Ultra-low Volume Applications Research Articles

Ground-Based Pyrethroid Adulticides Reduce Mosquitoes But Not Nontarget Insects in Central Florida.

As stewards of public and environmental health, mosquito control agencies are rightfully concerned about impacts on nontarget organisms. This study examined the impact of a modern, pyrethroid based ground adulticide program using ultra-low volume applications in a metropolitan county in central Florida. Nontarget insects and mosquitoes were collected in a before-after control-impact design at 21 sites over 1.5 years. While mosquitoes were reduced, we found no evidence for reduction of nontarget insects, regardless of taxon. Night-flying Lepidoptera may experience greater risk than other nontarget taxa, but overall effects of adulticide missions on this group were low and inconsistent. Instead, meteorology, habitat, and phenology dominate patterns of nontarget abundance. Mosquito reduction was more clearly observed and corrected post-mission reduction was consistent with results expected in complex urban and suburban treatment zones.

A Future for Ultra-Low Volume Application of Biological and Selected Chemical Pesticides

There is now increasing awareness that Global temperatures are increasing and one result of this is the movement of more water from the Oceans up into the atmosphere. This increases the amount of rain falling which can have an impact on crops. While the rain can be welcome by the crops, the raindrops can remove any deposits of pesticides applied to control pests of crops, especially if the pesticide had been formulated to mix in water.

Benefits of ULV Application to Control Locusts in Caucasus and Central Asia

This paper discusses the state-of-the-art of Ultra-Low Volume (ULV) spray application with rotary atomisers in the Caucasus and Central Asian (CCA) region to control locusts. The technology is widely used around the world for locust control and promoted by the UN Food and Agriculture Organisation (FAO) as an effective and efficient control intervention that meets the scale and challenge posed by large area locust outbreaks. The technology utilises precisely controlled spray droplets in the range 50–100um using ready-to-use oil-based ULV formulations to target locusts more efficiently. Volume rates as low as 0.5–1.0 l/ha are utilised which greatly improves productivity of ground and aerial spray applications, timeliness, and reduces cost and waste of pesticide and water. ULV has become more widely adopted in CCA during recent years to control major economic pests such as Moroccan, Italian, and Asian migratory locusts. Its further adoption is hampered by the lack of available ULV formulations in the region and need for investment and training in the technology. ULV technology is highly appropriate for use of biological products to reduce risks to operators and the environment and efforts to increase regional cooperation and the registration of safer pesticides across the region present opportunities for its wider adoption.

A Future for Ultra-Low Volume Application of Biological and Selected Chemical Pesticides

A project to improve the yields of cotton in Rhodesia and Nyasaland involved a study on a key pest, the Red Bollworm (Diparopsis castanea), which included laboratory studies to determine the impact of certain insecticides, a change in spray equipment to minimise exposure of the operator to the spray and timing of sprays to control the first instar larvae.

Are Adult Mosquito Control Products (Adulticides) Harmful? A Review of the Potential Human Health Impacts from Exposure to Naled and Dichlorvos (DDVP)

We performed a thorough systematic review of published literature to determine potential links between human health impacts and naled, a registered adult mosquito control product (adulticide), and its major degradate, dichlorvos (DDVP). A search query was performed on 8 September 2023, capturing all articles published up to that date on the Scopus and PubMed databases. Inclusion criteria were the presence of either pesticide and a measured or modeled human health outcome or risk. The search string resulted in 382 articles; however, 354 articles were excluded, resulting in only 28 articles that met the inclusion criteria. The studies that directly relate to aerosolized ultra-low volume (ULV) mosquito control applications did not report any associated deleterious human health outcomes. Results from the reviewed papers displayed no negative health effects or led to inconclusive results. No studies showed adverse health effects from aerial ULV applications for mosquito management. Our findings are congruent with the United States Environmental Protection Agency and Centers for Disease Control and Prevention recommendations that aerial applications of naled, following label parameters, do not pose an adverse risk exposure to humans, wildlife, and the environment.

Evaluation of ultra-low volume treatments on Culex quinquefasciatus (Diptera: Culicidae) abundance and relative age by parity dissection.

St. Tammany Parish Mosquito Abatement District relies on ultra-low volume (ULV) insecticides to manage adult Culex quinquefasciatus (Say 1823), the primary vector of West Nile virus in Louisiana, but abundance rarely declines post-treatment. Three field ULV applications each of adulticides containing deltamethrin, naled, or resmethrin were conducted from May through October 2022 to measure efficacy against free-flying Cx. quinquefasciatus. Female mosquitoes trapped before and after treatment were identified, counted, and age-graded by parity dissection. No insecticide applications reduced Cx. quinquefasciatus abundance, but trials with deltamethrin and naled significantly lowered average mosquito age in the area post-treatment. No trials with resmethrin reduced mosquito age, which corroborates laboratory susceptibility data indicating local resistance toward the pyrethroid. These trials establish parity dissections and relative age gradation as a means of measuring treatment success against Cx. quinquefasciatus.

Field Assessment of Naled and Its Primary Degradation Product (Dichlorvos) in Aquatic Ecosystems Following Aerial Ultra-low Volume Application for Mosquito Control

Naled, an organophosphate insecticide, is applied aerially at ultra-low volumes over aquatic ecosystems near Sacramento, California, USA, during summer months for mosquito control. Two ecosystem types (rice fields and a flowing canal) were sampled in 2020 and 2021. Naled and its primary degradation product (dichlorvos) were measured in water, biofilm, grazer macroinvertebrates, and omnivore/predator macroinvertebrates (predominantly crayfish). Maximum naled and dichlorvos concentrations detected in water samples one day after naled application were 287.3 and 5647.5 ng/L, respectively, which were above the U.S. Environmental Protection Agency’s aquatic life benchmarks for invertebrates. Neither compound was detected in water more than one day after the application. Dichlorvos, but not naled, was detected in composite crayfish samples up to 10 days after the last aerial application. Detections in water from the canal showed that the compounds were transported downstream of the target application area. Factors such as vector control flight paths, dilution, and transport through air and water likely affected concentrations of naled and dichlorvos in water and organisms from these aquatic ecosystems.Graphical

Avian assemblages are maintained after aerial applications of ULV fenitrothion for control of the Australian plague locust (Chortoicetes terminifera (Walker)) in arid and semiarid agroecosystems

Context Risk assessments currently undertaken to approve pesticides for use against locusts in Australia are predominated by laboratory-generated data, often collected from non-endemic species. Very little information exists concerning the potential ecological effects of insecticides used for locust control. Aim To determine the effect of aerial ultra-low volume (ULV) applications of the organophosphorous insecticide, fenitrothion (used for locust control), on avian assemblages in arid and semiarid agro-ecosystems. Methods Avian abundance was surveyed in pesticide-exposed and unexposed locations during standard locust control operations, using fenitrothion, in western New South Wales and Queensland in the spring and summer of 1996, 1997 and 2000, using a transect-point method. Temporal changes in assemblages were analysed using multi-dimensional ordination (MDS) and permutational analysis of variance (PERMANOVA) with PRIMER (V7). Key results Avian assemblages varied over time, independent of pesticide application, reflecting significant redistribution and mobility of birds across a highly disturbed agricultural landscape, irrespective of pesticide exposure. Additionally, pesticide exposure did not affect species abundance or diversity. Conclusions There was no evidence that ultra-low volume (ULV) applications of fenitrothion, currently used in locust control, are impacting avian assemblages, despite previous research indicating that individual birds co-occurring with spray operations suffer suppressions in the enzymatic biomarker for OP exposure, plasma acetylcholinesterase (AChE). Implications Although the risk to avian assemblages associated with the aerial application of locusticides is reduced by the small proportion of the landscape where locust control activities are focused, any change in spray application parameters would necessitate a re-evaluation of the risks associated with insecticide exposure.

Reduced Potential for Consecutive Truck-Mounted Ultra-Low Volume Mosquito Adulticide Applications in Chicago Metropolitan Area Due to Weather Conditions.

To increase the effectiveness of adult mosquito control, more frequent ultra-low volume (ULV) applications have been suggested. In the Chicago area, weather may be a limiting factor to more frequent applications. To investigate this, ULV adulticidal application dates from the Northwest Mosquito Abatement District during June 2011 to September 2020 were compared to historical weather data-wind and rain patterns to determine optimum conditions for conducting ULV treatments. During the 85 applications performed during 2011-20, there would have been an opportunity, based on weather conditions, for an additional consecutive night for about half (48.2%) of the time. These opportunities diminished with each additional application. The most intensive response possible would have been a spray of 5 consecutive nights, which occurred once in 3 of the 10 years investigated.

Desert locust (Schistocerca gregaria Forskal) and its management: A review

The desert locust [Schistocerca gregaria (Forskal)] (Orthoptera: Acrididae) is one of the world’s most dangerous and destructive migratory pests. It is a highly voracious and polyphagous insect. Its swarms can travel hundreds of kilometers per day and infest areas covering millions of square kilometers, resulting in substantial crop losses. We synthesize published research data and reports on the life cycle, behavior, phases, and damage of the desert locust, as well as its possible management practices, in this study. There are diffi-culties involved in estimating locust populations because locust swarms are highly mobile. Cultural control, baiting, dusting with insecticide, and spraying liquid insecticides (chemical or biological) using ultra-low volume (ULV) application are all options for control-ling locust swarms. Improved knowledge on pest biology, as well as more efficient monitoring and control strategies, are essential com-ponents of an effective management strategy.

When vector control and organic farming intersect: Pesticide residues on rice plants from aerial mosquito sprays

Conflicts often exist between the use of pesticides for public health protection and organic farming. A prominent example is the use of insecticides for mosquito control in rice fields designated for organic farming. Rice fields, with static water and other conducive conditions, are favorable mosquito habitats. Best management practices are urgently needed to ensure the integrity of organic farming while addressing the need for public health protection. In this study, we evaluated aerial ultra-low-volume (ULV) applications of two classes of mosquito adulticides, pyrethrins and organophosphates, and their deposition and residues on rice plants throughout an active growing season in the Sacramento Valley of California. Frequent applications of pyrethrin synergized with piperonyl butoxide (PBO) and rotating applications of synergized pyrethrins and naled, an organophosphate, were carried out on two large blocks of rice fields. Aerial ULV application of either synergized pyrethrins or naled was able to generate uniform droplets above the fields with high efficacy for mosquito control. Rice leaf samples were collected before and after a subset of applications, and rice grains were sampled at harvest. Frequent applications of synergized pyrethrins resulted in some accumulation of the synergist PBO on rice leaves, but pyrethrins and naled dissipated rapidly from the leaves after each application with no noticeable accumulation over repeated applications. At harvest, no detectable residues of the pesticides or PBO were found in the rice grains. The absence of pesticide residues in the rice grains at harvest suggested that the ULV aerial application led to deposition of only very low levels of residues on rice plants during the growing season. When coupled with the short persistence and/or poor mobility of the insecticides, such applications resulted in negligible pesticide residues in rice grains.

Potential of Outdoor Ultra-Low-Volume Aerosol and Thermal Fog to Suppress the Dengue Vector, Aedes aegypti, Inside Dwellings.

A field study investigated penetration of outdoor ground ultra-low-volume (ULV) aerosol and thermal fog adulticide applications into a dwelling to control the dengue vector Aedes aegypti (L). Four applications of Kontrol 4-4 (4.6% permethrin active ingredient [AI], 4.6% piperonyl butoxide) at the maximum label rate were made at 25-30 m in front of a house at Camp Blanding Joint Training Center, Starke, FL, during summer 2016. The ULV sprayer and thermal fogger nozzles were oriented horizontally, and vehicle travel speeds were 16 and 24 km/h, respectively. All doors and windows of the house were left open. Spray efficacy was assessed using caged female mosquitoes positioned 30 cm above ground, outside and inside of the house. Interior cages were placed in open areas and cryptic sites (i.e., in a closet or cardboard box). A spinner holding 2 rods sized 3 mm × 75 mm was deployed next to each cage (except cryptic sites) to sample droplets and to quantify AI deposition. Thirty minutes after application, cages were removed, slides collected, and mosquitoes transferred to clean cages in the laboratory where mortality was assessed at 24 h posttreatment. The ULV application to the south side of the house produced 100% mortality in outdoor and indoor cages and 24% mortality at cryptic sites. Similarly applied thermal fog resulted in 85% mortality outdoors, 34% indoors, and only 4% in cages at cryptic sites. Application of either method from the west resulted in 19-61% mortality outdoors and 0.5-6.5% indoors. Droplet volume median diameter (Dv0.5) on rods from the ULV application was significantly larger compared with the thermal fogger outdoors, but similar indoors. Outdoors and indoors, the AI deposition from ULV was significantly higher than from thermal fog. Our results show the potential for controlling dengue vectors inside houses with outdoor ground ULV applications in areas where doors and windows are left open for ventilation.

Distance Diminishes the Effect of Deltamethrin Exposure on the Monarch Butterfly, Danaus plexippus.

The monarch butterfly, Danaus plexippus (Lepidoptera: Nymphalidae), is threatened by substantial loss of habitat, extreme weather events linked to global climate change, and nontarget impacts of broad-spectrum insecticides. To investigate the impact of chronic ingestion of pyrethroids on monarchs, wild-type Florida D. plexippus were reared on milkweed (Asclepias curassavica) that was exposed to ultra-low volume applications of DeltaGard by a truck-mounted fogger, at distances of 25 and 50 m. We observed significant negative impacts on monarchs reared on milkweed at 25 m from the DeltaGard spray route, including significant decreases in survival, and significantly longer development times, compared with untreated controls. Larvae reared on host plants closest to the truck spray route were 3 times more likely to experience a mortality event than the control cohort in trial 1 and 6 times in trial 2. Survival of monarch caterpillars reared on milkweed sprayed at 50 m was not significantly different from controls. For monarchs that survived to adulthood, we did not observe statistically significant differences among cohorts for variables measured. These data demonstrate that ultra-low volume treatments of pyrethroids can result in significant mortality in monarchs, but that the effects diminish with distance from the spray route.

Entomological Efficacy of Aerial Ultra-Low Volume Insecticide Applications Against Aedes aegypti (Diptera: Culicidae) in Mexico.

A cluster-randomized controlled trial quantified the entomological efficacy of aerial ultra-low volume (AULV) applications of the insecticide chlorpyrifos against Aedes aegypti in Puerto Vallarta, México, during November–October 2017. The trial involved 16 large (1 × 1 km) clusters distributed between treatment-control arms. Primary endpoint was the abundance of Ae. aegypti indoors (total adults, females, and blood-fed females) collected using Prokopack aspirators. After four consecutive weekly cycles of AULV, all adult Ae. aegypti infestation indices were significantly lower in the treatment arm (OR and IRR ≤ 0.28). Efficacy in reducing indoor Ae. aegypti increased with each weekly application cycle from 30 to 73% (total adults), 33 to 76% (females), and 45.5 to 89% (blood-fed females). Entomological indices remained significantly lower in the treatment arm up to 2 wk after the fourth spraying round. Performing AULV spraying can have significant and lasting entomological impact on Ae. aegypti as long as multiple (ideally four) spray cycles are implemented using an effective insecticide.

EFFICACY OF ULTRA-LOW VOLUME DISINFECTION WITH HYDROGEN PEROXIDE VAPOUR IN A POULTRY HATCHERY

Good hygiene in the hatcheries is one of the most important factors for normal hatching, low embryonic mortality and healthy chickens. The best disinfectant in these sites should combine high antimicrobial efficiency, lack of damages on the eggs and embryos, and has to be harmless for the staff and the environment. One of the few disinfectants which meets all these conditions is hydrogen peroxide. This study presents data on the effectiveness of disinfection with hydrogen peroxide vapour in a poultry hatchery. Nocolyse One Shot disinfectant (Oxy Pharm, France), containing 12% hydrogen peroxide and silver ions was used, which was applied by Nocospray (an ultra-low volume application device, Oxy Pharm, France) in a dose of 5 mL per 1 m3. The results obtained show high efficiency of the disinfection treatments. The achieved microbial reduction in the hatchers was in the range from 95.51% (1.35 log10) for the floor to 99.89% (2.95log10) for the air. The reduction of microbial contamination during the processing of hatching eggs was in the rate of 99.75% (2.6 log10). The high efficiency of the treatments, the low toxicity and ecological safety of the hydrogen peroxide and the ease way of its application are the reasons to extend the implementation of the method in hatchery hygiene practices.

Ultra-Low Volume Application of Spinosad (Natular 2EC) as a Residual in a Hot-Arid Environment Against Aedes aegypti.

The invasive Aedes aegypti is an important disease vector increasing in frequency in hot-arid regions of the USA such as the Southwest. Within hot-arid surroundings this mosquito may be confined to peridomestic locations that tend to be cooler and humid, such as in lush, irrigated ornamental vegetation surrounding homes. However, to reach these habitat refugia, ultra-low volume (ULV) applications of insecticides targeting this mosquito must retain efficacy after being sprayed from the air or street where hot-arid conditions are prevalent. We investigated the efficacy of a biologically based larvicide, spinosad (Natular 2EC), applied as a ULV in a hot-arid environment targeting Aedes aegypti. We found that this pesticide is able to penetrate this environment and has the potential to act as a residual.

Ultra-Low Volume Application of Spinosad (Natular 2EC) Larvicide as a Residual in a Tropical Environment Against Aedes and Anopheles Species.

We investigated the efficacy of a liquid larvicide, Natular 2EC® (spinosad), applied with ultra-low volume sprayer as a residual application during the dry season in southeastern Thailand against 4 medically important species-Aedes aegypti, Ae. albopictus, Anopheles dirus, and An. minimus. We found that this larvicide could be applied as a residual to dry areas known to collect water and potentially still be effective after rains or irrigation, which could increase the flexibility and efficiency of an integrated vector management program targeting these species. This investigation also demonstrated, for the 1st time, efficacy of spinosad against An. minimus and An. dirus.

Effect of Travel Speed on Dispersion of Aqualuer 20-20 Sprayed by a Truck-Mounted Ultra-Low-Volume Sprayer Against Caged Aedes aegypti1.

The effect of travel speed of a truck-mounted ultra-low-volume (ULV) sprayer on its application efficacy was studied at St. Johns County Fairground, Elkton, FL, during summer 2015. The efficacy was assessed by spray deposition, droplet size spectrum, and 24-h mortality of caged adult Aedes aegypti, using 2 rows of sampling locations, 15 m apart and spread up to 122 m from the spray. Each location had a bioassay cage and an impinger droplet sampler, 1 m apart from each other, at 1.5 m off the ground. Aqualuer® 20-20 (20.6% permethrin AI and 20% piperonyl butoxide) was applied at the maximum label rate, travelling at 8, 16, and 32 km/h. Three replications were completed on 3 days at least a week apart, with 1 replication of each travel speed per day. On each application day the travel speeds were rotated. Overall, a travel speed of 32 km/h achieved the highest efficacy of Aqualuer® 20-20, followed by 16 km/h, and then 8 km/h, in an open field. In general, droplet size, deposition, and mosquito mortality increased with increasing travel speed. The increased travel speed will also enhance the work rate of a sprayer and operator, thus reducing the cost of ULV applications.

Quantitative Analysis of Aedes albopictus Movement Behavior Following Sublethal Exposure To Prallethrin.

The pyrethroid prallethrin, an AI in DUET™ (Clarke Mosquito Control, St. Charles, IL), is widely marketed ultra-low volume (ULV) mosquito adulticide. Volatilized prallethrin is intended to stimulate mosquito flight, increasing its adulticide effectiveness. However, field tests using volatilized prallethrin have not produced significant differences in mosquito trap catches, leading to questions regarding prallethrin's behavioral impact efficacy. Thus, we conducted laboratory tests of prallethrin's effect on flight behavior of adult female Asian tiger mosquitoes, Aedes albopictus. Mosquitoes were divided into 3 groups: untreated control, exposed to volatilized prallethrin, and exposed to a liquid spray calibrated to simulate a ULV application at label rates. After exposure, mosquito behavior in an airstream of 0.5 m/sec was recorded and analyzed using motion-tracking software. No significant differences in flight behavior were found between the control and treated mosquitoes exposed to volatilized prallethrin. The ULV-sprayed mosquitoes exhibited a significant increase in the number of flight events, the turning frequency, overall movement speed, and flight speed compared to the control-a significant difference in locomotor stimulation response that would increase exposure to a ULV spray cloud. However, our results showed that volatilization alone was insufficient to increase ULV efficacy in the field and suggested that incorporating a more volatile flight stimulant into ULV adulticides would provide a measurable improvement in mosquito control.

Field cage insecticide resistance tests against Culex quinquefasciatus Say (Diptera: Culicidae) in Harris County, Texas, U.S.A.

The ground adulticiding program in densely populated Harris County has been employed on the basis of virus-positive mosquitoes almost exclusively using the 'rotation of chemicals best practices' stratagem. To evaluate its effectiveness, 15 comparative field cage testing events were conducted from 2011-2015 using seven wild population samples from repeatedly collected locations of Culex quinquefasciatus Say and a laboratory susceptible Sebring strain colony reared to adults. A 3 × 3 plot design was employed for exposure to ultra-low volume applications of malathion and synergized permethrin. No significant differences were found in mortality rate among testing dates, year, row placement, or relative humidity. Mortality was significantly different between adulticides (p<0.001) with mean mortality rates for malathion 96.42% (±7.95%) and permethrin 92.38% (±14.04). There was a significant temperature difference for permethrin (p<0.001) but none for malathion (p=0.644). Mosquito population mortality was statistically different by study operational area (p<0.011) and chemical (p<0.001). Susceptible colony adults used as positive controls downwind strongly aided determination of efficacy and resistance to each adulticide, providing evidence of individual application coverage, though comparative analysis was done with overall mortalities by normal methodology.