Insecticide Sprays Research Articles

Caregivers’ vector control methods and its effect on malaria infection in febrile children presenting in a Tertiary Hospital in Nigeria

Background: Malaria is a major public health problem in sub-Saharan Africa. Several efforts are being made to reduce its prevalence and morbidity in Nigerian children with emphasison vector control measures.Methods: This was acrosssectional descriptive study conducted on 382 febrile children seen at a tertiary hospital in Nigeria over an eight-month period. A structured questionnaire was used to collect information on sociodemographic, vector control measures and care given to the subjects. Investigations conducted included malaria microscopy and total leukocyte count.Results: Eighty percent (308/382) employed at least one vector controlmeasures to prevent malaria infection, and majority 232 (75.2%) use only one control measure. The commonest control measures used included always keeping doors and windows shut 298 (96.7%) and/or netted 280 (90.9%), use of conventional insecticide sprays 183 (59.4%), use of insecticide treated bed nets (ITNs) 178 (57.8%) and ensuring child sleeps at night with body adequately covered 77(25%). Approximately half (178/315) of households who owned ITN used it, and only 40.4% (72/178) used it daily. It was noted that children that slept under an insecticide treated bed net (RR 0.56, 95% CI 0.33-0.94; P=0.029) and those who slept well covered at night (RR 0.26, 95% CI 0.12-0.61; P=0.002) had less risk of malaria infection. The use insecticide treated bed net however lost significance following adjustment for other control measures used and socio-demographic factors of interest (RR 0.63, 95% CI 0.36-1.10;P=0.101).Conclusion: There is need to intensify education on appropriate malaria control measures especially proper use of insecticide-treated nets and suitable clothing during sleep at night.

Mosquirix™ RTS, S/AS01 Vaccine Development, Immunogenicity, and Efficacy.

Malaria is a parasitic infection caused by bites from Plasmodium falciparum (P. falciparum)-infected mosquitoes with a present scale of symptoms ranging from moderate fever to neurological disorders. P. falciparum is the most lethal of the five strains of malaria, and is a major case of morbidity and mortality in endemic regions. Recent advancements in malaria diagnostic tools and prevention strategies have improved conjugation antimalarial therapies using fumigation and long-lasting insecticidal sprays, thus lowering malarial infections. Declines in the total number of infected individuals have been correlated with antimalarial drugs. Despite this, malaria remains a major health threat, affecting more than 30 million men, women, and children around the globe, and 20 percent of all children around the globe have malaria parasites in their blood. To overcome this life-threatening condition, novel therapeutic strategies, including immunization, are urgently needed to tackle this infection around the world. In line with this, the development of the RTS, S vaccine was a significant step forward in the fight against malaria. RTS, S is a vaccine for P. falciparum in which R specifies central repeat units, T the T-cell epitopes, and S indicates surface antigen. The RTS, S/AS01 malarial vaccine was synthesized and screened in several clinical trials between 2009 and 2014, involving thousands of young children in seven African countries, showing that children who received the vaccine did not suffer from severe malaria. Mosquirix™ was approved by the World Health Organization in 2021, indicating it to be safe and advocating its integration into routine immunization programs and existing malaria control measures. This paper examines the various stages of the vaccine’s development, including the evaluation of its immunogenicity and efficacy on the basis of a total of 2.3 million administered doses through a routine immunization program. The protection and effectiveness provided by the vaccine are strong, and evidence shows that it can be effectively delivered through the routine child immunization platform. The economic cost of the vaccine remains to be considered.

Bionomic aspects of dengue vectors Aedes aegypti and Aedes albopictus at domestic settings in urban, suburban and rural areas in Gampaha District, Western Province of Sri Lanka

BackgroundThe lack of information on behavioural patterns of Aedes aegypti and Aedes albopictus has become a significant limitation in vector control and disease management programmes. Therefore, the current study was focused on determining some bionomics aspects: breeding, resting, host-seeking and feeding preferences of Ae. aegypti and Ae. albopictus in Sri Lanka.MethodsLarval and adult surveys were conducted from April 2017 to April 2019 monthly in six selected Medical Officer of Health (MOH) areas in Gampaha Distinct, Western province, Sri Lanka, representing urban, suburban and rural settings. Resting preferences of adult mosquitoes were observed from indoor and outdoor places using a Prockopack aspirator. The information on resting height, surface, material and locality was recorded. Human-baited double-net traps were used to determine the host-seeking time of Aedes mosquitoes. Statistical differences in the spatial distribution of mosquitoes in selected MOH areas and prevalence of vectors were analysed using general linear model (GLM). A chi-square test was used to analyse the resting behaviour.ResultsTotal of 19,835 potential breeding sites were examined at 13,563 premises, and 18.5% (n = 1856) were positive for Aedes larvae. Distribution of Ae. aegypti and Ae. albopictus was statistically significant at species level (df = 1; F = 137.134; P < 0.05 GLM) and study setting (df = 2; F = 8.125; P < 0.05). Aedes aegypti breeding was found mainly in temporary removals (18.8%; n = 34), discarded non-degradables (12.15%; n = 22) and tyres (9.95%; n = 18). Natural (14.7%; n = 246) and temporary removals (13.6%; n = 227) and discarded non-reusable items were the key ovipositing sites for Ae. albopictus. In the adult mosquito survey, the majority was comprised of Ae. albopictus (54.5%; n = 999), which denoted exophilic nature (90.8%; n = 758), and 45.5% (n = 835) represented by Ae. aegypti mosquitoes who were mainly endophilic (84.3%; n = 842). Aedes aegypti rested on cloth hangings and curtains, followed by the furniture, while Aedes albopictus was predominant in outdoor vegetation. In both vectors, biting patterns denoted a typical diurnal pattern with two peaks of host-seeking and biting activity in the morning and afternoon.ConclusionsThe majority (80%) of the larval habitats were artificial containers. The use of larvicides for vector control as the prominent measure is questionable since applying these chemicals may target only 20% of the total breeding grounds, which are permanent. The resting places of adult mosquitoes are mainly indoors. Therefore, using thermal space spraying of insecticide may not be appropriate, and indoor residual spraying is recommended as a suitable intervention to target adult mosquitoes. This study warrants a holistic vector control approach for all medically important mosquitoes and insects, ensuring the rational use of finance and resources.Graphical

Reduction in malaria burden following the introduction of indoor residual spraying in areas protected by long-lasting insecticidal nets in Western Kenya, 2016-2018.

Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the main malaria vector control measures deployed in Kenya. Widespread pyrethroid resistance among the primary vectors in Western Kenya has necessitated the re-introduction of IRS using an organophosphate insecticide, pirimiphos-methyl (Actellic® 300CS), as a pyrethroid resistance management strategy. Evaluation of the effectiveness of the combined use of non-pyrethroid IRS and LLINs has yielded varied results. We aimed to evaluate the effect of non-pyrethroid IRS and LLINs on malaria indicators in a high malaria transmission area. We reviewed records and tallied monthly aggregate of outpatient department (OPD) attendance, suspected malaria cases, those tested for malaria and those testing positive for malaria at two health facilities, one from Nyatike, an intervention sub-county, and one from Suba, a comparison sub-county, both located in Western Kenya, from February 1, 2016, through March 31, 2018. The first round of IRS was conducted in February-March 2017 in Nyatike sub-county and the second round one year later in both Nyatike and Suba sub-counties. The mass distribution of LLINs has been conducted in both locations. We performed descriptive analysis and estimated the effect of the interventions and temporal changes of malaria indicators using Poisson regression for a period before and after the first round of IRS. A higher reduction in the intervention area in total OPD, the proportion of OPD visits due to suspected malaria, testing positivity rate and annual malaria incidences were observed except for the total OPD visits among the under 5 children (59% decrease observed in the comparison area vs 33% decrease in the intervention area, net change -27%, P <0.001). The percentage decline in annual malaria incidence observed in the intervention area was more than twice the observed percentage decline in the comparison area across all the age groups. A marked decline in the monthly testing positivity rate (TPR) was noticed in the intervention area, while no major changes were observed in the comparison area. The monthly TPR reduced from 46% in February 2016 to 11% in February 2018, representing a 76% absolute decrease in TPR among all ages (RR = 0.24, 95% CI 0.12-0.46). In the comparison area, TPR was 16% in both February 2016 and February 2018 (RR = 1.0, 95% CI 0.52-2.09). A month-by-month comparison revealed lower TPR in Year 2 compared to Year 1 in the intervention area for most of the one year after the introduction of the IRS. Our findings demonstrated a reduced malaria burden among populations protected by both non-pyrethroid IRS and LLINs implying a possible additional benefit afforded by the combined intervention in the malaria-endemic zone.

Household modifications after the indoor residual spraying (IRS) campaign in Mozambique reduce the actual spray coverage and efficacy.

Indoor residual spraying of insecticides (IRS) is a key malaria vector control strategy. Whilst human attitude towards IRS is monitored before or shortly after implementation, human activities leading to the modification of insecticide-treated walls post-IRS are not. This could inadvertently reduce the protective effects of IRS. We monitored the extent of modifications to the sprayed indoor wall surfaces by household owners for six months post-IRS campaigns in two districts targeted for malaria elimination in southern Mozambique. In parallel, we assessed building of any additional rooms onto compounds, and mosquito net use. We quantified the contribution of wall modifications, added rooms, prolonged spray campaigns, and product residual efficacies on actual IRS coverage and relative mosquito bite reduction, using a mechanistic approach. Household owners continually modified insecticide-treated walls and added rooms onto compounds. Household surveys in southern Mozambique showed frequent modification of indoor walls (0-17.2% of households modified rooms monthly) and/or added rooms (0-16.2% of households added rooms monthly). Actual IRS coverage reduced from an assumed 97% to just 39% in Matutuine, but only from 96% to 91% in Boane, translating to 43% and 5.8% estimated increases in relative daily mosquito bites per person. Integrating post-IRS knowledge, attitude, and practice (KAP) surveys into programmatic evaluations to capture these modification and construction trends can help improve IRS program efficiency and product assessment.

On-farm trials towards reduced insecticides in main crop potatoes in the Waikato Region of New Zealand

Tomato potato psyllid (TPP), Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is the vector for “Candidatus Liberibacter solanacearum” (CLso), which causes the serious disease “zebra chip” (ZC) of potatoes. Between 2016 and 2019, a reduced-insecticide approach to control TPP was evaluated. We compared a standard-insecticide weekly spray regime that included Integrated Pest Management (IPM)-compatible insecticides plus JMS Stylet Oil® (JMS) as a wetting agent, with a reduced-insecticide regime where we used the oil on its own on alternate weeks with the insecticide/oil mixtures. Spray programme start dates were determined by: (1) crop scouting; (2) sticky-trap monitoring; and (3) degree-day calculation. Crop scouting combined with a sticky-trap action threshold and degree-day data was an effective method for determining when to start spraying. The most substantial reduction in insecticides was achieved by alternating weekly insecticides with the oil formulation on its own. Sub-samples of TPP from sticky traps situated in the trials tested for CLso confirmed the presence of the bacteria in (commonly known as ‘hot’) TPP throughout the trials. The reduced-treatment approach gave statistically similar levels of ZC to the standard insecticide spray programme.

Regional and caste‐specific variation in insecticide susceptibility in odorous house ants, Tapinoma sessile (Hymenoptera, Formicidae)

AbstractAnts consistently rank as the number one household pest, and many species are pests in agricultural and natural habitats. Despite economic and ecological impact of pest ants, effective management still faces many challenges and control failures with liquid spray insecticides are common. The odorous house ant (Tapinoma sessile Say) is an adaptive and widespread pest ant found in North America. This study examined regional variation in T. sessile insecticide susceptibility to three classes of insecticides commonly used in ant control. T. sessile showed significant regional variation in insecticide susceptibility on a relatively small geographic scale. A comparison of colonies collected in urban vs. natural areas showed no significant difference in susceptibility in tests with lambda‐cyhalothrin and fipronil. In tests with dinotefuran, urban colonies were significantly more tolerant relative to natural colonies. These results suggest that habitat type and previous insecticide exposure do not reliably predict susceptibility levels in individual populations. Queens were significantly more tolerant relative to their worker counterparts across all insecticides. Higher insecticide tolerance in queens may explain why T. sessile is such a persistent pest in urban environments. The results provide a foundation for the development of more effective and efficient control methods for T. sessile and warrant further investigation of spatial and potentially temporal variability in insecticide susceptibility in ants.

Why Using Biological Control Approaches Against Sugar Beet Aphid Pests Will Not Control Virus Yellows – a Post-script

As an advocate of natural pest control wherever possible, the author has no quarrel with Professor Loxdale?s appeal for research funders to consider enhancing the resources already available in the natural environment. In an ideal world, this would be the most acceptable method for producing healthy crops for our benefit, not to mention encouraging biodiversity within the landscape. However, in the real world, a more pragmatic approach is sometimes required to avoid catastrophic yield losses, such as those which occurred in sugar beet in the mid 1970s, and most recently in 2020, when it was estimated that 25% of sugar beet yields were lost to the aphid-transmitted yellowing viruses that infected 38% of the national sugar beet crop. Controlling up to 50 % of aphids by parasitoids or other natural enemies, whilst commendable in a situation where aphids might cause significant yield loss by direct-feeding, is certainly not sufficient to prevent widespread virus infection within crops, simply because it does not take many aphids to spread viruses. The threshold for aphid control using insecticide sprays in sugar beet in the UK is, and has been for decades, one green wingless aphid per four plants. This level of infection is actually quite difficult for a human to detect to make the judgement to use a spray or not, and it is a population level that does not attract many parasitoids or predators, even though they are better at finding them than we humans. But that threshold is necessary to help reduce the spread of the yield-reducing viruses and protect the yield of sugar beet.

The success of a habitat specialist biological control agent in the face of disturbance

AbstractNatural enemies that can use multiple habitats are thought to better withstand disturbances in agricultural systems than natural enemies that are habitat specialists. This is because habitat generalists have populations in multiple habitats that can serve as sources of immigrants into an agricultural crop following a disturbance. In contrast, the dynamics of habitat specialists are tightly coupled with those of one agricultural crop. Nonetheless, some habitat specialists are successful in highly disturbed environments. To test how the magnitude of within‐field disturbance affects biological control agents, we conducted a large‐scale field manipulation in alfalfa fields and monitored the response of pea aphids, habitat‐generalist predators, a habitat‐specialist parasitoid (Aphidius ervi), and hyperparasitoids of A. ervi. The manipulation involved three treatments: harvesting normally (intermediate disturbance); spraying insecticide immediately after harvesting (high disturbance); and harvesting in strips (low disturbance). As a group, the habitat‐generalist predator species showed a range of responses to disturbances, from no response to decreases in abundance in the high‐disturbance treatment, indicating differences in their response to the density of pea aphids following disturbances. Surprisingly, percentage parasitism by the habitat‐specialist parasitoid was little affected by experimental disturbance manipulations. Furthermore, two of the four hyperparasitoids of A. ervi were negatively affected by the magnitude of disturbance, suggesting that disturbance could have an indirect positive effect on A. ervi. These results suggest that a habitat specialist can overcome the detrimental effects of disturbances without using alternative habitats. In addition, disturbance can sometimes benefit biological control agents by disproportionally negatively affecting their enemies from the fourth trophic level.

Control of Curculio caryae (Coleoptera: Curculionidae) with Reduced Rates of a Microbial Biopesticide

Control of Curculio caryae (Coleoptera: Curculionidae) with Reduced Rates of a Microbial Biopesticide

Timely Application of Four Insecticides to Control Corn Earworm and Fall Armyworm Larvae in Sweet Corn.

Simple SummaryCorn earworm and fall armyworm are the most important Lepidopteran pests in sweet corn worldwide. Timely application of insecticides during pollination is crucial to control both species and produce kernels with higher quality. Our results showed that applications of insecticides should be conducted at 48 h after pollination. Emamectin benzoate and chlorantraniliprole provided an adequate control of fall armyworm and corn earworm larvae. Furthermore, emamectin benzoate should be applied to larvae in later instars (fourth–sixth) while chlorantraniliprole and spinetoram should be sprayed when infestations of larvae in earlier instars (first–third) are observed.Insecticide sprays are a common practice to control corn earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), in corn (Zea mays L.) at reproductive stages. Our objectives were to determine (1) the most appropriate time for insecticide applications and (2) the effect of four insecticides on the survival of larvae as well as their weight. ß-cyfluthrin (0.4 mL/L), chlorantraniliprole (0.6 mL/L), emamectin benzoate (0.2 g/L), and spinetoram (1.5 mL/L) were sprayed on silks of sweet corn planted in Isabela and Lajas, Puerto Rico 3 h before and 24 and 48 h after pollination. The number of kernels produced and the damage of larvae on kernels were quantified at harvest. In addition, percentages of mortality and changes on larval weight were noted at 96 h after insecticide applications. Insecticide sprays at 3 h before pollination reduced the number of kernels or were similar to the control in all treatments. However, emamectin benzoate sprayed in Lajas and chlorantraniliprole applied in Isabela at 48 h after pollination increased the number of kernels (281–294) and reduced the damage of larvae on kernels (<0.5%) compared to the control (201–229; >7%). Furthermore, applications of emamectin benzoate caused higher percentages of fall armyworm larval mortality (>70%). Conversely, ß-cyfluthrin and chlorantraniliprole caused lower percentages of mortality (<30%) and only chlorantraniliprole and spinetoram reduced the weight of corn earworm and fall armyworm larvae collected in both locations. This information may help pest management programs and corn breeders to schedule insecticide sprays and pollination in the field.

Comparison of Mineral Oil, Insecticidal, and Biopesticide Spraying Regimes for Reducing Spread of Three Potato virus Y Strains in Potato Crops.

In-field management of Potato virus Y (PVY) faces challenges caused by the changing availability and environmental acceptability of chemical agents to control aphid vectors of the virus and by proliferation of PVY strains with different symptoms and rates of spread. From 2018 to 2020, foliar spray treatments were compared in field experiments in New Brunswick, Canada, to measure effectiveness at reducing spread of PVYO, PVYN:O, and PVYNTN strains. Mineral oil, insecticide, combined oil and insecticide spray, and a biopesticide (i.e., LifeGard WG) were compared. Insecticide-only and mineral oil-only treatments were not effective, but several combined oil and insecticide treatments and biopesticide treatments significantly reduced PVY spread. The biopesticide was proportionately more effective with recombinant PVYN:O and PVYNTN strains, possibly by exciting the plant's hypersensitive resistance response, caused naturally only in cultivar 'Goldrush' by PVYO. Pesticide residue analysis showed that mineral oil increased the retention of pyrethroid insecticide in the potato foliage longer than with insecticide applied alone, which may explain the beneficial synergistic effect of combined sprays for reducing PVY spread. Tuber yields were generally unchanged in chemical insecticide treatments but were slightly lower in biopesticide treatment. The cost per PVY treatment was competitive across all effective treatments, including biopesticide; however, there was some revenue loss from lower yield with the biopesticide. This biopesticide is certified organic, however, and thus a small premium on the price for organic production could offset this yield deficit.

Development of bio-rational pest management module against hog plum beetle, &lt;i&gt;Podontia&lt;/i&gt; 14-&lt;i&gt;punctata&lt;/i&gt; (Coleoptera: Chrysomelidae)

The hog-plum, locally known as amra, is a deciduous perennial tree with thick succulent leaves and it grows all over the country, but the quality fruits are produced only in the southern districts of Bangladesh especially in Barishal and Jhalokathi districts. Its cultivation is seriously hampered by hog- hog plum beetle or 14 spotted leaf beetle, &lt;em&gt;Podontia&lt;/em&gt; 14-&lt;em&gt;punctata&lt;/em&gt; L. (Chrysomelidae: Coleoptera). In most of the cases, insecticidal spray is not effective for controlling this pest as pupation occurs in the soil. Therefore current study was carried out in both laboratory and field condition to develop environment friendly management approaches against hog plum beetle as well as producing of toxic chemical pesticide free hog-plum. From laboratory test, it is revealed that spraying of spinosad (Success 2.5 SC) at hog plum leaflet and drenching with microbial pesticides, soil recharge namely Lycomax (&lt;em&gt;Metarhizium anisopliae&lt;/em&gt; +&lt;em&gt; Trichoderma harzianum&lt;/em&gt; + &lt;em&gt;Beauveria bassiana&lt;/em&gt; + &lt;em&gt;Trichoderma viride&lt;/em&gt;) causes 72.22% adults and 51.85% pupal mortality of &lt;em&gt;P.&lt;/em&gt; 14-&lt;em&gt;punctata&lt;/em&gt; respectively. Then some pest management modules were developed based on the laboratory result and it’s were verified in field during two fruiting season 2018-19 and 2019-20. From field study it is observed that module 1: Hand picking + trunk banding with packaging tape + soil drenching with lycomax + spraying of spinosad treated trees offered lowest leaf and fruit infestation; even though trunk banding with packaging tape did not show any effect to control this pest. Fruit yield was also increased 39.04-39.66% in module 1 imposing hog plum trees compare to control. Therefore, it is clear that without banding of the hog plum trunk, hand picking + soil drenching with microbial pesticides, lycomax + spraying of spinosad might be sustainable and environment friendly pest management module against &lt;em&gt;P.&lt;/em&gt; 14-&lt;em&gt;punctata&lt;/em&gt;.

Sustainable pest management approach against the hog plum leaf beetle, Podontia 14-punctata Linn. (Coleoptera: Chrysomelidae)

BackgroundThe hog-plum, locally known as “amra”, is a deciduous perennial tree with thick succulent leaves and it grows all over the country, but the quality fruits are produced only in the southern districts of Bangladesh. Its cultivation is seriously hampered by hog-plum leaf beetle or 14 spotted leaf beetle, Podontia 14-punctata Linn. (Coleoptera: Chrysomelidae). In most of the cases, insecticidal spray is not effective for controlling this pest as pupation completed in the soil. Therefore, the present study was carried out under both laboratory and field conditions to develop environment friendly sustainable management approaches against the hog-plum beetle.ResultsLaboratory test revealed that spraying with green pesticide spinosad (Success® 2.5% SC) at hog-plum leaflet and drenching with microbial pesticide Metarhizium anisopliae + Trichoderma harzianum + Beauveria bassiana + Trichoderma viride (Lycomax, Russell IPM) causes 75.00% larvae, 72.22% adults and 51.85% pupal mortality,, respectively. Some pest management approaches were developed based on the laboratory results, they were verified in field, during the two successive fruiting seasons 2018 and 2019. Field study indicated that approach 1: Hand picking + trunk banding with packaging tape + soil drenching with lycomax, Russell IPM + spraying of spinosad treated trees offered lowest leaf and fruit infestation; even though trunk banding with packaging tape did not show any effect to control this pest. Fruit yield was also increased 39.04–39.66% in approach 1 imposing hog-plum trees compared to control.ConclusionThe study showed that without banding of the hog-plum trunk, hand picking + soil drenching with microbial pesticides, lycomax, Russell IPM + spraying of spinosad might be sustainable and environment friendly pest management approach against P. 14-punctata.

Permethrin-treated baby wraps for the prevention of malaria: results of a randomized controlled pilot study in rural Uganda

BackgroundProgress against malaria has stalled and may even be slipping backwards in high-burden countries. This is due to a range of factors including insecticide resistance and mosquito feeding behaviours that limit contact with widely-employed interventions including long-lasting insecticidal nets and indoor-residual spraying. Thus, further innovations in malaria control are urgently needed.MethodsThe pilot was a randomized, placebo-controlled pilot study of permethrin-treated baby wraps—known locally as lesus—in children 6–18 months of age at a single site in rural western Uganda. Fifty mother–infant pairs were assigned to permethrin-treated or untreated lesus in a 1:1 allocation. Participants and clinical staff were blinded to group assignments through use of sham treatment and re-treatment of lesus. Participants attended scheduled clinic visits every 2 weeks for a total 12 weeks. The primary outcome of interest was the safety of the intervention, assessed as changes in the frequency of use, rates of discontinuation, and incidence of adverse events, such as skin rash. Secondary outcomes included acceptability and feasibility of the intervention as measured through participant satisfaction and completion of study activities, respectively.ResultsOverall, rates of retention and participation were relatively high with 86.0% (43 of 50) of participants completing all scheduled visits, including 18 (75.0%) and 25 (96.2%) in the intervention and control arms respectively. By the conclusion of the 12-week follow-up period, one adverse event (0.35 events per 100 person-weeks, one-sided 95% CI 0.0–1.65) was reported. Satisfaction with the lesu was high in both groups. In each study arm, there were five incident RDT positive results, but the only PCR-positive results were observed in the control group (n = 2).ConclusionsPermethrin-treated baby wraps were well-tolerated and broadly acceptable. Adverse events were infrequent and mild. These findings support future trials seeking to determine the efficacy of treated wraps to prevent P. falciparum malaria infection in young children as a complementary tool to existing household-based interventions.Trial registration: ClinicalTrials.gov Identifier: NCT04102592, Registered 25 September 2019. Available at: https://clinicaltrials.gov/ct2/show/NCT04102592

Flower strips, crop management and landscape composition effects on two aphid species and their natural enemies in faba bean

Wildflower strips and biodiversity-friendly management are promoted as ways of enhancing biodiversity and natural pest control in agroecosystems. Their efficacy for providing resources and shelters for natural enemies has been well studied, but little is known about how wildflower strip efficacy is mediated by local field management and landscape composition. In this study, we explored the effects of floral resources in perennial flower strips on faba bean aphids and their antagonists in contrasting cropping systems and landscapes. We surveyed 13 faba bean crops in northern France in 2019, and 19 in 2020. We sampled aphids (Aphis fabae and Acyrthosiphon pisum) and their antagonists (Syrphidae, Coccinellidae and mummy-forming parasitoids) on three dates during the spring, by visual observation. We assessed the floral resources provided by wildflower strips and spontaneous field margins and collected data on field management practices and land use in the surrounding landscape. We found that the percentage of flowering species in field edges providing accessible nectar to natural enemies had a positive effect on the abundance of Syrphidae and aphid mummies on faba bean plants. The positive effect of nectar resources on Syrphidae and aphid mummies decreased with increases in the proportion of semi-natural habitats in the landscape, but no interaction was observed with local management techniques. The growth rate of Aphis fabae and Acyrthosiphon pisum populations were unaffected by their antagonists. The growth rate of A. fabae populations was driven principally by local management practices (i.e. insecticide spraying and tillage). Conversely, the growth rate of A. pisum populations was driven principally by landscape composition (i.e. the proportion of semi-natural habitats and leguminous plants) and was negatively related to insecticide use. Nevertheless, insecticide spraying did not prevent increases in the growth rates of both aphid species, highlighting the need for alternative methods for controlling aphid populations.

Dynamical behavior of a stage-structured Huanglongbing model with time delays and optimal control

In this paper, we propose a delayed Huanglongbing transmission model with latent period and incubation period in the citrus trees. The basic reproductive number for Huanglongbing is calculated, meanwhile, the threshold dynamics and the global attractivity of equilibria are analyzed. Furthermore, to investigate the effects of insecticide spraying and symptomatic infected trees removing, we make use of the optimization theory and the two time-dependent control variables to establish the optimal control system, and investigate the existence and uniqueness of the optimal solution. Numerical simulations are carried out in both models to show the feasibility of our theoretical results. Our numerical results illustrate that (i) spraying insecticide plays an important role in controlling the spread of HLB, (ii) ignoring stage structure of infected trees would underestimate the transmission risk of HLB.

Screening organic repellent compounds against Lutzomyia longipalpis (Diptera: Psychodidae) present in plant essential oils: Bioassay plus an in silico approach

In the Americas, Lutzomyia longipalpis is the most relevant sand fly species for the transmission of visceral leishmaniasis. For its vector control in Brazil, insecticide spraying has not shown persistent reduction in disease prevalence while some sand fly populations are reported resistant to the insecticides used in spraying. The usage of repellents and personal protection behavior can reduce vector borne diseases prevalence. Therefore, the search for new repellent compounds is needed to use together with insecticide spraying, especially from natural sources to overcome the resistance developed by some sand fly populations to the compounds commercially used. In silico strategies have been applied together with repellency bioassays successfully identifying new bioactive compounds from natural sources. Thus, the present study aimed to screen repellent potential of neem (Azadirachta indica), citronella (Cymbopogon winterianus), bushy matgrass (Lippia alba) and ‘alecrim do mato’ (Lippia thymoides) essential oils against L. longipalpis and to identify potential repellent compounds by chemical analysis and in silico approach. Plant essential oils were extracted from leaves and repellency bioassays were performed on volunteers using colony reared L. longipalpis. Aside from neem oil, all other tested essential oil has shown a reduced number of sand fly bites using higher concentrations. Chemical composition from oils was assessed and its compounds were screened on a pharmacophore model using odorant binding protein 1 (OBP1). All essential oils were majorly composed of either oxygenated monoterpenes, except for the oil extracted from neem which was composed of sesquiterpene hydrocarbons. Molecular docking was performed with the compounds that best superimposed in the OBP1 pharmacophore model, identifying those binding to OBP4, which is associated with insect repellency behavior. Citronellol, Citronellol acetate, Citronellal and Geranyl acetate showed similar interactions with OBP4 binding site as DEET. Thus, it is suggested that these compounds are able to bind to L. longipalpis OBP4 generating repellent behavior in sand flies.

Impact of Different Sowing Windows and Legume Intercrops on the Incidence of Fall Army Worm (FAW) (Spodoptera frugiperda) and Yield of Hybrid Maize in Western Agro Climatic Zone of Tamil Nadu

The present investigation was undertaken during the Kharif and Rabi seasons of 2019 to study the influence of different sowing windows and intercropping of legumes on the level of infestation of fall armyworm on maize crop. Three dates of sowing were adopted in each season and intercrops like cowpea, soybean, sunnhemp, and tephrosia were included besides sole maize with and without insecticide sprays. The results showed that the maize sown during July and October months has reported less FAW infestation and provided a higher grain yield than the rest of the sowing windows taken in Kharif and Rabi seasons, respectively. The maize intercropped with cowpea and sunnhemp has performed well in terms of yield and the leaf damage was also found to be lower apart from the insecticide applied maize crop.

Residual efficacy of Fludora Fusion against Anopheles arabiensis in simple huts in Ethiopia.

Emergence and spread of malaria vectors resistant to the available insecticides required a new and efficacious insecticide. Residual efficacy of Fludora® Fusion was evaluated against insecticide susceptible Anopheles arabiensis in ten circular huts similar to the residential huts. Fludora® Fusion WP-SB 56.25, FICAM WP80 and Clothianidin WG70 were sprayed, by experienced technician, on interior wall surfaces: paint, dung, smooth mud, and rough mud. WHO cone bioassays were carried out a month after spraying and thereafter on monthly intervals for 12 months. Knockdown was recorded at 60 minutes and mortality at 24 hours, 48 hours and 72 hours holding time post-exposure. Fludora Fusion induced 100% An. arabiensis mortality during the first four months post-treated on all surface types at 24 hours holding time post-exposure. Its activity remained over 80% from the fifth to the twelfth month post-treated on the surfaces with the exception of two assessment points, at seventh month and eleventh month, on paint and smooth mud surfaces. FICAM induced 100% mortality rate during the first 4 months and 92% mortality during the fifth month post-treatment on painted surfaces. Its activity was over 96% mortality 1-month post-treatment on smooth mud and rough mud surfaces and 92% mortality 2-month post-treatment on dung surfaces. Clothianidin caused 89% and 86% mortality 1-month post-treatment on smooth mud and rough mud surfaces. Fludora Fusion can be used as alternative indoor residual insecticide spraying against An. arabiensis in Ethiopia.