Parasitoid community of Protopulvinaria pyriformis (Hemiptera: Coccidae) on laurel: Influence of host size, seasonal trend and aggregation on its main parasitoid

摘要

The phenology of Protopulvinaria pyriformis (Cockerell) (Hemiptera: Coccidae) and its parasitoid complex were studied on laurel Laurus nobilis L. in urban green spaces of Eastern Spain from March 2008 to January 2010. P. pyriformis is bivoltine, gravid females peaked on spring and fall and the 2nd and 3rd instars were present throughout the year. The natural parasitoid community of P. pyriformis consisted of three primary parasitoids and four facultative hyperparasitoid species. Metaphycus helvolus (Compere) (Hymenoptera: Encyrtidae) accounted for 98% of the parasitoids recovered. Although M. helvolus parasitized all the scale instars, it attacked P. pyriformis mostly at the end of the spring, when scales were larger. M. helvolus behaved as a solitary parasitoid and its secondary sex ratio was male biased when it parasitized the 2nd instar. Its secondary sex ratio became female biased when it parasitized scales larger than 1.1 mm. M. helvolus behaved as a facultative gregarious parasitoid and its secondary sex ratio was always female biased (0.3 males per scale) when it parasitized the 3rd instar and the adults. The number of eggs allocated per host, as well as the number of parasitoids that emerged, increased with scale size. Mostly, broods of two to four parasitoids emerged from these scales. M. helvolus showed inverse host density dependence, parasitism decreased as the number of scales per leaf increased. The implications of these results on the biological control of this and other soft scales are discussed