Granular Pesticides Research Articles

CHILO INFUSCATELLUS SNELLEN'S (LEPIDOPTERA: PYRALIDAE) BIOLOGY AND ITS MANAGEMENT

SUGARCANE stem borer, Chilo infuscatellus is the most devastating pest, causing huge economic losses in the sub-tropics and therefore requiring effective management strategies. The current research was conducted to study the biology and management of C. infuscatellus. Moreover, we checked the efficacy of Trichogramma chilonis and granular insecticides against this key pest. Theincubation period for C. infuscatellus was 2.30 days, with a total developing time of 23.30 days for the larvae and 5.90 days for the pupa. Male and female C. infuscatellus had a 36.80-day and 38.00-day total life span, respectively, with the female living longer (4.8 days) than the male (3.90 days). The total female fecundity was 315.90 eggs with a 90.87 egg hatchability rate. The mean percent parasitism (87.01%) and percentage of adult emergence (76.11%) of T. chilonis on C. infuscatellus were both very high, with a total developmental time of 8.74 days in laboratory environment. Additionally, there were notable differences between the findings on the effectiveness of granular pesticides and T. chilonis in the field. The plot treated with Fipronil had the least mean percent infestations (3.58%), followed by Carbofuran (4.26%), and T. chilonis (5.63%). The control plot had the highest mean incidence of infestations (13.34%). Future IPM initiatives should incorporate the introduction of Trichogramma or the utilization of Fipronil @ 16 kg ha-1 for the treatment of C. infuscatellus. This practice will play a critical role in environmental protection and natural resource conservation against insecticides.

Predicting rice pesticide fate and transport following foliage application by an updated PCPF-1 model

The Pesticide Concentration in Paddy Field (PCPF-1) model has been successfully used to predict the fate and transport of granular pesticides applied to the paddy fields. However, it is not applicable for pesticides in foliar formulation while previous studies have reported that foliar application may increase the risks of rice pesticide contamination to the aquatic environment due to pesticide wash-off from rice foliage. In this study, we developed and added a foliar application module into the PCPF-1 model to improve its versatility regarding pesticide application methods. In addition, some processes of the original model such as photodegradation were simplified. The updated model was then validated with data from previous studies. Critical parameters of the model were calibrated using the Sequential Uncertainty Fitting version 2 (SUFI-2) algorithm. The calibrated model simulated pesticide dissipation trend and concentrations with moderate accuracy in the two paddy compartments including rice foliage and paddy water. The accuracy of the predicted soil concentrations could not be evaluated since no observed data were available. Although the p-factor and r-factor obtained using the SUFI2 algorithm indicated that the uncertainty encompassed in the predicted concentrations was rather high, the daily predicted pesticide concentrations in rice foliage and paddy water were satisfactory based on the NSE values (0.36–0.89). The updated PCPF-1 model is a flexible tool for the environmental risk assessment of pesticide losses and the evaluation of agricultural management practices for mitigating pesticide pollution associated with rice production.

Optimised dispensing of predatory mites by multirotor UAVs in wind: A distribution pattern modelling approach for precision pest management

Multirotor unmanned aerial vehicles (UAVs), or drones, are increasingly being used to spray liquid pesticides to control emerging pest infestations in field crops. In recent years, UAVs have been used to release predatory mites and other natural enemies to optimise and promote sustainable pest management practices by relying less on conventional insecticides. Drone dispensed samples of predatory mites are typically mixed with a granular material, vermiculite, which serves as a filler. The low density of the vermiculite and weather conditions (mainly wind), influences the distribution pattern of predatory mites when delivered by a UAV-based system. The purpose of this paper is to present a data-driven methodology to develop a mathematical model that can be used to optimise UAV-based autonomous dispensing of predatory mites. The model characterises the distribution of vermiculite as a function of wind speed and direction, and the UAVs altitude and forward speed. The model is constructed by first conducting outdoor experiments and then using machine-learning techniques on the collected data. The constructed model produced an average generalisation error of 12.8%, RMSE. Due to its parametric and predictive nature, the model is amenable for the future design of UAV flight controllers that can compensate for the targeting error caused by wind. The proposed modelling methodology could be useful not only for the dispensing of predatory mites, but also for other UAV dispensing applications, such as liquid or granular pesticide deliveries.

Performance evaluation of lysimeter experiments for simulating pesticide dissipation in paddy fields. Part 1: Submerged application of granular pesticides.

Three-year comprehensive experiments were conducted to compare the dissipation patterns of a total of 16 pesticides, including 3 metabolites, as granular formulations applied in lysimeters and paddy fields with two soil types. Analytical concentrations of the target pesticides in paddy water were analyzed using a granular kinetic model consisting of the following parameters: release rate, decrease rate, and dissolved concentration. Results of parameter grouping analyses of the kinetic models showed that 56% of data reproducibility (entire grouping) was obtained between replicates for the lysimeters. In comparisons between the lysimeters and paddy fields, 48% of decrease rates and 34% of release rates were grouped, although significant differences were observed with a nearly 90% difference for dissolved concentrations. These differences might be attributed to the hydrological components such as water management and meteorological covariates in paddy fields, the daily percolation in lysimeters and the adsorption-desorption kinetics between paddy water and soil.

Probabilistic risk‐assessment model for birds exposed to granular pesticides

For granular formulations of pesticides, direct consumption by birds is generally the most important route of exposure. A probabilistic exposure model was developed that estimates how many pesticide granules a bird ingests and, from that, the quantity of pesticide ingested. This model, referred to as the "granular pesticide avian risk assessment model" (GranPARAM), has input variables not included in current screening-level assessments for granular pesticides, such as proportion of time for which birds forage in the field, grit ingestion rates, attractiveness of pesticide granules compared with natural grit, and proportions of soil particles and pesticide granules in the size range consumed by birds. For input variables that are uncertain, variable, or both, distributions are used rather than point estimates. Monte Carlo analysis is then performed to propagate input variable uncertainties through the exposure model for granular pesticides. The outputs from the exposure portion of GranPARAM are estimated pesticide doses for each of 20 birds of a selected species on each of 1000 fields. The dose for each bird is compared with a randomly chosen dose from the dose-response curve for that species or an appropriate surrogate. If the exposure dose for a bird exceeds the randomly chosen effects dose, the bird is considered dead; otherwise, the bird is assumed to be alive. Thus, the risk output from GranPARAM is a bar chart showing the percentages of fields with 0/20 dead birds, 1/20 dead birds, 2/20 dead birds, and so forth.

Refined avian risk assessment for aldicarb in the United States

AbstractAldicarb was recently reviewed by the US Environmental Protection Agency (USEPA) for re‐registration eligibility. In this paper, we describe a refined avian risk assessment for aldicarb that was conducted to build upon the screening‐level methods used by USEPA. The goal of the refined ERA was to characterize and understand better the risks posed by aldicarb to birds in areas where the pesticide is applied. Aldicarb is a systemic insecticide sold in granular form under the trade name Temik®. It is applied directly to soil and is used to control mites, nematodes, and aphids on a variety of crops (e.g., cotton, potatoes, peanuts). Consumption of grit is necessary for proper digestion in many bird species, particularly for granivores and insectivores. Thus, aldicarb granules may be mistaken for grit by birds. The Granular Pesticide Avian Risk Assessment Model (GranPARAM) is described in a companion paper and was used to estimate the probability and magnitude of effects to flocks of birds that frequent aldicarb‐treated fields. One hundred thirty‐five exposure scenarios were modeled that together include a range of bird species, crops, application methods and rates, and regions in the United States. The results indicated that, even for the most sensitive bird species, the risks associated with the agricultural use of granular aldicarb are negligible to low. There are several reasons for the limited risk: 1) the Temik formulation includes a gypsum core and a graphite coating and is black in color, all of which have been shown to be unattractive to birds, and 2) the pesticide is applied subsurface and rapidly dissolves following contact with water. The fact that no bird kill incidents involving appropriate label uses of aldicarb have been conclusively documented in the United States over its 38 years of use supports the results of this refined risk assessment. Integr Environ Assess Manag 2010; 6:83–101. © 2009 SETAC

Development of a Dry Applied Dispersible Granular Pesticide Carrier

Abstract Granular pesticide carriers that possess high quality attributes are needed. Some of the main considerations with which pesticide formulators and users contend include physical durability, flowability, ballistics properties, chemical compatibility, favorable econometrics, and pesticidal efficacy. An evaluation of the commercially available mined and recycled materials, as well as an analysis of the requirements for efficacious granules, has led the researchers to define a combination of criteria that was previously unrealized in any of the selections of the then commercially available granular pesticide carriers. The research objective that emerged, developing a more optimal pesticide granule, was defined by these criteria. Many dozens of prototype formulations were produced in a laboratory granulation system and were evaluated by various physical test methods until the original design criteria were met. Subsequently, a period of field efficacy trials took place in which suitability for particular active ingredients, target pests, and cultural conditions was determined. An engineered composite granule and production process was developed during the course of this research. The resulting granules have a unique combination of characteristics: robust enough to withstand the physical stresses of bulk handling, formulating and field application, good flowability and compositional characteristics, plus a unique degree of dispersion upon the application of a small amount of moisture over the treated area after the granules have been applied. This post-application water dispersion mechanism appears to allow enhanced pesticidal efficacy for soil treatment and systemic active ingredients, and has demonstrated numerous aesthetic and hazard reduction attributes of interest. The resulting material has competitive economics, and has been patented and trademarked as DG Lite®.

Agricultural Granule Particle Size Considerations

Abstract When developing a granular pesticide formulation, the choice of an appropriate particle size is crucial. Particle size may or may not affect the desired performance parameters. Some of the properties to consider are sorptivity, bulk density, particle count per unit weight, hardness, drift potential, and application pattern. Depending on the nature of the carrier, particle size has little effect on bulk density and sorptivity. Particle size affects particle count per unit weight, drift potential, and possibly application pattern.

Characterization of grit in arable birds to improve pesticide risk assessment

To describe the grit in bird gizzards, we examined the gizzard content of some 200 birds of varying size and diet (e.g., granivores and nongranivores). Grit use (frequency, size, amount, and shape) was characterized for 27 bird species that forage, at least part of the year, on arable land in the Netherlands. Three different groups could be recognized: the nongranivores with predominantly small “grit” particles (the result of inadvertent ingesting soil while foraging), the granivores with larger grit particles (the result of intentionally selecting soil particles), and the group in between (omnivores), which shows features of both other groups. Sample calculations made in this article show a probability of 3–277 in 1000 times for unintentionally consuming one granule. Therefore, attention should also be paid to nongranivorous birds when assessing the hazard or risk of the use of granular pesticide formulations. A risk assessment model is presented in the Appendix.

Influence of Daily Grit Consumption Rate and Diet on Gizzard Grit Counts

We evaluated the relationship between the number of grit particles in gizzards and the grit consumption rate. House sparrows (Passer domesticus) were given, via oral gavage, doses of 9, 18, 36, 72, 144, 288, or 576 particles/day, and northern bobwhites (Colinus virginianus) were given 9, 18, 36, 72, 144, or 288 particles/day. Test birds were fed either a hard food (wild bird seed mix) or soft food (canned dog food) diet and were given equal numbers of grit particles from 3 different size classes (house sparrows: 0.2-0.4, 0.6-0.8, and 1.2-1.4 mm; northern bobwhites: 0.6-0.8, 1.4-1.7, and 2.4-2.8 mm). For both species, the number of grit particles in gizzards increased as dose increased, but the percentage that the gizzard grit count constituted of the daily grit dose decreased at higher doses. The fact that the birds eliminated large amounts of grit at the higher dose levels but retained most of the grit at lower levels suggests that birds need a certain target amount of grit in their gizzards. As daily grit dose increased, house sparrows on a hard diet had more small and medium-size grit in their gizzards than did house sparrows on a soft diet; the amount of large grit was similar between diets. As the daily grit dose increased, northern bobwhites had more small and medium-size grit in their gizzards than large grit. The high grit counts for some northern bobwhites may have resulted from incomplete flushing of the gizzard grit before dosing began. Our study improved upon previous efforts to evaluate the relationship between gizzard grit counts and grit consumption rates and provides information useful in assessing the potential for avian exposure to granular pesticides.

Effects of exposure time, material type, and granular pesticide on glove contamination.

Chemical-resistant gloves are recommended for pesticide applicators to reduce their exposure to agricultural chemicals. In this research, three chemical-resistant glove materials-nitrile, neoprene, and barrier laminate-were studied in relation to contamination with granular terbufos and tefluthrin. Surfaces of specimens backed with alpha cellulose were contaminated with 300 mg of either granular terbufos or tefluthrin for 1-, 2-, 4-, 8-, 16-, and 24-h time periods in petri dishes in the laboratory. Residues were extracted using ethyl acetate for terbufos and iso-octane for tefluthrin in test tubes for 24 h. Analysis of extracts by gas chromatograph and statistical analysis of the data showed that contamination levels varied with the time of exposure, material type, and pesticide used. Pesticide was not detected in the alpha cellulose even after 24 h contamination time. A linear relationship was found between contamination level and exposure time for terbufos in the three materials, with longer exposure times causing higher contamination levels. Contamination of nitrile was significantly less than neoprene or barrier laminate. Exposed glove materials contained higher levels of contamination of terbufos than tefluthrin.

Applicability of Granular Pesticides in Long-mat of Hydroponically Grown Rice Seedlings used for Transplanting

Applicability of Granular Pesticides in Long-mat of Hydroponically Grown Rice Seedlings used for Transplanting

TECHNICAL NOTES: EFFECT OF AGGLOMERATED CORNCOB ADDITIVE ON SPREADER PERFORMANCE OF CORNCOB CARRIER PRODUCT

Agglomerated corncob fines have been proposed by the primary supplier of ground corncob, as an additive toground corncob for use as a granular pesticide carrier, but how much agglomerated corncob product can be added withoutchanging spreader rate or pattern performance is not known. Pesticide formulations on plain corncob and cob amended with5, 10, and 20% agglomerated cob material were evaluated for pattern and rate effects in three homeowner rotary spreadersand for rate effects in three homeowner drop spreaders. Two of the three rotary spreaders had differences in pattern skewing.Rate changes due to material were noted with five of the six spreaders, but changes were not consistent with the percentageof agglomerated material added. It is necessary to test each formulation using agglomerated corncob additive to determinewhether setting changes will be required on the product labels.

Dibber Drill for Precise Placement of Seed and Granular Pesticide

The objective of the work was to produce a lightweight dibber drill, employing simpler mechanisms than previous experimental designs, capable of precisely metering small doses of granular pesticide with each seed. A simple, novel solution to the problem of transfer, acceleration and delivery of seeds and granules from a slow speed, 0·2 m/s, cell wheel metering system into a high-speed, 1·8 m/s, dibber placement system using a venturi air jet device was developed. A compact dibber wheel employing pneumatically actuated, rapid-acceleration dibber plungers was also produced. High-speed video was used for visualizing and refining seed transfer trajectories and dibber plunger timing control. Using lettuce as a benchmark crop, the new drill performed equally well (84% emergence) to its more complicated predecessor (82%) and significantly better than a conventional coulter drill (71%).

Bird response to grit and pesticide granule characteristics: Implications for risk assessment and risk reduction

Granular pesticides (insecticides and nematicides) pose a hazard for birds because of the potential for birds to ingest the granules. Avian risk from granular pesticides is currently assessed by using a U.S. Environmental Protection Agency risk index based on the acute toxicity of the pesticide, the pesticide concentration on the granules, and the number of granules available on the soil surface after application (LD50/ft2). Recent evaluations have demonstrated that avian response to pesticide granules as a source of grit also can influence exposure to pesticide granules; such information should be included in the risk assessment process. Herein we review the limitations of the current risk assessment process and summarize the extant information regarding bird response to grit and granule characteristics (i.e., granule carrier type, color, size, shape, and surface texture) and pesticide load per granule. Suggestions are made for assessing and reducing avian risk from granular pesticides by testing granular formulations against standards for various granule characteristics and by using frequency distributions of avian responses to granules. Granule characteristics selected as standards should be similar to grit used by free-ranging birds (e.g., silica particles, earth-tone hues). Comparisons of granular formulations against the standards would demonstrate the potential for birds to consume pesticide granules as grit, relative to naturally occurring particles. Frequency distributions constructed for grit sizes used by birds and gizzard grit counts can be used to estimate the effect of granule size and pesticide load per granule, respectively, on avian risk. Because bird response to pesticide granules is highly variable, we recommend using probabilistic approaches when assessing avian risk from pesticide granules to account for the ranges of response.

Evaluation of bird repellent additives to a simulated pesticide carrier formation

No-till agriculture involves the use of pelleted and granular pesticides and chemically treated seeds. Some of these products kill birds. The present experiments were designed to investigate whether four candidate repellents (methyl anthranilate, ortho-aminoacetophenone, d-pulegone, and pine oil) would reduce consumption by European starlings ( Sturnus vulgaris) of clay particles similar in size and shape to particles normally used for pesticide delivery. All substances reduced consumption ( P < 0.05), although none completely eliminated it. To achieve further reductions in consumption, other particle characteristics might be considered. These include the use of colors that make particles indistinct from the substrate, and a texture or particle size that diminishes the likelihood that particles will be ingested as grit.

Modelling the incidence of virus yellows in sugar beet in the UK in relation to numbers of migrating Myzus persicae

1. The incidence of virus yellows diseases in sugar beet crops in eastern England during 1965–96 was analysed in relation to numbers of migrating Myzus persicae, the principal vector. 2. A non‐linear model was fitted to the data incorporating dual routes of infection: primary infection, arising from winged immigrant aphids carrying the virus, and secondary infection, arising from local dispersion of their wingless offspring transferring the virus from infected to uninfected plants. 3. The model was fitted to the data assuming that (i) the epidemic commenced when the first migrating aphid was recorded, (ii) the rate of primary infection was dependent on the total number of aphids migrating up to the end of June, and (iii) the rate of secondary infection was dependent on the proportion of diseased plants in the crop. 4. A good description of virus yellows incidence in August depended on allowing the rate parameters for primary and secondary infection to decrease sigmoidally over the years during 1965–96. The shape of this function depicted a major change in the epidemiology of virus yellows since 1974–76. Amongst several contributory factors, this change coincided with the introduction and subsequent wide use of systemic granular pesticides. 5. Good fits also depended on allowing the rates of disease progress to decay with time to accommodate effects of increasing host resistance with plant age to feeding aphids. This meant that early epidemics rose faster than late epidemics, which is consistent with general observations. 6. Given that the changes in the epidemiology of virus yellows over the years are associated with improvements in pest management practices, the model presents a useful extension to disease forecasting by providing predictions of disease risk in the absence of pesticides. Such predictions indicate that during the last decade up to five severe epidemics would have been likely.

Effects of application rate on avian risk from granular pesticides

AbstractFensulfothion was formulated on silica granules to evaluate the relationship between avian risk of adverse effects from granular pesticides and granule availability. Captive house sparrows (Passer domesticus) were offered the granular pesticide in bands on soil surfaces at application rates of 50, 100, 200, 400, 800, 1,200, 1,600, or 2,000 LD50/ft2. Individual pesticide granules were formulated with ½ the LD50 for house sparrows (0.3 mg/kg). Bird behavior, survival, and brain cholinesterase activity were used to assess pesticide exposure. A significant negative correlation between brain ChE activity and the natural logarithm of application rate indicated that the relationship between avian risk and granule availability was asymptotic rather than linear. Thus, the assumption, implicit in the LD50/ft2 risk index, that the potential exposure of birds to granular pesticides increases as granule availability increases may result in overestimates of risk to birds from granular pesticides, particularly at higher granule application rates.

Effects of granular pesticide formulations and soil moisture on avian exposure

AbstractTwo experiments were conducted to evaluate the influence of granular carrier type, pesticide load per granule, and soil moisture on avian risk of adverse effects from granular pesticides. Bird behavior, survival, and brain and plasma cholinesterase activity were used to assess exposure. In the first experiment, silica and corncob granules formulated with fensulfothion at either 1/2 or 1/32 of the median lethal dose (LD50) were offered to captive house sparrows (Passer domesticus) in bands on dry soil. The corncob carrier and granules formulated with 1/2 the LD50 presented the greatest risk to birds. In the second experiment, fensulfothion was formulated on three carrier types (silica, clay, and corncob) and offered to house sparrows in bands on wet or dry soil. Overall, formulations with corncob as the carrier and dry soil conditions presented the greatest risk to birds. Wet soil conditions reduced the risk of adverse effects for all three granular carrier types, but the greatest risk reduction occurred with corncob and silica granules. Differences in adverse effects associated with various carrier types and soil moisture conditions can add complexity when assessing risk to birds from granular pesticides.

Reducing bird repellent application rates by the addition of sensory stimuli

Red-winged Blackbirds ( Agelaius phoeniceus ) cause substantial damage to a variety of crops throughout North America. Nonlethal methods for controlling damage are generally ineffective, and environmental and cost concerns have limited the availability of chemical repellents such as methiocarb. One means of potentially lowering the effective application rate of methiocarb and similar aversive compounds is by combining the treatment with sensory cues. We tested groups ( n = 4) of male Red-winged Blackbirds in a series of 4-day feeding trials using brown rice treated with 0.025% (g/g) methiocarb, five times less than the previously established effective bird repellent rate. Each methiocarb treatment suppressed rice consumption, whether the repellent was alone or combined with a visual (red dye) and/or volatile (methylpyrazine) cue. When rice treated with just the sensory cues was subsequently presented, the red dye, but not the methylpyrazine, continued to deter feeding on rice. These results show that postingestive chemical repellents such as methiocarb can be effective at reduced rates provided the repellent is paired with an aversive visual cue. The addition of aversive stimuli may be particularly useful in reducing damage to seeded crops and in protecting birds from incidental ingestion of toxic granular pesticides.