Granular Formulations Research Articles

Preemergent Bittercress Control on a Gravel Groundcover

Abstract Bittercress (Cardamine hirsuta) is a problem weed year round in Southeastern U.S. container nurseries. It readily establishes itself on gravel production surfaces and in containers, producing seeds in 4 to 5 weeks. Gravel has limited adsorption sites for herbicides, and higher use rates are required for control. Many preemergent herbicides provide short-term (3 month) control of bittercress. Sprayable formulations provided more persistent control than granular formulations. Factor (prodiamine) and Goal (oxyfluorfen) controlled bittercress for 8 months at 2× normal rates under nursery conditions of daily irrigation. Half-lives of Factor and Goal were 3 and 1 month, respectively. Extraction of herbicides from the gravel indicated that bittercress was controlled by 0.31 ppm of both herbicides.

Chlorpyrifos: Ecotoxicological Risk Assessment for Birds and Mammals in Corn Agroecosystems

A tiered risk assessment was conducted for the use of granular and liquid formulations of chlorpyrifos in corn agroecosystems in the U.S. The initial screening Tier I assessment suggested that under high-exposure scenarios the granular and some spray formulations present potential hazards to birds. Higher tiered probabilistic risk assessments were conducted separately for the granular and liquid formulations. The probabilistic assessment indicated that risk to birds from exposure to granular formulation is small and that this route of exposure would not be a significant source of mortality. Similarly, the assessment of potential exposure of birds to food items contaminated with chlorpyrifos showed that the risk from exposure via food was small, even if it was assumed that birds feed only on the treated fields. Although they have potentially greater sensitivity to chlorpyrifos, effects in nestling birds consuming food items from fields treated with granular chlorpyrifos were negligible. However, risks to young birds may be greater where the major source of food is from fields treated with liquid formulations of chlorpyrifos. A review of field studies showed that wildlife mortality incidents associated with use of either granular or liquid formulations of chlorpyrifos are not widely apparent in agroecosystems. Based on the multiple lines of evidence, we conclude that the presumption that chlorpyrifos use in corn agroecosystems will result in extensive mortality of terrestrial wildlife, particularly birds and mammals, is not supported by the scientific evidence.

Effects of Storage on Viability and Efficacy of Granular Formulations of the Microbial Herbicides Alternaria alternata and Trematophoma lignicola

Alternaria alternata Pesta (gluten matrix) granules stored at 12% relative humidity were still viable and infective, giving total control of Amaranthus retroflexus after 24 months storage. Viability of the propagule in the granule was an important factor of the evaluation test and not just the viability of the granule. The concentration of inoculum in the granule was important, with 10 5 to 10 6 conidia g -1 being the ideal, since lower concentrations may not be able to out-compete the soil micro-flora. Even with soil application, the effect of local humidity was still important. Trematophoma lignicola was also formulated as microbial herbicide granules but the conidia were severely damaged in the production process.

Response of bobwhite quail and gray-tailed voles to granular and flowable diazinon applications

We used gray-tailed voles (Microtus canicaudus) and northern bobwhite quail (Colinus virginianus) as experimental model species to field test whether small mammals and birds respond differently to equivalent concentrations of a pesticide applied in granular and flowable formulations. In mid-May 1998, we placed voles into 15, 0.2-ha enclosures planted with a mixture of pasture grasses. In mid-July, we placed quail into the same enclosures with the voles. In late July, we applied the organophosphorus insecticide diazinon in five treatments; a control (all habitats sprayed with water), liquid formulation of diazinon at 0.55 kg/ha, liquid formulation of diazinon at 1.11 kg/ha, broadcast of granular diazinon at 1.11 kg/ha, and broadcast of granular diazinon at 2.22 kg/ha. The diazinon treatment in liquid and granular formulations did not depress population size or growth rate, or survival rate of voles. We found a significant difference in the survival rate of the quail between the controls and treatments; granular diazinon caused a measurable decline of quail survival, whereas the liquid application at an equivalent rate did not significantly affect quail survival. Analysis of our results suggests that ground-feeding birds are more susceptible to granular insecticides than flowable applications, but voles were not susceptible to either formulation at the rate we used.

Response of bobwhite quail and gray-tailed voles to granular and flowable diazinon applications.

We used gray-tailed voles (Microtus canicaudus) and northern bobwhite quail (Colinus virginianus) as experimental model species to field test whether small mammals and birds respond differently to equivalent concentrations of a pesticide applied in granular and flowable formulations. In mid-May 1998, we placed voles into 15, 0.2-ha enclosures planted with a mixture of pasture grasses. In mid-July, we placed quail into the same enclosures with the voles. In late July, we applied the organophosphorus insecticide diazinon in five treatments; a control (all habitats sprayed with water), liquid formulation of diazinon at 0.55 kg/ha, liquid formulation of diazinon at 1.11 kg/ha, broadcast of granular diazinon at 1.11 kg/ha, and broadcast of granular diazinon at 2.22 kg/ha. The diazinon treatment in liquid and granular formulations did not depress population size or growth rate, or survival rate of voles. We found a significant difference in the survival rate of the quail between the controls and treatments; granular diazinon caused a measurable decline of quail survival, whereas the liquid application at an equivalent rate did not significantly affect quail survival. Analysis of our results suggests that ground-feeding birds are more susceptible to granular insecticides than flowable applications, but voles were not susceptible to either formulation at the rate we used.

Changes in Serum Phenytoin Concentrations in Epileptic Patients Produced by Changing Phenytoin Preparation from Granular Form to a Novel 10% Powder.

Purpose: It is well known that there is a significant difference in the bioavailability of different preparations of phenytoin (PHT). A novel 10 % powder formulation of PHT (Aleviatino‐10 % powder), which was believed to have equivalent bioavailability to the tablet and granular formulations, was developed by Dainippon Pharmaceutical Co., LTD. in 1997. This lead us to switch 12 outpatients with epilepsy from the granular preparation of PHT (Aleviatino‐granules) to the novel 10 96 powder. Here, we report that changing the PHT formulation from the granular to the novel powder form produced a significant change in hioavailability. Methods: Subjects consisted of 8 men and 4 women with epilepsy; mean age, 32.7 years; range, 21–58 years; 2 generalized epilepsies and 10 localization‐related epilepsies recruited from the outpatient clinics. The dose of the granular form of PHT was 90‐390 mg/day (mean, 258.3 mg/day). Four patients received only PHT and the remaining patients received PHT and at least 1 other AED. The serum PHT concentrations were determined prior to and more than 2 weeks after changing the formulations. We used the same dose for each preparation, and the dose of any other anticonvulsant drug taken by the patients was not changed during the study. Results: The mean serum PHT level was significantly elevated from 9.66 to 19.51 pg/ml after switching the patients to the 10% powder formulation (p < 0.01). The mean ratio of serum PHT concentrations (S, pg/ml) to dose (D, mgikgiday), i.e. S/D ratio, was also increased significantly from 2.1 to 4.3 after switching preparations (p < 0.01). A decrease in the dose (mean, 85 %) was required in 6 patients. There was a significant positive correlation between extent of the elevation of serum PHT concentration after switching to the 10 % powder and serum PHT concentration before the switch (r = 0.86, p c 0.0003). Furthermore, the elevation of serum PHT levels in the patients receiving only PHT was significantly greater than that in the patients receiving 1 or more other anticonvulsants (p < 0.05). Cuncbsion: These results suggest that the 10% powder formulation of PHT (Aleviatino‐10% powder) has a significantly greater bioavailability than the granular form (Aleviatino‐granules). Therefore, one must be vigilant when switching patients from one formulation of PHT to another, particularly in patients receiving only PHT. In addition, upon switching, one should consider adjusting the dose to decrease the likelihood of adverse effects and interactions between PHT and other anticonvulsants.

Targeted spot vegetation management inPinus radiataandP. elliottiiplantations, Tsitsikamma, South Africa

SYNOPSIS Towards the end of 1995, granular herbicides were introduced in South African forestry. Traditionally, weed control was done by manual slashing or herbicides were applied by knapsack sprayer. Targeted, spot herbicide application is more environmentally friendly, less expensive and easier manageable than traditional weed control methods. Three formulations of hexazinone each at four rates, including a control of manual slashing were applied to two different crop species, i.e. Pinus radiata D. Don and P. elliottii Engelm., planted in herbaceous shrub vegetation (fynbos/macchia). Two granular formulations of hexazinone, a 10% and 20% active ingredient (a.i.) and a 24% liquid formulation, were tested together with a control. Herbicide rates were applied on equivalent a.i. basis to each tree for the three formulations, so that equivalent a.i. rates could be statistically compared. Tree height and diameter were measured three and twelve months after application, to determine efficacy of the treatments....

Experimental vertebroplasty using osteoconductive granular material.

Osteoporotic human cadaveric thoracic vertebral bodies and vertebral bodies from mature sheep were used as model systems to assess coral resorption and new bone formation after injection of coral granules. To evaluate the use of natural coral exoskeleton, an osteoconductive material, for the filling of vertebral bodies. Percutaneous injection of polymethylmetacrylate (PMMA) is often proposed for prophylactically stabilizing osteoporotic vertebral bodies at risk for fracture or augmentation of vertebral bodies that have already fractured. Recently, the possibility of using osteoconductive materials in granular formulation was assessed in pilot studies. As a first step, the possibility of injecting coral granules percutaneously within osteoporotic human cadaveric thoracic vertebral bodies was assessed. As a second step, cavities were drilled into vertebral bodies of 10 mature ewes and were either left empty (control group) or filled with coral alone (CC) or coral supplemented with fibrin sealant (CC+FS). Quantitative evaluation of coral resorption and new bone formation was made 2 months and 4 months after implantation. The distribution of coral granules injected into human cadaveric thoracic vertebral bodies was homogenous as assayed radiographically. In the experimental animal model, osteogenesis was increased in cavities filled with coral in comparison with cavities left empty at both 2 months and 4 months (P < 0.005 and P < 0.02, respectively). Surprisingly, supplementation of coral with a fibrin sealant had no positive influence on osteogenesis (P < 0.0008 at 2 months; P < 0.002 at 4 months). In addition, it led to an increase in coral resorption by as soon as 2 months (P < 0.0008). These results demonstrate the osteoconductivity of coral in granular form for vertebral filling. Interestingly, interconnectivity between adjacent bone trabeculae and newly formed bone was restored; however, its mechanical significance remains to be determined. Further investigations are needed to evaluate the efficacy of coral in osteopenic animals and in relieving pain.

New method of acephate application to potted plants for control of Aphis gossypii, Frankliniella occidentalis and Bemisia tabaci

A novel method for delivering the systemic insecticide acephate was tested with chrysanthemums and gerbera daisies. The method involves applying the insecticide to the interior surface of plant pots in paint. Two paints were tested, a latex paint and SpinOut, a paint already in use for controlling plant growth. The SpinOut used lacked the cupric hydroxide component used to limit root elongation. Acephate, in the form of Orthene WPS, was applied to the pots in two separate experiments. The first was a dose-response experiment with four rates (0, 5, 15, and 25 mg/pot) to test the efficacy of acephate in paint using caged melon aphids on chrysanthemum plants conducted over a 23 day period. In this experiment Orthene in paint was also compared with a granular acephate formulation, Pinpoint 15G. The second was conducted on gerbera over 60 days and tested the efficacy of Orthene-painted pots in controlling caged melon aphids and free-flying western flower thrips and silverleaf whiteflies. In this experiment 5 rates (0, 8, 41.25, 82.5, and 165 mg/pot) of Orthene were used. In both experiments the efficacy of Orthene was compared with that of the standard rate of Pinpoint (165 mg/pot). In addition to efficacy, a marketability score of the plants and the phytotoxic effects of the two formulations were compared. Results showed that applying acephate in painted pots is a viable alternative to granular application. It reduced the effects of phytotoxicity, at equivalent rates lasts as long as the granular application, and at lower rates provides improved control over melon aphids, western flower thrips, and silverleaf whiteflies. Interestingly, the paint used may have an effect. Better control was obtained with Orthene in latex paint at lower rates and for longer than Orthene in SpinOut. It is not clear whether this was due to toxicity of latex paint, better release of acephate from latex, or possibly a synergistic effect of the latex paint.

Efficacy of aqueous suspension and granular formulations of Bacillus thuringiensis (Vectobac) against mosquito vectors

The efficacy of aqueous suspension (AS) and granular (G) formulation of Bacillus thuringiensis var. israelensis (Vectobac) was tested against the immatures of mosquito vectors in the laboratory and under field conditions. Laboratory tests showed that the aqueous suspension was relatively more effective against Culex quinquefasciatus than Aedes aegypti and Anopheles stephensi, the respective LC 50 values being 0.046, 0.060 and 0.190 mg/l. In stream pools, with the application of Vectobac AS at 1.2 l/ha, more than 80% reduction in immature density of Anopheles larvae (Anopheles fluviatilis and Anopheles culicifacies) was observed for 2–8 days, and at 2.4 l/ha for 3.5–9.0 days. At the dosage of 7.0 kg/ha of the granular formulation, a reduction in immature density by more than 80% was observed for 2–9 days. In polluted habitats such as cesspits, U-drains and cement tanks, the effectiveness of Vectobac AS lasted for 1–4 days when applied at 1.2 and 2.4 l/ha, and Vectobac G was effective for 1–3 days at application rates of 7.0 and 14.0 kg/ha against C. quinquefasciatus. There was no significant difference in the effectiveness between the two formulations and the two application rates.

Enhanced ambient storage stability of an entomopathogenic nematode through anhydrobiosis

Limited shelf-life is a major obstacle to large-scale use of entomopathogenic nematodes in biological control. Recently, the development of a water-dispersible granular formulation (WG) containing entomopathogenic nematodes was described. This paper reports that storage stability of Steinernema carpocapsae Weiser infective juveniles at 25 °C is enhanced from three to six months in this WG. It is also demonstrated that the enhanced stability is achieved through the induction of partial anhydrobiosis that reduces oxygen and lipid reserve utilization by infective juveniles. Nematode infectivity is unaffected during storage under partial anhydrobiosis in the WG formulation. © 2000 Society of Chemical Industry

Controlled release of aldicarb from carboxymethyl cellulose microspheres:in vitro and field applications

Aldicarb is a carbamate pesticide that is widely used throughout the world in the protection of crops (eg cotton, nuts, potatoes, onion, tobacco, sugar beet and sugar cane). In Turkey, especially in the Çukurova region, it is used for the control of the cotton white fly (Bemisia tabaci) which attacks cotton plants cultivated in this region. Aldicarb contamination in surface and ground water is a serious problem in several countries, partly due to its high water solubility. It is also highly toxic to mammals. In order to overcome these problems, microspheres of aldicarb were prepared using carboxymethyl cellulose (CMC) as the biodegradable support material cross-linked with aluminium chloride. A strong hysteresis behaviour was observed upon drying and reswelling. Encapsulation efficiency was in the range 12–23% and aldicarb contents of 5.7–10.3 mg per 100 mg of microspheres was achieved. In vitro release was distinctly Fickian, and Higuchi constants were very close to 0.5. Release in pots revealed that only one sample had a release capability for more than four weeks. In the cotton plot much longer durations of release (more than seven weeks) were observed while a commercial granular formulation released its content immediately. It was thus possible to construct a controlled pesticide release system that prolonged the bioavailability to about eight weeks. © 1999 Society of Chemical Industry

Controlled release of aldicarb from carboxymethyl cellulose microspheres:in vitroand field applications

Aldicarb is a carbamate pesticide that is widely used throughout the world in the protection of crops (eg cotton, nuts, potatoes, onion, tobacco, sugar beet and sugar cane). In Turkey, especially in the Cukurova region, it is used for the control of the cotton white fly (Bemisia tabaci) which attacks cotton plants cultivated in this region. Aldicarb contamination in surface and ground water is a serious problem in several countries, partly due to its high water solubility. It is also highly toxic to mammals. In order to overcome these problems, microspheres of aldicarb were prepared using carboxymethyl cellulose (CMC) as the biodegradable support material cross-linked with aluminium chloride. A strong hysteresis behaviour was observed upon drying and reswelling. Encapsulation efficiency was in the range 12-23% and aldicarb contents of 5.7-10.3 mg per 100 mg of microspheres was achieved. In vitro release was distinctly Fickian, and Higuchi constants were very close to 0.5. Release in pots revealed that only one sample had a release capability for more than four weeks. In the cotton plot much longer durations of release (more than seven weeks) were observed while a commercial granular formulation released its content immediately. It was thus possible to construct a controlled pesticide release system that prolonged the bioavailability to about eight weeks. # 1999 Society of Chemical Industry The control of pests often requires periodic applica- tion of pesticide to the crop using conventional formulations, eg powders, granules, or concentrated emulsions. These lead to significant levels of environ- mental pollution due to the application of extensive quantities of pesticide required to prolong effective- ness. Losses can occur due to wash-out, evaporation, surface run-off and dispersion to unintended regions, 1-3 which also has undesirable economical consequences. Such disadvantages can be overcome by providing low levels of the pesticide over the desired period using a bioactive material release system based on the diffusion of the bioactive compound through a matrix or membrane. 4-6

Observations of fire ants (Solenopsis invicta Buren) attacking apple snails (Pomacea paludosa Say) exposed during dry down conditions

Apple snails (Pomacea paludosa Say) in Florida wetlands and lakes must contend with water level fluctuations that periodically result in dry downs.1 In recent years we have conducted field and laboratory studies to investigate the impacts of such drying events on snail populations. Our research has focused mainly on direct mortality due to desiccation. However, during one laboratory study we identified a potential threat to snail populations from the red imported fire ant, Solenopsis invicta Buren. Since their introduction to Alabama around 1940, S. invicta has expanded its range to include all of Florida.2 S. invicta in Florida prefer disturbed sites in areas with a relatively high water table.3 The highly fragmented wetland systems of Florida provide the moisture levels and disturbance profile (periodic dry downs, as well as disturbed substrata along canals and levees) favored by S. invicta. Fire ants can be found along levees adjacent to parcels of the Everglades and Upper St. Johns River marsh, on tree islands, and along the margins of central Florida lakes (Darby, pers. obs.). Fire ant colonies were reported in up to 20% of alligator nests in central Florida lakes.4 During periods of inundation S. invicta emerge from their mounds and form floating balls, thus prolonging colony survival and aiding dispersal.5 Their adaptations to seasonal flooding and their highly successful invasion of Florida may reflect the evolution of S. invicta in South American ecosystems subjected to regular flooding.6 S. invicta are predators observed killing numerous invertebrate2,6,7 and vertebrate species4,8 and have been associated with biodiversity declines in the southeastern fauna.9 The distribution of S. invicta encompasses the entire range of the Florida apple snail. Given the critical position of the apple snail in the food web of Central and South Florida wetlands,10 vulnerability to S. invicta is of concern. We observed S. invicta attacking apple snails while conducting experiments on snail survival during dry down conditions. Ten tanks (120 cm 3 61 cm 3 46 cm), each with a sand substratum, were set up in a grassy area outside the Florida Caribbean Science Center (USGS-Biological Research Division, Gainesville, FL) in June 1998. S. invicta mounds were present in the grassy area around the tanks. These were treated throughout the experiment with a granular bait formulation of the insecticide hydramethylnon (AMDRO®). [S. invicta identification was verified at the USDA Red Imported Fire Ant Laboratory, Gainesville, FL]. Each tank contained 18–20 adult apple snails with mean (6SD) shell widths of 33.5 mm (63.5 mm). Four tanks were used as controls and kept filled with water, while the other six were Moll. Stud. (1999), 65, 507–510 © The Malacological Society of London 1999

A Field Experimentation on Bioremediation: Bioren

Most shoreline bioremediation strategies are based on the addition of limiting nutrients to contaminated environments to cause an acceleration of the natural biodegradation process. Before approval for operational use, these products designed to be used in the environment, should be validated in field trials to assure their efficiency in reducing residual contaminant concentrations and toxicity. This paper describes the design, implementation and preliminary results of an experimental field study to evaluate the effectiveness of the bioremediation agents BIOREN 1 and BIOREN 2 of interest to the EUREKA BIOREN program. The agents BIOREN 1 and 2 are proprietary formulations of nutrients synthesised from fish meal and they were proven effective in laboratory studies of the two granular nutrient formulations. BIOREN 1 is unique in that it is augmented with a biosurfactant. To provide equivalent nitrogen concentrations the quantities of BIOREN 1 and 2 added were respectively 10 and 14.4 % of the oil quantity. The results showed a “starter effect” for the formulation BIOREN 1: biodegradation was significantly enhanced during the first five weeks of the experiment; after that the enhancement was weaker and significant differences were not observed between treatments. These results may be attributed to the fact that significant nutrient depletion may not occur in small scale controlled spill experiments. In addition, it has been proven that oxygen availability limited biodegradation. There is a need to develop aeration techniques, such as raking, that aerate the sediment without further burying the pollutant. Final oil balance assessment proved to be very instructive as it is the main practical factor taken into consideration by the operational team: the aim of the shoreline cleaning operation remains to reduce oil sediment content.

Mortality of Two Lepidopterans in Response to Selected Commercial Formulations of Bacillus thuringiensis Berliner2

Five commercial granular formulations of Bacillus thuringiensis Berliner marketed for controlling the European corn borer, Ostrinia nubilalis (Hübner), were compared for insecticidal activity using treated discs of bean leaves. Three formulations, Dipel 10G®, Full-Bac ECBG™, and Strike BT®, were similar in terms of both mortality and speed of kill. A formulation containing a strain of B. thuringiensis developed by plasmid fusion, Condor G®, caused mortality similar to the other three formulations, but the speed of kill was slower. A fifth formulation containing a B. thuringiensis toxin produced by Pseudomonas fluorescens Migula as result of a gene transfer, M-Peril™, caused substantially less mortality than any of the other formulations. An experimental water dispersible formulation, based on a previously developed granular matrix formulation containing B. thuringiensis and a nutrient-based phagostimulant, caused significantly higher mortality of the European corn borer than a similar formulation without the phagostimulant. Simulated field studies were conducted to study the effects of the phagostimulant on feeding and protection of B. thuringiensis from ultraviolet (UV) light. Bean plants treated with B. thuringiensis and the phagostimulant were exposed to different UV regimes outdoors under canopies made of specialized acrylic plastics and then infested with larvae of the corn earworm, Helicoverpa zea (Boddie). A significant interaction between the UV regimes and the phagostimulant was found, indicating that the phagostimulant acted both as a feeding stimulant and as a UV protectant to enhance the activity of B. thuringiensis.

Effects of soil insecticide treatments on maize aphids and aphid predators in Catalonia

The effect on maize aphids and aphid predators of granular formulations of carbofuran and lindane applied at sowing was evaluated from plant emergence to flowering in a three-year study at two commercial farms. Plots treated with carbofuran showed lower total aphid and alate densities during the first week after plant emergence. Later, densities in carbofuran-treated plots were significantly higher than in lindane-treated or untreated plots. No differences in the presence of predators on plants were found, but at one farm catches of polyphagous ground-foraging predators in pitfall traps were greater in untreated plots, coinciding with lower aphid density on plants. Results indicate that the use of carbofuran, in our crop conditions, for controlling aphids and preventing MDMV was ineffective because aphid colonization and reproduction was not avoided, so allowing virus transmission, and ground-foraging predators were negatively affected. Lindane had no direct effect on aphids; and no indirect effects through its impact on predators were observed.

Susceptibility of Various Accessions ofConvolvulus arvensistoPhomopsis convolvulus

The susceptibility ofConvolvulus arvensisL. accessions from different geographic locations to disease caused by the fungal pathogen,Phomopsis convolvulusOrmeno, was evaluated. In a postemergence application experiment, single excised plant shoots ofC. arvensiscollected from 11 different regions in North America and Europe were inoculated withP. convolvulusconidia. AllC. arvensisaccessions showed similar disease reactions. However, plants originating in Canada (Québec) and Spain showed significantly greater disease development than plants from a USA accession (Montana). In a separate preemergence application experiment, plants from two selected accessions originating in Greece and the USA (Montana) were grown from root stock and subjected to a granular formulation ofP. convolvulusapplied to the soil surface. The emerging shoots of both accessions showed severe disease development and the fungal application on Greek and Montana accessions reduced above-ground biomass 83 to 100% and 65 to 86%, respectively. Results of this study indicate that control ofC. arvensisusingP. convolvulusmight be achieved in various geographic regions.

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.

The establishment of alfalfa into different maize residues by conservation‐tillage and its effect on insect infestation

The effect of management of maize residues on the population of insects inimical to the establishment of alfalfa, Medicago sativa L., was examined 1 month after sowing. Alfalfa was sown in early and late April, and late May for 3 consecutive years in Centre County, Pennsylvania, USA. The sowings were made by conservation tillage (direct drilled into maize residue with minimal disturbance of soil) into three different maize residues after (1) silage, (2) silage‐plus‐winter rye cover and (3) grain. A fourth sowing was by conventional tillage (spring ploughing and harrowing maize residue) after grain. A pesticide, carbofuran (granular formulation) was applied at sowing to half of the plots. Methiocarb bait, a molluscicide, was applied as a split application to the same plots, one‐half at sowing and the remainder 2 weeks later. Alfalfa plots in the silage‐plus‐rye maize residues were colonized with fewer insects than the other residue treatments. Excessive growth of rye in early spring that was not successfully suppressed by herbicide treatment produced vigorous rye plants and fewer alfalfa seedlings. Consequently, silage plus rye had the lowest yield of alfalfa in early April sowings in 2 out of 3 years. Insects known to feed on alfalfa, such as tarnished plant bugs, Lygus lineolaris (Palsot de Beauvois), the plant bug, Plagiognathus politus Uhler, pea aphids, Acyrthosiphon pisum (Harris), and meadow spittlebugs, Philaenus leucophthalmus spumarius (L.), were collected by sweep net 1 month after sowing and less often in the silage‐plus‐rye treatment. These species were present in greater numbers in the other maize residues that had significantly more alfalfa forage.The insidious flower bug, Orius insidious (Say), and a damsel bug, Nabis americoferus Carayon, were collected in significantly greater numbers in the early April sowings, which corresponded with the peak populations of pea aphid. The potato leafhopper, Empoasca fabae (Harris), was most abundant in plots sowed in late April or late May.Pesticide treatment applied at the time of sowing had very little effect on numbers of insects collected by sweep net 1 month later in 1986 and 1988. However, pesticide treatment significantly increased yield by 280 kg ha−1 in 1987, even though sweep net collections of insects were not reduced by the pesticide treatment. Therefore, the beneficial effect of the pesticide could not be explained on the basis of the insects collected.The highest yields of alfalfa were obtained from the early April sowing into maize residues. This coincided with the time when the majority of alfalfa pests were less abundant than in later sowings; fewer pests were found on the sowings into silage‐plus‐rye residue. Also, when the rye forage yield was combined with the alfalfa yield, this became the most productive system.