Potential host range of Cotesia vanessae (Hymenoptera: Braconidae), a parasitoid new to North America and a possible biological control agent of noctuid pest species.

The likelihood of parasitoids establishing in new geographic regions depends upon the availability of suitable host species. Identifying these hosts and the degree of their suitability is particularly important when they include species that are economically important as pests. In laboratory studies, we examined the suitability of 47 species of Lepidoptera as potential hosts of a parthenogenetic strain of the gregarious parasitoid Cotesia vanessae (Hymenoptera: Braconidae). Previously known from Eurasia and northern Africa, the first known recovery of C. vanessae in North America was in 2009. C. vanessae completed development in 34 species, of which three were known hosts (Noctuidae) and 31 (30 Noctuidae, 1 Nymphalidae) were not. Many of these noctuid species are economic pests. Parasitoid fitness was generally highest on species of Plusiinae (Noctuidae), measured as either percentage of successful parasitism, developmental time, or number and mass of F1 progeny. Closely related species were generally similar in their suitability as hosts. In some cases, parasitoid eggs or larvae were killed by the immune system of the parasitized host, but the host eventually failed to excrete food waste, did not pupate, and ultimately died. Such cases reached up to 100% mortality depending upon the lepidopteran species. The suitability of many species of noctuid pests as hosts for C. vanessae suggests that this parasitoid will become established widely throughout North America and may help to suppress populations of some pest species.

Changes in the recovery of insects in pitfall traps associated with the age of cow dung bait fresh or frozen at the time of placement.

Pitfall traps baited with cattle dung are commonly used to characterize local assemblages of coprophilous insects. Baits can be made fresh or be prepared in advance and kept frozen until needed. Insect recoveries are expected to decline with the age of the bait and may be affected by the use of fresh vs. frozen baits. To assess the effect of these two factors on insect recoveries, we performed a pitfall trap experiment that was repeated in four trials spanning 2 years and two locations in southern Alberta, Canada. The experimental design allowed us to minimize the potential confounding effect of short-term weather events. For results combined across trials, baits aged >3 days were largely ineffective for attracting coprophilous species. Frozen baits attracted significantly more insects than did fresh dung for the first 3 days after placement in the field with no difference thereafter. Our findings suggest that insect recoveries in dung-baited pitfall traps can be maximized with the use of frozen baits with replacement every 3-4 days.

Control of Trogoderma granarium (Coleoptera: Dermestidae) Using High Temperatures.

Khapra beetle, Trogoderma granarium Everts, is one of the world's most important pests of stored grain. Common in Africa and Asia, it is a quarantine insect for much of the rest of the world where methyl bromide has traditionally been used for its control. However, this ozone-depleting fumigant is now heavily restricted, and alternate methods of control are required. In a two-step process, we examined the use of high-temperature exposure as one such method of control. First, different life stages were held at 45°C for different periods to calculate LT50 (lethal time to 50% mortality) values. In descending order, the most heat-tolerant life stages at 45°C were diapausing larvae (LT50 = 41 - 122 h) > nondiapausing larvae (LT50 = 47 h) > adults (LT50 = 33 h) > pupae (LT50 = 25 h) > eggs (LT50 = 10 h). Second, diapausing larvae (the most heat-tolerant stage) were held at 45, 50, 55, and 60°C for different periods to calculate LT50, LT95, LT99, and probit 9 (99.9968% mortality) values. Estimated LT99 values for diapausing larvae were 288 h at 45°C, 6 h at 50°C, 1.1 h at 55°C, and 1 h at 60°C. Based on these results, an exposure of 2 h at 60°C is recommended to control T. granarium with high temperatures. To meet requirements for control of quarantine pests, exposure of between 2 and 12 h at 50-60°C is recommended to cause probit 9 mortality, but additional experiments are needed to get a better estimate of probit 9.

Effects of Tetracycline and Rifampicin Treatments on the Fecundity of the Wolbachia -Infected Host, Tribolium confusum (Coleoptera: Tenebrionidae).

We examined the effects of Wolbachia bacteria on the reproduction of the flour beetle Tribolium confusum (Coleoptera: Tenebrionidae) using different antibiotics and across generations. We first removed infections by rearing insects on a diet with tetracycline (T; 1.0, 2.0, 3.0, 5.0, 10.0 mg/g) or rifampicin (R; 0.1, 0.2, 0.3, 0.5, 1.0 mg/g). We then performed experimental crosses using adults two generations (G2) and four generations (G4) removed from antibiotic treatments. Results showed that use of rifampicin more readily cured infections. Egg hatch from crosses of uninfected females and infected males was 0, but averaged 84 to 91% for eggs from all other crosses. Elevated fecundity was observed for T-G2 females, but not for T-G4, R-G2, or R-G4 females. Cross type had little or no effect on the sex of F 1 offspring, which averaged 52% female. These collective results support previous findings that show that Wolbachia in T. confusum causes 100% cytoplasmic incompatibility and emphasize that the antibiotic treatment used to remove infections may have additional consequences (e.g., elevated fecundity) that may not be apparent in subsequent generations.

A Review of the McMorran Diet for Rearing Lepidoptera Species With Addition of a Further 39 Species.

Research on cutworms led us to explore the use of the McMorran diet to rear lepidopteran species, mainly Noctuidae, under laboratory conditions. We documented the development of 103 lepidopteran species, including 39 species not previously reported in the literature, to be reared on this diet. Given its low cost, ease of preparation, and wide species' acceptance, this diet provides a powerful tool for facilitating Lepidoptera and other insects rearing and research in the laboratory.

Geographical barriers and climate influence demographic history in narrowleaf cottonwoods.

Studies of genetic variation can clarify the role of geography and spatio-temporal variation of climate in shaping demography, particularly in temperate zone tree species with large latitudinal ranges. Here, we examined genetic variation in narrowleaf cottonwood, Populus angustifolia, a dominant riparian tree. Using multi-locus surveys of polymorphism in 363 individuals across the species' 1800 km latitudinal range, we found that, first, P. angustifolia has stronger neutral genetic structure than many forest trees (simple sequence repeat (SSR) FST=0.21), with major genetic groups corresponding to large apparent geographical barriers to gene flow. Second, using SSRs and putatively neutral sequenced loci, coalescent simulations indicated that populations diverged before the last glacial maximum (LGM), suggesting the presence of population structure before the LGM. Third, the LGM and subsequent warming appear to have had different influences on each of these distinct populations, with effective population size reduction in the southern extent of the range but major expansion in the north. These results are consistent with the hypothesis that climate and geographic barriers have jointly affected the demographic history of P. angustifolia, and point the importance of both factors as being instrumental in shaping genetic variation and structure in widespread forest trees.

A review of the natural history and laboratory culture methods for the yellow dung fly, Scathophaga stercoraria.

The yellow dung fly Scathophaga stercoraria (L.) (Diptera: Scathophagidae) is a widespread and locally abundant fly associated with the dung of large mammals, especially farm animals. This species has recently become a standard test organism for evaluating toxic effects of veterinary pharmaceuticals in livestock dung. In this context, a review of its natural history and a general description of the field and laboratory rearing methods of this species are provided here to benefit the scientific community as well as government regulators and applicants of eco-toxicological studies. For guidance, means and ranges are included for all relevant standard life history traits stemming from previously published data on Swiss populations.

Endectocide residues affect insect attraction to dung from treated cattle: implications for toxicity tests.

A 3-year study was performed in southern Alberta, Canada to assess the effect of endectocide residues on the attractiveness of cattle dung to colonizing insects. In 2003 and 2004, insect captures were compared between pitfall traps baited with dung of untreated cattle and paired traps baited with dung of cattle that had been treated 7 days previously with topically applied doramectin, eprinomectin, ivermectin or moxidectin. Faecal residues associated with each compound affected insect captures in both spring and autumn of each year. Effects were detected (P < 0.05) for a total of 94 cases representing 27 insect taxa from 13 families in three orders (Coleoptera, Diptera, Hymenoptera). Two-fold differences in captures were common. Up to six-fold differences were observed. Eleven cases of attraction and 11 cases of repellency were associated with residues of doramectin. Eprinomectin tended to repel insects, with decreased captures for 19 of 29 cases of effect. Ivermectin showed a strong attractive effect, with increased captures for 17 of 25 cases. Moxidectin also showed a strong attractive effect, with increased captures for 17 of 18 cases. Comparisons between compounds suggested that results for doramectin best predicted results for eprinomectin and vice versa. In 2005, insect captures were compared between pitfall traps baited with dung of untreated cattle and traps baited with dung from cattle treated 3, 7 or 14 days previously with topically applied doramectin. Effects were detected in 14 cases plus one case of near significance (P= 0.053). Significant differences between control vs. days 3, 7 and/or 14 dung were detected in nine cases. Residues enhanced captures in seven of these cases. Day 14 dung affected captures in six of these cases. This study shows that endectocide residues can affect the number of insects attracted to colonize and oviposit in dung. Hence, the emergence of their offspring from field-colonized dung of untreated vs. endectocide-treated cattle should not be used as a measure of residue toxicity per se, but rather as a measure of 'insect activity'. Insect activity is a composite measure of residue toxicity, the number and species composition of insect colonists, and the mortality factors (e.g. predation, parasitism, competition) associated with the co-occurrence of these species in the dung pat.

Response of ground beetle (Coleoptera: Carabidae) field populations to four years of Lepidoptera-specific Bt corn production.

Pitfall traps were used to monitor populations of ground beetles (Coleoptera: Carabidae) in plots of corn grown in continuous cultivation during a 4-yr period (2000-2003). Treatments included transgenic corn expressing a Bt Cry protein with efficacy specific against Lepidoptera (Bt), conventional corn grown with insecticide application (I), and the same conventional cultivar grown without insecticide application (NI). Mixed-model analyses of variance were performed on pitfall captures of beetles combined across weeks to give seasonal sums. Effects of corn treatment were not detected (P > 0.05) on total beetle abundance or species richness in any year. Effects of corn treatment on individual taxa were detected (P < 0.05) for 3 of the 39 species-by-year combinations examined. Effects of near significance (P < 0.08) were detected for an additional two species. In 2001, captures of Amara farcta Leconte and Harpalus amputatus Say were lower in Bt plots than in I or NI plots. In 2003, captures of Amara apricaria (Paykull) and Amara carinata (Leconte) were higher in Bt plots than in I or NI plots. Also in 2003, captures of Poecilus scitulus Leconte were higher in I plots than in Bt or NI plots. These patterns were not repeated among years. Results of this study indicate that cultivation of Lepidoptera-specific Bt corn in southern Alberta does not appreciably affect ground beetle populations.

On the ubiquity and phylogeny of Wolbachia in lice.

Wolbachia are intracellular bacteria that occur in an estimated 20% of arthropod species. They are of broad interest because they profoundly affect the reproductive fitness of diverse host taxa. Here we document the apparent ubiquity and diversity of Wolbachia in the insect orders Anoplura (sucking lice) and Mallophaga (chewing lice), by detecting single or multiple infections in each of 25 tested populations of lice, representing 19 species from 15 genera spanning eight taxonomic families. Phylogenetic analyses indicate a high diversity of Wolbachia in lice, as evidenced by the identification of 39 unique strains. Some of these strains are apparently unique to lice, whereas others are similar to strains that infect other insect taxa. Wolbachia are transmitted from infected females to their offspring via egg cytoplasm, such that similar species of lice are predicted to have similar strains of Wolbachia. This predicted pattern is not supported in the current study and may reflect multiple events of recent horizontal transmission between host species. At present, there is no known mechanism that would allow for this latter mode of transmission to and within species of lice.

Winter survival of nuisance fly parasitoids (Hymenoptera: Pteromalidae) in Canada and Denmark.

Independent studies were performed in Canada and in Denmark to assess the survival of parasitic wasps (Hymenoptera: Pteromalidae) wintering in puparia of house fly, Musca domestica Linnaeus (Diptera: Muscidae). Data in Canada were collected for Muscidifurax raptorGirault & Saunders, M. raptorellus Kogan & Legner, M. zaraptor Kogan & Legner, Nasonia vitripennis(Walker), Spalangia cameroni Perkins, Trichomalopsis sarcophagae (Gahan) and Urolepis rufipes (Ashmead) in three microsites at an outdoor cattle facility in southern Alberta. Survival was highest for N. vitripennis, T. sarcophagae and U. rufipes, ranging from near zero to c. 7%. No survival was observed for S. cameroni. Daily mean values for ambient air temperature (DMAT) averaged about -3.5 degrees C during exposure periods. Data for Denmark were collected for M. raptor, S. cameroni and U. rufipes in a dairy barn and in a swine barn. Survival of M. raptor and U. rufipes was higher than that of S. cameroni in the dairy barn (DMAT = 8.6 degrees C), with the three species having similar survival in the swine barn (DMAT = 15.4 degrees C). In both studies, parasitoids in egg stages were least likely to survive. These results identify the potential for T. sarcophagae and U. rufipes to be commercialized for use in northern climates as biocontrol agents for nuisance flies, compare directly the cold-hardiness of commercialized species (i.e. all of the above species excluding T. sarcophagae and U. rufipes), and document the importance of microsite on winter survival.

Parasitization by pteromalid wasps (Hymenoptera) of freeze-killed house fly (Diptera: Muscidae) puparia at varying depths in media.

Three laboratory experiments were performed to assess parasitization of freeze-killed house fly puparia, buried 0 to 6 cm in media, by Muscidifurax raptor Girault & Saunders, Muscidifurax raptorellus Kogan & Legner, Muscidifurax zaraptor Kogan & Legner, Trichomalopsis sarcophagae (Gahan) and Urolepis rufipes (Ashmead) (Hymenoptera: Pteromalidae). Virtually no parasitization occurred at depths greater than 1 cm in large arenas (988 cm2) with densities of 0.3 puparia and 0.008 female parasitoids per cm2. Parasitization was observed at depths as great as 4 cm for three of five species in small arenas (3 cm2) with densities of 6.4 puparia and 1.0 female per cm2. Combined across experiments, M. raptor achieved the highest level of parasitization, followed by M. zaraptor, M. raptorellus, U. rufipes, and T. sarcophagae. The greatest number of F1 females was produced by the gregarious species T. sarcophagae (834 female female) and M. raptorellus (708 female female), and then by the solitary species M. raptor (530 female female), M. zaraptor (365 female female) and U. rufipes (163 female female). High parasitization by M. raptor and high production of offspring by T. sarcophagae identify these species as being particularly attractive as biological control agents.

Reductions of non-pest insects in dung of cattle treated with endectocides: a comparison of four products.

Pour-on formulations of four endectocide products were compared to assess the effect of faecal residues on insects developing in naturally-colonized dung of treated cattle. In each of three independent experiments, suppression of insects was associated with application of doramectin, eprinomectin and ivermectin, but no effect was observed for moxidectin. When data were combined across experiments to increase sample sizes, suppression of insects was observed for each compound, with the least effect being observed for moxidectin. Based on the number of species affected and duration of suppression, doramectin > ivermectin > eprinomectin >> moxidectin were ranked in descending order of adverse effect. A second set of three independent experiments was performed to assess the effect of endectocide treatment on dung degradation. Delayed degradation was observed for dung of cattle treated with doramectin, eprinomectin and moxidectin in the first experiment. No effect of treatment was detected in the second experiment. An effect of moxidectin was detected in the third experiment, but differences could not be detected with subsequent post-hoc tests. When data were combined across experiments to increase sample sizes, delayed degradation was detected only for eprinomectin. The apparent discrepancy between the low effect of moxidectin on insects versus its effect of dung degradation suggests the confounding action of other unidentified factors. Results of the current study indicate that use of moxidectin is least likely to affect the natural assemblage of insects associated with cattle dung.

Larvicidal activity of endectocides against pest flies in the dung of treated cattle.

Cattle were treated with topical formulations of endectocides to assess the larvicidal activity of faecal residues against horn fly, Haematobia irritans (L.), house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae). In laboratory bioassays, doramectin, eprinomectin and ivermectin suppressed horn fly in dung of cattle treated at least 4 weeks previously and suppressed house fly and stable fly in dung of cattle treated 1-5 weeks previously. Moxidectin suppressed horn fly in dung from cattle treated no more than one week previously and did not suppress house fly and stable fly. Results combined for the three species across two experiments suggested that, ranked in descending order of larvicidal activity, doramectin > ivermectin approximately = eprinomectin >> moxidectin.

Positive interactions between leafrollers and other arthropods enhance biodiversity on hybrid cottonwoods.

We examined the potential of a common herbivore to indirectly influence other diverse community members by providing habitat. Larvae of the leafroller Anacampsis niveopulvella commonly construct shelters by rolling leaves of cottonwood trees. These leaf rolls are later colonized by other arthropods. We first documented 4 times greater species richness and 7 times greater abundance on cottonwood shoots that contained a rolled leaf compared to adjacent shoots without leaf rolls. Second, with both removal and addition experiments, we showed that leaf rolls are responsible for these differences in arthropod assemblages. Leaf roll removal caused a 5-fold decline in richness and a 7-fold decline in abundance; leaf roll addition resulted in a 2.5-fold increase in richness and a 6-fold increase in abundance. Third, to determine whether rolled leaves are colonized for food or for shelter, we compared colonization of natural and artificial leaf rolls. Both richness and abundance were approximately 2-fold greater in artificial leaf rolls, indicating that leaf rolls are colonized primarily for shelter. Fourth, in a natural hybrid zone we found that leafroller densities were 2-fold greater on backcross hybrids than on F1 hybrids. These differences are likely associated with genetically-based differences in leaf morphology and/or leaf chemistry. Ultimately, plant genotype affects positive indirect interactions that have the potential to affect community structure. This study and others demonstrate that shelter builders (i.e., leafrollers and gall formers) enhance biodiversity, while free-feeders are more likely to negatively affect biodiversity.

Thin-layer chromatographic detection of ivermectin in cattle dung.

A qualitative method based on thin-layer chromatography (TLC) is described that reliably detects ivermectin as a fluorescent derivative in extracts of cattle dung. The limit of detection (LOD) was < or = 40 ng/g of wet dung. These observations were statistically documented and shown visually using digital imagery. Residues were detected in fresh dung deposited by animals treated 10 days previously with a topical dose (500 microg/kg body weight) of ivermectin.

Field bioassay to evaluate contact and residual toxicities of insecticides to carabid beetles (Coleoptera: Carabidae).

A 2-yr field study evaluated the effects of selected insecticides on Bembidion obscurellum Motschulsky and Bembidion quadrimaculatum L., carabid predators of the wheat midge, Sitodiplosis mosellana (Géhin). A bioassay method using caged beetles indicated that insecticides differed significantly in their contact and residual toxicities when applied at maximum recommended field rates. Deltamethrin, the least toxic insecticide, caused approximately 30% mortality in both beetle species, but its residual toxicity on the soil remained constant for 1 wk. Dimethoate was initially more toxic (73% mortality) than deltamethrin but less toxic after 1 wk (12% mortality). Carbofuran and chlorpyrifos, the most toxic contact sprays, caused 83 to 100% mortality. After 1 wk, the residual toxicity of carbofuran had declined markedly (5% mortality) whereas the toxicity of chlorpyrifos remained high (82% mortality). Pitfall trapping was an inconclusive method of evaluating the toxicity of insecticidal sprays to carabid adults. In plots treated with carbofuran, pitfall catches of Bembidion species were not significantly different from those in control plots during a 6-wk period after spraying. In plots treated with chlorpyrifos, catches of Bembidion species were significantly lower than those in control plots 3-16 d after spraying, but not thereafter. Results suggested that adult immigration and residual toxicity influence pitfall catches and recovery of carabid populations after spraying.