Published online by Cambridge University Press: 28 February 2020
Eriococcus spurius (Modeer) (Hemiptera: Eriociccidae) is a pest of American elm (Ulmus americana Linnaeus; Ulmaceae) trees in western North America, but no effective biological control agent has been reported. This study took place in Calgary, Alberta, Canada, where urban American elms have been heavily and negatively impacted by E. spurius. Although the parasitoid Coccophagus gossypariae Gahan (Hymenoptera: Aphelinidae) was recovered from an E. spurius infested American elm in Calgary, little is known about its ecology. Prior to implementing biological control, the basic ecology of a candidate species must be understood. We documented the geographic establishment, sex ratios, and parasitism rate of C. gossyparaie on its host within the study area. Coccophagus gossypariae had established at 89% of study trees sampled and accounted for 98% of the parasitoids caught. They had a female-biased sex ratio of 13.7 females per male, and both males and females developed to maturity using the host. We found evidence of a highly consistent aversion to superparasitism by females in the field. This first investigation established a baseline of information on field populations of C. gossypariae that could lead to biological control of E. spurius.
Subject editor: Roselyne Labbé