A gravimetric method for determining the relative volatilities of non-aqueous pesticide formulations and spray diluents

A simple gravimetric method was developed for determining the relative volatilities of non-aqueous pesticide formulations and spray diluents, and was compared with the droplet method. The technique involved evaporation of a liquid film from a filter paper surface, and provided greater precision than the droplet method. With both methods, the percentage of mass or volume remaining at time t followed an exponential decay curve, and the coefficients of the equations showed a good correlation between the two methods. The rates of evaporation were consistently lower in the gravimetric method than in the droplet method, and because of this, subtle differences in the relative volatilities of different formulations could be identified by the gravimetric method but not by the droplet method.     

The influence of molasses on the physical properties and sprayability of two pesticide formulations

The effects of molasses on some of the physicochemical properties and on the sprayability of a carbaryl wettable powder (w.p.) and triazophos emulsifiable concentrate (e.c.) were studied in the laboratory and the field. When sprayed in the laboratory on bean leaves, the deposit obtained from either formulation decreased as the percentage of molasses was increased. In an aerial application field trial on cotton, 10% molasses gave a smaller deposit of active ingredient than obtained in the absence of additive, while 20% molasses gave a greater deposit, with either formulation. Molasses had an adverse effect on some properties of the spray mixtures, which resulted in lower deposits when spraying was done at high humidity in the laboratory. This effect was offset when spraying was done at lower humidity in the field, because molasses improved the impaction of droplets by increasing their density and by preventing the complete evaporation of small droplets.     

喷头和施药液量对水稻植株上农药沉积和药剂防治效果的影响

为明确喷头及施药液量对水稻植株上农药沉积及药剂防治效果的影响,采用丽春红-G示踪法测定了4种喷头ST11001、ST11002、TR8001、TR8002在不同施药液量条件下喷雾农药在水稻植株上的沉积分布特性,并比较了4种喷头施用相同剂量的40%氯虫苯甲酰胺·噻虫嗪WDG对水稻纵卷叶螟Cnaphalocrocis medinalis和褐飞虱Nilaparvata lugens的防治效果。结果表明,选择ST11002和TR8001喷头,在施药液量300 L/hm~2条件下喷雾,单株水稻上的丽春红-G沉积量分别达到27.55μg和28.16μg;选择ST11001和TR8002喷头,在施药液量900 L/hm~2条件下喷雾,单株水稻上的丽春红-G沉积量仅分别为12.27μg和14.86μg。喷头和施药液量的改变不影响水稻植株上农药沉积分布特性,均为上层沉积量中层沉积量下层沉积量。当施药液量从300 L/hm~2增加到900 L/hm~2,4种喷头ST11001、ST11002、TR8001、TR8002喷雾在水稻基部的雾滴密度分别增加了8.21、8.54、7.79和9.69倍;但在相同施药液量下,4种喷头在水稻基部的雾滴密度没有显著差异。同一剂量下,喷头和施药液量不同组合的防治效果间差异显著。表明针对稻田不同防治对象,选择合适的喷头及施药液量将有助于提高农药沉积及防治效果。     

The physical stability of suspension concentrates with particular reference to pharmaceutical and pesticide formulations

The word stability is ubiquitous in colloid science but means different things to different people. In a suspension concentrate it is possible to identify three different physical processes which may lead to instability in a particulate system, namely a change in particle size due to Ostwald ripening, particle aggregation and particle sedimentation. Although these processes may occur simultaneously they are here treated separately in order to promote understanding of the physical forces involved.     

Inactivation of triforine by u.v. and sunlight on glass and on leaves of bean plants

Triforine is sensitive to u.v. and sunlight. The photochemical inactivation rate was higher in aqueous solution than in the solid state. In aqueous solution 50% of triforine was inactivated after 3 h irradiation with u.v. light and after 30 h exposure to sunlight. Eighty hours were necessary to decompose 25% of triforine in the solid state with sunlight on glass. The half life of triforine residues on the leaves of bean plants was about 60 h when exposed to solar irradiation. The inactivation of triforine by u.v. light and sunlight was accelerated in the presence of the sensitising chemicals riboflavin and xanthene; however, rhodamine B (C.I. 45170) showed only a small photosensitising activity.     

喷雾助剂对不同剂型吡虫啉药液理化性能与沉积的影响

为明确4种不同类型喷雾助剂对吡虫啉5种剂型的增效效果,测定了助剂与农药混用后药液的表面张力、接触角、干燥时间、扩展直径与叶面持留量,之后根据上述试验结果,选择增效作用较好的2种助剂与吡虫啉各剂型混用,对枸杞木虱进行大田防效试验,最终得到喷雾助剂与农药剂型的最优搭配。试验结果表明,添加喷雾助剂可降低药液表面张力、接触角与干燥时间,增加药液在枸杞叶片上的扩展直径与叶面持留量。其中,强力源对5%吡虫啉SL、70%吡虫啉WP的增效效果较好,矿物油对5%吡虫啉SL、70%吡虫啉WG的增效效果较好,迈润与步锐丝效果相对较差。田间试验结果表明,强力源分别与70%吡虫啉WP和5%吡虫啉SL混用防治枸杞木虱,药后7、10 d的防效较好。表面活性剂类助剂强力源可有效改善5%吡虫啉SL、70%吡虫啉WP药液物理性能,增加药液在叶片上的沉积量,并有效防治枸杞木虱,故生产上推荐使用该搭配。     

Assessment of a mathematical model to predict spray deposition under laboratory track spraying conditions. II: Examination with further plant species and diluted formulations

Mean spray depositions onto leaves of five plant species (Zea mays L., Vicia faba L., Sinapsis alba L., Glycine max (L.) Merr, Vitis vinifera L.) were measured following spraying of an array of 36 solutions of acetone + aqueous “Triton X-100” varying systematically in composition and properties. The spraying was carried out on five occasions using a standard laboratory track sprayer delivering the equivalent of 600 litre ha^?1 onto a plane surface around plant height. The results, plotted as response surfaces, showed that there was little variation in spray deposition with solution composition for V. vinifera, there were some slight decreases in deposition with increase in “Triton X-100” concentration on V. faba and S. alba, though not with increase in acetone concentration, and that there were slight systematic increases for G. max and large systematic increases for Z. mays with increase in acetone and “Triton X-100” up to concentrations of 350 ml litre^?1 and 0.5 g litre^?1 respectively. At higher concentrations of these components, there were no further increases in deposition on these latter species. The results were in agreement with those predicted by a mathematical model derived previously, with the exception of the slight decreases in deposition on V.fana and S.alba and smaller increases in deposition than predicted on G.max. The decreases in deposition on the former species were attributed to slight run-off from their easy-to-wet leaves at the higher “Triton X-100” concentrations at the spray volume rate (600 litre ha^?1) used. The poor fit of the observed and predicted spray depositions on G. max was attributed to the nature of its leaves. These are hairy and it is speculated that the fine hairs, rather than the true leaf surface, played a major role in capturing the small spray drops (115-130 μm) created by the laboratory sprayer used in this work. The observed and predicted spray depositions with a set of diluted commercial-type formulations were in good agreement for Setaria viridis (L.) Beauv., Pisum sativum L., Z. mays, with correlation coefficients (r) of 0.985, 0.988 and 0.935 respectively, and also for the more constant depositions on the easy-to-wet species Beta vulgaris L., but slightly less so for Triticum aestivum L. (r = 0.886) in this test. Overall the model was well-behaved, giving a good prediction of the variation in spray deposition on leaves of a range of plant species, provided that these were not extensively hairy, with variation in the dynamic surface tension of the spray solution.     

红火蚁入侵对荔枝园土壤性理化质的影响

对红火蚁Solenopsis invicta Buren荔枝园发生区土壤理化性质进行了研究,结果表明:3类红火蚁不同发生区之间、红火蚁蚁巢4个不同方位之间以及距红火蚁蚁巢中心不同距离之间的土壤各项理化性质均有显著的差异(p<0.01)。从对照区、轻度发生区到重度发生区土壤粘粒变得越来越细,酸性逐渐升高。土壤有机质、碱解N、有效P的含量在轻、重度发生区较对照区分别下降了29.0%与39.9%、42.1%与53.6%、43.3%与52.6%,但速效K的含量在轻、重度发生区较对照区则分别升高了8.5%与34.0%。此外,在红火蚁发生区,蚁巢上的土壤理化性质与蚁巢以外的土壤理化性质明显不同(p<0.01)。蚁巢上的土壤明显比蚁巢以外的土壤酸性强。土壤有机质、碱解N、有效P的含量在蚁巢上明显最小,但土壤速效K的含量在蚁巢上明显最高。蚁巢不同方位上土壤的理化性质相对差异较小,红火蚁在荔枝园的分布存在一定的空间随机性。     

Influence of the physical and chemical properties of soil on the retention process of isoxaflutole and its two main derivatives

Isoxaflutole is a new pre‐emergence herbicide for use in maize and sugarcane. Its two main derivatives are a diketonitrile derivative, the 2‐cyano‐3‐cyclopropyl‐1‐(2‐methanesulfonyl‐4‐trifluoromethylphenyl)propan‐1,3‐dione, named DKN, and a benzoic acid derivative, the 2‐methanesulfonyl‐4‐trifluoromethylbenzoic acid, named BA. The adsorption/desorption processes have never been studied for isoxaflutole (IFT) at high concentrations nor for BA, and the present work aimed at completing the knowledge of the behaviour of these three molecules in conditions close to those encountered in the context of agricultural use. The adsorption/desorption study was conducted on seven soils of different physical and chemical properties, using the batch equilibrium technique. During the experiments, IFT was chemically converted into DKN in a continuous manner. This reaction appeared to be dependent on the pH of the soil and was taken into account in the calculations of the adsorbed and desorbed amounts. The adsorption isotherms obtained were predominantly C‐shaped for IFT and DKN and S‐shaped for BA, but some differences appeared on a few soils. They fitted well the Freundlich equation, and the values of the Freundlich coefficient K_fa showed that, whatever the soil, IFT was more adsorbed than its two derivatives. The main parameter influencing the adsorption of IFT appeared to be the organic matter content, whereas this effect was not evident for DKN and BA. No correlation was found between the extent of adsorption and either clay content or pH of the soil, for the three molecules.     

Influence of topsoil tilth and soil moisture status on losses of pesticide to drains from a heavy clay soil

Twelve lysimeters with a surface area of 0.5 m² and a length of 60 cm were taken over mole drains from a Denchworth heavy clay soil and divided into two groups with either a standard agricultural tilth or a finer topsoil tilth. The influence of topsoil tilth on leaching of the herbicide isoproturon and a bromide tracer was evaluated over a winter season. The effect of variations in soil moisture status in the immediate topsoil on leaching of isoproturon, chlorotoluron and linuron was investigated in the following winter season. Here, water inputs were controlled such that lysimeters received 50 mm at a maximum intensity of 2 mm h^?1 over a 4‐week period with herbicides applied on day 15. Three treatments received the water either all prior to application, all after application, or evenly spread over the 4‐week period. Leaching losses of the three herbicides were monitored for a subsequent drainage event. Analysis of covariance showed a significant effect of topsoil tilth and total flow on both the maximum concentrations (P = 0.034) and total losses (P = 0.012) of isoproturon in drainflow. Both concentrations and losses were c 35% smaller from lysimeters with the finer tilth. However, generation of the fine tilth in the field was restricted by a wet autumn and this is not considered a reliable management option for reducing pesticide losses from heavy clay soils. In the second experiment, variation in soil moisture content prior to and after application did not have any significant effect (P < 0.05) upon subsequent losses of the three herbicides to drains. © 2001 Society of Chemical Industry     

The phytotoxicity of narrow distillation range petroleum spraying oils to valencia orange trees in South Australia. Part II: The influence of distillation temperature and spray timing on fruit quality

Petroleum oils sprays are used as pesticides on citrus in South Australia to control California red scale (Aonidiella aurantii Maskell), but may have phytotoxic effects on trees and fruit. As part of a programme to establish improved specifications for spray oils for South Australia, three oils with different 50 %-distillation temperatures were applied to trees each month from October to May for two seasons in order to observe their effects on fruit quality. The 50 %-distillation temperatures of the three oils were 211, 224 and 240°C at 10 mmHg (in order of increasing molecular weight) and the oils are subsequently referred to as the 211, 224 and 240 oils. The 224 and 240 oils significantly reduced the amounts of sugar and acid in the juice, and delayed and inhibited colouring. These effects increased in severity, the closer to harvest the trees were sprayed and the higher the distillation temperature of the oil. The 240 oil prevented full colour development, and caused ‘re-greening’ if sprayed later than February. Oil sprays applied to the same trees in the following season caused similar effects. However, if oil sprays were omitted in the following season, there was no residual effect, of the previous season's spray, on the sugar and acid contents or the colour of the fruit. Individual fruit weight was not affected in the first spraying season, but there was an increase in the average individual fruit weight in the second season, regardless of whether a second spray was applied that season or not. The effect was more severe, the closer to harvest the trees were sprayed and the greater the distillation temperature of the oil. The effects on yield resulted from a change in the number of fruit per tree.     

Effect of temperature on herbicidal properties of MTB-951, a mycoherbicide to control Echinochloa crus-galli L.

MTB-951 is a potential mycoherbicide using a fungal plant pathogen ( Drechslera monoceras ) isolated from native Echinochloa species in Japan. Conidia of this pathogen were used as the active ingredient and the effect of temperature on its properties was examined in a laboratory. The optimum temperature for conidium germination was broad between 15 and 35°C and no difference in the germination ratio existed within this temperature range. Mycelial growth was the fastest at 25°C but was slower outside of the range 15–35°C. When leaves of Echinochloa crus-galli L. were immersed in deionized water containing the conidia, cellular electrolyte leakage from the leaves was observed. However, no electrolyte leakage occurred from leaves of rice ( Oryza sativa L.) under the same conditions. The occurrence of electrolyte leakage from E. crus-galli was dependent on the temperature and was the highest at 25°C. Herbicidal activity of MTB-951 against E. crus-galli was high between 25°C and 30°C, but decreased at 35°C in a glass vessel. In the present study, it was revealed that the physiological and herbicidal properties of MTB-951 depended on the temperature.     

The phytotoxicity of narrow distillation range petroleum spraying oils to valencia orange trees in South Australia. Part I: The influence of distillation temperature and spray timing on yield and alternate cropping

Petroleum oil sprays are used on citrus to control California red scale (Aonidiella aurantii Maskell), but may have phytotoxic effects on trees and fruit. As part of a programme to establish improved specifications for spray oils for South Australia, three oils with various 50%-distillation temperatures were applied to trees each month from October to May to observe their effects on crop yield. Some treatments were applied once in each of three consecutive seasons while others were applied only once in the first season. The 50%-distillation temperatures of the three oils were 211, 224 and 240°C at 10 mmHg. The oils caused significant reductions in yield, and caused or accentuated alternate cropping cycles. The higher the 50%-distillation temperature of the oil, the greater the effect. The time of application was also important. The greatest yield reductions (expressed as two averages) occurred when the oils were sprayed in November; the tendency to alternate cropping increased with the month of application from December to May. For the oil with the highest 50%-distillation temperature, the yield reductions were about 30%, and the yields from trees in a severe alternate cropping cycle, in the ‘light crop’ year, were as low as 25% of those on unsprayed trees.     

The phytotoxicity of narrow distillation range petroleum spraying oils to valencia orange trees in South Australia. Part III: The influence of distillation temperature and spray timing on leaf and fruit drop

Petroleum oil sprays are used as pesticides on citrus to control California red scale (Aonidiella aurantii Maskell), but may have phytotoxic effects on trees and fruit. As part of a programme to establish improved specifications for spray oils for South Australia, three oils with different 50 %-distillation temperatures were applied to trees each month from October to May to observe their effects on leaf and fruit drop. The 50%-distillation temperatures of the three oils were 211, 224 and 240°C at 10 mmHg (in order of increasing molecular weight). The oils caused significant leaf drop. The higher the 50%-distillation temperature of the oil, the greater the leaf drop. Most leaf drop was caused when natural leaf drop was greatest. Oils applied from October to February caused severe leaf drop for periods of about 1–2 months, while oils applied from March to May caused severe leaf drop for up to 6 months or more. There was also a tendency for oils with a lower 50%-distillation temperature to cause leaf drop sooner after spraying than oils with a higher 50%-distillation temperature. Significant fruit drop was caused in only a few treatments, but the maximum fruit drop was less than 5% of the total fruit number and of little consequence when compared with the effects of oils on yield through reduced fruit set. Visually, a significant proportion of the total number of leaves present fell in many of the oil spray treatments, and the rate of disappearance of the oil film was directly related to the 50%-distillation temperature of the oil, and to the spraying date.     

Influence of pesticide applications on pest and predatory arthropods associated with transgenic<Emphasis Type="Italic">Bt</Emphasis> cotton and nontransgenic cotton plants

The effects of pesticide applications on pests (aphids and acarid mites) and predators (ladybeetles and spiders) were investigated in transgenicBt cotton and nontransgenic cotton agroecosystems in 1999, 2000 and 2001. Transgenic cotton did not cause changes in populations of acarids and did not reduce numbers of predators considerably; its effects on aphids were inconsistent. Although insecticides were not applied against the main pest — cotton bollworm — on transgenic cotton, the total number of insecticide applications in 3 years was no less than the total applied on nontransgenic cotton, because additional applications were required against sucking pests on transgenicBt cotton. Pesticide applications decreased numbers of aphids, acarids and predatory spiders significantly on both transgenic and nontransgenic cottons. The results suggest that the use ofBt cotton should be evaluated carefully in China. http://www.phytoparasitica.org posting April 30, 2004.     

The effect of some Frescon analogs on the aquatic snail,Lymnaea stagnalis: III. Relation of some physical and chemical properties to neurotoxicity and molluscicidal effectiveness

The hydrolysis rates, particle sizes in suspension, and the relative lipophilicity of Frescon and its analogs were determined and compared with their neurotoxic and molluscicidal effectiveness. The hydrolysis rates of these compounds were closely correlated to their neurotoxicity, and, with one exception, to their molluscicidal effectiveness as well. The aberrant behavior of the one analog could not be attributed to a retarded penetration rate or an excessively large particle size in suspension. There appears to be some, as yet, unidentified factor which determines the molluscicidal activity of this analog. However, it is likely that both neurotoxicity and molluscicidal action are the result of a nucleophilic displacement reaction, although at different targets. Also, differences in the relative molluscicidal effectiveness of the Frescon analogs at different concentrations were possibly due to variations in particle size, which appears to be a function of the type and amount of emulsifier used.     

Influence of temperature on the activity of AC 222,293 against Avena fatua L. and Alopecurus myosuroides Huds.

Foliage applications of AC 222,293 were more active against Alopecurus myosuroides Huds. plants growing at high (26/16°C day/night) compared to either medium (16/10°C) or low (11/7°C) temperatures. Soil activity was unaffected by temperature. Enhanced activity against A. myosuroides required exposure to the high temperatures for only 24 h immediately post spraying and correlated with the accumulation of greater levels of the biologically active acid in the apical meristem region during this period. Both foliage and soil activity of AC 222,293 were greatest against Avena fatua L. plants growing at medium (16/10°C) compared to either high (26/16°C) or low (11/7°C) temperatures. Foliar activity decreased slowly with increasing periods of high temperatures post spraying and then only at doses lower than those recommended for field use. Reduced performance at the high temperatures correlated with lower levels of the biologically active acid in the meristem region, despite greater uptake and translocation. This was due to increased metabolism of the parent herbicide and formation of metabolites other than the free acid.     

Fate of a water-soluble herbicide spray on foliage: Part I. Spray efficiency: Measurement of initial deposition and absorption

MSMA (monosodium methylarsonate) is non-volatile and degrades in the environment to arsenic species which can be determined at the nanogram level. It is thus an excellent tracer for the study of the efficiency of deposition (defined as the fraction of material sprayed that deposits on target foliage) and subsequent fate of a water-soluble pesticide applied to foliage. MSMA was applied to rice (Oryza sativa L. cv. Labelle) foliage at two rates and at various stages of growth. After spraying the foliage was sampled and analysed for surface (removable by water-washing) and absorbed MSMA. Absorption of MSMA was so rapid that within the two hours between application and washing nearly one-half of the recovered MSMA became unavailable for wash-off. The total amounts of MSMA recovered were approximately proportional to plant size and application rate. When the rice foliage reached approximately 80 cm in height, the canopy closure (ground cover) was complete; nevertheless, only about 50% of the sprayed MSMA was found on and in the plants. As the rice canopy approached maturity, or approximately 130 cm high, complete interception of the spray occurred. These results indicate that canopy volume rather than ground cover was more important in determining the efficiency of spray deposition in this case, and that deposition efficiency may approach 100% with non-volatile active ingredients.     

Distribution and activity of spray deposits in an oak canopy following aerial application of diluted and undiluted formulations of Bacillus thuringiensis Berliner against the gypsy moth,Lymantria dispar L. (Lepidoptera: Lymantriidae)

The distribution and biological activity of spray deposits resulting from aerial applications of diluted and undiluted Bacillus thuringiensis, ‘Dipel 64AF’ against the gypsy moth, Lymantria dispar L., were examined in oak stands in south-eastern Ontario, Canada. The sprays were applied by fixed-wing aircraft equipped with four ‘Micronair AU4000’ atomizers. Application of diluted formulation at 30 BIU ha^?1 in 6.0–6.4 litre generally resulted in a higher droplet density (10–28 cm ^?2 leaf) than application of undiluted product at the same dosage rate in 1.8 litre ha^?1 (4–10 cm ^?2). However, spray deposits of undiluted product with a volume median diameter (D_v.5) of 90–130 μm caused as much mortality of gypsy moth larvae in bioassays of sprayed foliage as deposits of diluted product with a D_v.5 of 150–350 μm despite a two- to three-fold reduction in droplet density. Our data suggest that by using fine spray atomization, undiluted application of these formulations can offer the same efficacy against gypsy moth as coarsely atomized sprays of diluted product.