Insecticide Deposits Research Articles

Bean weevil Acanthoscelides obtectus (Say) survival and progeny production affected by residual insecticide deposits, and related damage of two types of bean

The bean weevil, Acanthoscelides obtectus (Say) is a serious pest of stored bean seeds. In an effort to improve current management programs the intention of our study was to assess in the laboratory the impact of insecticide deposits on weevil survival and progeny production after 0, 7, 14, 30, 75, 120 and 165 days of residual activity on beans, and the related bean damage. Two bean types (Gradištanac and Biser) were dusted by malathion (10 mg AI/kg, DP formulation), and treated by water dilutions of spinosad (1 mg AI/kg, SC formulation) and two deltamethrin products, either without the synergist piperonyl butoxide – PBO (0.25 mg AI/kg, SC formulation) or with PBO (0.25 mg AI/kg + 2.25 mg AI/kg, EC formulation). Weevil survival was assessed after 2, 7 and 14 days of exposure and after 0 and 7 days of recovery. Progeny production and damage (kernel damage and weight loss), were assessed after additional 8 weeks. Malathion residual deposits showed the highest effectiveness on survival (no survived weevils), while deltamethrin deposits with PBO were the least effective, i. e at the same level or lower than weevil survival in untreated beans. The highest impact in terms of progeny production and damage were showed by the residual deposits of both deltamethrin formulations (no progeny or damage). In the presence of spinosad and malathion deposits, we recorded low progeny and damage, significantly under the economic threshold. No significant differences between Gradištanac and Biser types were recorded in treatments, while higher progeny and damage we recorded by the control Gradištanac bean than the Biser type, which exceeded economic threshold. Our data show that residual deposits of all tested insecticides on bean kernels demonstrated high control potentials against A. obtectus but deltamethrin deposits, especially with PBO, caused high variation in weevils response.

Tallgrass prairie wildlife exposure to spray drift from commonly used soybean insecticides in Midwestern USA

Insecticides are widely used in the Midwestern USA to combat soybean aphids (Aphis glycines), a globally important crop pest. Broad-spectrum foliar insecticides such as chlorpyrifos, lambda-cyhalothrin, and bifenthrin (hereafter, “target insecticides”) are toxic to wildlife in laboratory settings; however, little information exists regarding drift and deposition of these insecticides in fragmented tallgrass prairie grasslands such as those in Minnesota, USA. To address this information gap, target insecticide spray drift and deposition were measured on passive samplers and arthropods in grasslands adjacent to crop fields in Minnesota. Samples were collected at focal soybean field sites immediately following target insecticide application and at reference corn field sites without target insecticide application. Target insecticides were detected 400 m into grasslands at both focal and reference sites. Residues of chlorpyrifos, an insecticide especially toxic to pollinators and birds, were measured above the contact lethal dose (LD50) for honey bees (Apis mellifera) up to 25 m from field edges in adjacent grasslands. Chlorpyrifos residues on arthropods were below the acute oral LD50 for several common farmland bird species but were above the level shown to impair migratory orientation in white-crowed sparrows (Zonotrichia leucophrys). Deposition of target insecticides on passive samplers was inversely associated with distance from field edge and percent canopy cover of grassland vegetation, and positively associated with samplers placed at mid-canopy compared to ground level. Target insecticide deposition on arthropods had an inverse relationship with vertical vegetation density and was positively associated with maximum height of vegetation. Tallgrass prairie with cover ≥25 m from row crop edges may provide wildlife habitat with lower exposure to foliar application insecticides. Prairie management regimes that increase percent canopy cover and density of vegetation may also reduce exposure of wildlife to these insecticides.

A colorimetric test for the evaluation of the insecticide content of LLINs used on Bioko Island, Equatorial Guinea

BackgroundInsecticide-treated nets and indoor residual spraying of insecticides are used as the vector control interventions in the fight against malaria. Measuring the actual amount of deposits of insecticides on bed nets and walls is essential for evaluating the quality and effectiveness of the intervention. A colorimetric “Test Kit” designed for use as a screening tool, able to detect the type II pyrethroids on fabrics and sprayed walls, was used for the first time to detect deltamethrin on long-lasting insecticidal nets (LLINs) deployed on Bioko Island, Equatorial Guinea.MethodsLLINs were analysed using the colorimetric Test Kit performed in situ, which leads to the formation of an orange-red solution whose depth of colour indicates the amount of type II pyrethroid on the net. The kit results were validated by measuring the amount of extracted insecticide using high-performance liquid chromatography (HPLC) with diode array detection (DAD).ResultsDeltamethrin concentration was determined for 130 LLINs by HPLC–DAD. The deltamethrin concentration of these nets exhibited a significant decrease with the age of the net from 65 mg/m2 (< 12 months of use) to 31 mg/m2 (> 48 months; p < 0.001). Overall, 18% of the nets being used in households had < 15 mg/m2 of deltamethrin, thus falling into the “Fail” category as assessed by the colorimetric Test Kit. This was supported by determining the bio-efficacy of the nets using the WHO recommended cone bioassays. The Test Kit was field evaluated in situ and found to be rapid, accurate, and easy to use by people without laboratory training. The Test Kit was shown to have a reliable linear relationship between the depth of colour produced and deltamethrin concentration (R2 = 0.9135).ConclusionThis study shows that this colorimetric test was a reliable method to assess the insecticidal content of LLINs under operational conditions. The Test Kit provides immediate results and offers a rapid, inexpensive, field-friendly alternative to the complicated and costly methods such as HPLC and WHO cone bioassays which also need specialist staff. Thus, enabling National Malaria Control Programmes to gain access to effective and affordable monitoring tools for use in situ.

Pyrethroid Exposure Reduces Growth and Development of Monarch Butterfly (Lepidoptera: Nymphalidae) Caterpillars.

Insecticide exposure has been identified as a contributing stressor to the decline in the North American monarch butterfly Danaus plexippus L. (Lepidoptera: Nymphalidae) population. Monarch toxicity data are currently limited and available data focuses on lethal endpoints. This study examined the 72-h toxicity of two pyrethroid insecticides, bifenthrin and β-cyfluthrin, and their effects on growth and diet consumption. The toxicity of bifenthrin to caterpillars was lower than β-cyfluthrin after 72 h. Survival was the most sensitive endpoint for bifenthrin, but diet consumption and caterpillar growth were significantly reduced at sublethal levels of β-cyfluthrin. Using AgDRIFT spray drift assessment, the aerial application of bifenthrin or β-cyfluthrin is predicted to pose the greatest risk to fifth-instar caterpillars, with lethal insecticide deposition up to 28 m for bifenthrin and up to 23 m for β-cyfluthrin from treated edges of fields. Low boom ground applications are predicted to reduce distances of lethal insecticide exposure to 2 m from the treated field edge for bifenthrin and β-cyfluthrin. Growth and survival of fifth-instar monarch caterpillars developing within the margins of a treated field may be significantly impacted following foliar applications of bifenthrin or β-cyfluthrin. These findings provide evidence that pyrethroid insecticides commonly used for soybean pest control are a potential risk to monarch caterpillars in agricultural landscapes.

Plant-Derived Insecticides Under Meta-Analyses: Status, Biases, and Knowledge Gaps.

Plant-derived or botanical insecticides are biopesticides experiencing substantial ongoing increase in interest. The 74 years of our literature survey tracked over 2500 papers on botanical insecticides published between 1945 and 2019 (Web of Science database). Such a survey allowed meta-analyses to recognize current status and biases of the studies providing important insights into the research topic. They include the recognition of the exponential growth of such studies since the 1990s, the prevalent interest on the Meliaceae plant species and a dozen additional families, although some 190 families have been investigated. The arthropods targeted by such studies were pest species (ca. 95%) with rather little attention devoted to non-target species (p < 0.001). This bias is followed by another one-mortality assessments are prevalent among target and non-target arthropod species when contrasted with sublethal assessments (p < 0.01). These omissions are pivotal, as they fail to recognize that sublethal effects may be as important or even more important than mortality, and that initial insecticide deposits quickly degrade over time leading to prevailing sublethal exposure. Furthermore, although the target of control is limited to few species, non-target species will be exposed and as such need to be factored into consideration. Thus, these biases in studies of botanical insecticides incur in knowledge gaps with potential consequences for the practical use of these compounds as pest management tools.

Evaluating insecticide coverage and determining its effect on the duration of control for navel orangeworm (Amyelois transitella Walker) (Lepidoptera: Pyralidae) in California almonds.

Insecticide application is essential to control navel orangeworm (Amyelois transitella) in California almonds (Prunus dulcis), but coverage is challenging. Laboratory and field trials were conducted from 2014 to 2017 to quantify insecticide deposition and duration of control. In the laboratory for filter paper, photolysis reduced the contact toxicity of bifenthrin, and its half-life was 6.2 days. For chlorantraniliprole applied in the field, there was 87-94% less insecticide deposited in the almond suture, the most vulnerable part of the nut, than on the hull. For chlorantraniliprole, adjuvant choice (alcohol ethoxylate versus mineral oil) affected both initial insecticide deposition and half-life. Chlorantraniliprole degradation was greater at 6.1 m than at 3 m for both adjuvants assessed, whereas contact mortality was similar at both heights for the alcohol ethoxylate adjuvant. The combination of photolysis and differential distribution of insecticide on the nut can account for the variable control observed in the field. This was particularly problematic in the upper canopy and adjuvant choice affected deposition and insecticide degradation. Less than 1% of the insecticide in the tank was deposited on the almond suture. These results demonstrating the fraction of the insecticide in the sprayer tank deposited on the nut target, combined with reduced coverage in the upper canopy are also applicable to the control of A. transitella in pistachio (Pistacia vera) and walnut (Juglans regia) orchards. © 2019 Society of Chemical Industry.

Evaluating insecticide coverage in almond and pistachio for control of navel orangeworm (Amyelois transitella) (Lepidoptera: Pyralidae).

Insecticide application is essential to control navel orangeworm (Amyelois transitella) in California almond and pistachios. Coverage is difficult because of tree height and applicator practices. Studies were conducted to characterize insecticide deposition by both ground and air, and to develop alternatives to the use of water-sensitive cards to assess spray coverage. We used almond challenge bioassays to demonstrate that insecticide application failed first in the upper canopy (5.2-6.1 m) when application speed exceeded 2.9 kph. In pistachios, we used filter paper and insecticide extraction from hulls to demonstrate that deposition increased with application volume. Typically, in ground applications, coverage decreased with height, whereas for application by air, coverage was greatest at the top of the canopy (6 m) and decreased as the spray penetrated the canopy. In the best ground applications there was no loss over height. We were able to demonstrate a dose-response relationship for methoxyfenozide using contact toxicity bioassays. Coverage was best at or below the recommended speed of 3.2 kph and improved when water volume increased. There was a 50% loss in insecticide efficacy at the height of 4-4.8 m; we suggest that future monitoring concentrate on this portion of the canopy. The best ground application provided uniform deposition throughout the canopy, whereas the applications by air were most effective in the upper canopy. The use of filter paper can provide information for chemical deposition and enable contact toxicity bioassays, whereas water-sensitive paper cannot do this. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Effects of Different Surfaces and Insecticide Carriers on Residual Insecticide Bioassays Against Bed Bugs, Cimex spp. (Hemiptera: Cimicidae).

The performance of five insecticides (bendiocarb, deltamethrin, DDT, malathion, and imidacloprid) using three application methods (oil-based insecticide films on filter paper, and acetone-based insecticide deposits on two substrates: filter paper and glass) was assessed against a susceptible strain of Cimex lectularius (L.) and two resistant strains of Cimex hemipterus (F.). Substrate type significantly affected (P < 0.05) the insecticide knockdown response of the susceptible strain in acetone-based insecticide bioassays, with longer survival time on filter paper than on the glass surface. With the exception of deltamethrin, the different diluents (oil and acetone) also significantly affected (P < 0.05) the insecticide knockdown response of the susceptible strain in the filter paper-based insecticide bioassays, with longer survival time with acetone as the diluent. For both strains of C.hemipterus, there were no significant effects with the different surfaces and diluents for all insecticides except for malathion and imidacloprid, which was largely due to high levels of resistance. The lower effectiveness for the insecticide acetone-based treatment on filter paper may be due to crystal bloom. This occurs when an insecticide, dissolved in a volatile solvent, is applied onto absorptive surfaces. The effect is reduced on nonabsorptive surfaces and slowed down with oil-based insecticides, whereby the oil forms a film on absorptive surfaces. These findings suggest that nonabsorptive surfaces should be used in bioassays to monitor insecticide resistance. If absorptive surfaces are used in bioassays for testing active ingredients, then oil-based insecticides should be preferably used.

Behavioral effects of sublethal exposure to a combination of β-cyfluthrin and imidacloprid in the bed bug, Cimex lectularius L.

Bed bugs (Cimex lectularius) are blood-feeding insect pests with public health relevance. Their rapid evolution of resistance to pyrethroids has prompted a shift to combination products that include both a pyrethroid and neonicotinoid insecticide. Insecticides have both a direct impact on mortality and an indirect effect on behavior. Thus, we assessed the sublethal effects of a widely used combination product containing β-cyfluthrin (a pyrethroid) and imidacloprid (a neonicotinoid), as unexpected behavioral changes after exposure have been known to affect efficacy of insecticides. We found that bed bugs exposed to sublethal doses of a combination product containing β-cyfluthrin and imidacloprid did not feed as effectively as untreated bugs. Their locomotion behavior was also reduced. However, aggregation in response to the presence of conspecific harborages was not affected by sublethal exposure. Bed bugs exhibit behavioral changes after sublethal exposure to a combination product that could affect pest management choices and outcomes. A reduction in host-finding efficiency and feeding could complement the lethal effects of the insecticide. Alternatively, reduced locomotion following exposure could limit ongoing contact with insecticide deposits. However, an overall reduction in movement indicates that treatments are unlikely to cause dispersal of bugs to adjacent dwellings. © 2016 Society of Chemical Industry.

Relative toxicity of insecticides to the crucifer pests Plutella xylostella and Myzus persicae and their natural enemies

The widespread and intensive use of conventional pesticides, particularly insecticides, presents a major risk to natural enemies of target pests, as well as to the environment in general. The aim of this study was to investigate the differential intrinsic toxicity of insecticides to two key pests of crucifers, Plutella xylostella and Myzus persicae and their respective hymenopteran parasitoids, Cotesia vestalis and Aphidius colemani. Such knowledge can help inform effective integration of insecticides and biological control in IPM systems. Three insecticides generally regarded as being compatible with natural enemies (abamectin, spinosad and indoxacarb) and one compound regarded as harmful to natural enemies (lambda-cyhalothrin) were examined. A comparative measure of the intrinsic toxicity of fresh deposits of insecticides on Chinese cabbage leaf discs was determined for both pest and parasitoids species after exposure to insecticide for 24 h and 120 h, and after 24 h exposure to insecticide plus 96 h on untreated leaf discs. Differences in the susceptibility of pests and parasitoids to different insecticides were marked for P. xylostella and C. vestalis, LC50 values being significantly lower for the pest species. Such differences were not observed for M. persicae and A. colemani. There was a direct relationship between dose, exposure time and toxicity for all insecticides tested. All insecticides tested showed lower toxicity to both parasitoids compared with P. xylostella, which suggests that for this pest species side-effects on parasitoids can be minimised through IPM practices that reduce exposure time to such non-target organisms.

Dissipation and decontamination of imidacloprid and lambda - cyhalothrin residues in brinjal

Residues ofimidacloprid at 20 g a.i. ha -1 and lambda - cyhalothrin at 15 g a.i. ha -1 were estimated quantitatively by HPLC/GLC in/on brinjal fruits. Initial deposits of insecticides were higher in imidacloprid than lambda - cyhalothrin. Initial deposits of 0.652 mg kg -1 of imidacloprid dissipated to 93.17 per cent on 10 th day. In lambda - cyhalothrin the initial deposits were 0.138 mg kg -1 which dissipated to 92.75 per cent on 10 th day. The degradation of imidacloprid was relatively higher as compared to lambda - cyhalothrin. Both imidacloprid and lambda - cyhalothrin had half - life values of 1.92 and 2.65 days, respectively on brinjal fruits. The safe waiting period for imidacloprid was found 4.70 days. In lambda - cyhalothrin, no waiting period is required after its application as the initial deposits were less than its MRL (0.3 mg kg -1 ).

Deposition from Ultra-Low Volume Application of Public Health Insecticides in a Hot Desert Environment.

Three insecticides commonly used for mosquito and sand fly control were applied 30 min to 3 h after sunset during June and July 2010, at Camp Buehring, Kuwait, to determine the relative quantity of pesticides to height and distance traveled in a hot desert environment. A BVA dilution oil was used for the control. Oil-based adulticides were sprayed using a truck-mounted Curtis DynaFog Maxi-Pro 4 ultra-low volume (ULV) sprayer. Malathion (Fyfanon ULV, 96% active ingredient [AI]), resmethrin (Scourge 4+12, 4% AI), pyrethrins (ULD BP-300, 3% AI), and BVA Spray 13 (100% refined petroleum distillate) were mixed with Uvitex optical brightener fluorescent dye and applied at 2 speeds on evenings when wind speed was less than 16.1 km/h (10 mph). Collection targets using biodegradable cotton ribbons (1 m×2.5 cm) were later read with a fluorometer to quantify the amount of insecticide deposited on targets set at heights of 15.2, 76.2, and 152.4 cm (6, 30, and 60 in.) and distances of 1.5, 6.1, 15.2, 30.5, 61.0, and 91.4 m (5, 20, 50, 100, 200, and 300 ft). Mean insecticide deposition across all distances was 31% on 76.2-cm targets and 49% on 152.4-cm targets, while 15.2-cm targets typically collected <20% of test spray. Mean ground temperatures were typically within 5°C of air temperatures at 152.4 cm and within 1 to 5°C of air at 15.2 cm or 76.2 cm. Collectively, mean insecticide deposition was 80% at or above 76.2 cm for all insecticides. This finding may explain in part why control of low-flying phlebotomine sand flies with ULV insecticides has been met with less than optimal success by US military forces deployed in the Middle East.

Aerial, ground and chemigation spray deposition on corn for the control of spodoptera frugiperda (lepidoptera: noctuidae)

Pesticides can be applied by aircraft, ground-sprayers or sprinkler irrigation. However, selecting the best option is complicated by the limited number of studies comparing these techniques. Thus, the objective of this work was to study the chlorpyrifos insecticide deposition applied by aircraft (30 L ha-1), tractor-mounted sprayer (200 L ha-1) and chemigation (70,000 L ha-1) for the control of Spodoptera frugiperda (J.E. Smith) in two corn (Zea mays L.) populations (70,000 and 100,000 plants ha-1). Active ingredient residue on the corn plant leaves was evaluated by gas chromatography, immediately and ten days after the treatments. Armyworm numbers in each plot and control were also evaluated. The experiment was set up in randomized blocks with four replications. Aerial and ground applications of chlorpyrifos led to greater active ingredient deposition in the leaves than chemigation. Neither plant population (70,000 and 100,000 plants ha-1) affected the insecticide deposition in the corn leaves. S. frugiperda control was similar for all three application methods. Chemigation, however, resulted in less deposition on the plants and consequently in a greater insecticide loss to the soil, which should be considered in environmental impact.

Chemical characteristics of aerosol insecticide deposition in indoor surfaces

We investigated the deposition rate of aerosol insecticide on through woollen surfaces inside a test chamber. Compared to floor surface, the deposition rate of aerosol insecticide active ingredient on table of 1m high was up to 2.07 times for piperonyl butoxide, 1.64 times for tetramethrin and 2.95 times for permethrin represented by 0.51, 0.37 and 0.23μgcm−2 for the three molecules, respectively. Application of the household used cleaning to the woollen table surface decrease these concentrations by 61.32%, 45.01% and 59.80% for the three pesticides respectively, this cleaning procedure still not efficient for the floor surfaces. Moreover, indoor conditions permit the removal of 46.42%, 21.92% and 14.35% of the table surface deposition rate after one week, for the three pesticides, respectively. These conditions ensure the removal of only 28.72%, 20.69% and 24.05% of the three deposit molecules respectively on floor surface.

The effects of different drying methods and sun exposure on the concentrations of deltamethrin in nets treated with K-O Tab®tablets

The method used to dry bednets after they have been treated with an insecticide solution may affect the levels of insecticide and the uniformity of the insecticide deposits on the dry nets. In an attempt to see how the drying method may affect the insecticide deposits on the dry net, and to select the best drying method, laboratory and field studies have recently been carried out (in the U.K. and Iran, respectively). Conventional polyester nets were each treated with a deltamethrin solution (made with one K-O Tab tablet in 500 ml water) and then dried, either while hanging vertically or laid horizontally on the floor, in the sun or shade. The concentrations of deltamethrin in 25-cm2 samples cut from the dry nets (from the inner folds, surface folds, and top and bottom of each net dried vertically, and from the upper and lower surfaces of each net dried horizontally) were then determined using high-performance liquid chromatography (HPLC). Drying the treated nets in the sun or the shade did not make a significant difference to deltamethrin concentrations on the nets. Mean deltamethrin concentrations were, however, higher on the lower parts of the nets that had been hung to dry vertically than on the upper parts of these nets, and greater on the upper surfaces of nets dried horizontally than on the lower surfaces of such nets. In general, the layers and folds of the nets that had been on the outside of the drying nets contained more deltamethrin than the inner folds. These patterns are consistent with the hypothesis that deltamethrin tends to accumulate at the points where the water from the insecticide solution evaporates from the drying nets and also, in the case of nets dried vertically, at the lower points of the drying nets (as the result of gravity). In order to obtain an even and adequate distribution of insecticide, it is therefore not necessary to dry the net in the shade. To achieve a uniform deposit of deltamethrin, the drying net should be folded as little as possible and dried quickly.

Effectiveness of the standard evaluation method for hydraulic nozzles employed in stored grain protection trials

In stored grains, smaller depositions and great variation with respect to theoretical insecticide doses are frequently found. The objective of this work was to study the effectiveness of the standard method (ISO 5682/1-1996) employed to evaluate hydraulic nozzles used in stored corn and wheat grain protection experiments. The transversal volumetric distribution and droplet spectrum of a model TJ-60 8002EVS nozzle were determined in order to calibrate a spraying system for an application rate of 5 L/t and to obtain theoretical concentrations of 10 and 0.5 mg/kg of fenitrothion and esfenvalerate, respectively. After treatment, the corn and wheat grains were processed and deposition was analyzed by gas chromatography. The type of grain did not have any influence on insecticide deposition and was dependent upon insecticide only. The insecticide deposits on the grains only reached 42.1 and 38.2% of the intended theoretical values for fenitrothion and esfenvalerate concentrations, respectively. These results demonstrate the ineffectiveness of the standard evaluation method for hydraulic nozzles employed in stored grain protection experiments.

A system to evaluate the performance of hydraulic nozzles used in stored grain preotection trials

We developed a system to evaluate the performance of hydraulic nozzles used in stored corn and wheat grain protection experiments. An insecticidal mix was used as test fluid to determine the transversal volumetric distribution and droplets spectrum of a model TJ-60 8002EVS hydraulic nozzle. A mobile application system was built to apply a rate equivalent to 5 L t-1 and obtain theoretical concentrations of 10 and 0.5 mg kg-1 of fenitrothion and esfenvalerate, respectively. The corn and wheat grains were spread out as a fine layer. Three glass slides (0.1 × 0.05 m) were placed on the top surface of the grains to ensure that the intended application rate was achieved. After treatment, the deposits on both matrices were analyzed by gas chromatography. The fenitrothion deposit was higher than esfenvalerate, and the deposit on wheat was higher than on corn grains (P &lt; 0.05). The deposits on the glass slides reached values of 100 and 93% of the intended theoretical fenitrothion and esfenvalerate concentrations, respectively. Deposits on the grains were lower than on the glass slides, with values of 64 and 52% of the intended theoretical fenitrothion and esfenvalerate concentrations, respectively. The results obtained demonstrate a high effectiveness of the method for evaluation of the performance of hydraulic nozzles when an insecticidal mix is used as test fluid. The factors that influenced insecticide deposition on glass slides and on grains are discussed in the present work.

Influence of Emulsifiable Concentrate Formulation on the Physical Properties of the Fluid, Spray Characteristics, and Insecticide Deposits on Stored Grains

In stored grains, smaller depositions and great variations with regard to theoretical insecticide doses are frequently found. The objective of this work was to evaluate the influence of the emulsifiable concentrate formulation on the physical properties of the liquid, volumetric distribution, droplet spectrum, and insecticide deposits on stored grains. To determine its physical properties, the applied mix was prepared at a concentration of 0.4% of commercial product. Volumetric distribution was used as an evaluation parameter in a model TJ-60 8002EVS hydraulic nozzle study, and clean water and insecticidal mix were used as test fluids. After the effective swath width (esw) had been determined for both fluids, an application system was built to apply theoretical concentrations of 10 and 0.5 mg kg-1 of fenitrothion and esfenvalerate, respectively. Mix viscosity was 82% higher than water viscosity; conversely, surface tension in the mix corresponded to 49% of the water surface tension value. For water and mix, esw values were 0.425 and 0.60 m, respectively. Deposits of both insecticides at the 0.60 m esw were significantly higher (P<0.05) than deposits at the 0.425 m esw. The results obtained demonstrate the great influence of emulsifiable concentrate formulation on the physical properties of the fluid, spray characteristics, and insecticide deposits on stored grains.

Insecticide drift deposition on noncrop plant surfaces and its impact on two beneficial nontarget arthropods, aphidius colemani viereck (hymenoptera, braconidae) and coccinella septempunctata L. (coleoptera, coccinellidae)

Drift of the pyrethroid insecticide lambda-cyhalothrin into field margins bordering wheat and its effect on nontarget arthropods was investigated under field conditions. Insecticide deposition on leaf surfaces of broad beans exposed within field margins at 1-, 2-, and 3-m distance from the field edge and directly within the crop was quantified using a fluorescent tracer. The toxicity of leaf deposits to the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae) and to larvae of the ladybird Coccinella septempunctata L. (Coleoptera: Coccinellidae) was estimated. Mean corrected mortalities of A. colemani were < 50% (1 m) and < 30% (2 and 3 m), and mortalities of C. septempunctata larvae were < or = 80% (1 m), < or = 67% (2 m), and < or = 52% (3 m) 12 and 24 h postexposure to drift deposits. High positive correlation coefficients proved the relationship between leaf deposits and mortalities of test organisms. The connection of drift deposit measurement and exposure bioassay provides a promising approach to determining effects of insecticide drift on nontarget arthropods. However, due to the patchiness of drift deposition on noncrop plant surfaces, risks to nontarget arthropods at defined distances from the sprayed crop are not highly predictable.

Efficacy, persistence, ground deposition, and human exposure of polymer-encapsulated lindane and chlorpyrifos used for control of the southern pine beetle

Formulations of lindane and chlorpyrifos were evaluated to determine if polymer encapsulation extended the duration of southern pine beetle (Dendroctonusfrontalis) control, reduced ground deposition, increased persistence on bark or reduced potential human exposure relative to emulsifiable concentrate formulations. Encapsulation did not extend efficacy or reduce ground deposition of either insecticide when compared with the standard emulsifiable formulations. Encapsulation extended residue persistence of chlorpyrifos on bark, but not of lindane. The potential risk of human exposure to bark which was still wet with chlorpyrifos was increased 2.2 times by encapsulation, whereas, similar exposure to lindane was unaffected by encapsulation. After the insecticides had dried on the bark, the encapsulated formulations reduced risk to lindane by approximately 90% and by 83 % for chlorpyrifos.