Field-based evaluation of novaluron EC10 insect growth regulator, a chitin synthesis inhibitor against dengue vector breeding in leaf axils of pineapple plantations in Gampaha District, Sri Lanka.

BACKGROUND: Insect growth regulators (IGRs) are considered a novel group of insecticides to control mosquitoes. Novaluron is an IGR with benzoylphenyl urea insecticide, which inhibits chitin synthesis in insects and can reduce insect population density; it is also known to have a high margin of safety for mammals. METHODS: The effective minimum concentration of novaluron formulation EC10 was tested. Six pineapple plantations [control (n = 3) and test (n = 3)] were selected from Meerigama Medical Officer of Health area in Gampaha District, Sri Lanka. Fifteen plots (10 × 10 m) were demarcated in each site with a 200 m distance apart. Leaf axils of 450 pineapple plants (30 plants × 15 plots) were screened for immature stages of Aedes mosquitoes weekly for 12 weeks. The required concentration (20 ppm) of novaluron was sprayed onto the selected pineapple plants (n = 1350) individually in 3 selected test sites for 5-10 s. The reduction in the vector population was interpreted as the percentage of reduction in immature stages of Aedes mosquitoes. RESULTS: The 100% mortality of the Ae. aegypti larvae within 24 h was observed at 20 ppm (0.05 ml of novaluron 100 g/l in 250 ml of water) as the minimum dose. Variation in the number of Aedes larvae present in the control and intervention sites was found to be significantly different throughout the entire observational period (χ2 = 128.29, df = 11, P < 0.001). The total elimination of Aedes larvae continued for up to 2 weeks and a 50% reduction was observed until the 8th week. CONCLUSIONS: The present study emphasizes that novaluron (10% EC) can be used as an effective larvicide at the treatment dose of 20 ppm. The residual effect of the IGR lasted for 12 weeks with a functional efficacy of 8 weeks. The 100% reduction of larval breeding was observed up to the 2nd week after application and the percentage reduction of immature stages remained > 50% until the 8th week. The lowest reduction (34.2%) was observed at 12 weeks after the initial treatment. Therefore, re-treatment may be recommended based on the reduction in the efficacy of the IGR.

Burkholderia gut symbiont modulates titer of specific juvenile hormone in the bean bug Riptortus pedestris.

Recent studies have provided molecular evidence that gut symbiotic bacteria modulate host insect development, fitness and reproduction. However, the molecular mechanisms through which gut symbionts regulate these aspects of host physiology remain elusive. To address these questions, we prepared two different Riptortus-Burkholderia insect models, Burkholderia gut symbiont-colonized (Sym) Riptortus pedestris insects and gut symbiont-noncolonized (Apo) insects. Upon LC-MS analyses, juvenile hormone III skipped bisepoxide (JHSB3) was newly identified from Riptortus Apo- and Sym-female and male adults' insect hemolymph and JHSB3 titer in the Apo- and Sym-female insects were measured because JH is important for regulating reproduction in adult insects. The JHSB3 titer in the Sym-females were consistently higher compared to those of Apo-females. Since previous studies reported that Riptortus hexamerin-α and vitellogenin proteins were upregulated by the topical abdominal application of a JH-analog, chemically synthesized JHSB3 was administered to Apo-females. As expected, the hexamerin-α and vitellogenin proteins were dramatically increased in the hemolymph of JHSB3-treated Apo-females, resulting in increased egg production compared to that in Sym-females. Taken together, these results demonstrate that colonization of Burkholderia gut symbiont in the host insect stimulates biosynthesis of the heteroptera-specific JHSB3, leading to larger number of eggs produced and enhanced fitness in Riptortus host insects.

RNAi-mediated knockdown of SPOOK reduces ecdysteroid titers and causes precocious metamorphosis in the desert locust Schistocerca gregaria.

The Halloween gene SPOOK (SPO) is involved in the production of the active metabolite of ecdysteroid, 20-hydroxyecdysone (20E), in insects. A previous study showed that RNAi-mediated knockdown of SPO in Schistocerca gregaria last instar nymphs markedly reduced the hemolymph 20E titer, but did not affect metamorphosis. In the present study, the effects of SPO interference on development were re-examined in this locust. Injections of SPO double-stranded RNA (dsSPO) into nymphs at mid and late instars significantly delayed nymphal development and interfered with molting. The 20E levels of dsSPO-treated nymphs were generally low, with a delayed, small peak, suggesting that disturbance of the 20E levels caused the above developmental abnormalities. A small proportion of the dsSPO-injected nymphs metamorphosed precociously, producing adults and adultoids. Precocious adults were characterized by small body size, short wings with abbreviated venation, and normal reproductive activity. Fourth instar nymphs that precociously metamorphosed at the following instar exhibited temporal expression patterns of ecdysone-induced protein 93F and the juvenile hormone (JH) early-inducible gene Krüppel homolog 1 similar to those observed at the last instar in normal nymphs. Adultoids displayed mating behavior and adultoid females developed eggs, but never laid eggs. JH injection around the expected time of the 20E peak in the dsSPO-injected nymphs completely inhibited the appearance of adultoids, suggesting that appearance of adultoids might be due to a reduced titer of JH rather than of 20E. These results suggest that SPO plays an important role in controlling morphogenesis, metamorphosis, and reproduction in S. gregaria.

Identification and expression analyses of vitellogenin in Bactericera cockerelli (Sulc).

The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is a phloem-feeding insect with preference for Solanaceae. This insect species is vector of the pathogenic bacteria 'Candidatus Liberibacter solanacearum' the causative agent of zebra chip, an important disease of commercial potatoes in several countries worldwide. The recent classification of psyllids among the most dangerous vectors has promoted their study, but still many biological processes such as reproduction and vitellogenesis need to be investigated. As a first step towards the elucidation of vitellogenesis in B. cockerelli, one candidate vitellogenin transcript (6622 bases long) was identified and the expression of the transcript and the protein were analyzed in virgin and mated females between 1 and 7days old. In virgin females, Vg expression increased up to 5days old; while mating significantly up-regulated Vg expression in 5- and 7-day-old females. To determine the role of juvenile hormone in B. cockerelli Vg expression, topical applications of juvenile hormone III were performed on virgin females, resulting in an up-regulation of Vg expression and an increase in the number of mature oocytes present in female reproductive organs. Overall, this study represents the first step to understand vitellogenesis of B. cockerelli and it highlights the role of JH III in the hormonal regulation of Vg expression and oocyte development.

C3H/He Mice as an Incompatible Cholangiocarcinoma Model by Clonorchis sinensis, Dicyclanil and N-Nitrosodimethylamine.

Clonorchis sinensis is a Group-I bio-carcinogen, associated with cholangiocarcinoma (CCA). The hamster is the only experimental model of C. sinensis-mediated CCA, but we oblige another animal model. The present study intended to develop a C. sinensis (Cs) mediated CCA model using C3H/He mice, co-stimulated with N-nitrosodimethyl-amine (NDMA) and dicyclanil (DC). The mice were divided into 8 groups with different combinations of Cs, NDMA, and DC. Six months later the mice were sacrificed and subjected to gross and histopathological examination. The body weights were significantly reduced among the groups treated with 2 or more agents (eg. Cs+NDMA, Cs+DC, NDMA+DC, and Cs+NDMA+DC). In contrast, liver weight percentages to body weight were increased in above groups by 4.1% to 4.7%. A Change of the spleen weight was observed only in Cs+NDMA group. Though C. sinensis infection is evident from hyperplastic changes, only 1 worm was recovered. T wo mice, 1 from Cs and the other from Cs+DC group, showed mass forming lesions; 1 (281.2 mm(3)) from the Cs group was a hepatocellular adenoma and the other (280.6 mm(3)) from the Cs+DC group was a cystic mass (peliosis). Higher prevalence of gray-white nodules was observed in Cs group (42.9%) followed by Cs+NDMA+DC group (21.4%). The mice of the Cs+NDMA+DC group showed hyper-proliferation of the bile duct with fibrotic changes. No characteristic change for CCA was recognized in any of the groups. In conclusion, C3H/He mice produce no CCA but extensive fibrosis when they are challenged by Cs, NDMA, and DC together.

Synergism of the IGRs Methoprene and Pyriproxyfen Against Larval Cat Fleas (Siphonaptera: Pulicidae).

Insect growth regulators (IGRs) methoprene and pyriproxyfen are widely used as topical treatments to pets or applied to the indoor environment to control cat fleas, Ctenocephalides felis (Bouché). The toxicity of methoprene, pyriproxyfen, and combinations of both IGRs to cat flea larvae was determined. The LC50 of methoprene and pyriproxyfen applied to larval rearing medium was 0.39 and 0.19 ppm, respectively. Combinations of methoprene:pyriproxyfen in ratios of 1:1, 5:1, 10:1, and 20:1 produced LC50s of 0.06, 0.09, 0.19, and 0.13 ppm, respectively. The pyriproxyfen synergized the activity of methoprene as indicated by the combination indices (CI). The ratio of methoprene:pyriproxyfen (40:1) provided an LC50 of 0.42 ppm and the pyriproxyfen was not synergistic. Combinations of pyriproxyfen:methoprene in ratios of 5:1, 10:1, and 20:1 provided LC50s of 0.14, 0.20, 0.20 ppm, respectively, and the methoprene did not synergize the activity of pyriproxyfen. The dose-reduction indices (DRIs) indicated that the concentrations of IGRs in the combinations of methoprene:pyriproxyfen (ratios of 20:1 or less) could be reduced by at least one-third of the amount required by methoprene alone to provide similar larval mortality. Combinations of methoprene and pyriproxyfen may be effective in increasing the residual activity on pets and assist in reducing the likelihood of insecticide resistance developing to IGRs.

Regulatory roles of biogenic amines and juvenile hormone in the reproductive behavior of the western tarnished plant bug (Lygus hesperus).

Mating induces behavioral and physiological changes in the plant bug Lygus hesperus Knight (Hemiptera: Miridae). After receiving seminal products, which include the systemic regulator juvenile hormone (JH), females enter a post-mating period lasting several days during which they enhance their oviposition rate and lose interest in remating. To elucidate the regulation of these behavioral changes in L. hesperus, biogenic amines were quantified in the heads of females at 5 min, 1 h and 24 h after copulation and compared to levels in virgins using high-performance liquid chromatography coupled with electrochemical detection. Mating significantly increased dopamine (DA) after 1 and 24 h, and decreased octopamine (OA) after 5 min and 1 h. Serotonin did not change with mating, but tyramine was significantly reduced after 5 min. While injection of amines into virgin females did not influence sexual receptivity, OA caused a decrease in oviposition during the 24 h following injection. Topical application of the JH analog methoprene to virgins caused an increase in DA, and a decline in mating propensity, but did not influence other amines or the oviposition rate. The results suggest the decline in OA observed immediately after mating may promote egg laying, and that male-derived JH may induce an increase in DA that could account for the post-mating loss of sexual receptivity.

Toxicity and resistance of field collected Musca domestica (Diptera: Muscidae) against insect growth regulator insecticides.

The house fly, Musca domestica, is a serious pest of public health importance with the ability to develop insecticide resistance. The focus of the present study was to evaluate toxicity and resistance of the field collected house flies from Punjab, Pakistan, against insect growth regulator (IGR) insecticides. House flies collected from six different localities exhibited very low levels of resistance to cyromazine, triflumuron, and methoxyfenozide compared with the Lab-susceptible reference strain, with resistance ratios (RRs) ranging between 3.56- to 8.19-fold, 1.45- to 3.68-fold, and 2.20- to 8.60-fold, respectively. However, very low to low levels of resistance were observed for pyriproxyfen and very low to moderate levels for lufenuron with RRs ranged from 4.13- to 11.63-fold to 8.57- to 22.75-fold, respectively. There was a significant correlation between RRs of cyromazine and triflumuron (r = 0.976, p < 0.001), suggesting the possibility for cross-resistance. Susceptibility status of different IGRs in Pakistani strains of house flies is reported here for the first time. The trend observed in decreasing susceptibility towards different IGR insecticides tested will continue unless resistance management practices are followed.

Timing Spring Insecticide Applications to Target both Amyelois transitella (Lepidoptera: Pyralidae) and Anarsia lineatella (Lepidoptera: Gelechiidae) in Almond Orchards.

Amyelois transitella (Walker) (Lepidoptera: Pyralidae) and Anarsia lineatella Zeller (Lepidoptera: Gelechiidae) are key Lepidoptera pests of almonds in California. Spring insecticide applications (early to mid-May) targeting either insect were not usually recommended because of the potential to disrupt natural enemies when broad-spectrum organophosphates and pyrethroids were applied. The registration of reduced risk compounds such as chlorantraniliprole, methoxyfenozide, and spinetoram, which have a higher margin of safety for natural enemies, makes spring (early to mid-May) application an acceptable control approach. We examined the efficacy of methoxyfenozide, spinetoram, and chlorantraniliprole at three spring application timings including the optimum spring timing for both A. lineatella and A. transitella in California almonds. Our study also examined the possibility of reducing larval populations of A. lineatella and A. transitella simultaneously with a single spring insecticide application. There were no significant differences in the field efficacy of insecticides targeting either A. lineatella or A. transitella, depending on application timing for the three spring timings examined in this study. In most years (2009-2011), all three timings for each compound resulted in significantly less A. transitella and A. lineatella damage when compared with an untreated control, though there was some variation in efficacy between the two species. Early to mid-May applications of the reduced-risk insecticides chlorantraniliprole and spinetoram can be used to simultaneously target A. transitella and A. lineatella with similar results across the potential timings.

Control of Aedes aegypti and Ae. albopictus, the vectors of dengue and chikungunya, by using pheromone C21 with an insect growth regulator: Results of multicentric trials from 2007-12 in India.

BACKGROUND & OBJECTIVES: Aedes mosquito control has gained much importance nowadays in view of rise in number of reported cases of dengue and chikungunya in India and other countries. In the present study, C21 attracticide (containing a pheromone and an insect growth regulator­IGR, developed by Defence Research and Development Establishment (DRDE), Gwalior, India was tested for its feasibility for surveillance and control of Aedes mosquito in a multicentric mode from October 2007 to June 2012 in urban (Delhi, and Bengaluru district, Karnataka) and suburban (Alappuzha district, Kerala) settings of the country in three phases. METHODS: Across the randomly selected households in each study area, two to four containers treated with attracticide (experimental) and untreated (control) were placed and monitored by trained surveillance workers on weekly/ fortnightly basis for determining the presence of eggs, larvae and pupae. Container positivity, percent larvae, egg and pupae collected were determined during different phases and analyzed statistically using SPSS 18.0. RESULTS: Container positivity was found statistically significant at Bengaluru and Alappuzha, Kerala while in Delhi, it was found non-significant. Eggs collected from experimental containers were significantly higher in comparison to control at all the locations except Delhi. Also larvae collected from control containers were significantly higher at all the locations except Bengaluru. Pupae collected from control containers remained significantly higher at all the locations as no pupal formation was recorded from experimental containers. INTERPRETATION & CONCLUSION: The use of C21 attracticide hampered pupal formation, thus inhibiting adult population in the study areas. The study established that C21 attracticide was efficacious in the field conditions and has potential for use in surveillance and management of dengue and chikungunya mosquitoes.

Survival advantage of cyromazine-resistant sheep blowfly larvae on dicyclanil- and cyromazine-treated Merinos.

OBJECTIVE: To determine whether a cyromazine-resistant strain of Lucilia cuprina was able to establish strikes sooner than a susceptible strain on cyromazine- or dicyclanil-treated sheep. METHODS: Groups of 7 sheep were treated with cyromazine or dicyclanil in accordance with label directions. Beginning 5 weeks after treatment, 5 sheep from each group were challenged by implantation of neonate larvae belonging to the cyromazine-resistant strain 'Nimmitabel-selected' and the susceptible blowfly strain 'Field 2011' according to standard larval implant technique. The implant sites were alternated between the shoulder, mid-back and rump within the treatment zone. Similarly, implants of the resistant and susceptible strain larvae were alternated at each challenge such that the strain implanted on the left side of the sheep at one challenge was implanted on the right side at the next. Challenges were conducted at 3-weekly intervals until the susceptible larvae formed strikes on at least 2 of the 5 sheep in a treatment group or until 29 weeks after treatment. RESULTS: Sheep treated with cyromazine or dicyclanil were protected from flystrike by the cyromazine-susceptible strain for periods consistent with, or longer than, the registered product label claims. The cyromazine-resistant strain created strikes several weeks sooner after treatment than did the susceptible strain. Accordingly, the protection periods provided by cyromazine and dicyclanil against the resistant strain were reduced from 14 and 18-24 weeks to <8 weeks and <11 weeks, respectively. CONCLUSION: Resistance, even in the pure-breeding resistant strain, was not so severe as to cause treatment failure with cyromazine or dicyclanil, but was sufficient to reduce the protection period provided. It is recommended that producers adopt management practices that minimise the development of resistance to these and other compounds.

Exploring new thermal fog and ultra-low volume technologies to improve indoor control of the dengue vector, Aedes aegypti (Diptera: Culicidae).

Control of the mosquito vector, Aedes aegypti (L.), inside human habitations must be performed quickly and efficiently to reduce the risk of transmission during dengue outbreaks. As part of abroad study to assess the efficacy of dengue vector control tools for the U.S. Military, two pesticide delivery systems (ultra-low volume [ULV] and thermal fog) were evaluated for their ability to provide immediate control of Ae. aegypti mosquitoes with a contact insecticide inside simulated urban structures. An insect growth regulator was also applied to determine how well each sprayer delivered lethal doses of active ingredient to indoor water containers for pupal control. Mortality of caged Ae. aegypti, pesticide droplet size, and droplet deposition were recorded after applications. In addition, larval and pupal mortality was measured from treated water samples for 4 wk after the applications. The ULV and the thermal fogger performed equally well in delivering lethal doses of adulticide throughout the structures. The ULV resulted in greater larval mortality and adult emergence inhibition in the water containers for a longer period than the thermal fogger. Therefore, the ULV technology is expected to be a better tool for sustained vector suppression when combined with an effective insect growth regulator. However, during a dengue outbreak, either delivery system should provide an immediate knockdown of vector populations that may lower the risk of infection and allow other suppression strategies to be implemented.

Attractive toxic sugar baits mixed with pyriproxyfen sprayed on plants against adult and larval Aedes albopictus (Diptera: Culicidae).

The effect of spraying a mixture of the insect growth regulator (IGR) pyriproxyfen (1 mg/liter) and either 1% boric acid sugar bait or eugenol sugar bait on croton petra plants (Codiaeum variegatum L.) was evaluated against the container-inhabiting mosquito, Aedes albopictus (Skuse). Treatments were applied to plants and evaluated against adult and larval Ae. albopictus in the laboratory through contact and wash off experiments, respectively. The control treatment lacked an active ingredient and were treated with an attractive sugar bait. The plants treated with attractive toxic sugar baits plus the IGR resulted in 60-100% mortality of laboratory-reared adult Ae. albopictus. The pyriproxyfen solutions collected from the plant wash experiment resulted in 80-100% emergence inhibition to the exposed third- and fourth-instar larvae, compared with the untreated control. Attractive toxic sugar baits mixed with the IGR not only provide effective control of adult mosquitoes, but also provide additional control of larval mosquitoes after being washed off from the treated plants.

Dual-treatment autodissemination station with enhanced transfer of an insect growth regulator to mosquito oviposition sites.

BACKGROUND: The Asian tiger mosquito, Aedes albopictus (Skuse), transmits important arboviral diseases and displaces native species. This peridomestic mosquito deposits eggs in natural and artificial containers. Container larval habitats tend to be cryptic and, therefore, difficult to reach by conventional insecticide treatments. We have developed an autodissemination station that transfers the insect growth regulator, pyriproxyfen, from the station to oviposition sites. Mosquitoes visiting the station become contaminated with an oil sticker followed by pyriproxyfen powder before exiting. RESULTS: In a room (31 m(3) ) bioassay a single station consistently achieved 100% Ae. albopictus pupal mortality against 10 oviposition containers. In a greenhouse (200 m(3) ) assay with two stations and 12 oviposition cups, 91.7% of the cups had been contaminated as shown, and 57.1% pupal mortality was recorded. Pyriproxyfen transfer was also detected by visualizing mosquito 'tarsal prints' using a fluorescent dye. CONCLUSIONS: The oil and pyriproxyfen powder dual-treatment station enhanced autodissemination efficacy by increasing toxicant attachment and retention on contaminated females. The autodissemination station offers a targeted, less environmentally damaging approach to manage cryptic container species.

Efficacy of pyriproxyfen-treated nets in sterilizing and shortening the longevity of Anopheles gambiae (Diptera: Culicidae).

Pyrethroid-resistant malaria vectors have become a serious threat for malaria control, and bed nets that reduce the development of resistance are urgently needed. Here, we tested the effects of bed nets treated with the insect growth regulator pyriproxyfen against adult female Anopheles gambiae Giles (Diptera: Culicidae) under laboratory conditions. Noninsecticidal nets made of 195 denier monofilament polyethylene with a mesh size of 75 holes per square inch (equivalent to the Olyset Net) were dipped in a 0.1, 0.01, or 0.001% (wt:vol) alcohol solution of pyriproxyfen and dried overnight. Adult females of an insecticide-susceptible An. gambiae strain were exposed to treated and untreated nets before and after a bloodmeal. Bioassays showed that females were completely sterilized after exposure to 0.1% (35 mg [AI]/m2) and 0.01% pyriproxyfen-treated nets both before and after a bloodmeal. In addition, adult longevity decreased after exposure to the pyriproxyfen-treated nets in a concentration-dependent manner. The sterilizing and life-shortening effects of pyriproxyfen on the vector mosquito indicate that the combined use of pyriproxyfen and pyrethroids on bed nets has the potential to provide better malaria control and prevent the further development of pyrethroid resistance in malaria vectors.

Pyriproxyfen and house flies (Diptera: Muscidae): effects of direct exposure and autodissemination to larval habitats.

Pyriproxyfen is an insect growth regulator with juvenile hormone-like activity that has potential uses for dipterans that are difficult to manage with conventional insecticides, such as house flies (Musca domestica L.). The objectives of this study were to determine the efficacy of this insect growth regulator against house flies using variety of delivery systems and target life stages, including an evaluation of the potential for autodissemination by female flies to larval development sites. Adult female house flies exposed to filter paper (3.75% active ingredient) or sugar treated with pyriproxyfen (0.01-0.1%) produced significantly fewer F1 pupae than untreated flies. Adult emergence from pupae was unaffected. In contrast, treatment of larval rearing medium with 0.35 ml/cm2 of a 12 mg pyriproxyfen/liter preparation had no effect on the number of pupae developing from eggs but markedly inhibited adult emergence from those pupae. There was little difference in susceptibility between an insecticide-susceptible and a wild strain of house fly. The LC50 for inhibiting fly emergence of dust formulations in diatomaceous earth incorporating commercial pyriproxyfen products ranged from 8 to 26 mg/liter, with little difference among products. Compared with untreated flies, significantly fewer pupae were produced at concentrations > 0.5% and no adults were produced at concentrations > 0.05% pyriproxyfen. When gravid females were exposed for 1 h to treated fabric (6 mg pyriproxyfen/cm2) and allowed to oviposit in rearing media containing eggs, sufficient pyriproxyfen was autodisseminated to reduce adult emergence from those eggs by > 99%. Intermittent contact with treated fabric over 2 d reduced adult emergence by 63-76%.

Prevalence of breech-strike in mulesed, clipped and unmulesed Merino hoggets in south-eastern Australia.

OBJECTIVE: To compare the prevalence of breech flystrike ('breech-strike') on 12-20-month-old Merino hoggets that were mulesed, had breech and tail clips applied ('clipped') or were left unmulesed but treated strategically with long-acting insecticide. DESIGN: A cohort study on three farms in southern Victoria. METHODS: Three treatment groups were established at lamb marking on each farm. The unmulesed group was treated with dicyclanil when 12 months old in September or October ('early-season treatment'). The prevalence of breech-strike and key risk factors, including soiling of the breech with faeces ('dag') and urine ('stain'), and breech wrinkle, were compared between the groups. RESULTS: Over all the farms, breech-strike occurred on 1.1% of mulesed sheep and 7.7% of clipped sheep. Clipped sheep had a relative risk of breech-strike of 18.2-, 16.8- and 3.0-fold that of mulesed sheep on the three farms. Unmulesed sheep treated with dicyclanil had a similar prevalence of breech-strike to that of mulesed sheep (overall 0.9%, range 0-2.5%), but had significantly more dag, stain and wrinkle. CONCLUSION: Early-season treatment of unmulesed sheep prevented most breech-strikes during the spring and early summer, and offers a short- to medium-term option for the control of breech-strike in south-eastern Australia. There were some benefits associated with using clips, namely less dag and stain, and a shorter time spent crutching. However, to control breech-strike the clipped sheep should be treated the same as unmulesed sheep. Reducing the prevalence and severity of dag will be a major component of strategies to control breech-strike of Merinos in this region.

Evaluation of dicyclanil (CLiKZiN®) treatment for the early-season protection of ewes against blowfly strike.

Protecting sheep against early season myiasis (strike) is a significant problem in northern temperate farming systems, where fully-fleeced ewes and early-season lambs approaching market weight, are at high initial risk. Here, the prevention of early-season blowfly strike in ewes was examined on matched commercial sheep farms in south west England, using a new formulation of dicyclanil (CLiKZiN(®) pour on) with a short withdrawal period of 7 days. The ewes on seven farms received a prophylactic treatment with dicyclanil (CLiKZiN 1.25% pour-on suspension) in April 2011; ewes on three control farms received no treatment. The lambs at all farms remained untreated. No adverse reactions to treatment were recorded. On the treatment farms no ewe strikes were recorded between April and June (10 weeks). On control farms, there were 16 strike cases in ewes over the same period, giving a cumulative incidence of 31 cases per 1000 ewes. On the treatment farms only one lamb was struck whereas at the control farms 10 lamb strikes were recorded. The data demonstrate that CLiKZiN was highly effective at protecting ewes against early season strike-challenge.

An autodissemination station for the transfer of an insect growth regulator to mosquito oviposition sites.

A prototype autodissemination station to topically contaminate oviposition-seeking container-dwelling mosquitoes with the insect growth regulator, pyriproxyfen, was developed and tested in the laboratory. Our test subject was the Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae), an urban species that colonizes small-volume cryptic larval habitats and is a skip ovipositor that visits multiple containers. The station consists of a water reservoir to attract gravid females, which is joined to a transfer chamber designed to contaminate visiting mosquitoes. The unit is easily constructed by moulding wet shredded cardboard using corn starch as a binder. The essential criteria that must be met to prove the efficacy of an autodissemination station require it to demonstrate effectiveness in attracting the target insect, in transferring the toxicant to the insect that will disperse the agent, and in facilitating the subsequent transfer of the toxicant from the insect to target habitats at a lethal concentration. Cage experiments demonstrated that the unit was readily accepted by gravid females as an oviposition site. A powder formulation of pyriproxyfen-impregnated silica particles adhered to visiting Ae. albopictus females (mean: 66 particles/female), although particles were lost over time. In cage (2.2 m(3) ) trials, pyriproxyfen-charged stations resulted in 100% inhibition of adult emergence, whereas in small-room (31.1 m(3) ) trials, 81% emergence inhibition was recorded. The venereal transfer of pyriproxyfen from contaminated males to virgin females was also observed, and pyriproxyfen was subsequently transferred to water-holding containers at concentrations that inhibited emergence. Key autodissemination station features include lack of maintenance requirements, biodegradable construction, low cost and low risk.

Improved chemical control for the Mexican rice borer (Lepidoptera Crambidae) in sugarcane: larval exposure, a novel scouting method, and efficacy of a single aerial insecticide application.

A three-treatment aerial application insecticide experiment was conducted in five commercial sugarcane, Saccharum spp., fields in south Texas to evaluate the use of pheromone traps for improving chemical control of the Mexican rice borer, Eoreuma loftini (Dyar), in 2009 and 2010. A threshold of 20 moths/trap/wk was used to initiate monitoring for larval infestations. The percentage of stalks with larvae on plant surfaces was directly related to the number of moths trapped. Reductions in borer injury and adult emergence were detected when a threshold of >5% of stalks with larvae present on plant surfaces was used to trigger insecticide applications. Novaluron provided superior control compared with beta-cyfluthrin; novaluron treated plots were associated with a 14% increase in sugar production. A greenhouse experiment investigating establishment and behavior of E. loftini larvae on two phenological stages of stalkborer resistant, HoCP 85-845, and susceptible, HoCP 00-950, sugarcane cultivars determined that more than half of larvae on HoCP 00-950 and > 25% on HoCP 85-845 tunneled inside leaf mid-ribs within 1 d of eclosion, protected therein from biological and chemical control tactics. Exposure time of larvae averaged < 1 wk for all treatments and was shortest on immature HoCP 00-950 and longest on mature HoCP 85-845. This study shows a short window of vulnerability of E. loftini larvae to insecticide applications, and demonstrates the potential utility of pheromone traps for improving insecticide intervention timing such that a single properly timed application may be all that is required.