Towards Integrated Protection from the Southern Pine Beetle

Current southern pine beetle ( Dendroctonus frontalis Zimm.) control depends heavily upon direct approaches having short-term payoffs. Chemical or physical tactics have fidled to check epidemics in the Gulf South. A major challenge lies in developing and using indirect methods for managing this pest. Promotion of stand resistance and biotic agents, and manipulation of stand density and cutting practices, hold prospect for reducing the incidence and severity of beetle-caused losses

Endoparasitic Nematodes of Ips Bark Beetles in Eastern Texas

East Texas Ips species contained 4 specific internal nematodes; I. avulsus (Eichhoff) were infected with Parasitylenchus avulsi Massey, I. grandicollis (Eichhoff) with Contortylenchus grandicolli (Massey) Rlihm, and I. calligraphus (Germar) with Contortylenchus elongatus (Massey) Nickle and Parasitaphelenchus sp. In all 3 bark beetles, infection peaked in July and August when 50-58% of adults from naturally attacked pine trees contained nematodes. Infection levels declined to 20-30% during January and February. Infected I. grandicollis and I. avulsus adults appeared lighter in color than noninfected adults. Nematode infection apparently delayed emergence of both sexes of I. grandicollis and females of I. avulsus. In I. grandicollis, nematode infection did not affect ability to construct egg galleries or number of offspring produced. Supercooling temperatures for infected I. grandicollis and I. calligraphus were no different than those of noninfected beetles

Effects of Feeding and Mating on Pheromone Release in the Southern Pine Beetle

Response of field populations of Delldroetoll1lS frontalis Zimmermann to their aggregating pheromone was correlated with pheromone content of dissectted hindgut tissues of adult beetles a determined by the gas-liquid chromatography (GLC) technique. Adult beetles in various stages of feeding activity and reproductive states were used for this purpose. Two major components of the aggregating pheromones, frontalin and trans-verbenol, were found in the largest quantities in emergent unfed females. After 48 hours of feeding, frontal in content of the hindguts was 29% and trans-verbeno content was only 5% of that of emergent females. Continuous bioassays of females feeding in host material showed increasing response of field populations to the beetle until 24-48 hours after feeding had begun, then response declined. The fact that pheromone content declined steadily following beetle attack while field response increased was thought to be due to capture of the pheromone in frass particles, thus slowing its rate of release. The decline of pheromone components in hindguts of mated females was not precipitous or abrupt a suggested by behavioral studies on other species of DendroctollllS. Field bioassays confirmed the GLC studies and showed that in both virgin and mated females peak attractiveness occurred 24-48 hours after the tree was attacked the beetles

Distribution of Some Predators and Parasites of the Southern Pine Beetle in Two Species of Pine

Southern pine beetle, Dendroctonus frontalis Zimmerman, and its natural insect enemies were reared from infested loblolly pines, Pinus taeda L., and shortleaf pines, P. echinata Mill. Southern pine beetle broods were most dense during spring (Mar.-May) and least dense in late summer. Populations were higher in late winter than in midsummer. There were no differences in beetle densities between the pine species. Twelve predators and 9 parasites comprised ca. 99% of the natural enemy complex. Total density of the 12 predators did not vary with either season or tree species. Total parasite density, however, was highest in midsummer, lowest in late winter, and was significantly higher in shortleaf pine. Species diversity of predators and parasites was highest during spring and summer seasons and varied significantly between tree species

Characterizing Flight Aggregation of the Southern Pine Beetle

Spatial aggregation patterns of flying southern pine beetles, Dendroctonus frontalis Zimm., were studied using a systematic grid of sticky flight traps placed in 3 beetle infestations. Five methods of characterizing dispersion were compared: Lloyd\u27s index of patchiness (IP), Morisita\u27s index of dispersion (15), the coefficient of dispersion (CD), the slope of Taylor\u27s power function (b) and the slope of Iwao\u27s regression of mean crowding on mean density (m). All indices indicated a high degree of aggregation of flying southern pine beetles within the infestations. The indices varied, however, in their ranking of aggregation for the 3 study sites. IP and 15 gave the same relative results while CD showed a different pattern. The two regression techniques showed no significant differences between slopes for the various study sites. The m-m regression provided more information for interpretation and more potential for evaluating influences of system manipulations. It is recommended, therefore, for characterization of southern pine beetle aggregation within infestations. IP (which serves as the theoretical basis of the regression), is suggested for comparisons between daily aggregation patterns. The m-m regression may be useful for evaluating behavioral chemical effects on aggregation through comparison of daily m-m pairs to the 95% prediction limits about the regression line; pairs falling outside these limits represent aggregation patterns significantly different from the norm

Probability of Attack by Southern Pine Beetle in Relation to Distance from an Attractive Host Tree

The pattern of southern pine beetle (SPB) attack was examined in two infestations in East Texas to determine the probability of host tree attack (PA) as a function of distance (X) from a recently attacked tree (pheromone source). In an infestation having a low rate of newly attacked trees per day and only a few pheromone sources occurring simultaneously, distance was a critical factor in determining PA. The probability decreased as In X, and was described by the regression model, PA=0.06757- 0.2583 In X. Distance, however, was less critical in a larger infestation which had multiple pheromone sources occurring simultaneously and a high rate of new trees attacked each day. Implications for pheromone control strategies utilizing SPB attractants are discussed. FOREST SCL 24:574-580