Ronda L. Hamm

Frequencies of the pyrethroid resistance alleles of Vssc1 and CYP6D1 in house flies from the eastern United States.

House flies were collected from four dairies in Maine, New York, North Carolina, and Florida, where high levels of resistance to permethrin have been documented. Regions of two genes, CYP6D1 and Vssc1, having alleles that confer resistance to permethrin (and other pyrethroids) were analysed from individuals at each collection site. The combinations of resistance alleles for Vssc1 and CYP6D1 were highly variable between each state. The resistance allele CYP6D1v1 was found at a high frequency (0.63–0.91) at all sites. Individuals homozygous susceptible for CYP6D1 were very rare and detected only at the dairy in Maine. In addition to the typical Vssc1 mutation responsible for resistance, kdr (L1014F), we also identified individuals with a L1014H mutation. Although house flies homozygous for the L1014H mutation had a lower level of resistance to permethrin, compared to L1014F, the H1014 resistance allele was frequently detected. No individuals with the super‐kdr allele (M918T + L1014F) were detected from the field collections. The intron 3 bp downstream of the kdr mutation was found to be extremely variable, providing an opportunity to reconstruct a phylogeny of Vssc1 alleles. Based on this analysis it appears the kdr‐his mutation had multiple evolutionary origins, but that the kdr mutation may have had a single origin. The impacts of these findings on resistance management are discussed.

Resistance to cyfluthrin and tetrachlorvinphos in the lesser mealworm, Alphitobius diaperinus, collected from the eastern United States.

Abstract The lesser mealworm, Alphitobius diaperinus (Panzer), is an important pest in poultry facilities. The toxicity of cyfluthrin and tetrachlorvinphos to five strains of the lesser mealworm was compared with the toxicity to a susceptible laboratory strain. Bioassays were carried out with both larvae and adults. For the susceptible strain, cyfluthrin and tetrachlorvinphos had similar toxicity to adults, but cyfluthrin was 5 times more toxic to larvae when compared with tetrachlorvinphos. High levels of resistance to tetrachlorvinphos in two beetle strains were detected in both larvae and adults, although these strains were heterogeneous and still contained susceptible individuals. Resistance to cyfluthrin ranged from 1.7‐ to 9.5‐fold for adults and from 0.5‐ to 29‐fold for larvae at the LC95. Overall, the patterns of resistance did not mirror the insecticide use patterns reported at these facilities. The implications of these results to management of the lesser mealworms are discussed. Copyright

A High Frequency of Male Determining Factors in Male Musca domestica (Diptera: Muscidae) from Ipswich, Australia

ABSTRACT The male sex determining factor (M) in the house fly is linked to the Y chromosome in the ancestral condition, but can also be linked to another chromosome (I-V or X). However, descriptions of the linkage and frequency of M factors in different populations throughout the world are vastly incomplete. We collected house flies from a dairy in Ipswich, Australia, and determined that M was linked to chromosomes II, III, IV, and Y. Most males (69.8%) were homozygous for M on autosome II and/or III, and 92.3% of the males had multiple M factors. In all, there were 13 different male genotypes found. The high frequency of M, the presence of M on four different linkage groups, and the large number of male genotypes found in this population make it unique relative to other populations of house flies that have been examined.

Comparison of two acetylcholinesterase gene cDNAs of the lesser mealworm, Alphitobius diaperinus, in insecticide susceptible and resistant strains.

Abstract Two cDNAs encoding different acetylcholinesterase (AChE) genes (AdAce1 and AdAce2) were sequenced and analyzed from the lesser mealworm, Alphitobius diaperinus. Both AdAce1 and AdAce2 were highly similar (95 and 93% amino acid identity, respectively) with the Ace genes of Tribolium castaneum. Both AdAce1 and AdAce2 have the conserved residues characteristic of AChE (catalytic triad, intra‐disulfide bonds, and so on). Partial cDNA sequences of the Alphitobius Ace genes were compared between two tetrachlorvinphos resistant (Kennebec and Waycross) and one susceptible strain of beetles. Several single nucleotide polymorphisms (SNPs) were detected, but only one non‐synonymous mutation was found (A271S in AdAce2). No SNPs were exclusively found in the resistant strains, the A271S mutation does not correspond to any mutations previously reported to alter sensitivity of AChE to organophosphates or carbamates, and the A271S was found only as a heterozygote in one individual from one of the resistant A. diaperinus strains. This suggests that tetrachlorvinphos resistance in the Kennebec and Waycross strains of A. diaperinus is not due to mutations in either AChE gene. The sequences of AdAce1 and AdAce2 provide new information about the evolution of these important genes in insects. Arch Insect Biochem Physiol.

The Evolving Puzzle of Autosomal Versus Y-linked Male Determination in Musca domestica

Sex determination is one of the most rapidly evolving developmental pathways, but the factors responsible for this fast evolution are not well resolved. The house fly, Musca domestica, is an ideal model for studying sex determination because house fly sex determination is polygenic and varies considerably between populations. Male house flies possess a male-determining locus, the M factor, which can be located on the Y or X chromosome or any of the five autosomes. There can be a single M or multiple M factors present in an individual male, in heterozygous or homozygous condition. Males with multiple copies of M skew the sex ratio toward the production of males. Potentially in response to these male-biased sex ratios, an allele of the gene transformer, Md-traD, promotes female development in the presence of one or multiple M factors. There have been many studies to determine the linkage and frequency of these male determining factors and the frequency of Md-traD chromosomes in populations from around the world. This review provides a summary of the information available to date regarding the patterns of distribution of autosomal, X-linked and Y-linked M factors, the relative frequencies of the linkage of M, the changes in frequencies found in field populations, and the fitness of males with autosomal M factors vs. Y-linked M. We evaluate this natural variation in the house fly sex determination pathway in light of models of the evolution of sex determination.

Selective Advantage for IIIM Males over YM Males in Cage Competition, Mating Competition, and Pupal Emergence in Musca domestica L. (Diptera: Muscidae)

ABSTRACT In the house fly, Musca domestica L. (Diptera: Muscidae), sex is usually determined by a dominant factor, M, located on the Y chromosome. However, there are autosomal male (AM) populations in which the M factor is located on one or more of the five autosomes (I-V), most commonly on the third chromosome. Herein we report the use of isogenic strains to determine the relative fitness of YM versus IIIM males in three different experiments. First, cages were started with 50% YM and 50% IIIM males, and the frequencies of YM and IIIM males were evaluated across generations. Second, mating competition studies were preformed with these isogenic strains. Third, the relative emergence rates of IIIM versus YM male pupae held at three temperatures for 3 d were examined. All three studies indicate that IIIM males have a greater fitness than YM males. In the cage competition studies, >90% of the males were IIIM after seven generations. IIIM males were more likely to mate than YM males, and a higher percent of IIIM males emerged after being held as pupae at 4, 16, or 28°C for 3 d. The implications of these studies to the distribution of IIIM and YM males in field populations are discussed.

A quantitative analysis of a modified feeding method for rearing Cimex lectularius (Hemiptera: Cimicidae) in the laboratory

BACKGROUND A modified artificial feeding system was developed for rearing Cimex lectularius and compared with the most widely used artificial feeding method which requires custom-made glassware and a circulating water bath to warm the blood. The petri dish method reduces some of the drawbacks from the current water bath method, such as the possibility of flooding bed bug rearing jars with water or blood and the need for expensive custom-made glassware. RESULTS Field and lab strain first instar nymphs were given a 15 or 30 min interval to feed for 6-9 weeks. Analysis of bed bugs that fed during a 6 week time period showed that there was no significant difference in the numbers that fed using the petri dish method compared with those that fed using the water bath method. Development of the nymphs also showed that there was no significant difference in the time required to produce adults by either method. CONCLUSION The petri dish method is an attractive alternative to the water bath method. Set-up is less complex, quicker, multiple jars of bed bugs can be fed at the same time, petri dishes of blood are disposable for easy clean-up and the potential of fatality due to flooding with blood or water is reduced.

Durability of a Novel Durable Bait for Control of Subterranean Termites (Isoptera: Rhinotermitidae): Results of Five-Year Field Aging Studies

ABSTRACT A durable termite bait containing 0.5% noviflumuron was evaluated for physical durability, retention of active ingredient, consumption by termites, and toxicity to termites over 5 yr in field studies at locations in Indiana, Mississippi, and South Carolina. Plots in Indiana and Mississippi included both natural rainfall and irrigated plots, while plots in South Carolina received only natural rainfall. Samples collected every 3 mo for the first 4 yr were evaluated for consumption with a 7 d no-choice bioassay using Reticulitermes flavipes (Kollar). Consumption and toxicity of 5 yr samples were evaluated in similar bioassays conducted for 42 d. Durable baits received from field sites had some cracking, and a small amount of external flaking, but no major deterioration based on visual observation. There were no significant differences in noviflumuron concentration over the 5-yr period and no trend toward reduced concentrations of noviflumuron over time. Consumption of aged durable baits over 4 yr was variable, but termites usually consumed more aged durable bait than fresh durable bait and the differences were frequently significant. There were some exceptions, but termites consumed significantly more fresh durable bait than aged durable bait in only 4% of observations. When 5 yr samples were evaluated, consumption was lowest for fresh durable bait and termites consumed significantly more aged durable bait from irrigated plots in Indiana and from both natural and irrigated plots in Mississippi than fresh durable bait. Survival of termites fed blank durable bait was significantly higher than that for termites fed any of the baits containing noviflumuron and there were no significant differences in survival among the noviflumuron durable baits. Our results suggest that the bait would be durable for at least 5 yr and possibly longer under most environmental conditions.

Consumption of a durable termite bait matrix by subterranean termites (Isoptera: Rhinotermitidae) and resulting insecticidal activity.

BACKGROUND A novel durable termite bait was developed to enable continuous bait availability and lengthen the monitoring interval to 1 year. Laboratory studies were conducted to determine the palatability and insecticidal activity of this bait to Reticulitermes flavipes (Kollar), R. virginicus (Banks), R. hesperus Banks, Coptotermes formosanus Shiraki and Heterotermes aureus (Synder). RESULTS Consumption of the blank durable bait matrix was significantly higher than consumption of a blank preferred textured cellulose matrix (PTC) by R. virginicus, R. flavipes and C. formosanus. R. flavipes, R. hesperus and H. aureus consumed significantly more durable bait than PTC when both contained the active ingredient noviflumuron. All bait treatments resulted in significant mortality relative to the untreated controls. Survivorship of R. virginicus, C. formosanus and H. aureus was 2% or less and not significantly different between the durable bait and PTC treatments containing noviflumuron. The durable bait matrix lagged behind the PTC matrix in mortality over time for all species tested except H. aureus. CONCLUSION The durable bait was highly palatable and effective in inducing mortality to R. flavipes, R. virginicus, R. hesperus, C. formosanus and H. aureus in the laboratory. This unique bait matrix will be available to termites continuously and allows for an annual monitoring interval. The durability of this bait matrix is unprecedented, allowing for bait to remain active for years and thus providing continuous structural protection.

RNAi targeting of rootworm Troponin I transcripts confers root protection in maize

Western corn rootworm, Diabrotica virgifera virgifera, is the major agronomically important pest of maize in the US Corn Belt. To augment the repertoire of the available dsRNA-based traits that control rootworm, we explored a potentially haplolethal gene target, wings up A (wupA), which encodes Troponin I. Troponin I, a component of the Troponin-Tropomyosin complex, is an inhibitory protein involved in muscle contraction. In situ hybridization showed that feeding on wupA-targeted dsRNAs caused systemic transcript knockdown in D. v. virgifera larvae. The knockdown of wupA transcript, and by extension Troponin I protein, led to deterioration of the striated banding pattern in larval body muscle and decreased muscle integrity. Additionally, the loss of function of the circular muscles surrounding the alimentary system led to significant accumulation of food material in the hind gut, which is consistent with a loss of peristaltic motion of the alimentary canal. In this study, we demonstrate that wupA dsRNA is lethal in D. v. virgifera larvae when fed via artificial diet, with growth inhibition of up to 50% within two days of application. Further, wupA hairpins can be stably expressed and detected in maize. Maize expressing wupA hairpins exhibit robust root protection in greenhouse bioassays, with several maize transgene integration events showing root protection equivalent to commercial insecticidal protein-expressing maize.