Spreading of spray mixtures on leaf surfaces: I. relative effectiveness of various physico-chemical predictors

Surface tension, contact angles and critical micelle concentration were not effective as practical predictors of spreading. Contact angles could not quantify spreading past the point where the angles became zero, although differences could be discerned by eye. Measurement of diameter of spread allowed quantification of these differences. Hansen parameters, used instead of surface tension, underlined the importance of hydrogen-bonding and charge effects, but could not explain all the observed phenomena. The results emphasise the complexity of spreading on leaf surfaces, and problems experienced with several approaches encountered in the literature are discussed.     

四种喷雾助剂对嘧菌酯在玉米叶片上耐雨水冲刷能力及其对玉米安全性的影响

在室内模拟雨水冲刷条件下,分别通过荧光显微镜法和高效液相色谱法探究了添加4种自制喷雾助剂AY904-1 (含有40%乙酸乙烯酯-丙烯酸共聚物和10%异构醇聚氧乙烯醚)、AY904-2 (含有30%乙酸乙烯酯-丙烯酸甲酯共聚物和10%异构醇聚氧乙烯醚)、AY904-3 (含有20%乙酸乙烯酯-丙烯酸乙酯共聚物和10%异构醇聚氧乙烯醚) 和AY904-4 (含有10%乙酸乙烯酯-丙烯酸丁酯共聚物和10%异构醇聚氧乙烯醚) 对提高嘧菌酯在玉米叶片表面耐雨水冲刷效果的影响,并测定了喷雾助剂对嘧菌酯药液物理性状及其玉米安全性的影响。结果表明:在室内模拟冲刷试验中,两种检测方法所测结果具有良好的相关性;在嘧菌酯中添加质量分数为0.1%~1.0%的AY904-1和AY904-2以及添加质量分数为0.5%~1.0%的AY904-3和AY904-4均可显著提高嘧菌酯在玉米叶片上的持留量,且助剂的添加量越大,耐冲刷效果越好,其中以AY904-1的效果最好。在嘧菌酯药液中添加4种喷雾助剂,均能降低药液在玉米叶片表面的接触角,但与嘧菌酯药剂对照相比无显著差异。AY904-1和AY904-2的干燥薄膜在水中溶胀度较低,成膜性能较好。将4种喷雾助剂与氯虫苯甲酰胺药液桶混后喷雾,发现其对3个品种玉米均有很高的安全性。     

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。     

Factors affecting the foliar absorption and redistribution of pesticides. 1. Properties of leaf surfaces and their interactions with spray droplets

Foliar uptake into eleven plant species, grown under controlled environment, has been determined for spray deposits of glyphosate, 2, 4-D and prochloraz applied as solutions in aqueous solvents in the presence and absence of an ethoxylated nonylphenol surfactant. Over 24 h, uptake of glyphosate did not exceed 6% of applied chemical into any species whereas uptake of 2, 4-D and prochloraz differed between species and was modified significantly by the addition of surfactant. Uptake of prochloraz was increased consistently by adding surfactant, but the response of 2, 4-D was variable. Increased uptake was attributed mainly to surfactant-enhanced wetting of the leaf surfaces. Uptake of prochloraz per unit wetted area increased in the presence of surfactant but that of 2, 4-D decreased. Uptake of either chemical did not correlate with the presence of specialised leaf surface structures, cuticular morphology or distribution of the chemicals within the dried deposits. The dried chemicals were distributed either uniformly or as annuli as a result of complex interactions between the active ingredient, surfactant and the leaf surfaces. Regression analysis indicated that the epicuticular wax and cuticular membrane were the major sinks for both 2, 4-D and prochloraz during the 24-h period.     

The use of a computerised digitiser for the analysis of spray droplet sizes on oat leaf surfaces

The use of fluorescence photomicrography, and a graphic digitiser tablet controlled by a minicomputer, is suggested as the means of rapid and accurate measurement of deposits traced by fluorescence on plant leaves; this method gives the added advantage of a permanent record of the deposits. As an example of the technique, an analysis of 1630 droplets on the upper and lower surfaces of oat leaves, traced with reversibly soluble fluorescent pigments, is described. Measurement on the digitiser, and computer analysis of droplet size data, took less than 20 min.     

叶片倾角、雾滴大小与施药液量对毒死蜱在水稻植株沉积的影响

为提高农药的有效利用率,用丽春红为示踪剂研究了毒死蜱药液在水稻叶片上的沉积特性.随着水稻叶片的倾角变小,毒死蜱的沉积量相应地减少.用体积中径(VMD)为149.5 μm的雾滴处理,在设定叶片倾角为90°、60°、30°时,毒死蜱沉积量分别是直立叶片上沉积量的10.2、5.8、2.9倍.随着叶片倾角变小,雾滴VMD对沉积的影响增大,在90°、60°、30°、0°四个叶片倾角,用VMD149.5 μm雾滴处理的沉积量分别是用VMD 233.7 μm雾滴处理沉积量的1.5、2.1、3.3、5.5倍.在施药液量170～1.36×103L/hm2范围内,毒死蜱沉积量随施药液量的增加而减少.用浓度为800mg/L毒死蜱药液在水稻叶片上测定的最大稳定持留量约为4.66μg/cm2.结果表明,采用小雾滴与低容量喷雾,可显著提高毒死蜱在水稻叶片的沉积量.     

喷雾助剂和静电喷雾对喷施炔草酯的减量增效作用

为了明确喷雾助剂和静电喷雾器对炔草酯的减量增效作用,采用田间小区试验测定了63％激健水剂、3％安融乐悬乳剂和75％超加必乳油3个喷雾助剂以及采用静电喷雾器施药对炔草酯除草效果的影响.结果表明:喷雾助剂激健、安融乐和超加必对常规背负式喷雾器喷施炔草酯增效作用明显,在有效成分剂量(下同)34 g/hm2的15％炔草酯可湿性...     

Effect of spray volume on the deposition, viability and infectivity of entomopathogenic nematodes in a foliar spray on vegetables

BACKGROUND: Spray volume can influence the amount of free water on the leaf surface and subsequently the ability of entomopathogenic nematodes (EPNs) to move. In this study, an investigation was made of the effect of spray volume (548, 730 and 1095 L ha⁻¹) on the deposition, viability and infectivity of EPNs against Galleria mellonella on savoy cabbage, cauliflower and leek. RESULTS: Increasing spray volume decreased nematode deposition on 7.1 cm² leek leaf discs at a 15° angle with the spray nozzle. Although the number of living nematodes observed on leek after 240 min of exposure was not significantly different between the low-volume application (548 L ha⁻¹) and the high-volume application (1095 L ha⁻¹), a greater infectivity was obtained in the latter application. The higher number of droplets deposited on the leek discs in the high-volume application may have stimulated nematode movement. No significant effect of spray volume was observed on the relative deposition of Steinernema carpocapsae on the bottom side of cauliflower and savoy cabbage leaf discs. In spite of the low S. carpocapsae deposition on the bottom side of the savoy cabbage discs, high infectivity was obtained against G. mellonella. Using the lowest spray volume on savoy cabbage, infectivity decreased with increasing exposure time, while infectivity was not affected by exposure time when a spray volume of 730 L ha⁻¹ or more was used. CONCLUSION: Spray volume is an important application parameter, as it affects nematode infectivity. Future research should investigate the effect of spray volume in the field and its influence on the effect of adjuvants. Copyright © 2012 Society of Chemical Industry     

Tracing insecticide spray droplets by sizes on natural surfaces. The state of the art and its value

Recent trends in integrated chemical and biological pest control call for further refinement of the effectiveness of existing chemical pesticides by more efficient spray application. One aspect of improving spray efficiency is by the use of the correct range of droplet sizes. In this way the volume of spray, and the amount of active ingredient used, particularly in ultra-low volume techniques, can be further optimised, and when combined with correct application time, gives maximum biological efficiency with minimum disturbance of the environment. This necessitates a study of the size spectrum of droplets deposited on rigorously defined biological targets which in turn calls for an investigation of suitable tracer methodology. Additional details of the previously published fluorescent particle method are discussed, and its reappraisal shows that it is a unique method capable of estimating droplet sizes on all biological surfaces, especially insect larvae. The reversibly soluble fluorescent pigment method based on the relative balance between soluble and insoluble state of the pigment proves highly successful in imprinting fluorescent droplets on broad leaves, particularly on cotton.     

喷雾助剂及施液量对植保无人机喷雾雾滴在水稻冠层沉积分布的影响

为提高农药沉积率,利用黏度计、表面张力仪、药液润湿性测试卡、激光粒度仪测定不同喷雾助剂添加量对蒸馏水溶液性质的影响,并分析喷雾助剂及施液量对水稻冠层不同位置雾滴沉积密度、沉积量以及有效沉积率的影响。结果表明,添加喷雾助剂对蒸馏水溶液的性质有显著影响,与蒸馏水相比,当添加喷雾助剂为0.5%和1.0%时,雾滴体积中径变为108.9、98.7μm,表面张力降低64.7%、64.9%,黏度增加为2.3、2.3 m Pa·s,铺展系数为蒸馏水的74.5、58.5倍,能有效促进雾滴铺展并避免药液流失;植保无人机喷施试验结果显示,增加施液量可显著提高雾滴沉积密度,添加喷雾助剂可以显著提高雾滴沉积量以及有效沉积率,当施药量为13.5 L/hm~2且添加1.0%喷雾助剂时,雾滴在水稻冠层的有效沉积率最大,为48.9%。     

喷雾压力和药液流量对井冈·枯芽菌在水稻叶片定殖的影响

研究了施药机具不同工作压力和药液流量对生物农药井冈.枯芽菌在水稻叶片上定殖数量及活性的影响。盆栽试验结果表明:担架式机动喷雾机、机动弥雾喷粉机和背负式机动喷雾器对生防菌的活性无不利影响。其中担架式机动喷雾机工作压力超过2.5 MPa以上有利于生防菌的定殖;机动弥雾喷粉机同一风速挡、不同流量挡的处理中,流量挡达到2.0 L/m有利于生防菌的定殖。同时生防菌在水稻叶片上定殖数量与水稻纹枯病的防效呈正相关的关系。     

Aspects of the selective phytotoxicity of methazole. I. Measurements of species response, spray retention and leaf surface characteristics

The responses of onion (Allium cepa). Veronica persica, Matricaria matricarioides and Stellaria media to post-emergence applications of methazole were measured in field and glasshouse experiments. Stellaria media was the most susceptible species and V. persica the least. Plants of all species became more tolerant the larger they were at the time of treatment, and this was most pronounced in onion. Onion generally retained less spray per unit of dry weight than the other three species and retention was less on old compared with young plants, whereas with the weed species, this did not change appreciably with age. There was a progressive increase in the amount of structured crystalline wax on successive onion leaves which resulted in larger contact angles between droplets and the leaf surfaces and lower spray retention per unit of dry weight. There was less wax development on the leaf surfaces, increased spray retention, and increased susceptibility to methazole in onion treated pre-emergence with ethofumesate thus confirming that these factors are interrelated. While the increased tolerance of onion to methazole with age could be explained in part by decreased retention of herbicide, this was not so for the weed species, and other factors must determine their change in tolerance with age.     

Effects of temperature and humidity on the contact angle of pesticide droplets on rice leaf surfaces

The effects of external factors such as temperature, humidity, pesticide formulation, and pesticide concentration on the contact angle of pesticide droplets on rice leaf surfaces were analyzed. The experiments showed that there were significant differences in the contact angles of droplets on the leaf surfaces under different temperatures and humidity. As the ambient temperature increased, the contact angle first decreased and then increased, reaching a minimum value at 25°C. With a gradual increase in humidity, the contact angle significantly increased and reached a maximum at 100% humidity. Finally, it was concluded that both the formulation and concentration of the pesticide had a significant effect on the contact angle of droplets on rice leaf surfaces. The experiments also illustrated that the effects of the pesticide formulation and concentration on the contact angle were more significant than those of temperature and humidity.     

The effect of molasses on the evaporation and impaction of spray droplets

The addition of 20% molasses to water did not reduce the rate of evaporation of water from spray droplets. The 20% molasses droplets evaporated at the same rate as water droplets until ca 20% of their volume was left. When sprayed under field conditions at 30% relative humdity (r.h.) the volume median diameter (v.m.d.) of the 20% molasses spray (132 μm) was larger than the v.m.d. of the water spray (116 μm) and more droplets smaller than 19 μm were captured on magnesium oxide slides than with the water spray. The addition of molasses improved the impaction efficiency of droplets by increasing their density, and increased the minimum size to which a given droplet could evaporate.     

Cultivar mixtures for the simultaneous management of multiple diseases: tan spot and leaf rust of wheat

ABSTRACT Because of differences in life histories between Puccinia triticina, a highly specialized, polycyclic, windborne pathogen with a shallow dispersal gradient, and Pyrenophora tritici-repentis, a residue-borne pathogen with a steep dispersal gradient, wheat mixtures are expected to be more effective at controlling leaf rust than tan spot. The objectives of this research were to determine the effect of two-cultivar mixtures with varying proportions and different pathogen resistance profiles on the severity of tan spot and leaf rust, to evaluate yield of the mixtures in the presence or absence of disease, and to directly compare the relative effectiveness of cultivar mixing for tan spot versus leaf rust. In a field experiment at two sites in Kansas over two growing seasons, winter wheat cvs. Jagger and 2145, which have differential resistance reactions to leaf rust and tan spot, each were planted in proportions of 0.25, 0.50, 0.75, and 1.00. Plots were inoculated with each pathogen alone, both pathogens, treated with a fungicide, or exposed to ambient conditions. For both diseases for all siteyears, severity decreased substantially on the susceptible cultivar as the proportion of that cultivar decreased in mixture. Mixtures were significantly more effective at reducing leaf rust than tan spot in three of four site-years. Mixtures generally yielded the same as the weighted mean of components in monoculture although, in two of three site-years, at least one fungicide-treated and one diseased mixture each yielded higher than expected values. Although this particular mixture produced only modest yield benefits, the potential for simultaneous reductions in tan spot and leaf rust was demonstrated.     

Soil surface roughness change and its effect on runoff and erosion on the Loess Plateau of China

As an important parameter in the soil erosion model, soil surface roughness（SSR） is used to quantitatively describe the micro-relief on agricultural land. SSR has been extensively studied both experimentally and theoretically; however, no studies have focused on understanding SSR on the Loess Plateau of China. This study investigated changes in SSR for three different tillage practices on the Loess Plateau of China and the effects of SSR on runoff and erosion yield during simulated rainfall. The tillage practices used were zero tillage（ZT）, shallow hoeing（SH） and contour ploughing（CP）. Two rainfall intensities were applied, and three stages of water erosion processes（splash erosion（I）, sheet erosion（II） and rill erosion（III）） were analyzed for each rainfall intensity. The chain method was used to measure changes in SSR both initially and after each stage of rainfall. A splash board was used to measure the splash erosion at stage I. Runoff and sediment data were collected continuously at 2-min intervals during rainfall erosion stages II and III. We found that SSR of the tilled surfaces ranged from 1.0% to 21.9% under the three tillage practices, and the order of the initial SSR for the three treatments was ZT〈SH〈CP. For the ZT treatment, SSR increased slightly from stage I to III, whereas for the SH and CP treatments, SSR decreased by 44.5% and 61.5% after the three water erosion stages, respectively, and the greatest reduction in SSR occurred in stage I. Regression analysis showed that the changes in SSR with increasing cumulative rainfall could be described by a power function（R2〉0.49） for the ZT, SH and CP treatments. The runoff initiation time was longer in the SH and CP treatments than in the ZT treatment. There were no significant differences in the total runoff yields among the ZT, SH and CP treatments. Sediment loss was significantly smaller（P〈0.05） in the SH and CP treatments than in the ZT treatment.     

Comparison of empirical models depicting density of Amaranthus retroflexus L. and relative leaf area as predictors of yield loss in maize (Zea mays L.)

The outcome of crop-weed competition should be predicted as early as possible in order to allow time for weed control measures. Maize grain yield losses caused by interference from Amaranthus retroflexus L. (redroot pigweed) were determined in 1991 and 1992. The performance of three empirical models of crop-weed competition were evaluated. Damage functions were calculated based on the weed density or relative leaf area of the weed. In the yield loss-weed density model, values of I (percentage yield loss at low weed density) were relatively stable for similar emergence dates of A. retroflexus across years and locations. Estimated maximum yield loss (A) was more variable between locations and may reflect environmental variation and its effect on crop-weed competition, at least in 1991. The two-parameter yield loss-relative leaf area model, based on m (maximum yield loss caused by weeds) and q (the relative damage coefficient) gave a better fit than the single-parameter version of the model (which includes only q). In both relative leaf area models, the values of q varied between years and locations. Attempts to stabilize the value of q by using the relative growth rate of the leaves of the crop and weed were successful; however, the practical application of such relative leaf area models may still be limited owing to the lack of a method to estimate leaf area index quickly and accurately.     

Allelopathic effect of leaf debris, leaf aqueous extract and rhizosphere soil of Ophiopogon japonicus Ker-Gawler on the growth of plants

Laboratory and greenhouse experiments were conducted to evaluate the allelopathic potential of dwarf lily turf ( Ophiopogon japonicus Ker-Gawler) on lettuce, alfalfa, timothy and mustard plant growth. Dry leaf debris, aqueous extract of fresh leaves and O. japonicus grown soil were investigated. Emergence, dry weight, and root and shoot length of all bioassay species were inhibited when grown in soil incorporated with oven-dried leaves of O. japonicus. The inhibitory effects were often dependent on the concentration. However, the degree of inhibition varied among the test plant species. The aqueous leaf extract was highly phytotoxic and it significantly reduced germination, seedling growth, and the fresh weight of all the test species at all rates. The emergence and growth of all four tested plants were severely inhibited when planted in O. japonicus contaminated soil. These results indicate that O. japonicus incorporated leaf debris, leaf aqueous extract and its rhizosphere soil suppress seed germination, radicle growth, seedling emergence and seeding growth of certain weeds and suggest that these responses were attributed to an allelopathic effect.     

灭多威、辛硫磷及其混剂对棉铃虫的毒力测定和田间药效试验

采有点滴法测定灭多威、辛硫磷及其混剂对棉铃虫的毒力，结果表明，灭多威与辛硫磷混配，各个配比均行增效作用，其中以1：2．6(有效成分)的配比增效作用最大，毒性比率和共毒系数分别为1．58和151．41。田间试验表明，灭多威与辛硫磷的混剂对棉铃虫有较好的防治效果，室内结果在田间试验中得到验证。