Persistence of Bacillus thuringiensis deposits in a hardwood forest,after aerial application of a commercial formulation at two dosage rates

Abstract

A commercial formulation of Bacillus thuringiensis Berliner var. kurstaki (BTK), Foray® 48B, was sprayed aerially over four blocks B13, B14, B15A and B15B in an oak forest in Wayne County, Pennsylvania during May 1990. B13 and B14 were sprayed at 75 billion international units (BIU) in 5.91 litres/ha and the other two at 50 BIU in 3.94 litres/ha. Oak foliage was collected at different intervals of time after treatment. Three types of bioassays were conducted against fourth instar gypsy moth larvae, viz., direct feeding of sprayed foliage, feeding on diet containing homogenized foliage, and force‐feeding of foliar extracts. Larval mortalities were converted into international units of BTK activity per unit area (IU/cm²) of foliage. Foliar extracts were also subjected to enzyme‐linked immunosorbent assay (ELISA) to determine the concentration of delta‐endotoxin protein. Regardless of the type of bioassay used, bioactivity of BTK persisted in foliage for about a week in all the blocks. The half‐life of inactivation, DT₅₀, ranged from ca 12 to 22 h. The immunoassay data indicated a shorter duration of persistence (i.e., about 2 d) of the delta‐endotoxin protein, with DT₅₀ values ranging from 10 to 15 h. Formulation ingredients present in Foray 48B played a role in the toxicity of BTK to gypsy moth larvae.     

An improved method to study the impact of pesticide sprays on small song birds

Abstract

Four test groups of small songbirds (Zebra Finch, Poephila guttata) were sprayed in a chamber with varying concentrations of fenitrothion. Exposure levels were assessed by monitoring air concentrations, deposits of the active ingredient (AI) on glass plates and droplets/cm² on Kromekote® cards. All indices of exposure were linearly correlated and the mean AI deposit on glass plates for the four groups tested were equivalent to 38, 51, 139 and 255 g/ha or 14%, 18%, 50% and 91% of the highest permissible emitted rate for broadscale forest spraying in Canada. Significant depression in body weights and brain acetylcholinesterase levels were noted only for the highest exposure group. Fenitrothion residues in blood were detectable only at the highest exposure level, and in liver at the two higher levels. Carcass and feather residues were much higher than those in blood and liver, and were detectable at all exposure levels but the residues did not increase linearly with exposure. For one of the spray groups, we were able to compute an equivalent acute oral dose based on matching acetylcholinesterase inhibition.     

Carbon abatement in the fuel market with biofuels: Implications for second best policies

A carbon tax on fuel would penalize carbon intensive fuels like gasoline and shift fuel consumption to less carbon intensive alternatives like biofuels. Since biofuel production competes for land with agricultural production, a carbon tax could increase land rents and raise food prices. This paper analyzes the welfare effect of a carbon tax on fuel consisting of gasoline and biofuel in the presence of a labor tax, with and without a biofuel subsidy. The market impacts of a carbon tax are also compared with that of a subsidy. Findings show that if a carbon tax increases biofuel demand, the tax interaction effect due to higher fuel prices is exacerbated by higher land rent and food prices and greater erosion of the carbon tax base. Thus, the second best optimal carbon tax for fuel is lower with biofuel in the fuel mix, especially if biofuel is subsidized.     

Conflicting perspectives of forest management in Bastar, Central India

This article enters the debate on shifting cultivation and tropical forests, and the role of the State forest departments in managing these regions. The article focuses on the adivasi (indigenous) people and their use of forests in the Bastar region of Madhya Pradesh in Central India. It examines the different landscapes, resulting from human interaction, in order to observe the vegetative changes and progressions in their characteristics; in particular, the author challenges the view that adivasi forest use has been detrimental to the ecology of the forest. A botanical comparison is made between three sites that allow us to note specific characteristics of a fallow, a secondary forest and a primary sal (Shorea robusta) forest. The wider aspects of the adivasi manner of forest use are also discussed.
A major portion of the Bastar region is legally under the authority of the Madhya Pradesh State Forest Department. However, the official policies and laws, pertaining to the conservation of forests and the generation of revenue, are often insensitive to the adivasi perceptions and use of the various vegetative zones within the forest. The effect of a standardised form of demarcation, coupled with the State legislation, has overlooked the adivasi people's needs and their ecologically sound way of relating to the forest. The paper concludes with a few recommendations.     

Biomimicry: How the environment serves as a guide for technological advancements

Multiple ecological tactics, like the ones described here, can be imitated to strongly affect these two components in the construction sector. This article provides an in-depth examination of the literature on biomimicry-based strategies intended to enhance building designs. This analysis is motivated by the rising need for energy legislation to achieve future local goals and provide a framework for use in Panama. These biomimicry-based methods have undergone more review and evaluation, and the incorporation of organism-based design for three of Panama's climate types has been proposed. Therefore, a SWOT analysis assisted in realizing the full potential that biomimicry-based techniques might have in raising the likelihood of satisfying local and international regulatory standards. In order to design constructions using biomimicry, multidisciplinary collaboration is required. This gives a competitive edge for better-trained human resources and expands horizons in the conventional construction industry. Finally, the analysis provided here might act as the preliminary step for the additional technical assessment using numerical and experimental procedures.     

Influence of formulation properties on droplet spectra and soil residues of aminocarb aerial sprays in conifer forests

The influence of formulation properties on spray droplet spectra and soil residues was studied in conifer forests in New Brunswick following aerial application of two oil-based aminocarb formulations of variable viscosities and volatilities. For a given volume rate of application, the formulation of low viscosity and high volatility provided a spectrum of small droplets and a low volume deposit on ground cards. For the same volume rate, the nonvolatile formulation of high viscosity provided a spectrum of larger droplets and consequently a higher volume deposit. Both formulations provided low soil residues, although those obtained with the nonvolatile formulation were much higher and persisted for much longer periods than those obtained with the volatile formulation. However, with both formulations the soil residues decayed to undetectable levels (less than 3 ng/g) within 5 days after spraying, indicating that none of the formulations caused any undue persistence of aminocarb in forest soils.     

Distribution and persistence of aminocarb in stream water, sediment and fish after application of three Matacil formulations

Three aminocarb formulations, water-based Matacil 180F, oil-based Matacil 180F and oil-based Matacil 180D, were applied separately to the surface of a stream at 2.40 g a.i./min for 5 minutes. The highest aminocarb concentration in the top 1 cm of water was found 5 min after application of oil-based 180F (5000 ppb). The next highest concentration was 1862 ppb found in the top 1 cm layer of water 3 min after application of oil-based 180D, followed by 1306 ppb found 5 min after application of water-based 180F. Residue accumulations were first observed in sediment at 3 min and in fish tissues 0.5 h after application. The levels of accumulation were in the order of water-based 180F greater than oil-based 180F greater than oil-based 180-D. After the application of water-based 180F, the highest concentrations were 20.2 ppb in sediment after 5 min and 127 ppb in fish tissues after 3 h. Residues disappeared rapidly from all three matrices and could not be detected after a period of 3-25 h.     

Residue levels of fenitrothion and aminocarb in the air samples collected from experimental spray blocks in New Brunswick in 1982

Abstract

Fenitrothion and aminocarb formulations were aerially sprayed over mixed coniferous forests near Fredericton and Bathurst, New Brunswick, Canada. Insecticide concentrations inside the spray blocks were measured at intervals of time by trapping the airborne toxicants in a fritted‐glass bubbler containing dimethylformamide (DMF). The residues in DMF were analysed by gas chromatography. Concentrations of the insecticides in the air sampled decreased rapidly with time from peak levels of 1997 ng/m³ (fenitrothion) and 1201 ng/m³ (aminocarb). Concentrations of the two insecticides in the air samplers were dependent upon the nature of the chemicals, type of formulation used, spray timings and other environmental factors.     

Foliar and ground deposits of fenitrothion following aerial application over a plantation forest

Abstract

Spray deposits were measured on spruce foliage at tree canopy level and on glass plates at ground level, after aerial application of an emulsion formulation of fenitrothion at the rate of 0.21 kg AI in 1.46 L per ha over a 16 ha plot in a plantation forest. Fenitrothion deposits were quantified by gas‐liquid chromatography. A wide variation was observed in deposits on foliage and at the forest floor. Deposits were relatively higher on foliar samples collected from the upwind side of a tree canopy than those on the downwind side. Similarly, the glass plate placed under a tree on the upwind side received relatively higher deposit than the one on the downwind side. However, the glass plates placed in the adjacent forest openings collected markedly higher deposits. Results clearly indicate filtration of the spray droplets by canopy foliage. Assessment of the average deposit of fenitrothion at ground level (mean deposit from all sampling locations) indicated that ca. 19.4% of the applied material reached the forest floor. Within a sampling station, correlation was poor between foliar depsits and those on glass plates under the same trees or in nearby clearings. Analysis of fenitrothion deposits on foliage collected at 1 and 2 h after application indicated that the droplets took, more than 1 h for deposition on the tree canopy. On the other hand, deposition on the glass plates at ground level appeared to be practically complete within 1 h post‐treatment. This was attributed to the higher sedimentation velocities of the larger droplets which tend to travel faster to the floor level than the smaller droplets which float for a longer period near the tree canopy.