Relative Abundance and Seasonal Distribution of the Major Hymenopterous Parasites of the Southern Pine Beetle, Dendroctonus frontalis Zimmermann 1 , on Loblolly Pine

Abstract

Relative abundance and seasonal occurrence of hymenopterous parasites of the southern pine beetle ( Dendroctonus frontalis Zimm.) were studied in loblolly pine ( Pinus taeda L.) stands located in southeastern and western Louisiana. The 6 most abundant parasites were: Roptrocerus eccoptogastri (Ratz.)–65% of total complex, Coeloides pissodis (Ash.)–10%, Dendrosoter sulcatus Mues.–8%, Spathius pallidus Ash.–7%, Heydenia unica (Cook and Davis)–7%, and Dinotiscus (= Cecidostiba ) dendroctoni (Ash.)–3%. Parasite abundance peaked between Apr.-June and remained at low levels from Dec. to Mar. Parasite populations within trees differed little between areas of opposing site conditions and geographic location. The relationship between host and parasite populations and bark thickness of loblolly pine, host egg gallery length (number of beetle eggs) and site differences at 2 ecologically different areas were also investigated. Bark thickness significantly affected populations of the parasitic species that oviposit through the bark but did not influence populations of R. eccoptogastri which enter host galleries and oviposit through host egg niche plugs.