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1.
Since the sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B invaded southern China in the mid-1990s, it had spread to most other regions of the country, and become an important pest in agricultural and horticultural production. Investigations on overwintering of B. tabaci biotype B and its spring reproduction in northern China were conducted to determine the main factors that might contribute to an understanding of the population dynamics of this pest for developing improved pest control strategies. A cold hardiness test showed that when exposed for 10 h at −10 °C, mortalities of eggs, nymphs, and adults reached to 86.6%, 88.4%, and 100%, respectively, suggesting that it is probably impossible for feral populations of B. tabaci to survive in the winter under natural environmental conditions in northern China. A survey on vegetables, ornamental plants and weeds in greenhouses at Hebei Province and Beijing in northern China revealed at least 14 species of plants on which B. tabaci fed during the winter and spring. Lycopersicon esculentum Mill, Brassica alboglabra Bailey, Ficus carica L., Euphorbia pulcerrima Wild, and Hemelia patens Haence were the main host plants. Further research on the population dynamics of B. tabaci on three major greenhouse hosts; tomato, cucumber, and melon, indicated that densities remained at a low level during the winter, but increased steadily from February to March until migration into field crops in April. It is concluded that the control of the insect in greenhouse in winter and spring can play an important role for seasonal management of this pest in northern China. 相似文献
2.
Avoidable losses and economic injury levels (EILs) were computed for the sorghum head bug, Calocoris angustatus Leth., on three cultivars during three rainy seasons (1985–1987) at ICRISAT. Grain yield in plots protected with 2–5 insecticide sprays (carbaryl at 500 g a.i./ha) between the half-anthesis and the dough stage was significantly higher than in untreated plots, with cost-benefit ratios > 1. Plots that were not protected at half-anthesis and/or complete-anthesis, and at milk and dough stages, suffered a significant loss in yield. Bug damage spoiled the grain quality in terms of germination, 1000-grain mass, grain hardness and percentage floaters. Three to four sprays between complete-anthesis and the dough stage prevented a significant reduction in grain quality. Head bug density at half-anthesis, complete-anthesis, milk and dough stages was significantly and negatively associated with grain yield. Bug density at different stages explained 43–94% of the variance in yield. Direct effects of bug numbers at the milk stage and the indirect effects of head bug density at other stages through the milk stage contributed towards maximum reduction in yield. Maximum avoidable losses were recorded in cultivar ICSV 1 (88·6%), followed by CSH 1 (69·9%), and CSH 5 (53·9% in 1986 and 55·0% in 1987). Loss in grain yield/ha due to one insect/panicle at half-anthesis and that based on natural increase, were 548 and 232 kg in CSH 5 during 1986 and 1987, respectively, 251 kg in ICSV 1, and 77 kg in CSH 1. EILs based on a cost-benefit ratio of 1:1 ranged from 1·3–1·4 insects/panicle for CSH 1, 0·4 for ICSV 1, and 0·4–0·6 and 0·2–0·4 for CSH 5 during 1986 and 1987, respectively. Simple cost estimates for insecticide sprays and the resultant saving in grain yield are a useful tool for decision-making in pest management. 相似文献
3.
Breeding cotton, Gossypium spp., for resistance to leafhoppers of the genus Empoasca and to sweetpotato whitefly, Bemisia tabaci (Gennadius), poses a dilemma. Glabrous (smooth-leaved) cotton plants have higher leafhopper populations but fewer whiteflies and less leaf and bract trash in mechanically harvested seedcotton than plants with pubescent leaves. In this study, both leafhopper and whitefly populations were observed in 31 cotton entries planted at Bet She'an, Israel, in 1987. Leafhopper populations decreased but the whitefly populations increased as the number of trichomes increased. At the end of June, plants with 40 trichomes per 13.7 mm2 supported relatively low populations of both leafhoppers and whiteflies. However, the whitefly populations increased later in the season to 43 times the earlier population levels. Whitefly populations increased as the number of trichomes increased up to 70 trichomes per 13.7 mm2 and then decreased as the trichomes became more dense. Various control measures and breeding schemes that might interact to provide an answer to the control of these pests are discussed. 相似文献
4.
In field trials in Israel, piperonyl butoxide (PB) alone, at concentrations of 2000 and 5000 ppm exerted good control over nymphal Bemisia tabaci populations on cotton. Weekly doses of these concentrations exerted greater control than a recommended oil and were as effective as the standard single application of buprofezin. Cypermethrin caused marked resurgence within the plots, probably as a consequence of its detrimental effects on natural enemies. Neither PB, buprofezin nor the oil reduced the incidence of natural enemies. Treatment with 2000 or 5000 ppm PB resulted in a shift in age structure toward a greater proportion of young instars than in other treatments. There was some evidence that these effects facilitated a greater level of parasitism in PB-treated plots. 相似文献
5.
Anticipating the direction for change in the current cotton insect pest management system in francophone African countries, different pest management strategies were investigated to reduce cotton protection costs and to improve overall pest control decision-making at the farmer level. Four strategies aimed at timing and limiting insecticide applications, were designed to fit the semiliterate level of farmers and pest profiles. Strategy 1 focused on using control thresholds early in the season, Strategy 2 on reducing the dosage in mixtures, while Strategies 3 and 4 were associated with the use of single active ingredients instead of mixtures. These strategies were assessed at the main research station Bouaké, Côte d'Ivoire, and were shown to be effective when compared with the current protection programme. The number of treatments and the amount of insecticides applied was reduced while achieving equal or better pest control and yields. The strategies proved to be safer to some beneficial arthropods. Their cost-effectiveness needs to be assessed in more detail at farm level to select the most financially attractive strategy. 相似文献
6.
Field experiments were conducted during two cropping seasons at two sites in Botswana to determine the efficacy of combining glyphosate and tillage in controlling C. dactylon. Treatments consisted of no-tillage, single and double ploughing during winter and spring plus the application of glyphosate at 0, 1.08, and 2.16 kg ha−1 3–4 weeks after the last ploughing. Visual assessment indicated higher levels of grass control from combining glyphosate and tillage than when these elements were applied separately. However, biomass data indicated that either double ploughing or glyphosate application controlled C. dactylon. A single ploughing followed by glyphosate at 2.16 kg ha−1 after a regrowth of C. dactylon may provide an effective and affordable control method to small-scale farmers. 相似文献
7.
Chlorfluazuron sprayed on cotton seedlings was more efficient than cypermethrin against third-instar larvae of the Egyptian cotton leafworm, Spodoptera littoralis. At a concentration of 3·2 x 10−5% a.i., chlorfluazuron caused 98 ± 2% larval mortality and cypermethrin 35 ± 9%. All larvae in chlorfluazuron assays died during moulting; hence the leaf area consumed during the test instar was not appreciably affected. On the other hand, in cypermethrin assays, larvae died during the intermoult stage. Chlorfluazuron exhibited potency similar to that of cypermethrin on third-instar larvae of the grape berry moth Lobesia botrana, resulting in 90–95% and 33–34% mortality in treatment concentrations of 5 x 10−3% and 2 x 10−4% a.i., respectively. In another grapevine pest, Drosophila melanogaster, cypermethrin suppressed larval and adult formation to a greater extent than chlorfluazuron. The high potency of chlorfluazuron on various insects, together with its low toxicity to man and the environment, renders this compound a potential agent for controlling important agricultural pests. 相似文献
8.
L. M. Torres-Vila M. C. Rodríguez-Molina A. Lacasa-Plasencia P. Bielza-Lino 《Crop Protection》2002,21(10):1003-1013
Helicoverpa armigera is a major pest on a wide range of crops in Europe, Africa, Asia and Australia. Insecticide treatments are currently indispensable for its control in almost all crops, which has resulted in insecticide resistance occuring in some situations. However, since information about insecticide resistance of H. armigera in Europe is very limited, the current resistance status of this pest was investigated in Spain from 1995 to 1999. Toxicological bioassays were conducted in the laboratory, LD50's estimated by probit analysis and resistance factors (RF) calculated at the LD50 level. Eleven chemicals, including endosulfan, carbamates (carbaryl, methomyl, thiodicarb) and organophosphates (chlorpyrifos, fenitrothion, methamidophos, azinphos-methyl, trichlorphon, acephate, monocrotophos) were tested. Ninety-seven percent of insecticide–strain combinations showed susceptibility (RF=1) or low insecticide resistance (RF=2–10) (157 of 162, 97%). Moderate resistance (RF=11–18) was only recorded to carbamates (carbaryl, methomyl and/or thiodicarb) in five strains. Insecticide resistance of H. armigera in Spain was therefore not as high or widespread as in other areas of the world. Since insecticide pressure against the pest in Spain is not likely to be lower, nor IPM implementation better, than elsewhere, additional factors that potentially account for low levels of insecticide resistance of H. armigera, including migration and cropping structure leading to the existence of refugia are discussed from an agroecological perspective. 相似文献
9.
Lygus lucorum Meyer-Dür, Adelphocoris fasciaticollis Reuter and Adelphocoris lineolatus (Goeze) (Hemiptera: Miridae) are important secondary insect pests in cotton fields in northern China. The seasonal dynamics of their mixed populations on a transgenic variety expressing the insecticidal Bt protein Cry1A, and a cotton line expressing proteins of Cry1A and CpTI (cowpea trypsin inhibitor gene) were compared to seasonal dynamics on similar but non-transgenic varieties from 1998 to 2001. No significant differences were detected between population densities of these bugs on unsprayed normal cotton and unsprayed transgenic cotton. However, mirid damage on unsprayed transgenic cotton was significantly higher due to a reduced number of insecticide sprays against Helicoverpa armigera compared with the number of sprays in the normal cotton. This suggests that the mirids have become key insect pests in transgenic cotton fields, and that their damage to cotton could increase further with the expansion of the area planted to transgenic cotton if no additional control measures are adopted. 相似文献
10.
T. J. Wicks 《Crop Protection》1990,9(6):433-438
Propiconazole was more effective than either triadimenol or hexaconazole when applied after infection, for the control of Septoria apiicola on celery seedlings. In three out of four glasshouse experiments, 25 mg propiconazole I−1 controlled S. apiicola completely when applied within 3 days after inoculation. Propiconazole and triadimenol at 5–15 mg l−1 were also effective when applied 2 days after inoculation. Soil applications of a granular formulation of triadimenol (up to 20 mg per plant) controlled S. apiicola for 5 weeks on celery seedlings grown in pots and, in the field, granules at 100 mg per plant applied at planting were effective for 6 weeks. In two other field experiments the most effective treatments were foliar sprays of 25 mg propiconazole l−1 applied every 7–10 days with or without the addition of anilazine or chlorothalonil. 相似文献
11.
InfoCrop, a generic crop–pest simulation model, was used to validate yellow stem borer, Scirpophaga incertulas Wlk., damage mechanism on two rice cultivars, Pusa Basmati 1 and Ratna. Data sets consisted of three experiments, one under natural infestation of the pest and two involving artificial detillering. The simulated yields showed less than 10% variation from the observed yields, except in one treatment, where the difference was 10.5%. The simulated yield losses were also proximal to respective observed yield losses (R2=0.922, RMSE=3.825), indicating proper validation of damage mechanism of the stem borer. As the model simulated the pest damage appropriately under natural injury, as well under artificial detillering; artificial detillering seemed comparable to natural injury of the stem borer in its effect on rice growth and yield. Validated InfoCrop was used to simulate economic injury levels (EILs) of the stem borer at different rice growth stages for varied control expenditure, incurred on two and three sprays of monocrotophos and one granular application of carbofuran, and for three market prices of produce. The EIL consistently decreased with advancing crop age and it exhibited a positive relationship with control expenditure and a negative relationship with market value of the produce. The simulated EILs were observed to be comparable to empirical injury levels that were previously established. The validated model was also used to devise iso-loss curves that depicted same yield loss for different combinations of the stem borer injury and crop age. Crop simulation model-based EILs and iso-loss curves are useful in monitoring the stem borer injury and in need assessment for pesticide application, thereby avoiding unnecessary expenditure and environmental contamination. Due to their mechanistic nature, crop models can be used to formulate location-specific decision support tools and therefore, help improve decision making in pest management. 相似文献
12.
Diseases caused by Moniliophthora roreri (moniliasis), Crinipellis perniciosa (witches’ broom) and Phytophthora palmivora (black pod) are the most important factors limiting cocoa production in Peru and cultural management is considered to be the only practical means of control for the smallholder. The objective of this study was to develop an epidemiologically and economically sound control recommendation based on the frequency of phytosanitary pod removal. Weekly removal of diseased pods reduced the incidence of diseases significantly in comparison with fortnightly removal. In three fields, moniliasis was decreased by 26–41%, black pod by 35–66% and witches’ broom on pods by 14–57%. The cumulative effect was a consistent yield increase from an average of 504–660 kg ha−1 yr−1. Returns compensated for increased labour costs. Weekly pod removal was 32% more profitable. Time-course analyses indicated that weekly removal should be practised throughout the year under field conditions of eastern Peru. 相似文献
13.
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zberk Ayhan Atl&#x; Abuzer Yücel Fethiye
zberk Yalc&#x;n Cokun 《Crop Protection》2005,24(12):1054-1060
This study aimed to draw the attention of the all stake holders attention to an underestimated insect pest of wheat in Southeastern Anatolia. The field studies were carried out in the experimental field of GAP Training, Extension and Research Center in Koruklu in 2003–2004 cropping season.
It was found that the number of sawfly damaged spikes varied between 6 and 12% in durum wheat and 8 and 12% in bread wheat. Comparing healthy grains, grain weight spike−1 decreased significantly, giving 0.430 g less kernel weight in durum wheat and 0.385 g in bread wheat. Some of the grain quality characteristics of both sawfly damaged and healthy spikes were tested and it was found that protein content (%) in durum wheat, and 1000 kernel weight in bread wheat were reduced significantly, whilst, the SDS sedimentation value in bread wheat increased significantly for sawfly damaged grains. Grain yield losses by sawfly infestation were found to be 2.23% in durum wheat and 3.32% in bread wheat. Marketing price studies showed that sawfly damage reduced it significantly, resulting in $ 0.016 kg−1 less price in bread wheat. But this was not serious for durum wheat.
It was concluded that income loss, depending on grain yield loss, un-harvestable broken spikes and lower marketing price of sawfly damaged grains, could be no less than $ 68.8 ha−1 in durum wheat and $ 68.6 ha−1 for bread wheat. Therefore, some control methods are required for sawfly infestation, where damage is already over the economic threshold (10–15% stem cut by pest) especially in bread wheat. 相似文献
14.
Strains of B. lactucae insensitive to 0.01 g a.i. l−1 metalaxyl have been detected in all the lettuce-growing districts of South Australia. Despite this, applications of a formulated mixture of 0.25 g a.i. l−1 metalaxyl and 2 g a.i. l−1 mancozeb every 7–10 days controlled downy mildew in field experiments, where similar applications of either metalaxyl or mancozeb alone were ineffective. Protectant schedules of either 0.3 g a.i. l−1 dimethomorph or 2–2.4 g a.i. l−1 phosphonic acid also controlled downy mildew, but were less effective than the metalaxyl/mancozeb formulation. Mixtures of either dimethomorph or phosphonic acid with mancozeb enabled the time between the sprays to be increased to 14 days without significantly reducing control. Fungicide applications increased marketable yield by 60% compared with that of the unsprayed plants. Drenching seedlings with 4 g a.i. l−1 phosphonic acid controlled downy mildew for at least 14 days and should prevent the spread of the disease from plant production areas. 相似文献
15.
Rice planthoppers' damage on Pusa Basmati 1 cultivar was simulated with InfoCrop, a generic crop growth simulation model. The model was calibrated and validated with two experimental data sets on planthopper population and rice yield that were generated through differential insecticide application during the rainy season 2006 and 2007. Simulated yield and total dry matter (TDM) in various treatments over the two experiments were found to be proximal to the observed yields (R2 = 0.972, RMSE = 4.61%) and TDM (R2 = 0.949, RMSE = 3.25%), respectively. Likewise, the simulated yield and TDM losses were also respectively close to observed yield losses (R2 = 0.938, RMSE = 13.53%) and TDM losses (R2 = 0.835, RMSE = 19.12%), suggesting appropriate validation of planthopper damage mechanism on Pusa Basmati 1 rice. Economic injury levels (EILs) of planthoppers were simulated with two control expenditures involving two applications with each of monocrotophos and imidacloprid, and three market prices of Pusa Basamti 1 rice. The EIL exhibited a negative relationship with market value of produce but a positive one with expenditure on control measures. Simulated EILs were comparable to earlier established empirical EILs, indicating utility of simulation models for developing location specific EILs that may help in doing away with the use of blanket EILs. Iso-loss curves, devised through validated model, depicted combinations of crop age and planthopper population that resulted in similar yield losses. Both the EILs and iso-loss curves can be useful in monitoring planthopper populations and promoting judicious pesticide applications that would avoid unwarranted control expenditure and environmental contamination. The simulation models being based on detailed crop ecological and physiological processes and pest damage mechanism can thus aid in development of location-specific decision support tools and ensure precision in pest management decisions. 相似文献
16.
Drosophila suzukii is an invasive insect pest which has major impacts on small fruit production throughout North America. Current control programs use frequent applications of broad-spectrum insecticides. To prevent resistance, modes of action must be rotated. This study examines the acute and residual efficacy of rotational treatment programs designed to meet the needs of commercial growers in the southeastern United States, a region which experiences significant precipitation throughout the growing season. All insecticide applications had greater adult acute mortality than controls, and some had residual efficacy for three or more days after treatment. Programs had no residual effects at seven days after treatment. Within programs, organophosphates (phosmet and malathion) and pyrethroids (zeta-cypermethrin and fenpropathrin) were the most effective. Some programs also resulted in less offspring production by D. suzukii in bioassays and reduced field infestation compared to controls. Results show that effective, season-long rotational chemical treatment programs can be designed to minimize crop damage, meet exportation requirements and manage for resistance. Understanding the effect of regional climate on the performance of individual insecticide treatments and their efficacy will be critical for widespread implementation of effective control programs for D. suzukii. 相似文献
17.
Brigitte T. Nyambo 《Crop Protection》1989,8(6):417-421
The introduction of ULV (ultra-low-volume) spraying to cotton farmers in western Tanzania in the early 1970s was a major contribution to the cotton industry as the control of cotton insect pests was made easier and possible in many areas. However, spray drift and increased cost of ULV insecticides and batteries have been major constraints to ULV spraying in recent years, so a spraying technique allowing greater efficacy and reduced costs is needed. Trials to assess the potential of electrodynamic spraying as an alternative to ULV spraying started in western Tanzania in 1979. The present study assessed swath width, dosage rates and farmer's reaction to the ‘Electrodyn’® hand-held sprayer as compared with the hand-held spinning-disc sprayer (Micron ULVA), currently used by farmers in Tanzania, in order to identify the optimum combination package to be recommended to farmers. Cypermethrin ED applied at a dosage rate of 15·8–31·6 g a.i./ha by the Electrodyn sprayer over a swath width of 3·0 m gave good control of H. armigera. Yields of seed cotton were comparable to those with ULV cypermethrin applied at a dosage rate of 62·5 g a.i./ha. The spray volume was reduced from 2·5 l/ha applied with the spinning disc to 0·35 l/ha with electrodynamic spraying. Reduced drift, dosage of active ingredient and volume rates, and reduction in the number of batteries needed in a season, were among the major advantages of electrodynamic spraying over ULV spraying in western Tanzania. 相似文献
18.
Ugandan farmers were interviewed in order to investigate their knowledge, perceptions and ability to manage pests in agroforestry generally and on Alnus species particularly. Farmers’ ability to recognise pest problems on Alnus species was significantly influenced by their length of experience in cultivating the species, but not their age, sex or formal education. Most farmers (77%) were aware of pest problems on Alnus species. However, identification of pest problems was based largely on damage type rather than causal agents. Whereas farmers had good knowledge of vertebrate pests of Alnus, insects and diseases that infest the tree species were unknown to most farmers. Apis mellifera damage on Alnus was the most frequently described damage, but its cause was either unknown or misdiagnosed. Most farmers did not control insect and disease infestations on Alnus because they did not know the causal agents and/or appropriate control measures. Farmers were generally more knowledgeable on insect and disease infestations on crops than on multipurpose tree species (MPTS) and most of them (98%) perceived that crops suffer more damage from such pests than do MPTS. However, farmers’ ability to manage insect pests and diseases seemed weak on both crops and MPTS. Most farmers suggested the use of pesticides to combat pests, but they mentioned only one insecticide, permethrin and one fungicide, mancozeb. More alarming were the suggestions by a few farmers on the use of mancozeb against aphids, and permethrin to combat crop wilt and dieback. Farmers need to be educated about diagnosis, basic ecology and management strategies for both crop and tree pests to ensure sustainable pest control in agroforestry. 相似文献
19.
Bt-cotton varieties can control lepidopterous pests, hence offering the possibility to reduce chemical pesticide use. India, with the largest cotton-growing area globally, gave commercial approval for Bt cotton in 2002 and a rapid adoption of the technology is expected. This paper uses a stochastic partial budgeting approach that captures the key pest control properties of Bt cotton taking into account uncertainty of pest pressure, control effectiveness and prices to assess the profitability effects of Bt varieties and hence complements previous studies that generally excluded such issues. Results of the simulation model reveal that under the current price situation a prophylactic chemical control strategy dominates the use of Bt varieties in both, irrigated and non-irrigated cotton. The effect of a higher cotton price is assessed in a second scenario that depicts a Bt cotton variety with improved fiber quality than varieties currently approved for commercial planting. Under this assumption, the Bt strategy would be slightly better than the prophylactic use of chemical pesticides. The model can be extended to include pests other than the bollworm and correlations among variables, e.g. prices and yield, provided sufficient evidence for such correlation exists. Results of this analysis show the impact of uncertainty in the main variables that influence the profitability of Bt cotton and alternative crop protection methods. 相似文献
20.
Nguya K. Maniania 《Crop Protection》1993,12(8):601-604
The fungus Beauveria bassiana (Bals.) Vuill. and insecticide trichlorfon were compared for the control of stem borer, Chilo partellus (Swinhoe) in field experiments at different times of infestation. Egg masses of C. partellus at the blackhead stage were pinned to the undersurface of the maize leaves. Two fungal formulations, conidial aqueous suspensions and a granular formulation, were applied. Compared with the untreated checks, the numbers of surviving C. partellus larvae were significantly reduced in treatments where B. bassiana was applied at a concentration of 1013 conidia ha−1 as granules and as two aqueous spray formulations. No significant difference in numbers of stem borer larvae was found between trichlorfon and the untreated check. Fungus granules persisted longer in the field than did one spray of the fungus inoculum at the same concentration, or trichlorfon. A major increase in grain yield was obtained with two fungal sprays and with fungus granules both applied at a concentration of 1013 conidia ha−1. A granular formulation of B. bassiana should be considered for the control of the stem borer C. partellus. 相似文献