastern slopes and foothills of the Cascade Range in Washington State, are often infested with shelter-making (primarily leafrolling) Lepidoptera in the families Tortricidae, Gracillariidae, and Choreutidae. Over a 5 year survey period, 5,172 rolled leaves were examined from 3 species of alder, and their resident arthropods were identified. At least 11 species of shelter-making Lepidoptera in 3 families colonized Alnus in the survey area. Percentage of leafrolls that actually contained the rollmaker declined from highs in June to lows in August/September. Caterpillars in all three families were often parasitized by Hymenoptera and Diptera. Parasitoids from Gracillariidae were taxonomically distinct from those associated with Tortricidae hosts. Secondary colonists of leafrolls included a taxonomically diverse community of phytophagous and predatory arthropods. Herbivorous arthropods representing eight insect orders and 1arachnid order were found in leafrolls, with mites (Acari exclusive of rust mites) and thrips (Thysanoptera) represented in 48.6% and 30% of leafrolls respectively. Common predatory arthropods included the true bug species Anthocoris antevolens (Anthocoridae) in 4.4% of the leafrolls, and the spider Clubiona pacifica (Clubionidae) found in 8.3% of leafrolls. Both species frequently used rolled leaves as molting sites. Rolled leaves were almost 10-fold more likely to be occupied by predatory arthropods than adjacent roll-free leaves. A similar preference for rolled leaves was noted for phytophagous thrips and mites.