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1.
Trichlorfon has been cited as being a selective insecticide that has only minimal detrimental impact on natural enemies. However, when applied to alfalfa in Minnesota, trichlorfon has been found to enhance pea aphid populations to an even greater extent than does carbaryl, an insecticide notorious for inducing aphid outbreaks. We found a direct relationship between the number of trichlorfon applications that plots received during a regrowth period and the consequent pea aphid numbers that these plots supported. Pea aphid showed appreciable tolerance to both trichlorfon and carbaryl in laboratory dip tests. In small plots, effects of trichlorfon sprays on beneficials are transitory because of the short residual life of the insecticide and the relative mobility of many natural enemies. This gives trichlorfon the appearance of selectivity. Interactions between aphid parasitism, cultivar resistance, and insecticide were observed. Cv. Gladiator had the most resistance to pea aphid, with cv. Kanza a close second, and cv. Weevlchek the most susceptible. Pea aphids from trichlorfon-treated alfalfa plots had higher levels of parasitism, primarily Aphidius ervi Hal., than did pea aphids from untreated plots, suggesting a density-dependent response by the parasites to the insecticide-enhanced pea aphid numbers. Cultivar differences in pea aphid numbers were not sufficient to show a consistent effect on percentage parasitism.  相似文献   

2.
The parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is one of the key natural enemies of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Lethal and sublethal effects of imidacloprid and buprofezin on emergence and key biological and population parameters of E. mundus exposed during different developmental stages were studied. Dose–response bioassays were carried out on adult wasps using a leaf dipping method. The emergence rates of adults were reduced significantly by the field-recommended concentrations of the insecticides. However, the emergence rates were not affected either by the stage of the parasitoid at the time of exposure (larval and pupal stages), and there was no interaction between treatments and time of exposure. No significant mortality of E. mundus adults was observed following buprofezin treatment. The LC50 of imidacloprid on adults was 4.75 ppm. The results showed that the longevity and fecundity of E. mundus adults were reduced significantly by the two insecticides, though the sex ratio of E. mundus offspring was not affected. Population parameters of the parasitoid such as R0, rm and T were also significantly reduced by the insecticides. Our results indicated that, in addition to lethal effects, sublethal effects should also be considered when these insecticides are applied in IPM programs for this pest.  相似文献   

3.
The effects of vegetation background in the form of living mulches and weed cover on the population dynamics of foliage and soil arthropods were studied in corn, tomato and cauliflower crop systems in California. In Davis (Central Valley site) herbivores (especially aphids and lygaeids) were more abundant in the weed cover than in the clover mulch, whereas leafhoppers were most common in the clover mulch. Higher numbers of natural enemies were observed in the clover plots. Significantly more ground predators (Carabidae, Staphylinidae, spiders) were caught in pitfalls placed in the weedy and clover plots, than in the clean cultivated plots. In Albany (Coastal area), specialized herbivore (cabbage aphids and flea-beetles) densities were significantly reduced in plots with additional vegetation cover. It is not clear if this reduction was due to plant diversity or density effects, to the effects of natural enemies or to the lower quality of plants in the weedy and mulched plots, as crop growth and yields were drastically reduced in these plots at both sites. Further agronomic work is warranted to minimize the competitive effects of legume covers on crops, so that the entomological advantages reported here can be used in a practical way.  相似文献   

4.
连作晚稻前期施药种类和时间对褐飞虱种群动态的影响   总被引：7，自引：0，他引：7  
 田间试验研究了连晚前期施药种类和时间对褐飞虱种群动态的影响。结果表明施药后褐飞虱种群数量均有不同程度下降，但对褐飞虱主害代的控制作用与使用的农药种类和时间有密切的关系，而农药对褐飞虱的控制作用随种群的发展而下降。施药区褐飞虱种群增长倍数较对照区显著提高，其主要原因是农药对天敌尤其是对微蛛和黑肩绿盲蝽的杀伤作用。引起褐飞虱种群增长倍数提高的主要时期在四代成、若虫高峰期至五代卵高峰期，即施药后2～3周内。在各种供试药剂中，施用三唑磷的小区明显出现再增猖獗现象．根据以上结果，讨论了改善褐飞虱化学防治的途径。  相似文献   

5.
茶园间作芳香植物罗勒和紫苏对茶园生态系统影响的研究   总被引：4，自引：0，他引：4  
通过茶园间作芳香植物研究其对茶园害虫和天敌种群数量、土壤养分状况、茶树生长及茶叶生化成分等的影响,分析间作芳香植物对幼龄茶园的生态综合调控效果。幼龄茶园间种芳香植物能减少小贯小绿叶蝉和绿盲蝽的数量,增加茶园中瓢虫、草蛉、寄生蜂和蜘蛛等天敌的数量;芳香植物间作区土壤中铵态氮、有效磷和速效钾的含量高于绿肥间作区和对照;茶园间作芳香植物能在一定程度上促进茶树生长、培养幼龄茶园的树势和树冠、增加茶叶产量。茶园间作芳香植物能减少茶叶中茶多酚和咖啡碱含量,提高可溶性糖和儿茶素含量,改善茶叶品质。可见茶园间作芳香植物是一种具有较好生态效益的茶园栽培管理模式,能促进生态茶园的发展。  相似文献   

6.
Semi-natural field borders are frequently used in midwestern U.S. sustainable agriculture. These habitats are meant to help diversify otherwise monocultural landscapes and provision them with ecosystem services, including biological control. Predatory and parasitic arthropods (i.e., potential natural enemies) often flourish in these habitats and may move into crops to help control pests. However, detailed information on the capacity of semi-natural field borders for providing overwintering refuge for these arthropods is poorly understood. In this study, we used soil emergence tents to characterize potential natural enemy communities (i.e., predacious beetles, wasps, spiders, and other arthropods) overwintering in cultivated organic crop fields and adjacent field borders. We found a greater abundance, species richness, and unique community composition of predatory and parasitic arthropods in field borders compared to arable crop fields, which were generally poorly suited as overwintering habitat. Furthermore, potential natural enemies tended to be positively associated with forb cover and negatively associated with grass cover, suggesting that grassy field borders with less forb cover are less well-suited as winter refugia. These results demonstrate that semi-natural habitats like field borders may act as a source for many natural enemies on a year-to-year basis and are important for conserving arthropod diversity in agricultural landscapes.  相似文献   

7.
The efficacies of some next-generation insecticides against the rice yellow stem borer(YSB),Scirpophaga incertulas(Walk.), and their compatibilities with natural enemies were investigated during 2014 and 2015. Three newer insecticides, chlorantraniliprole 0.4% G, dinotefuran 20% SG, and methoxyfenozide 24% SC, and two commonly used insecticides, carbufuran 5 G and quinalphos 25 EC,were evaluated in the field for their efficacies against YSB and their non-target effects on natural enemies.Application of chlorantraniliprole 0.4% G at 10.96 kg/hm^2 resulted in the greatest reduction in YSB infestation(deadhearts and whiteheads) and greatest increase of yield compared to the untreated control plots, followed by methoxyfenozide 24% SC at 0.41 L/hm^2, dinotefuran 20% SG at 0.15 kg/hm^2,carbufuran 5 G at 10.96 kg/hm^2, and quinalphos 25 EC at 1.50 L/hm^2. All the insecticides reduced the numbers of predators viz., lady bird beetles, wolf spiders, carabid beetles, earwigs, green mirid bugs, and damselflies. Numbers of adults of the egg parasitoids Trichogramma sp., Telenomus sp. and Tetrastichus sp. were significantly reduced in insecticide-treated plots compared to untreated control plots. In all field trials, the harmful effects of the five insecticides were in the following rank order(least harmful to most harmful): chlorantraniliprole 0.4% G, carbufuran 5 G, dinotefuran 20% SG, methoxyfenozide 24% SC,and quinalphos 25 EC. On the basis of reduction in YSB infestation, increase in grain yield, and compatibility with natural enemies, chlorantraniliprole 0.4% G was proved to be the best of all the insecticides for YSB management system, although the study suggested minimizing its retail price for enhancement of cost effectiveness in farmers' fields.  相似文献   

8.
Abstract

Paclobutrazol (PB), an inhibitor of endogenous gibberellin synthesis, was applied to peanut plants altered dry-matter distribution and increased seed yield. PB solution at a concentration of 100, 200 or 400 ppm was sprayed on foliage at the beginning of the pod formation stage (BPFS), the early pod filling stage (EPFS) and the middle pod filling stage (MPFS) .The height of the plants treated with PB at BPFS and EPFS was shorter than that of the control plants by more than 10 and 5 cm, respectively. The pod number of the plants treated with 100 or 200 ppm PB at any developmental stage was higher than that of the plants treated with 0 or 400 ppm PB. The seed yield was increased by PB applied at any stage, and the yield after the treatment with 100 or 200 ppm PB at BPFS or EPFS was approximately 370 gm~2.  相似文献   

9.
The effects of cycloxaprid (a modified neonicotinoid insecticide) and buprofezin (a thiadiazine insecticide) on mortality of the white-backed planthopper (WBPH), Sogatella furcifera, were determined in laboratory assays. Cycloxaprid killed WBPH nymphs and adults but buprofezin killed only nymphs, and cycloxaprid acted faster than buprofezin. One day after infestation, mortality of third-instar nymphs was >65% with cycloxaprid at 125 mg liter−1 but was <38% with buprofezin at 148 mg liter−1. By the 4th day after infestation, however, control of nymphs by the two insecticides was similar, and cycloxaprid at 125 mg liter−1 caused ≥80% mortality of adults but buprofezin at 148 mg liter−1 (the highest rate tested) caused almost no adult mortality. LC50 values for cycloxaprid were lowest with nymphs, intermediate with adult males, and highest with adult females. Although buprofezin was slower acting than cycloxaprid, its LC50 for nymphs 5 d after infestation was 3.79-fold lower than that of cycloxaprid. Mean carboxylesterase (CarE) specific activity of nymphal WBPH treated with cycloxaprid and buprofezin was higher than that of control, but there was no significant difference between cycloxaprid and control (no insecticide), and it was significantly higher for buprofezin than those of cycloxaprid and control. For glutathione S-transferase and mixed function oxygenase, the specific activity of nymphal WBPH treated with buprofezin was significantly higher than those of cycloxaprid and control, too.  相似文献   

10.
在农业生产中由于化学农药的长期不合理使用,导致"3R"问题持续存在和人类赖以生存的环境日益恶化,生物防治产品及技术在有害生物综合治理中的作用越发重要。天敌昆虫的生长发育及存活期往往很短,探索其储存技术是天敌昆虫规模化生产中的关键性环节。低温贮藏可以延长天敌昆虫的寿命,进而可以为生物防治提供充足、稳定的天敌产品。因此,天敌昆虫低温贮藏一直是生物防治领域研究的热点。本文围绕天敌昆虫低温贮藏这一环节,就低温诱导天敌昆虫滞育虫态、冷驯化对昆虫低温贮藏效果的影响、低温贮藏对天敌昆虫适合度(寿命、羽化率、性比、个体尺寸大小、飞行扩散能力等)的影响等方面进行综述,以期为天敌昆虫产品的规模化生产及应用技术提供参考。  相似文献   

11.
Summary

This paper reports the results on safflower crops grown in a nine-year study, conducted on a 8 ha site, to determine the feasibility of using drainage water for irrigation in a 2-year cotton/1-year safflow-er rotation system. The cotton crops were irrigated with waters of 400, 1,500, 3,000, 4,500, 6,000, and 9,000 ppm total dissolved salts, and safflower was grown only with a preplant irrigation with nonsaline water. The use of drainage water for crop irrigation may be a means of decreasing its volume. Even though safflower was never irrigated with saline drainage water directly, the residual effect of using saline water for cotton irrigation adversely impacted safflower growth and development. Safflower seed yields were reduced in plots previously irrigated with waters of 4,500 ppm or higher salinity and even more severe effects on crop growth were seen as the numbers of years of irrigation with the saline water increased. After irrigating six cotton crops, the safflower seed yield in plots irrigated with 9,000 ppm waters was reduced to only 14% of the control. The safflower oil content and quality were not affected. Impacts on plant density, shoot height, shoot biomass, and leaf ionic content also are discussed.  相似文献   

12.
Widespread use of highly toxic pesticides primarily for agricultural purpose has generated increasing concerns about the negative impact of pesticides on human health and the environment. Integrated pest management (IPM) usually seeks to minimize the use of pesticides and can be utilized to solve pest problems while minimizing risks to people and the environment. A total of 220 vegetable farmers in Nakhon Ratchasima Province of Thailand was interviewed with the objective of investigating the factors determining their adoption or non-adoption of IPM practices. The findings demonstrated that farmers had different uncompromising reasons for determining the use of IPM for their insect pest management. Higher costs of insecticides (91%), adverse effects of insecticides on human health and the environment (80%), and a greater risk of insect pests developing resistance to insecticides (28%) were the primary reasons for the adoption of IPM by vegetable growers in the study area. The reasons for the rejection of IPM practice were unsuitability of IPM for a large farm (52%), implementation difficulties (80%) and a greater belief in synthetic insecticides and their efficacy for target pest control (39%). A comparison between the IPM and the non-IPM farmers showed a significant difference (P < 0.01) in farmers' knowledge of pest management, which influenced IPM adoption or non-adoption. The IPM farmers had greater knowledge about identifying natural enemies and their beneficial role in controlling insect pests, about plant extracts and their efficacy in controlling insect pests and about sticky traps and their efficacy in monitoring natural enemies and controlling insect pests. For example, 24% of IPM farmers had knowledge of natural enemies whereas it was only 4% for the non-IPM farmers. A logistic regression model was fitted which showed that lower cost of pest management, better knowledge on IPM after training and availability of extension services were the factors which influenced farmers' adoption of IPM practice. The non-IPM farmers rejected adoption of IPM due to the common belief that natural enemies would not be effective in controlling insect pests and yields of vegetables would not be increased by practicing IPM.  相似文献   

13.
High levels of phospholipids in linseed oil result in production line hold-ups due to gum formation in machinery during processing and irreversible cloudiness when high phospholipid oil is left to stand. Specific problems with oil from UK crushed linseed were experienced by linseed oil refiners in both the 1993 and 1997 seasons. The 1993 harvest was characterised by wet conditions suggesting that enhanced phospholipid content may be associated with weather damage which was reported in some linseed crops in that year. A study was undertaken to investigate the effect of agronomic factors which may influence phospholipid content. In a replicated field experiment spring linseed cv. Barbara, which had been desiccated with diquat, was sequentially harvested at six timings from both rainfed plots and others which were misted during the seed filling stage. Additional plots which had not been desiccated were also sampled at a normal, early September and late October harvest date. Seed samples were crushed and the resulting oil was analysed for total, hydratable and non-hydratable phospholipid contents. Mean total phospholipid contents were greater in non-misted plots than misted plots and increased dramatically between the final harvest dates, however, there were large variations in total phospholipid content for individual treatments. Desiccation of linseed is standard practice in the UK, but total phospholipid content of the non-desiccated samples taken in early September were low at 170 ppm and did not increase despite a further harvest delay of 3 weeks. The level of non-hydratable phospholipids, which are not removed during normal processing and cause the most difficult production problems, were unaffected by delayed harvest date, but they were always greater in the misted, compared to non-misted treatment. An additional study of unreplicated seed samples collected from a range of sites and varieties indicated a large variation in total phospholipid content from 43 to 1436 ppm. The highest levels were reported at one site where the harvest was delayed past physiological maturity by wet weather. Results from these studies suggest that crop desiccation, which causes drying and fracturing of the capsule wall, allowing water ingress, could increase the risk of increased phospholipid content in linseed if wet weather delays harvest. Variety choice may also be important, but survey results indicate this may be linked to the relationship between physiological maturity and weather conditions at individual sites.  相似文献   

14.
The fatty acid profiles and tocopherol and phytosterol contents of crude oils of cress (Lepidium sativum L.) and field pennycress (Thlaspi arvense L.) are reported, along with yields from the corresponding seeds. The physical properties of these oils were also determined, which included oxidative stability, kinematic viscosity, viscosity index, low temperature fluidity, specific gravity, acid value, lubricity, and iodine value. The oil content of dried cress and field pennycress seeds was 22.7 and 29.0 wt%, respectively. The primary fatty acids found in cress oil were oleic (30.6 wt%) and linolenic acids (29.3 wt%), whereas field pennycress oil was principally composed of erucic (32.8 wt%) and linoleic (22.4 wt%) acids. Cress oil contained high concentrations of γ- (1422 ppm) and δ- (356 ppm) tocopherols, whereas α-tocopherol (714 ppm) was the primary tocopherol discovered in field pennycress oil. The overall tocopherol concentrations of cress and field pennycress oils were 1799 and 851 ppm, respectively. The primary phytosterols elucidated in cress and field pennycress oils were sitosterol and campesterol, with avenasterol also present in significant quantity in cress oil. The total phytosterol concentration in cress oil (14.41 mg/g) was greater than that in field pennycress (8.55 mg/g) oil. Field pennycress oil exhibited excellent low temperature fluidity, whereas cress oil was more stable to oxidation and over a range of temperatures displayed lower kinematic viscosities as well as a higher viscosity index. The acid and iodine values of field pennycress oil were lower than those for cress oil, but both oils had excellent lubrication properties.  相似文献   

15.
在马铃薯同大豆间作中,采用喷洒蜂蜜水和早熟马铃薯刈秧的方法对马铃薯田内的天敌昆虫向大豆田内诱集和助迁,使得大豆田内天敌数量增加,从而使大豆蚜的防控更加有效。试验结果表明,喷洒蜂蜜水使得处理区内天敌总量增长率高于对照区,持续时间达7 d;早熟马铃薯刈秧使处理区内天敌数量增加,同时大豆蚜数量明显降低,该方法同马铃薯收获时间相吻合,具有良好的防控效果和较长的持效时间,因此在应用于促进马铃薯田中天敌向大豆田内转移具有一定的意义。  相似文献   

16.
西双版纳橡胶树主要害螨及优势种螨类天敌种类调查   总被引：4，自引：0，他引：4  
2010~2012年通过对西双版纳州橡胶林的害螨及其天敌进行2年多的调查。结果表明:西双版纳州橡胶树害螨主要有2种,分别为六点始叶螨(Eotetranychus sexmaculatus Riley)和海南小爪螨(Oligonychus hainanensis Ma,Yuan et Lin);并详细记述了2种害螨的形态特征、为害特点及发生数量;初步调查到六点始叶螨的天敌19种,隶属2个纲、7个目、10个科,采用优势度指数评价法得出优势种群为草蛉、食螨瓢虫和捕食螨,三者都具有较好的应用前景;初步摸清六点始叶螨主要天敌发生消长及其自然控制作用。  相似文献   

17.
Two varieties of potatoes viz. Kufri Chandramukhi and Kufri Sindhuri were treated with Isopropyl-N(3-chlorophenyl)carbamate at two different concentrations viz. 4000 and 5000 ppm. The treated potatoes were stored for a period of four months under different storage conditions i.e. room temperature, cold and evaporative cooling chamber storage and analysed for polyphenol oxidase activity, total nitrogen content and quality of dried slices produced from these at different stages of storage. Higher nitrogen content was observed in CIPC treated potatoes as compared to control. Polyphenol oxidase activity decreased more in Kufri Chandramukhi than in Kufri Sindhuri in CIPC treated as well as in control experiments. The changes in nitrogen content and polyphenol oxidase activity were more pronounced in evaporating cooling chamber and in room storage than in the cold storage. The quality of potato slices prepared from both varieties confirmed the superiority of Kufri Chandramukhi over Kufri Sindhuri for processing purposes.  相似文献   

18.
《Crop Protection》1986,5(3):182-189
Aphid-specific predators, aphid parasitoids and aphid-pathogenic fungi were sampled in 1980 and 1981 in plots of winter wheat treated or not with herbicides. Aphids and their natural enemies were also sampled from three abundant weed species. Aphid-specific predators were scarce in both years of the study, probably because of the scarcity of cereal aphids in the experimental plots, and no significant treatment effects on this group were recored. The syrphid, Platycheirus manicatus, was the only predator recorded from the weeds. Cereal aphids and the weed aphids, Brachycaudus helichrysi and Cryptomyzus galeopsidis, were attacked by the same species of aphid-pathogenic fungi but by different parasitoids. In the first year more Sitobion avenae were infected by fungal pathogens in weedy plots than in treated plots, either because of higher humidity or because of the spread of infection from weed aphids, or a combination of both. Weed removal had little effect on those parasitoid species which attacked cereal aphids. The small populations of cereal aphids which were present in the plots were unaffected by herbicide treatments.  相似文献   

19.
The effect of crude oil spillage on growth, productivity and nutrient uptake of maize (Zea mays L.) was assessed in a pot experiment using an Evwreni manifold sample of a petroleum development company, which had aspecific gravity of 0.8778. The Suwan 1 variety of maize was used in the experiment. In crude oil polluted soils, germination was delayed and the germination percentage was significantly affected by oil pollution. Growth was poor in polluted soils using parameters such as plant height, stem girth,ear height, leaf area at four weeks after planting, leaf area at maturity and average length of primary roots as growth indicators. Grain yield was significantly reduced at 95% level of probability with yield (when compared with the control) reduced by as much as 98.6%, 96.5% and 58.3% for preplant,five weeks after planting (5 WAP) and seven weeks after planting (7 WAP) treatments, respectively. Leaf analysis of the maize plants grown in soilscontaminated with crude oil a week before planting (preplant treatment) revealed mean levels of heavy metals (6.18 ppm Zn2+, 0.62 ppm Cu2+,26.24 ppm Fe2+, 10.84 ppm Mn2+, 2.96 ppm Pb2+ and 3.88 ppm Co2+) which are higher than the maximum permissible levels (MPL) for maize in tropical soils. Maize plants that were polluted at other time intervals showed no significant (p>0.05) variation in heavy metal concentrations when compared with the control, and were considered potentiallysafe for human consumption.  相似文献   

20.
为探究生草大叶油草种植对芒果园节肢动物群落的影响,将种植大叶油草的芒果园与传统清耕生境节肢动物群落结构进行比较,对2种不同生境2018年8月—2019年6月的节肢动物群落物种数量、物种多样性、群落稳定性进行了分析。结果表明,大叶油草生境下芒果园节肢动物物种数量、个体数量约为清耕生境的2倍;物种多样性指数、群落稳定性显著高于清耕生境,在天敌亚群落方面也表现出相似差异。而害虫亚群落方面,清耕生境害虫数量（4730头）约为大叶油草生境（2027头）的2倍。综合分析表明,芒果园种植大叶油草有利于增强节肢动物群落稳定性,减少害虫、提高天敌的种群数量、便于发挥天敌的自然控制作用,是一种较好的绿色防控措施。  相似文献   

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