Effects of food and environment on life history parameters of parasitoids of the southern pine beetle, Dendroctonus frontalis (Coleoptera: Scolytidae)

Four studies involving hymenopteran parasitoids of the southern pine beetle (Dendroctonus frontalis Zimmermann) were conducted. In the first study, seven species of parasitoids were reared from field-collected D. frontalis-infested pine bark and used to test the effect of an artificial diet on parasitoid longevity. Parasitoid adults were provided with water only or water plus the diet and longevities were recorded and compared. All parasitoid species fed on the artificial diet, and consumption of diet resulted in significantly increased longevity compared to the water control.; In the second study, a single parasitoid species, Coeloides pissodis (Ashmead), was used to test the impact of artificial diet on parasitoid longevity under extreme climatic conditions in an effort to explore realistic field-relevant conditions. Parasitoids were reared from field-collected D. frontalis-infested pine bark and used to test the effects of the artificial diet on adult longevity under 6 temperature/humidity settings. Parasitoid adults were provided with water only, or water plus diet and placed into environmental chambers set to {dollar}18spcirc , 24spcirc ,{dollar} or {dollar}rm 30spcirc C{dollar} and either high (80%), or low (30%) relative humidity, and longevity was recorded and compared. Across all treatments, relative humidity appeared to have a greater impact on longevity than temperature or availability of diet, though diet significantly increased longevity under some conditions.; For the third study, traps were placed on pine trees infested with D. frontalis in eastern Texas. Emerging hymenopteran parasitoids were collected, identified, and recorded. Numbers of parasitoids and beetles collected were used to calculate proportion parasitism. Sex ratios were also calculated for one parasitoid species, Roptrocerus xylophagorum Ratzeburg over 8 D. frontalis density categories. In addition, data were broken into 4 seasons based on D. frontalis activity patterns for further analysis. Overall proportion parasitism was 0.065, but was lowest during season 1 (0.037) and peaked in season 4 (0.093). The sex ratio (proportion males) of R. xylophagorum increased from 0.56 in season 1, to 0.67 in season 4.; In the fourth study, 5 species of adult female hymenopteran parasitoids of D. frontalis were collected from beetle-infested pines in north-central Mississippi. Collections were made in research plots where either artificial diet had been applied, or no diet had been applied. Dissections were performed in the forest to determine presence or absence of artificial diet in the gut, and number of mature, immature, and resorbed eggs in the oviducts. Just under 40% of all parasitoids collected from diet plots exhibited diet in the gut. Comparisons between parasitoids collected in diet plots and those from control plots showed no difference in mean number of mature eggs for all but one species. Similar comparisons of mean number of immature eggs showed significant differences for 2 of the 5 species.; Together, these studies provide insights into the southern pine beetle/parasitoid system by describing elements of parasitoid biology. A better understanding of the system provides the opportunity for successful conservation and/or augmentation of parasitoids, leading ultimately to increased control of a serious forest pest.