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1.
The rice water weevil (RWW), Lissorhoptrus oryzophilus (Kuschel) (Coleoptera: Curculionidae), is the most destructive insect pest of rice in the United States. Water-seeded rice, which is flooded at an earlier stage of crop development than drill-seeded rice, is at heightened risk of loss from root-feeding RWW larvae. Pyrethroids, the most widely used group of foliar insecticides for RWW control, have inherent limitations such as limited residual activity, narrow window of activity and extreme toxicity to non-target aquatic organisms. An array of field, lab and greenhouse experiments was conducted to compare the activity of two neonicotinoids with that of λ-cyhalothrin, a widely used pyrethroid, against the RWW. Small-plot efficacy trials were conducted during 2009, 2010 and 2011. Foliar clothianidin (Belay 2.13 SC) and a granular formulation (3%) of dinotefuran applied to plots were as effective as, and showed greater residual activity than, foliar applications of λ-cyhalothrin. Topical bioassays on adult weevils revealed that clothianidin possessed lower contact toxicity than λ-cyhalothrin. Residual assays using weevils placed on foliage of sprayed plots revealed that the toxic and sublethal behavioral effects of clothianidian on adult weevils were more persistent for clothianidin than for λ-cyhalothrin. Granular dinotefuran applied to greenhouse-grown plants previously infested with weevil larvae showed excellent larvicidal activity. Overall, these studies showed that neonicotinoids have potential as pyrethroid replacements against the RWW in water-seeded rice culture. 相似文献
2.
Spinetoram, imidacloprid, thiamethoxam and chlorantraniliprole are new insecticides with novel mode of actions, low mammalian toxicity and low impact to environment. In the present study, the efficacy of these insecticides was tested against Tribolium confusum Jacquelin du Val on concrete. Among the tested insecticides, spinetoram proved to be more effective, providing complete control of T. confusum adults and young larvae after 14 days of exposure. For the young larvae, thiamethoxam at the highest dose and chlorantraniliprole at both doses were equally effective with spinetoram. On the other hand, none of the tested insecticides were able to control T. confusum pupae. Moreover, none of the insecticides had ovicidal effect, with the exception of chlorantraniliprole in some combinations. From the mobile life stages, the most tolerant life stages were old larvae and the most susceptible young larvae. The presence of food (flour) moderated T. confusum mortality. From the results of the present study, we can conclude that spinetoram, thiamethoxam and chlorantraniliprole showed potential and need be further evaluated for surface treatments in stored product facilities. Our work underlined the need for good cleaning and sanitation procedures in warehouses and food processing facilities. 相似文献
3.
Dusting or soaking freshly cut potato seed pieces in systemic insecticides controlled the first generation larvae of the Colorado potato beetle at Yakima, Washington in 1970. The most promising materials were tested again in a larger experiment in 1971. Fifty days after treatment, Bay 37344 (4-(methylthio)-3,5,xylyl methylcarbamate), Dasanit® (O,O-diethyl-O-[p-(methylsulfinyl) phenyl] phosphorothioate), Shell SD 17250 (N-(methylcarbamoyl)oxy]thioacetimidic acid ester with 3-mercaptopropionitrile) and Plant Protection PP062 (dimethylamino)-4,5,6-dimethyl pyrimidinyl dimethylcarbamate) all gave significantly better control of the larvae than methomyl, azinphosmethyl and menazon. 相似文献
4.
The Bemisia tabaci whitefly is an important pest of many agricultural crops. Direct feeding by this pest can cause physiological plant symptoms including irregular ripening in tomatoes and silverleaf disorder in squash. In addition, B. tabaci can transmit more than 100 plant viruses that cause severe diseases that affect crop yield and quality. Insecticides are often applied to control this pest and they may be applied to the foliage and/or to the soil. Insecticides that kill quickly or cause feeding cessation reduce the damage caused by B. tabaci on the host plant most effectively. In this study fluorescence was used to assess B. tabaci feeding and to determine the effect of systemically applied insecticides on feeding by the pest. Cyantraniliprole (Verimark™) and imidacloprid (AdmirePro®) produced a rapid reduction in B. tabaci feeding. At 24 h after a systemic application, the percentage of whitefly nymphs still feeding in plants treated with cyantraniliprole (anthranilic diamide) and imidacloprid (neonicotinoid) were 19% and 33%, respectively. Both products showed a good reduction in insect feeding and since they have different modes of action they should be considered as rotational partners for B. tabaci control in areas where there is no resistance to neonicotinoid insecticides. While the fluorescein sodium salt cannot be used to trace the uptake of insecticides, it has been shown to reliably demonstrate feeding cessation of whitefly nymphs after foliar and systemic applications of insecticides. 相似文献
5.
The rice leaffolder, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae), is a leaf-feeding pest and the physical and chemical nature of the rice leaf affects its feeding, survival and fecundity. We examined changes in the survival rates of larvae and pupae, pupal weight and the number of eggs laid by adult females developed from a resistant variety (Huaidao 9) and a susceptible variety (Yangjing 9538) in hydroponic solutions containing different concentrations of magnesium (Mg). The concentration of Mg in the hydroponic solution significantly affected the survival rates of the larvae and pupae, the pupal weights and the numbers of eggs laid. Larval survival rates on the resistant variety were significantly higher for fourth instars exposed to 60 and 80 ppm Mg and pupae exposed to 20, 40, 60 and 80 ppm Mg than those for the control treatment (without Mg). For the susceptible variety, survival rates of first, second and third instars were significantly higher at high concentrations of Mg than those under control conditions. In addition, the number of eggs laid by adult females increased with increasing Mg concentrations, though there was a slight decrease at 80 ppm compared to 60 ppm. These results indicate that Mg is beneficial to the development, survival and fecundity of C. medinalis. They further suggest that high levels of nitrogen fertilizer in rice fields favour outbreaks of this pest because application of nitrogen elevates the chlorophyll content and Mg levels in the rice leaf. 相似文献
6.
Botanical insecticides based on plant extracts are not widely used as crop protectants even though they can be produced simply from locally available plants. Many studies have examined efficacy but there is a paucity of information on the cost:benefit ratio of their use compared with conventional insecticides. In the present study, crude extracts of Ageratum conyzoides (Asterales: Asteraceae), Chromolaena odorata (Asterales: Asteraceae), Synedrella nodiflora (Asterales: Asteraceae), Nicotiana tabacum (Solanales: Solanaceae), and Ricinus communis (Malpighiales: Euphorbiaceae) were compared with the synthetic insecticide, emamectin benzoate (Attack®) against insect pests of cabbage in randomised, replicated field experiments during the major and minor rainy seasons of 2012 in Ghana. The cost of each treatment including material and labour was calculated and the revenue of each derived using the value of the marketable yield of cabbage. The cost:benefit ratios of sprayed treatments were derived by comparing the cost of each plant protection regime against the additional market value of the treatment yield above that obtained in the control treatment. With the exception of plots sprayed with N. tabacum, the cost of plant protection using Attack® was higher than any of the botanicals in both seasons. The highest cost:benefit ratio of 1: 29 was observed for plots sprayed with C. odorata and was followed closely by N. tabacum treatment with 1: 25 and Attack® with 1: 18. In the minor season, plots sprayed with Attack® had the highest cost:benefit ratio of 1: 15 and was followed closely by N. tabacum with 1: 14. Botanical insecticides differed markedly in levels of pest control and cost:benefit but some were comparable to that from conventional insecticide use whilst being produced easily from locally available plant materials and are likely to be safer to use for smallholder farmers and consumers in developing countries. 相似文献
7.
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
8.
Lethal and sublethal insecticide effects on non-targeted pest species are frequently neglected but have potential consequences for pest management and secondary pest outbreaks. Here, the lethal and demographic effects of four soybean insecticides (chlorantraniliprole, deltamethrin, pyriproxyfen, and spinosad, which are used against caterpillars, whiteflies, and green stink bugs) on the brown stink bug Euschistus heros (F.), the main stink bug species currently attacking Neotropical soybean fields, were assessed. Deltamethrin exhibited drastic acute mortality in adult females of E. heros with a median lethal time (LT50) of 0.6 days, whereas pyriproxyfen treated females exhibited a survival similar to that of water-treated insects (LT50 of 89 and 67 days, respectively). Chlorantraniliprole and spinosad-treated females exhibited intermediate survival with a TL50 of 54 and 47 days, respectively. Further scrutiny of the three most selective insecticides (i.e., chlorantraniliprole, pyriproxyfen, and spinosad) using age-structured matrices to assess the demographic impact of these compounds under earlier exposure indicated that both pyriproxyfen and spinosad significantly reduced the population growth of the pest species by compromising the survival of eggs (<17% hatching) and 1st nymphs (LT50 of 3 and 2 days, respectively) and fertility; these results were unlike those obtained for chlorantraniliprole- and water-treated controls, which exhibited less than 50% mortality during development. However, chlorantraniliprole significantly compromised the fertility of adult insects (>50% reduction compared with water-treated insects) to a greater extent than pyriproxyfen and spinosad, but without impairing insect population growth as much. Therefore, although pyriproxyfen and spinosad, besides deltamethrin, are not used to target the Neotropical brown stink bug, these insecticides adversely affected this pest species at the dose recommended for application on the label, thereby preventing its outbreak under such conditions. 相似文献
9.
O. G. Bacon N. F. McCalley W. D. Riley R. H. James 《American Journal of Potato Research》1972,49(8):291-296
Six insecticides were evaluated in a replicated field experiment at Gonzales, California, for control of the potato tuberworm,Phthorimaea operculella (Zeller), and the green peach aphid,Myzus persicae (Sulzer). Azodrin®, methomyl, Stauffer N 4543 (O-isobutyl ethylphosphonodithioate S-ester with N-(mercaptomethyl) phthalimide) and azinphosmethyl were applied as foliage sprays by ground sprayer at 2-week intervals. The systemic insecticides, aldicarb (Temik®) and carbofuran (Furadan®) formulated as 10% granules, were applied to the soil as side dress treatments on the same day that the spray treatments were begun. Aldicarb granules were also applied topically so that the granules fell on the young plants and on the soil surface. Azinphosmethyl, Stauffer N 4543, Azodrin® and methomyl effectively controlled the tuberworm larvae in the foliage but effective control of tuberworms in the harvested tubers occurred only where azinphosmethyl, methomyl and Stauffer N 4543 were used. The granule applications of carbofuran and aldicarb were totally ineffective in controlling the potato tuberworm. Effective green peach aphid control was obtained with Azodrin® spray and the two granular aldicarb treatments. The side dressed application of aldicarb appeared to provide better green peach aphid control than did the soil surface application. 相似文献
10.
Although dozens of transgenic Bacillus thuringiensis (Bt) rice lines have been developed, none of them has been released to farmers. Under field conditions, we evaluated the influence of a hybrid Bt rice on the primary rice insect pests and rice yield in 2005 and 2006. Four treatments were evaluated, including Bt and non-Bt rice treated with insecticides when necessary, and unprotected Bt and non-Bt rice. Unprotected Bt rice exhibited stable and high control of the three primary lepidopteran pests, Chilo suppressalis Walker, Tryporyza incertulas Walker and Cnaphalocrocis edinalis Güenée. Under unprotected conditions, larval densities of these three pests in Bt plots decreased by 87.5–100% compared to those in non-Bt plots, and percentages of damaged stems and leaves remained less than 0.6% during the entire rice growing season. In early rice growth stages, populations of two important planthoppers, Nilaparvata lugens Stål and Sogatella furcifera Hovarth, were significantly affected only by protection level (protected vs unprotected). However, in late rice growth stages (filling and maturing), densities of planthoppers were significantly affected both by protection level and by rice type (Bt vs non-Bt), and densities of N. lugens were significantly higher in Bt plots than in non-Bt plots under unprotected conditions. Pesticide sprays were reduced by 60 and 50% in protected Bt vs protected non-Bt plots in 2005 and 2006, respectively. Yield of unprotected Bt rice increased by 60–65% compared to unprotected non-Bt rice, but decreased by 28–36% compared to protected Bt rice. These results show that Bt rice increased yield greatly, but still required pesticide sprays to avoid losses caused by non-target insect pests. 相似文献
11.
【目的】香根草能有效诱集水稻螟虫产卵,且孵化的幼虫取食香根草一定时间后死亡,可用于水稻螟虫的田间防控。但田间防治往往是多种防治措施相结合。为了研究取食香根草后的幼虫对常用杀虫剂的敏感度,【方法】利用稻苗浸渍法测定了茚虫威、氯虫苯甲酰胺、多杀菌素、甲氨基阿维菌素、氟虫胺、氰氟虫腙、阿维菌素、毒死蜱8种常用杀虫剂对水稻大螟和二化螟的毒力作用,以及取食香根草后螟虫对这些药剂的敏感度变化。【结果】8种杀虫剂(氰氟虫腙,甲氨基阿维菌素,氯虫苯甲酰胺,氟虫胺,多杀菌素,阿维菌素,茚虫威,毒死蜱)对大螟的LC50依次为1.04,1.40,2.67,3.48,7.59,13.03,16.57,23.28 mg/L;对二化螟的LC50依次为1.94,2.07,4.20,8.93,9.72,17.63,9.51,64.68mg/L。与取食水稻的螟虫比较,香根草饲喂3d后,大螟幼虫对8种药剂的敏感性均有所提高,致死率提高13.3～22.2个百分点,其中,对氯虫苯甲酰胺、多杀菌素、氟虫胺、氰氟虫腙、毒死蜱的敏感度显著提高;而香根草饲喂后的二化螟幼虫对所有测定药剂敏感度均显著提高,致死率提高26.7～33.3个百分点。二化螟幼虫对所有测定药剂敏感度升高更为明显。【结论】初步明确了水稻螟虫取食香根草后对杀虫剂的敏感度有不同程度提高。 相似文献
12.
对盘锦地区水稻病虫害的发生、发展特点及防治情况作了较系统的分析,并就病、虫害防治的未来发展趋势提出了较科学的论断。通过论述,便于对盘锦地区水稻病虫害的发生及防治情况加以全面掌握,为植保工作提供一定帮助。 相似文献
13.
This study investigated the correlation between insect mortality and insecticide residue levels in rice grain during the developing stages and at harvest, and also determined the relative toxicities of three insecticides, monocrotophos (Azodrin 16·8 EC), lindane (Agrocide 26 DP), and carbaryl (Sevin 85 WP) to Leptocorisa oratorius (Fab.), (Hemiptera: Alydidae). The insecticides were applied on field plots at 0·75 kg a.i./ha at the start of the milk stage of the developing grains. Sampling was conducted at 2 hours and 1, 2, 3, 4 and 5 days after spraying, which covered the milk stage to the soft dough stage. Mortality of insects exposed to the treated grain, the residue analysis of the treated grain during development and at harvest, and the LD50s of the insecticides were determined. Monocrotophos was the most effective insecticide against the rice bug; lindane provided control for only one day; carbaryl was ineffective. Maximum residue levels of lindane and carbaryl in the harvested grains were below the established tolerance limits provided by FAO/WHO. There is no established tolerance for monocrotophos in rice. 相似文献
14.
The systemic insecticides, Dasanit®, carbofuran (Furadan®), phorate (Thimet®), aldicarb (Temik®) and disulfoton (Di-Syston®) were applied in the planting furrow at 2–3 lb actual/acre for potato tuberworm (Phthorimaea operculella (Zeller)) control in Irish potato foliage. None of these compounds gave entirely satisfactory results. Dasanit was the best with slightly over 80% decrease in the number of mines and was followed closely by carbofuran; all treatments needed to be supplemented by foliage sprays for satisfactory tuberworm protection. Azinphosmethyl (Guthion®) gave consistently outstanding results as a foliage spray at 0.5 lb/acre with over 99% tuberworm reduction. Other foliar-applied insecticides giving at least 98% tuberworm control included: Monitor®, monocrotophos (Azodrin®), phosphamidon, Orthene®, Torak®, methomyl (Lannate®) and Dursban® (all at 0.5 lb/acre) and Phosvel® (1 lb/acre). 相似文献
15.
W.A. Smirnoff 《Crop Protection》1983,2(2):225-230
Biochemical analysis has shown that populations of Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae) which have survived treatment with chemical insecticides (organophosphates and carbamates) have greater energy reserves and vigour than those from untreated areas: conversely, populations surviving treatment with Bacillus thuringiensis (B.t.) are considerably less vigorous. Surviving pupae from untreated, organophosphate-treated and B.t.-treated areas gave, respectively, the following results on biochemical analysis: average weight, 69·5, 82·0 and 46·9 mg; Ca++, 80·0, 114·5 and 54·0 mg/kg; total proteins, 27·6, 36·3 and 19·2 mg/kg; 3-hydroxybutyrate dehydrogenase, 1004, 1091 and 200 mU/g; alkaline phosphatase, 541, 580 and 251 mU/g. These analyses confirmed that B.t. treatments had a detrimental effect on survivors whereas chemical insecticides encouraged the resurgence of vigorous populations of C. fumiferana as a result of stimulation of these insects by sub-lethal dosages (hormoligosis). 相似文献
16.
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
17.
The chilli thrips Scirtothrips dorsalis (Hood) (Thysanoptera: Thripidae), a new invasive pest in the USA, is an economically important pest of certain vegetable, ornamental and fruit crops in southern and eastern Asia, Oceania and parts of Africa. These crops cannot be protected from the pest without resorting to the use of chemical insecticides. In order to forestall or delay the development of insecticide resistance in S. dorsalis, we continued our focus on the discovery of insecticides with different modes of action for rotational use. In this study we evaluated candidate insecticides to control S. dorsalis on ‘Jalapeno’ pepper, Capsicum annuum L.; these materials belong to different IRAC mode of action classes as follows: (i) 4A – neonicotinoids, i.e., imidacloprid, thiamethoxam and dinotefuran, (ii) 5 – spinosyns, i.e., spinosad and spinetoram, (iii) 3A – pyrethroids, i.e., β-cyfluthrin, esfenvalerate, ζ-cypermethrin and λ-cyhalothrin and (iv) 8D – borax mixed together with orange oil and detergents in the TriCon® formulation. In addition we evaluated the entomopathogenic fungus, Beauveria bassiana (Botanigard®) alone and in combination with the borax formulation at ½ of their usual rates of application. Each of the 3 neonicotinoid insecticides when applied either as a single foliar spray or as a soil drench significantly suppressed both adults and larvae for at least 10 days; indeed imidacloprid did so for 15 days. Dinotefuran was more effective as a foliar spray than as a soil drench. Spinosyns applied as a single foliar spray, significantly suppressed both adults and larvae through 15 days after treatment (DAT). None of the 4 pyrethroids provided significant suppression of either adults or larvae. The borax formulation suppressed adults and larvae through 10 DAT. B. bassiana significantly suppressed only the larvae at 5 DAT and not at 10 DAT. This study brings the number of insecticides known to be effective against S. dorsalis to 10 and these belong to 7 different modes of action classes. The use of such insecticides in rotation belonging to different classes will help delay the development of insecticide resistance in S. dorsalis. 相似文献
18.
The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a major target of transgenic corn, Zea mays L., expressing Bacillus thuringiensis (Bt) proteins in both North and South America. A highly Cry1F-resistant strain of S. frugiperda was established from a field collection in Puerto Rico in 2011. In this study, three greenhouse trials were conducted to evaluate larval survival and leaf injury of Cry1F-susceptible, -resistant, and -heterozygous genotypes of S. frugiperda on whole plants of five non-Bt and eight Bt corn hybrids. The Bt corn products included two single-gene Bt corn hybrids containing Herculex®I (Cry1F) and YieldGard® (Cry1Ab) traits and six pyramided Bt corn hybrids representing four traits: Genuity® VT Double Pro™, Genuity®VT Triple Pro™, Genuity® SmartStax™, and Agrisure® Viptera™ 3111. In each trial, neonates of S. frugiperda were placed into the plant whorls at vegetative plant stages (V6–V10). Larvae of the three insect genotypes on non-Bt corn hybrids survived well and caused serious plant injury. Cry1Ab corn was ineffective against all three insect genotypes. On Cry1F corn plants, resistant larvae survived on 72.9% plants after 12–15 d and caused a leaf injury rating (Davis' 1 to 9 scales) of 5.7 after 7 d and 7.6 after 12–15 d. Both the larval survivorship and leaf injury rates of the resistant larvae on Cry1F corn plants were not significantly different from those observed on non-Bt corn hybrids. In contrast, no live larvae and little or no leaf injury were observed on the Cry1F corn plants that were infested with susceptible or heterozygous genotypes, or on the pyramided Bt plants. The results demonstrated that the Cry1F-resistant S. frugiperda was highly resistant to whole plants of Cry1F corn and the resistance was recessive. Hybrids that contained one of the four pyramided Bt traits were effective for managing the Cry1F resistance in S. frugiperda. 相似文献
19.
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
20.
Helicoverpa armigera is the key pest of cotton in Spain, resulting in many insecticide treatments against it. The resistance status of H. armigera to different insecticides currently used in cotton was evaluated in Spain in two different seasons, 1999 and 2004. Four populations were tested in total, two in each season. Toxicological bioassays were conducted in the laboratory, and performed on third instar larvae by topical application of the insecticides. LD50's were estimated by probit analysis and resistance factors (RF) were calculated at the LD50 level. Four insecticides were evaluated, but only endosulfan reached a moderate resistance level (RF = 11.4), and the others (methomyl, chlorpyrifos and lambda-cyhalothrin) showed low resistance (RF between 1.9 and 6.0). Such results indicate the generally low resistance of H. armigera to most of the insecticides used against this pest in cotton in Spain. Possible explanations for this situation are discussed. 相似文献