Investigation of Spray Application of Microbial Herbicides Using Alternaria alternata on Amaranthus retroflexus

Inclusion of Alternaria alternata conidia in a spray formulation affected the distribution pattern on the target. The dry weight of Amaranthus retroflexus plants was reduced by more than 83% when A. alternata conidia (107 ml -1 ) were applied at 200 L ha -1 or greater and when given a 24 h dew period. At low application volumes (25 or 50 L ha -1 ) plant dry weight was reduced by only 29 or 54%. After 7-8 h dew period, conidial germination on the leaf surface was 11-19%. This increased to 62-91% after 24 h dew period. Counts of conidia on leaves indicated that up to 86% of the conidia sprayed were not retained on the target plant, or did not reach it. This is reflected in lesion numbers per unit area being only 3-5% of the calculated theoretical numbers. The results cast doubt on the suitability of A. alternata as a microbial herbicide for the control of Am. retroflexus .     

球孢白僵菌分生孢子乳悬剂对甘蓝上桃蚜的田间控制效果

利用液-酵法生产球孢白僵菌(Beauveria bassiana)SG8702菌株的分生孢子粉,配制成含孢量为10^10个.ml^-1的孢子乳悬剂Ⅰ,在此基础上按1％(W／V)的比例舔加10％砒虫琳可湿性扮剂而得孢子乳悬剂Ⅱ．于2001年7月对两种孢子乳悬剂在云南昆明进行了自然条件下甘蓝上桃蚜(Myzus persicae)的田间小区(5．5m×4．8m)药效试验,各3个浓度(含孢量分别为10^7、10^6及10^5个·ml^-1常规喷雾处理,重复设清水喷雾对照,重复3次,随机区组排列．在喷菌后连续28d的田间蚜虫密度定期抽样调查中,乳悬剂Ⅱ的1000倍稀释液喷雾有效抑制了蚜虫数量增长,喷后策7—28天防效始终在90％以上．乳悬剂Ⅰ的相同稀释液喷雾对桃蚜的控制略逊于乳悬剂Ⅱ,但喷后第7天的相对防效也达到85％,此后维持防效70％以上达两周,策24天和28天才分别降至64．4％和52．6％．用含孢量10^6和10^5个·ml^-1的菌液喷雾,乳悬剂Ⅰ仍表现出明显的控蚜效果,而舔加微量砒虫琳的乳悬剂Ⅱ的控蚜效果总是优于同一浓度下的乳悬剂Ⅰ,昆明地区夏季温和而多小雨的气候有利于孢子乳悬剂发挥作用．     

Cage and field assessments of Beauveria bassiana-based Mycoinsecticides for Myzus persicae Sulzer (Hemiptera: Aphididae) control in cabbage

The efficiency of formulated Beauveria bassiana-based mycoinsecticides to control Myzus persicae (Sulzer) in cabbage was assessed under field conditions. Aqueous conidial suspensions (0.01% Tween 80 + 0.01% v/v Agral) of three fungal isolates were sprayed twice at different dates, each with 2.0 x 10(9) viable conidia per potted plant using screened cages. The number of nymphs and adults of M. persicae per leaf was significantly reduced in plots treated with isolates CG 864 and PL 63, with control efficiency ranging from 57% to 60%. Further field trials using screened cages with isolate CG 864 formulated as oil dispersion reduced the aphid population by 85-87% as compared to the control, whereas a 71% reduction was seen in plants treated with the aqueous conidial suspension 20 days following the first spray. The last experiment was conducted in a commercial cabbage field (without cages), in which the fungus was applied at three different dates, each with an equivalent of 1.0 x 10(13) viable conidia/ha. The reduction in the number of aphids per leaf was more evident between four and five weeks following the first spray, resulting in 76-83% and 57-65% control efficiency for oil dispersions and unformulated conidia, respectively. However, with the exception of imidacloprid-treated plants, rapid aphid re-infestation was observed in all treatments. In this study, the stand-alone use of mycoinsecticides for aphid control was not a satisfactory strategy, although utilization of B. bassiana in IPM strategies remains a field to be explored.     

Spray retention for liquid and mycoherbicide inoculum in three weed-biocontrol systems

Spray retention is often used to measure herbicide delivery to optimize application parameters, but little is known about retention characteristics of mycoherbicide inoculum applied for weed biocontrol. This study examined inoculum retention of three mycoherbicide agents, Pyricularia setariae, Colletotrichum truncatum and C. gloeosporioides f. sp. malvae, on their respective weed targets: green foxtail, scentless chamomile and round-leaved mallow. Conidium suspensions of these fungal pathogens containing a sodium-fluorescein tracer dye were applied at 500, 1000 and 2000 L ha^-1 using a cabinet sprayer, and the liquid volume and number of conidia retained on the plants were quantified. On all three weed species, liquid and conidium retention showed a high degree of correlation at varying application volumes although slight differences existed depending on the weed species. Based on the analysis of regression slopes, liquid retention reflected conidium retention most closely on green foxtail but slightly overestimated the number on scentless chamomile and round-leaved mallow, possibly due to different plant morphology and spray run-off at extremely high application volumes. Liquid retention can generally be used as an indicator in studying effects of spray quality on mycoherbicide retention for improved delivery and biocontrol in these weed-biocontrol systems.     

Acquisition of lethal doses of Beauveria bassiana conidia by western flower thrips, Frankliniella occidentalis, exposed to foliar spray residues of formulated and unformulated conidia

Secondary acquisition of Beauveria bassiana conidia was recorded on the whole bodies and selected body parts of second-instar nymphs and adult female western flower thrips exposed to foliar spray residues of three differently formulated conidial preparations, for 24 h. Conidia were formulated in emulsifiable oil or with clay (wettable powder), or were essentially unformulated conidia (technical grade powder suspended in water with a surfactant). Formulation had no significant effect on dose acquisition and no effect on virulence of acquired conidia. The mean nymphal LC50/LD50 was 116 conidia/mm2 and 52conidia/insect, respectively; the values for adults were 19 conidia/mm2 and 5conidia/insect. Greatest numbers of conidia were recorded on the legs and abdomens of nymphs and on the legs, wings, and thoraces of adults. As would be expected, numbers of conidia acquired increased with residue concentration (application rate). However, an inverse relationship was noted between acquisition rate (conidia acquired/total conidia applied) and residue concentration. The mechanism underlying this response was not determined. However, there was no indication that any body parts (e.g., tarsi) became saturated with spores, which suggests that either the thrips were repelled by the conidial residues or that as the concentrations of conidia on the substrate increased, conidia somehow became more difficult to acquire. Slopes of the LC probit regressions were lower than those of the LD regressions (mean 1.14 vs 1.78), suggesting that the low slopes often obtained in fungal pathogen assays could be partly an artifact of unequal rates of dose acquisition at low vs high application rates.     

Spray application technology

Spray application technology on perennial tree crops has been a poorly researched subject. Many of the nozzles and sprayers were originally developed for use on row crops which have an even, flat profile and spraying is downward. Some of the short-comings of these systems were exposed when tree crops were sprayed, particularly the large and dense trees of 30 years ago.Much of the variation experienced in experimental results where fruit trees had been thinned with bioregulators is likely to have been due to application methods. Air-blast sprayers using hydraulic nozzles resulted in inconsistent results causing many research workers to revert to the use of hand lances and small pumps for their trials. Translation of these results to commercial practices then became a problem, as growers were reluctant to revert to the use of hand lances for thinning, particularly as orchards increased in size.The increased emphasis on reducing the use of chemicals, including bioregulators, on food and the need to use ecologically less wasteful methods of applying them has recently promoted more research into spraying techniques.Early work with spray technology identified factors causing variation. Such factors as the range and size of spray droplets, effect of climate, use of wetters, spreaders and stickers, the carrier medium (oil, water or combination), the use of propelled air, the crop species and it's configuration all impacted on the results.     

Spray drift as affected by meteorological conditions

Spray drift can be defined as the quantity of plant protection product that is carried out of the sprayed (treated) area by the action of air currents during the application process. This continues to be a major problem in applying agricultural pesticides. The purpose of this research is to measure and compare the amount of drift for different climatological conditions under field conditions. Spray drift was determined by sampling in a defined downwind area at different positions in a flat meadow using horizontal drift collectors (sedimenting spray drift) and pipe cleaners (airborne spray drift) for a reference spraying. Meteorological conditions were monitored during each experiment. A drift prediction equation for the reference spraying was set up to predict the expected magnitude of sedimenting drift at various drift distances and atmospheric conditions (wind speed and temperature). This equation can be used to compare measurements using other spraying techniques under different weather conditions to the reference spraying. In 2005, more measurements will be performed to validate the statements and the model reflected in this paper.     

The effect of mode of exposure to Beauveria bassiana on conidia acquisition and host mortality of Colorado potato beetle, Leptinotarsa decemlineata

The effects of the mode of exposure of second instar Colorado potato beetles to Beauveria bassiana on conidia acquisition and resulting mortality were investigated in laboratory studies. Larvae sprayed directly with a B. bassiana condial suspension, larvae exposed to B. bassiana-treated foliage, and larvae both sprayed and exposed to treated foliage experienced 76, 34, and 77% mortality, respectively. The total number of conidia and the proportion of germinating conidia were measured over time for four sections of the insect body: the ventral surface of the head (consisting mostly of ventral mouth parts), the ventral abdominal surface, the dorsal abdominal surface, and the legs. From observations at 24 and 36 h posttreatment, mean totals of 161.1 conidia per insect were found on sprayed larvae, 256.1 conidia on larvae exposed only to treated foliage, and 408.3 conidia on larvae both sprayed and exposed to treated foliage. On sprayed larvae, the majority of conidia were found on the dorsal abdominal surface, whereas conidia were predominantly found in the ventral abdominal surface and mouth parts on larvae exposed to treated foliage. Between 24 and 36 h postinoculation the percentage of conidia germinating on sprayed larvae increased slightly from 80 to 84%). On the treated foliage, the percentage of germinated conidia on larvae increased from 35% at 24 h to 50% at 36 h posttreatment. Conidia germination on sprayed larvae on treated foliage was 65% at 24 h and 75% at 36 h posttreatment. It is likely that the gradual acquisition of conidia derived from the continuous exposure to B. bassiana inoculum on the foliar surface was responsible for the increase in germination over time on larvae exposed to treated foliage. The density and germination of conidia were observed 0, 4, 8, 12, 16, 20, and 24 h after being sprayed with or dipped in conidia suspensions or exposing insects to contaminated foliage. Conidia germinated twice as fast on sprayed insects as with any other treatment within the first 12 h. This faster germination may be due to the pressure of the sprayer enhancing conidial lodging on cuticular surfaces.     

白僵菌对茶小绿叶蝉田间防效的关键影响因素研究

白僵菌孢子萌发率和萌发速度是影响其田间防效的关键因素。通过对球孢白僵菌YP9(CCTCC No:M209238)孢子萌发的关键影响因素进行研究,得到以下田间应用条件:营养物质为2%麸皮浸出液(自然pH);孢子悬浮液喷洒浓度为5×10~7孢子/mL;在气温为23℃~28℃时喷洒。经昆明和无锡两试验地田间防效验证,该白僵菌在上述条件下对茶小绿叶蝉的田间防效高达65%,与茶农常用化学农药——天王星防效相当。     

Effect of exposure method to Beauveria bassiana and conidia concentration on mortality, mycosis, and sporulation in cadavers of Chilo partellus (Lepidoptera: Pyralidae)

The effects of exposure methods, conidial concentrations, and temperature on mortality, mycosis and sporulation in second instar Chilo partellus cadavers infected by Beauveria bassiana was investigated in laboratory studies. Larvae directly sprayed with conidia, exposed to conidia-treated leaves, and dipped into conidial suspension resulted in high mortality (98-100%). The longest LT50 (3.5 days) and days to mortality (2.6 days) were observed in the treated-leaves exposure method. The shortest LT50 (1 day) and days to mortality (1 day) were recorded for the dipping method. With increasing conidial concentrations, there were decreasing LT50 and days to mortality. Larvae exposed to treated leaves and larvae directly sprayed with conidial suspensions produced high mycoses in cadavers. Exposure of larvae to treated-leaves resulted in high sporulation. At lower concentrations of conidia, both mycosis and sporulation in cadavers were high. The optimum temperature for mycosis was 20 and 15 degrees C for sporulation.     

Application of a Four-fluid Nozzle Spray Drier to Prepare Inhalable Rifampicin-containing Mannitol Microparticles

The purpose of this study was to use a four-fluid nozzle spray drier as a new one-step method for preparing rifampicin (RFP)-containing mannitol microparticles. A RFP-acetone/methanol (2:1) solution and aqueous solutions of mannitol (MAN) were simultaneously supplied through different liquid passages of a four-fluid nozzle spray drier and then dried to obtain MAN microparticles containing RFP. Using a cascade impactor, the in vitro aerosol performance of RFP powder and RFP-MAN microparticles with 1:5, 1:10, and 1:20 ratios was compared. The in vivo retention of RFP in the lungs of rats after intratracheal administration of 1:20 RFP-MAN microparticles was also compared. The RFP-MAN microparticles had better aerosol performance than RFP powder and delivery to the lung stages improved as the fraction of MAN was increased. For the 1:20 RFP-MAN microparticles, deposition in stages 2–7 was approximately 43%, which is sufficient for treatment. Approximately 8% of the RFP-MAN microparticles were deposited in stages 6–7, which corresponds to alveoli containing alveolar macrophages. The initial retention of RFP in the lung following pulmonary delivery of 1:20 RFP-MAN microparticles was higher than following oral or intravenous administration of RFP, but the elimination was rapid, resulting in the disappearance of RFP from the lung within 4 h. The plasma concentration–time profile of RFP after intratracheal administration of 1:20 RFP-MAN microparticles was consistent with the profile for RFP retention in the lung. Addition of cholesterol or phosphatidylcholine to RFP had little effect on its retention in the lung. The RFP-MAN microparticles were effective for delivery of RFP to the lung, but the RFP rapidly removed from the lung into the blood circulation. This study demonstrated that RFP-containing MAN microparticles prepared in one step using the four-fluid nozzle spray drier efficiently deliver RFP to the lung, although methods must be developed to prolong its retention and improve targeting to alveolar macrophages.     

环境因子对努利虫疠霉产孢和孢子萌发的影响

探讨努利虫疠霉Pandoranouryi(Remaudi埁re&Hennebert)H櫣mber在田间蚜虫种群中发生与流行的规律,研究外界环境因子对感菌虫尸产孢和孢子萌发的影响。结果表明,处于水琼脂培养平板上感染努利虫疠霉的桃蚜虫尸在8~25℃的温度范围内均能产生大量的初生分生孢子,在30℃下,仅弹射极少量孢子。8℃下,孢子弹射可以持续120h,当温度高于15℃,大部分的孢子会在48h内完成弹射。相对湿度小于95%,虫尸停止产孢。20℃下,光照条件不会影响虫尸弹射孢子的总量。在8℃和30℃时,24h后处于水琼脂培养平板上的孢子萌发率分别为45.23%和61.74%,显著低于15~25℃温度范围内的孢子萌发率(95%以上)。处于叶片上的真菌孢子,当相对湿度大于74%时出现萌发,但在盖玻片的表面,当湿度低于100%时未发现孢子萌发。     

Fungal conidia distribution on chrysanthemum: varying spray parameters

The conidial deposition of BotaniGard® 22WP on chrysanthemum plants was assessed. Assessments were conducted on stationary and moving applications using different spray nozzles, application angles and tank pressures. In addition, the spray time and distance from the target plant were included. Conidial deposition was greater on the upper canopy of the plants and the upper sides of the leaves. The nozzle type, spray angle, and distance from the target plant had the most significant effects on conidial distribution. The optimal spray nozzles were found to be HC-22 and FAN-1, which provided the best coverage of both the plants in general, and on the lower surfaces of the leaves.     

A tritrophic effect of host plant on susceptibility of western flower thrips to the entomopathogenic fungus Beauveria bassiana

Adult female western flower thrips (Frankliniella occidentalis) were exposed 12-24h to bean (Phaseolus vulgaris) and impatiens (Impatiens wallerana) leaf disks treated with Beauveria bassiana conidia and then transferred to clean bean or impatiens at various times post-treatment. Significantly greater levels of fungal infection were observed when thrips were treated on bean versus impatiens, but exposure to impatiens following treatment had no effect on fungal infection (percent mortality). This result, combined with observations of no inhibition of germination of conidia exposed to intact or macerated impatiens foliage, indicated that the negative effect of the impatiens host plant was not due to plant chemical compounds (antibiosis). Further observations revealed that insects acquired (picked-up) 75% more conidia from treated bean disks than from treated impatiens disks. This difference in dose acquisition was determined to account for the observed difference in percent mortality (15%) following treatment on the two host plants. Median lethal doses (LD(50)) of B. bassiana were not significantly different on the two host plants, but median lethal concentrations were nearly 7-fold greater on impatiens. This difference was explained by disproportionate rates of conidial acquisition at measured rates of conidial deposition (an inverse relationship was observed between application rate expressed as conidia/mm(2) and the number of conidia acquired). The mechanism underlying the differential rates of conidial acquisition from bean versus impatiens was not determined.     

Mass Production of Conidia of Penicillium frequentans,a Biocontrol Agent Against Brown Rot of Stone Fruits

Conidial production of Penicillium frequentans , a biocontrol agent of the fungal pathogen Monilinia laxa , was tested in liquid and solid-state fermentation. Conidial production of P. frequentans in solid-state fermentation was higher than in liquid-state fermentation. Solidstate fermentation was made in specially designed plastic bags (VALMIC ® ) containing peat:vermiculite (1:1 w/w). Addition of nutrients to the peat:vermiculite increased conidial production of P. frequentans , especially when lentil meal was added. The number of conidia obtained in this solid-state fermentation was maintained in the range of 10 8 -10 9 conidia g -1 from 5 to 120 days after inoculation. Germinability of these conidia was > 90% until 90 days of incubation and declined at 120 days. Optimal initial moisture content in the substrate was 30-40% (v/w). At lower moisture contents, significant reductions in conidial production and germinability were observed, particularly at 10% (v/w). Conidial production was similar when the substrate was inoculated with 10 5 , 10 6 or 10 7 conidia g -1 dry substrate. Fresh conidia produced by solid-state fermentation reduced the incidence of brown rot on plums by 75%.     

Conidiation of Hirsutella thompsonii var. synnematosa in submerged culture

Fourteen monosporal isolates of Hirsutella thompsonii grew vegetatively in various liquid media producing typical phialidic-like conidiophores. Hirsutella thompsonii var. synnematosa from Ivory Coast (HtIC) was the only pathotype which produced true conidia in submerged culture. HtIC began producing conidia after 3 days incubation reaching a peak ranging from 6.8 × 10⁵ to 9.7 × 10⁷ conidia/ml between 6 and 11 days. A concentration of 10 g/liter of corn steep liquor and 0.2% Tween 80 were essential for maximum conidiation. Submerged conidia had a smooth but somewhat rugose conidial walls, whereas aerially formed conidia were distinctly verrucose. Germination of submerged conidia ranged from 5.2 to 12.9% and were virulent causing 32.5% infection to adult citrus rust mites when sprayed on citrus foliage at 1.2 × 10⁹ conidia/ml.     

Effect of relative humidity,temperature and fungicide on germination of conidia of Cercospora canescens caused the Cercospora leaf spot disease in mungbean

The aim of the present investigation was to determine the impact of relative humidity (RH) and temperature on conidial germination, nuclear position and effect of important fungicides on growth and conidial germination of Cercospora canescens. Germination of conidia was observed at RH range 92–100% at 5–35°C. Significant interaction between temperature and RH indicated that higher humidity and high temperature promoted quick germination both in the presence and absence of free moisture. Although in absence of free moisture at 92–95% RH higher temperatures 25–35°C promoted quick evaporation of moisture and no conidial germination. Number of germtube was increased significantly at the optimum temperature 25–30°C and higher humidity (98–100%). But higher temperature 25–35°C with lower RH did not support the conidial germination. This finding is very important for disease forecasting using meteorological data. The spray of Carbendazim as contact fungicide may not be useful since it is not effective against the conidia of C. canescens. Triadimefon did not inhibit the conidia germination but completely inhibited mycelium development at 50 μg/ml. Propriconazole inhibited both conidia germination and mycelial development. Therefore, Propiconazole may be taken as protective as well as curative spray. In non-systemic fungicide, Copper oxychloride gave anticipated result by inhibiting both conidial germination and mycelium development. Therefore, copper oxychloride can be used as protectant fungicides for Cercospora leaf spot caused by C. canescens.     

Relationship between number and type of adhesions of Penicillium oxalicum conidia to tomato roots and biological control of tomato wilt

We studied (a) the extent adhesion of Penicillium oxalicum conidia to tomato roots after application of P. oxalicum conidial formulations with or without stickers, (b) the relationship between the extent of conidial adhesion to roots and biocontrol of the conidial formulations against tomato wilt, and (c) colonisation of roots by P. oxalicum. Adhesion of P. oxalicum conidia to tomato roots occurred within the first minute of contact between the root and the conidial formulation and the bonding strength was sufficiently strong to prevent conidial removal from the roots. In addition, some formulations with stickers that increased conidial adhesion to roots improved the biocontrol of tomato wilt, when compared to that of formulations without stickers. A “dried conidia without stickers” with 0.025% Nu-Film 17 had no effect on the biocontrol of tomato wilt, despite good adherence of the conidia to the roots. The numbers of P. oxalicum conidia that adhered to the roots was constant for 60 days after application of a “dried conidia without stickers” conidial formulation. The significance of these results (speed of adhesion, number of adhered conidia, and variability of conidial external surface) are discussed in relation to the biocontrol success of tomato wilt using different types of conidial formulations with and without stickers.     

Infection of Psoroptes mites with the fungus Metarhizium anisopliae

The astigmatid mite, Psoroptes ovis (Hering) (Acari: Psoroptidae), is an obligatory ectoparasite that causes psoroptic mange in a range of domesticated animals, particularly sheep, where the clinical disease is known as sheep scab. A series of laboratory assays were used to assess the use of the fungus, Metarhizium anisopliae (Metchnikoff) (Deuteromycotina: Hyphomycetes) as a biocontrol agent for P. ovis derived from rabbits (syn. P. cuniculi). The immersion of mites in a suspension of conidia of M. anisopliae resulted in the acquisition of fatal infections. The number of mites which developed infections increased significantly with the increasing concentration of the conidial suspension to which they were exposed; 77% of mites developed infections when exposed to the highest concentration used (1 x 10(8) conidia ml(-1)). Controls developed no fungal infections. Mites allowed simply to walk across a surface which had been treated with a suspension of conidia also acquired fungal infections; the number infected was again related to the concentration of conidia present. After contact for 24 h with a surface treated with 1 x 10(8) conidia ml(-1), 73% of the mites became infected. To determine whether dead infected mites could act as sources of infection, infected cadavers were placed in chambers with live uninfected mites. The uninfected mites acquired fatal infections from the cadavers; a higher ratio of infected cadavers to uninfected mites resulted in greater transmission of infection. The time after death of the infected cadaver was also an important factor influencing the number infected, 5-day-old cadavers were the most infective and 18-day-old cadavers the least infective. The results indicate that M. anisopliae is a good candidate control agent for Psoroptes mites.     

A Simplified Geometric Model to Predict Nasal Spray Deposition in Children and Adults

A mathematical approach was developed to estimate spray deposition patterns in the nasal cavity based on the geometric relationships between the emitted spray plume and the anatomical dimensions of the nasal valve region of the nasal cavity. Spray plumes were assumed to be spherical cones and the nasal valve region was approximated as an ellipse. The effect of spray plume angle (15–85°) on the fraction of the spray able to pass through the nasal valve (deposition fraction) was tested for a variety of nasal valve (ellipse) shapes and cross-sectional areas based on measured dimensions from pediatric and adult nasal cavities. The effect of the distances between the tip of the nasal spray device and the nasal valve (0.2–1.9 cm) on the deposition fraction was also tested. Simulation results show that (1) decreasing spray plume angles resulted in higher deposition fractions, (2) deposition fraction was inversely proportional to the spray distance and the nasal valve (ellipse) major/minor axis ratio, and (3) for fixed major/minor axis ratios, improved deposition occurred with larger nasal valve cross-sectional areas. For a typical adult nasal valve, plume angles of less than 40° emitted from a distance of 1 cm resulted depositions greater than 90% within the main nasal cavity, whereas for a 12-year-old child, only the most narrow plume angles (<?20°) administered resulted in significant deposition beyond the nasal valve.