首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Cotton mealybug Phenacoccus solenopsis Tinsley is an important pest of cotton in Pakistan, and its management is difficult due to the development of insecticide resistance. This research was conducted to characterize the bifenthrin resistance in populations of P. solenopsis and different parameters such as cross-resistance, realized heritability and possible resistance mechanisms were studied to improve the management of this important pest. A field-collected population was selected with bifenthrin in the laboratory for 14 generations and developed a resistance of 178-fold. The realized heritability of bifenthrin resistance was 0.54 in the selected population. The toxicity of bifenthrin was synergized by the addition of either piperonylbutoxide (PBO) or S,S,S tributylphosphorotrithioate (DEF) which suggests a general metabolic resistance due to possible involvement of mono-oxygenases or esterases. However, the resistant population did not develop a significant cross-resistance to either buprofezin, chlorpyrifos or lambda-cyhalothrin. These data suggest that alternative insecticide-based management programs can be developed for this pest in the short-term, but resistance management strategies which can reduce the sole reliance on insecticides are still needed.  相似文献   

2.
Neoseiulus baraki Athias-Henriot (Acari: Phytoseiidae) is an important predatory mite of the coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae) and attempts are now being made to evaluate the effectiveness of augmenting N. baraki to control coconut mite in the field. These studies require a steady supply of N. baraki in large numbers. One major constraint of the existing method to mass rear N. baraki on Tyrophagus putrescentiae Shrank (Acari: Acaridae) in a closed arena without a water barrier was frequent contamination of cultures by other mites. This paper describes the development of an efficient method to mass rear N. baraki in the laboratory with less monitoring and relatively minimal contaminants. Three box-type arenas and a tray-type arena were tested to mass rear T. putrescentiae. Mites were successfully developed on two box-type arenas and the tray-type arena, but the production (2197 mites per tray in 4 weeks) of T. putrescentiae was significantly higher on the tray-type arena. A 110-fold increase of T. putrescentiae was achieved in tray-type arenas in 4 weeks. None of the box-type arenas could be maintained more than 5 weeks without acarine and fungal contaminations. N. baraki could be successfully reared on the tray-type arena at least for 6 weeks. More than 4800 mites per tray, a 240-fold increase was achieved in 5 weeks when T. putrescentiae was added at 3-week intervals. Advantages and disadvantages of the new method are described.  相似文献   

3.
The diamondback moth, Plutella xylostella (L.), is an important international pest of cruciferous vegetables. The effects of the new diamide insecticide chlorantraniliprole, at a lethal concentration inducing only 25% mortality (LC25), were assessed on the development and reproductive parameters of P. xylostella under laboratory conditions. In addition, effects on development time, pupation rate, larval and pupae weight, fertility, and survival in the parent and F1 generations were assessed. When 4th instar P. xylostella larvae were exposed to LC25 of chlorantraniliprole on a cabbage (Brassica oleracea var. capitata L.) leaf for 96 h, we observed increased developmental time for 4th instar larval to pupa period (4.27 days vs. 3.34 days in the control), lower pupal weight (3.58 mg vs. 4.17 mg in the control) and decreased adult fecundity (by 42%). F1 generation underwent transgenerational effects, i.e. higher developmental time from egg to pre-pupae and lower egg hatching rate occurred. Demographic growth parameters, such as the net reproductive rate (R0), the intrinsic rate of increase (rm), and finite rate of increase (λ) were significantly lower for the LC25 chlorantraniliprole treated group than for the untreated control. Our results suggest that exposure to LC25 of chlorantraniliprole may have negative effects both on exposed individuals and on subsequent generations in P. xylostella.  相似文献   

4.
Chemical control with insecticides, typically applied as foliar sprays or chemigation, is the primary tactic used to manage Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae). We evaluated the efficacy of 14 insecticides, including both systemic and non-systemic insecticides, against B. hilaris applied as a seedling tray drench. Experiments were conducted in both greenhouse and field settings. In all experiments, we used the maximum label rate of insecticides and calculated dose per seedling based on this rate and standard plant density per hectare. Each seedling in the tray received 2-mL insecticide solution, and the seedlings were then exposed to B. hilaris adults after transplanting in cages for greenhouse experiments or natural B. hilaris populations in the field experiments. A scale system (0–4) was used to evaluate the severity of B. hilaris feeding injury on leaves where 0 = no injury and 4 = >75% of the leaf margins with B. hilaris feeding injury. We evaluated damage using the rating system, percentage of damaged leaves, number of feeding injury sites, as well as plant height, leaf width, and fresh and dry weight. In the greenhouse experiment, percentage of injured leaves, number of injury sites, and damage rating were significantly lower for transplants treated with acetamiprid, clothianidin, dinotefuran, imidacloprid, and thiamethoxam, and cyclaniliprole compared with the untreated. There was a relationship between feeding injury sites and plant height, leaf width, fresh and dry weight (R2 > 0.5) in both 2015 field experiments. Similarly, the transplants treated with acetamiprid, clothianidin, dinotefuran, imidacloprid, thiamethoxam, thiamethoxam + chlorantraniliprole, imidacloprid + β-cyfluthrin and cyclaniliprole had significantly lower damage ratings than those treated with chlorpyrifos, bifenthrin, tolfenpyrad, flonicamid, cyantraniliprole, spinetoram and the untreated control. For transplanted broccoli, treatment of transplant plugs with neonicotinoid insecticides prior to planting can be an effective method for controlling B. hilaris.  相似文献   

5.
Western flower thrips, Frankliniella occidentalis (Pergande), is a major pest of strawberry and other horticultural and ornamental crops. Biological control of F. occidentalis with predatory mites is recommended as an additional management strategy to chemical control in glasshouse and protected crops. However, it is not known whether multiple (two or three) species releases of predatory mites are more effective than single species releases. The effect of an application of spinosad followed by mite releases could further increase suppression of F. occidentalis. In a series of trials in the glasshouse, we evaluated three commercially available predatory mite species, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese). Strawberry plants were sprayed once with either spinosad at the recommended rate or with water. F. occidentalis adults were released onto plants 24 h after spraying, and mites were released six days later. Spinosad significantly reduced F. occidentalis compared to the control (water). T. montdorensis, N. cucumeris and H. miles significantly reduced F. occidentalis compared to the ‘no mite’ treatment. Spinosad had no effect on T. montdorensis and N. cucumeris, as their numbers did not differ between the spinosad and control treatments; H. miles was not recovered. When mites were released after an application of spinosad, greater suppression of F. occidentalis was achieved than with releases of predatory mites alone. When released as a double species combination, ‘T. montdorensis and H. miles’ was the most effective combination. There was no difference in efficacy between releases of ‘T. montdorensis and H. miles’ or ‘T. montdorensis, N. cucumeris and H. miles’. We conclude that multiple species releases are more effective than single species releases, and that biological control of F. occidentalis with predatory mites can be used together with spinosad.  相似文献   

6.
Frankliniella occidentalis (Pergande) is a serious pest of a wide range of horticultural and ornamental crops. Populations resistant to most conventional insecticides, including–spinosad, have been detected. To control spinosad-resistant thrips, growers could use a ‘high-rate’/biological control strategy. The proposed strategy is based on a single application of spinosad at double the recommended application rate followed by releasing predatory mites (Acari), which are used as biological control agents of F. occidentalis. This study compared two resistance management strategies on a spinosad-resistant F. occidentalis strain: applying spinosad at twice the recommended rate, and spraying at twice the rate then releasing predatory mites, Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese). Direct exposure to twice the recommended rate of spinosad killed 100% of all adults of all species of predatory mites. Spinosad residues aged 2–48 h were also highly toxic to adults of all three mite species, causing 96–100% mortality. Spinosad residues aged 48–168 h were less toxic to N. cucumeris than to T. montdorensis and H. miles. LT25 of double the recommended rate of spinosad for T. montdorensis, N. cucumeris and H. miles were calculated as 6.02, 5.3, and 7.08 days, respectively. When released after applying spinosad, T. montdorensis was the most successful species in reducing thrips numbers, followed by N. cucumeris and H. miles. By releasing mites 6–7 days after a spinosad application, our results suggest that F. occidentalis can be effectively controlled. The practical implications of implementing a ’high-dose/biological control’ strategy are discussed.  相似文献   

7.
The present study aimed to determine the in vitro and in vivo effects of Ziziphora clinopodioides Lam. essential oil (ZCEO) against Sclerotinia sclerotiorum on rapeseed plants. Gas chromatography-mass spectrometry (GC-MS) detected 21 compounds that represented 98.3% of the total amount of extracted oil, which mainly comprised pulegone (53.5%), isomenthone (10.4%), and carvone (5.7%). The mycelial growth of S. sclerotiorum was completely inhibited at essential oil concentrations of 1.25 and 0.15 μl ml−1 under contact and vapor phase conditions, respectively. Under contact phase, the germination of sclerotial was inhibited at the concentration of 1.00 μl ml−1. The essential oil concentration of 0.15 μl ml−1 in the vapor phase showed a strong inhibitory effect on sclerotial germination. Sclerotinia sclerotiorum growth on detached rapeseed leaves and potted rapeseed plants were dose dependently inhibited by the essential oil. Considerable morphological changes were also observed in the fungal hyphae and sclerotia. Both in vitro and in vivo results indicated ZCEO can effectively inhibit the growth of S. sclerotiorum. Thus, ZCEO could be used for crop protection.  相似文献   

8.
We estimated the effect of 5, 10, 15 and 20 mg l−1 of neemazal (1% EC azadirachtin) on life table parameters of Helicoverpa armigera (Hübner) developing on chickpea (Cicer arietinum L.). The effects were assessed on the survivals emerged from 6th instar larvae that had ingested neemazal-treated chickpea pods. Survivorship (I) and expectancy of life (ex) were highest with the commencement of age (egg) and decreased gradually with the advancement of age with all the concentrations of neemazal including unexposed cohort. All the eggs hatched in the unexposed group while highest numbers of unhatched eggs (10%) were recorded with 20 mg l−1. Mortality of 1st instars was higher at 20 and 15 mg l−1 than that of other concentration tested. Potential fecundity (pf) was reduced in concentration dependent manner and was lowest with 20 mg l−1 (418 eggs/female/generation) and highest in control (898 eggs/female/generation). Net reproductive rate (R0) was significantly reduced with the increase in concentration of neemazal. The intrinsic (rm) and finite rate of increase (λ) were significantly decreased at 20 mg l−1 than that of unexposed population. The mean generation time (Tc) was prolonged at 20 mg l−1 and significantly differed with non-treated individuals. Development of immature stages was prolonged to 38 days with 20 mg l−1 while reduced to 32 days with 15 mg l−1 of neemazal as compared to 37 days in untreated individuals. Doubling time (DT) was significantly extended to 5.02 days with 20 mg l−1 as compared to 3.84 days in the non exposed ones.  相似文献   

9.
Lactobacillus buchneri was investigated as a silage inoculant and as a probiotic on feed intake, apparent digestibility, and ruminal fermentation and microbiology in wethers fed low‐dry‐matter (DM) whole‐crop maize silage. Maize forage (279 g/kg DM) was ensiled without inoculant (untreated) and with L. buchneri CNCM I‐4323 at 1 × 105 cfu/g fresh forage (inoculated). Six cannulated wethers were arranged in a double 3 × 3 Latin square and assigned to one of three diets: (i) untreated maize silage (untreated), (ii) inoculated maize silage (inoculated), and (iii) untreated maize silage with a daily dose of L. buchneri (1 × 107 cfu/g supplied silage) injected directly into the rumen (LB‐probiotic). Wethers fed the inoculated diet had a higher (p = .050) DM intake (1.30% body weight [BW]) than wethers fed untreated and LB‐probiotic diets (1.17% and 1.18% BW respectively). The relative proportion of Ruminococcus flavefaciens (proportion of total estimated rumen bacterial 16S rDNA) in the rumen of wethers fed inoculated and LB‐probiotic diets (both 0.42%) tended (p = .098) to be lower than in the untreated diet (0.83%). Lactobacillus buchneri as a silage inoculant or as a probiotic had little effect on the variables measured in wethers.  相似文献   

10.
Biological control is not common in citrus nurseries where chemical control is prevalent. The systemic neonicotinoid imidacloprid applied as a drench is effective against three out of four key pests of young clementine plants in Spain – aphids, whiteflies, and scales. However, mites, the fourth key pest, are not control by imidacloprid and could be regulated by introduction of the predatory Phytoseiid mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor). The aim of this study was to evaluate the effects of imidacloprid applied as a drench on the demographic parameters of these two predatory mites and the compatibility of P. persimilis releases with imidacloprid to control key pest populations in young clementine plants under field conditions. The results showed that some demographic parameters of P. persimilis were affected by imidacloprid. However, their combined effect on its intrinsic rate of increase was neutral. In contrast, imidacloprid negatively affected the demographic parameters of N. californicus. Field results proved that young clementine plants could be satisfactorily protected against key pests with releases of P. persimilis combined with drench applications of imidacloprid. The combination of imidacloprid with P. persimilis releases was highly effective for management of the key pests of young clementine plants in the nursery.  相似文献   

11.
Since the 1980s wheat sharp eyespot (WSE) caused mainly by Rhizoctonia cerealis has become one of serious diseases of wheat in China. In this study, the sensitivity of 89 R. cerealis isolates to different fungicides was evaluated using mycelial growth inhibition assays. The results showed that all R. cerealis isolates tested were sensitive to iprodione, difenoconazole and fludioxonil with mean EC50 (effective concentration that results in 50% of mycelial growth inhibition) values of 0.419, 0.062 and 0.033 μg/ml, respectively. To evaluate the risk of fungicide resistance in R. cerealis, an attempt was made to induce resistant mutants in the laboratory. Although difenoconazole- and fludioxonil-resistant mutants were not obtained, we obtained seven independently iprodione-resistant (IR) mutants from 89 parental isolates. The EC50 values for these IR mutants were greater than 100 μg/ml, whereas those for the original wild-type counterparts were less than 1 μg/ml. After having been subcultured on PDA for 10 generations, the IR mutants did not show any decrease in resistance to iprodione. Additionally, these IR mutants also showed resistance to fludioxonil but remained sensitive to difenoconazole. Osmotic sensitivity tests showed that the IR mutants were hypersensitive to osmotic stress generated by NaCl. Inoculation tests showed that all the IR mutants lost their ability to infect the host plant. Taken together, these results indicate that the current population of R. cerealis is sensitive to these fungicides and a fitness cost is associated with iprodione-resistant mutants of R. cerealis in both osmotic stress and pathogenicity. The information obtained in this study is useful in monitoring and managing fungicide resistance in R. cerealis populations in China.  相似文献   

12.
Field trials were conducted to determine the potential use of thiacloprid for integrated Meloidogyne incognita and Bemisia tabaci B biotype control in cucumber (Cucumis sativus Linn.) in China. The following five treatments were evaluated: three thiacloprid doses (7.5, 15, and 30 kg ha−1), an avermectin treatment (7.5 L ha−1) and an untreated control. All thiacloprid application rates were effective for reducing the M. incognita and B. tabaci B biotype populations. M. incognita was reduced by 51.0%∼86.7% on 60th day and B. tabaci B biotype was reduced by about 37.2%∼95.3% within 21 days, respectively. In addition, greater thiacloprid doses resulted in fewer nematodes and whiteflies. Over two successive years, the cucumber plants that were treated with thiacloprid at a dose of 15 kg ha−1 had the greatest plant height, plant vigor and marketable yield, which were 134.1 cm, 91, 1514.3 g plant−1, respectively in 2010–2011 and 151.9 cm, 93, 1651.4 g plant−1, respectively in 2011–2012. In addition, thiacloprid was superior to avermectin. The results of this study demonstrated that thiacloprid could be used in cucumber production for the integrated control of M. incognita and B. tabaci B biotype. Furthermore, a dose of 15 kg ha−1 of thiacloprid was recommended for controlling nematode and whitefly populations according to the control effect and marketable cucumber yield.  相似文献   

13.
In this study, the seeds of open-pollinated winter rapeseed cultivars, hybrid winter rapeseed cultivars, open-pollinated spring rapeseed cultivars and hybrid spring rapeseed cultivars were investigated. The physical, optical, mechanical, geometric and image texture properties of rapeseeds were compared. Statistical models were developed based on the analyzed parameters to discriminate between seed groups. Most parameters effectively discriminated between cultivars of winter and spring rapeseed, including true density, porosity, L*, a*, b*, and spectral values at 400 nm, 470 nm, 500–530 nm, 560–620 nm, 640–650 nm and 690 nm. Four homogeneous groups were identified based on linear dimensions: F (surface area), S (width) and shape factors W6 (circularity ratio), Rb (Blair-Bliss coefficient) and W13 (roundness). No statistically significant differences in the mean values of hardness or area under the force-displacement graph were observed between seed groups. The model developed based on image texture variables from channel Y (luminance) was characterized by the highest discrimination accuracy of 82–87%. The experimental groups were classified with 89–92% accuracy in the model combining the best variables from each group of physical parameters. Total classification accuracy in neural networks reached 75% for a validation set comprising geometric properties and 91–92% for a validation set containing physical characteristics.  相似文献   

14.
Foliar sprays of pesticides are frequently used to control two-spotted mites on rose flowers, but these also destroy predatory mites and pose a high risk of contamination for humans and the environment. Using a novel approach to avoid spray applications on rose plants, modified acaricide-treated string curtains were adapted to control the pest. Two main aims of this study were: (i) to identify the lethal concentration of string curtains treated with propargite, dicofol, flufenoxuron, acrinathrin or tau-fluvalinate (τ-fluvalinate) on Tetranychus urticae, and (ii) to test the design (feasibility) and efficiency of the string curtains to trap the phytophagous mites on the plants during their circadian migration. Bioassay results in the lab confirmed T. urticae circadian migration, toxicity of the five kinds of treated string curtains and a concentration-dependent repellent effect of each chemical on T. urticae females. Of the two products tested in the field, dicofol was more effective than acrinathrin in controlling T. urticae compared to an acaricidal spray of the same products. The effect of acaricide-treated string curtain use on Phytoseiulus persimilis did not differ significantly from the control. The string curtain technique proved to be effective, but because of some biotic and abiotic constraints and the low economic threshold of mites, even for the commercialized high canopy stem roses, the present device could be more appropriate for another horticultural crop, e.g. tomato.  相似文献   

15.
Anthonomus signatus, the strawberry bud weevil, is active in early spring coinciding with the bloom period of host plants and when managed and unmanaged pollinators are active. Female A. signatus cause injury to the host plant during egg laying when they deposit a single egg inside an unopened flower bud and then girdle or “clip” the bud at the pedicel. Past efforts to control A. signatus populations have relied on the use of broad spectrum insecticides. Fields are either treated at the first signs of damage, or precautionary treatments may be applied prophylactically in fields with a history of damage. Because A. signatus damage occurs during bloom, there is concern about the potential harm to pollinators caused by these treatments. In order to identify materials more compatible for use during bloom, the efficacy of reduced risk pesticides against A. signatus was tested in semi-field bioassays over two years. Beauveria bassiana, cyantraniliprole, novaluron, and pyrethrins were assessed in the first year, and none caused significant A. signatus mortality. Acetamiprid, flonicamid, and spinosad were compared in the second year, acetamiprid and spinosad had higher A. signatus mortality than an untreated control, and exposure to spinosad resulted in similar mortality to bifenthrin, an industry standard material.  相似文献   

16.
Tetranychus urticae (two-spotted spider mite) and Bemisia tabaci (sweet potato whitefly), two of the most important agricultural pests worldwide, have developed resistance to almost all chemical classes of insecticides. Here we investigated the efficacy of the ketoenols spirodiclofen and spiromesifen against, respectively, T. urticae and B. tabaci populations from Greece with variable levels of resistance to other pesticides in order to evaluate their potential role in insecticide resistance management strategies for sustainable control of both pests. No resistance of T. urticae populations against spirodiclofen was observed. Nine out of ten T. urticae populations exhibited moderate levels of resistance to pirimiphos-methyl (up to 23-fold), pyridaben (up to 39-fold) and fenazaquin (up to 42-fold). Two of them exhibited high resistance ratios (RR) to bifenthrin (RR = 81, 351) and one to fenbutatin oxide (RR = 146). Moreover these nine populations were not cross resistant to spirodiclofen (RR < 5). A single population from greenhouse roses exhibited high resistance levels to most of the pesticides tested (RR = 8413, 1494, 434, and 74 to bifenthrin, fenbutatin oxide, abamectin and pirimiphos-methyl, respectively) showed decreased susceptibility to spirodiclofen (RR = 12). In B. tabaci the variation in response to spiromesifen treatments was very low among the eleven field populations. Most of them exhibited high levels of resistance to imidacloprid, and alpha-cypermethrin. The LC50 of spiromesifen ranged from 4.5 to 14 mg/l and the corresponding LC95 values were in general well below the recommended field doses. Ketoenol resistance risk potential was also investigated by applying constant selection pressure under laboratory conditions against populations from both species, but no increase in LC50s was detected. Ketoenols can be used for resistance management purposes for both pests in Greece as an effective chemical tool in rotation with other pesticides.  相似文献   

17.
The mealybug Phenacoccus solenopsis is a destructive pest of cotton with the potential to develop resistance to most chemical classes of insecticides. Six populations of P. solenopsis from cotton crops at six different locations in Pakistan were evaluated for resistance to selected organophosphate and pyrethroid insecticides. Resistance ratios (RRs) at LC50 were in the range of 2.7–13.3 fold for chlorpyrifos, 11.6–30.2 fold for profenofos and for the three pyrethroids tested were 10.6–46.4 for bifenthrin, 5.8–25.2 for deltamethrin and 4.1–25.0 for lambda-cyhalothrin. This is the first report of resistance to organophosphate and pyrethroid insecticides in Pakistani populations of P. solenopsis. Regular insecticide resistance monitoring programs are needed to prevent field control failures. Moreover, integrated approaches including the judicious use of insecticides and rotation of insecticides with different modes of action are needed to delay the development of insecticide resistance in P. solenopsis.  相似文献   

18.
The widespread and intensive use of conventional pesticides, particularly insecticides, presents a major risk to natural enemies of target pests, as well as to the environment in general. The aim of this study was to investigate the differential intrinsic toxicity of insecticides to two key pests of crucifers, Plutella xylostella and Myzus persicae and their respective hymenopteran parasitoids, Cotesia vestalis and Aphidius colemani. Such knowledge can help inform effective integration of insecticides and biological control in IPM systems. Three insecticides generally regarded as being compatible with natural enemies (abamectin, spinosad and indoxacarb) and one compound regarded as harmful to natural enemies (lambda-cyhalothrin) were examined. A comparative measure of the intrinsic toxicity of fresh deposits of insecticides on Chinese cabbage leaf discs was determined for both pest and parasitoids species after exposure to insecticide for 24 h and 120 h, and after 24 h exposure to insecticide plus 96 h on untreated leaf discs. Differences in the susceptibility of pests and parasitoids to different insecticides were marked for P. xylostella and C. vestalis, LC50 values being significantly lower for the pest species. Such differences were not observed for M. persicae and A. colemani. There was a direct relationship between dose, exposure time and toxicity for all insecticides tested. All insecticides tested showed lower toxicity to both parasitoids compared with P. xylostella, which suggests that for this pest species side-effects on parasitoids can be minimised through IPM practices that reduce exposure time to such non-target organisms.  相似文献   

19.
The two-spotted spider mite, Tetranychus urticae Koch, is an important pest of many agricultural crops. Studies on artificial selections, stability of resistance and monitoring of spiromesifen resistance were carried out to provide basic information for a spiromesifen resistance management program in T. urticae. Artificial laboratory selections for resistance to spiromesifen were performed in a population originating from a mixture of four field populations collected in commercial chrysanthemum fields in the State of São Paulo, Brazil. After 20 cycles of selection for spiromesifen resistance, the resistance ratio (RR50) reached 121. Spiromesifen resistance was shown to be unstable in the absence of selection pressure under laboratory conditions. The frequency of spiromesifen resistance decreased from 75 to 0.15% in six months. The evaluation of 23 T. urticae populations from several crops in the States of Goiás, Mato Grosso and São Paulo in Brazil indicated that the susceptibility of the spider mites to spiromesifen was variable, with percentages of resistant mites ranging from 0.0 to 81.5%. The highest resistance frequencies were observed in ornamental plants (roses and chrysanthemum) in the State of São Paulo. Populations of T. urticae with up to 29.8% resistant mites were also detected in strawberry fields, in the same State. This is the first report on spiromesifen resistance in T. urticae on several crops in Brazil. Strategies for the management of acaricide resistance are discussed.  相似文献   

20.
The effects of neemarin at 5, 10, 15 and 20 mg l−1 on the life table indices of Plutella xylostella (L.) were studied on cauliflower in the laboratory. Survivorship was increased with increasing concentrations. A total of 69% eggs hatched at 20 mg l−1 compared 85% in the control. Mortality (dx) of 1st instars was higher than the other instars in both exposed and unexposed individuals. Life expectancy (ex) was high in the untreated control and reduced at 20 mg l−1. Development times of immatures were prolonged to 32 days at 20 mg l−1 as compared to 18.6 days in the untreated control. Neemarin significantly reduced the emergence of adults. Potential fecundity (Pf) was 34 females/female/generation at 20 mg l−1 and 92 in the control. The net reproductive rate (R0) was significantly reduced with the increase in concentration. The intrinsic rate of increase (rm) and finite rate of increase (λ) were significantly decreased at 20 mg l−1 as compared to other concentrations tested and in the control. Mean generation time (Tc) and corrected generation time (τ) were prolonged at 20 mg l−1 and significantly differed to those of the untreated control. Doubling time (DT) was significantly extended to 28.4 days at 20 mg l−1 as compared to 6.1 days in the control.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号