Temperature-dependent development of Agrotis ipsilon (Lepidoptera: Noctuidae) and its stage transition models

The black cut worm Agrotis ipsilon (Hufnagel) is a destructive crop pest worldwide and a typical cut worm damaging plant parts below the soil surface, which requires a thorough phenological prediction of the target stage for proper management. Temperature is an essential factor affecting the phenology and dynamics of insect populations. So, this study was conducted to evaluate the temperature-dependent development of A. ipsilon fed on Kimchi cabbage (Brassica campestris) in a wide range of temperatures (10 to 40 ℃) in the laboratory. The linear and nonlinear relationship between temperature and development rate (1/development time) was analyzed. The lower threshold temperatures (LT) for eggs, larvae, and pupae were estimated to be 12.1 °C, 9.6 °C, and 11.2 °C, respectively, with thermal constants (degree days for development completion) of 31.3, 342.2, and 181.3 DD at each stage, respectively. Additionally, the thermal constant for tracking the phenology of each stage was determined using a common LT of 10.4 ℃: 40.3 DD for eggs, 315.6 DD for larvae, and 199.6 DD for pupae. Consequently, we provided newly the stage transition models for all stages of A. ipsilon using two basic components of the nonlinear development rate and distribution models to simulate the proportion of individuals shifted from one stage to the next stage. These models in their current form will be useful for constructing a population model for A. ipsilon in the future. Furthermore, the variation in the development time of A. ipsilon reported in previous studies was discussed using 95% confidence limits of the estimated line of our nonlinear models.

     

Effect ofMelia azedarach fruit extract on juvenile hormone titer and protein content in the hemolymph of two species of noctuid lepidopteran larvae [insecta: Lepidoptera: Noctuidae]

The effect of an enriched methanolic extract ofMelia azedarach L. (Meliaceae) fruits on the size of the corpora allata (CA), the juvenile hormone (JH) titer and the protein content in the hemolymph of two lepidopteran pests in Egypt,Spodoptera littoralis (Boisd.) andAgrotis ipsilon (Hufn.), was studied. Different concentrations of the extract were incorporated into an artificial diet on which the larvae were allowed to feed. InS. littoralis, a significant reduction in the CA volume of larvae treated at the 1000 ppm extract levelvs that of control larvae was observed. In A.ipsilon, a reduction was found in the right CA gland only. Larvae of both species that had fed on a diet withMelia extract had a higher mean JH-II titer in the hemolymph than did control larvae. In both species, the content of hemolymph protein was decreased significantly after feeding for 6 days on a diet treated with concentrations above 50 ppm extract, followed by 6 days on a normal diet. The results show that aM. azedarach fruit extract has an effect on the neuroendocrine control in the insects. The effect on the hemolymph protein levels is discussed in connection with changes in the morphology/physiology of the gut.     

Can a chitin‐synthesis‐inhibiting turfgrass fungicide enhance black cutworm susceptibility to a baculovirus?

BACKGROUND: Developmental resistance, i.e. reduced virulence and speed of kill of late instars, is a limiting factor in the use of baculoviruses for caterpillar control. Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNPV) is highly infective to young black cutworms, Agrotis ipsilon, but too slow‐acting against late instars for effective curative control on golf courses or sports fields. Chitin‐synthesis‐inhibiting fungicides containing the active ingredient polyoxin‐d are used to control fungal diseases in turfgrass, and similar compounds have been shown in the laboratory to synergize baculoviruses by disrupting peritrophic membrane function. This study tested whether applying the virus together with such a fungicide can synergize AgipMNPV activity against A. ipsilon in turfgrass. RESULTS: The addition of a chitin synthesis inhibitor failed to increase AgipMNPV infectivity to A. ipsilon in the field. Rather, delayed and slightly reduced mortality from viral infection was seen when larvae fed on fungicide/virus‐treated grasses as opposed to virus‐only treatments. Choice tests revealed the fungicide residues to be a mild feeding deterrent. CONCLUSION: Because polyoxin‐d does not deactivate AgipMNPV, the two substances are compatible. However, combination applications of polyoxin‐d and Agip MNPV on turfgrass might interfere with larval ingestion of a lethal virus dose, resulting in prolonged larval feeding in the field. Copyright © 2011 Society of Chemical Industry     

Comparative biology and life table of Habrobracon hebetor (Hymenoptera: Braconidae) on Anagasta kuehniella (Lepidoptera: Pyralidae) at five constant temperatures

Habrobracon hebetor Say is an ectoparasitoid that has been used as a control agent of various lepidopteran pests. Temperature-dependent life table and thermal characteristics of H. hebetor are important in understanding the dynamics of host–parasitoid relationships and for optimizing biocontrol programmes. The influence of five constant temperatures (15, 20, 25, 30 and 35 °C) on the biology of H. hebetor when parasitizing Anagasta kuehniella Zeller was studied. The survival rate of immature stages increased from 16.67% to 83.81% as temperature increased from 15 to 30 °C and then decreased at 35 °C. Total development time ranged from 45.70 days at 15 °C to 7.10 days at 35 °C. The lower temperature threshold for immature stages varied slightly around a value of 11–12 °C. The net reproductive rate (R₀) values were significantly different among temperatures and the highest value was found at 30 °C (85.10). The high survival rate and net reproductive rate combined with a relatively short generation time at 30 °C resulted in the intrinsic rate of increase (r_m) being highest (0.312 d^?1) at this temperature. Considering the acquired results, the temperature range between 25 and 30 °C was optimal for H. hebetor.     

Life-table analyses for the tomato leaf miner,Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae): effects of plant genotype

BACKGROUND

Host plant resistance plays an important role in integrated pest management programs. Crop resistance assessments commonly focus on only a single dependent variable, such as larval survival/plant damage, which limits the ability to appreciate the impact of host plants on pest populations in the full sense. Therefore, we performed life-table analyses for tomato leaf miner Tuta absoluta, on 19 Solanum lycopersicum genotypes and a wild Solanum habrochaites accession. These analyses assess the ability of the pest to attain a high population density on different tomato genotypes. Based on the resulting ranking of tomato resistance at the vegetative stage (45-day-old plants), we tested the resistance of six selected genotypes at the reproductive stage (4-month-old plants).

RESULTS

T. absoluta performance was significantly inferior on vegetative-stage S. habrochaites plants (LA 1777); time taken for the first instars to mine the leaves (5 ± 0.14 days), development time of early- and late-stage larvae (8.8 ± 0.2 and 4.2 ± 0.2 days, respectively), pupal period (11.2 ± 0.58 days), and total developmental time (29.4 ± 0.83 days) were significantly longer, fecundity was significantly lower (18.66 ± 7.24 days), and the highest total mortality (63.33%) also recorded compared with other genotypes, resulting in the lowest net reproductive rate (R₀) (11.20 ± 2.51). For the six selected genotypes, the ranking of plant resistance did not change between plants at the vegetative and reproductive stages.

CONCLUSION

This study suggested that of 20 screened tomato genotypes, LA 1777 and EC-620343 are the least suitable hosts for T. absoluta to establish fast-growing populations, and thus can be employed in integrated T. absoluta management. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Demography and population projection of <Emphasis Type="Italic">Myzus persicae</Emphasis> (Sulz.) (Hemiptera: Aphididae) on five pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.) cultivars

The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is a major pest of pepper. In this study, we collected data on the development, survival, fecundity, and proportion of apterous and alate forms of green peach aphid reared on five commercial pepper cultivars (Amiral, Erciyes, Mert, Mertcan, and Naz) at 25?±?1°C, 60?±?5% RH, and a photoperiod of 16:8 (L:D) h. We analyzed the life history raw data by using the age-stage, two-sex life table. The shortest development time (6.66 days) and highest fecundity (62.68 individuals) occurred on the Erciyes cultivar. The highest intrinsic rate of increase (r?=?0.332 d^?1), finite rate of increase (λ?=?1.394 d^?1), net reproductive rate (R₀?=?62.7 offspring) and shortest mean generation time (T?=?12.45 d) also occurred on the Erciyes cultivar; while the lower fitness occurred on the Amiral, Mertcan and Naz cultivars. Our results compared differences in the population growth rate of M. persicae on different pepper cultivars. This information will be useful to individuals working in pest management programs particularly those involving M. persicae.     

Synthetic bis- and mono-chalcones with insecticide effects on Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

This is the first report on the antifeedant, toxic and nutritional effects produced by the synthetic chalcones on the lepidopteran Spodoptera frugiperda followed by structure-activity relationship. Bis (5a-c) and mono (8a-d) chalcones have been synthesized via Claisen-Schmidt condensation and have been purified and characterized. The mono chalcones 8b and 8d displayed toxic effects on early larval instars when incorporated to the larval diet at 100?µg per g of diet (40 and 60%, respectively) and low adults emergency with malformations leading to death. The remaining chalcones 8a, 8c, 5a, 5b and 5c do not displayed toxic effects at the same dose. The evaluation of nutritional indices indicated that 8a and 8c were the only tested chalcones to produce decrease in the growth rate and to reduce the efficiency with which larvae converted ingested food into biomass.     

Inoculum potential of Sclerotinia sclerotiorum sclerotia depends on isolate and host plant

The soilborne fungus Sclerotinia sclerotiorum infects many important crop plants. Central to the success of this pathogen is the production of sclerotia, which enables survival in soil and constitutes the primary inoculum. This study aimed to determine how crop plant type and S. sclerotiorum isolate impact sclerotial production and germination and hence inoculum potential. Three S. sclerotiorum isolates (L6, L17, L44) were used to inoculate plants of bean, carrot, lettuce, oilseed rape (OSR) and potato, and the number and weight of sclerotia per plant quantified. Carpogenic germination of sclerotia collected from different hosts was also assessed for L6. Production of sclerotia was dependent on both crop plant type and S. sclerotiorum isolate, with OSR and lettuce supporting the greatest number (42–122) and weight (1.6–3.0 g) of sclerotia per plant. The largest sclerotia were produced on OSR (33–66 mg). The three S. sclerotiorum isolates exhibited a consistent pattern of sclerotial production irrespective of crop type; L6 produced large numbers of small sclerotia while L44 produced smaller numbers of large sclerotia, with L17 intermediate between the two. Germination rate and percentage was greatest for larger sclerotia (4.0–6.7 mm) and also varied between host plants. Combining sclerotial production data and typical field crop densities suggested that infected carrot and OSR could produce the greatest number (3944 m^?2) and weight (73 g m^?2) of S. sclerotiorum sclerotia, respectively, suggesting these crops potentially contribute a greater increase in inoculum. This information, once further validated in field trials, could be used to inform future crop rotation decisions.     

三种寄主植物对小菜蛾实验种群特征的影响

为明确萝卜、白菜和油菜对小菜蛾实验种群特征的影响,测定了小菜蛾对3种寄主的取食量,通过构建两性生命表比较了不同寄主植物对其实验种群发育与繁殖的影响,并综合生命表与取食量参数,评价了小菜蛾对萝卜、白菜和油菜的危害。结果显示:小菜蛾幼虫在萝卜、油菜和白菜上的取食量差异显著,分别为93.3、105.0和114.7 mg/头。小菜蛾取食萝卜、白菜和油菜后,其幼虫的发育历期差异显著,依次为8.6、8.5和7.6 d;种群内禀增长率依次为0.18、0.23和0.23,周限增长率为1.19、1.26和1.26,净生殖率为18.7、46.1和30.6。取食萝卜的小菜蛾各发育阶段的存活率最低。小菜蛾对各供试寄主实际危害量占理论危害量的百分比为油菜(71.8%)白菜(70.8%)萝卜(53.0%)。表明同一时间内,小菜蛾对油菜危害程度最大,白菜次之,萝卜最小。     

Demographic parameters and biological features of <Emphasis Type="Italic">Phenacoccus solenopsis</Emphasis> Tinsley (Hemiptera: Pseudococcidae) on four ornamental plants

The development, reproduction and life table parameters of the cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) on four ornamental plants (Hibiscus rosa-sinensis L., H. syriacus L. (Malvaceae), Brugmansia aurea Lagerh., Cestrum nocturnum L. (Solanaceae)) were studied at 25 ± 2 °C, 60% ± 10% r.h., and 16 hours daily artificial light. Life table data were analyzed by using an age-stage, two-sex life table. The highest intrinsic rate of increase (0.2911 d^-1), finite rate of increase (1.3380 d^-1), net reproductive rate (258.0 nymphs/female) and gross reproduction rate (342.6 nymphs/female), as well as the shortest mean generation times (19.1 days) were obtained when the mealybug was reared on H. syriacus.     

Effects of petroleum spray oils on oviposition behaviour and larval survival of Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) and Ostrinia nubilalis Hubner (Lepidoptera: Pyralidae)

We determined the effects of petroleum spray oil (PSO) (Caltex Canopy®) on oviposition responses of Helicoverpa armigera Hubner and Ostrinia nubilalis Hubner adults, and larval survival of the pest moths on cotton and maize plants in the laboratory. Application of 2% (v/v) of the PSO deterred H. armigera oviposition. Increasing the rate from 2 to 5% (v/v) did not significantly reduce the number of eggs laid by H. armigera on the treated plants. In contrast, the minimum rate at which the oil could deter oviposition of O. nubilalis on maize plants was 5% (v/v). Increasing the rate from 5 to 10% (v/v) did not significantly reduce the number of eggs laid per plant. However, a reduction in the rate of the PSO from 5 to 3% (v/v) resulted in a 73.9% increase in oviposition activity on the maize plants. In wind tunnel bioassay tests, all mated H. armigera females tested could detect and settle on plants treated with water but with plants treated with PSO at various times, only 50% of tested females settled on the plants 4?–?5 days after treatment (DAT) and none on the plants 0?–?2 DAT. A solid phase micro-extraction (SPME) test to determine the effect of the PSO on volatiles released by the cotton plants showed that the quantity of volatiles released by the cotton plants treated with PSO was lower than for water treated plants. This indicates that the PSO sprays may be suppressing or masking the leaf surface volatiles of the cotton plants, thereby deterring oviposition of H. armigera. Larval survival data show that PSO sprays can cause direct mortality of first, second and third instar O. nubilalis larvae. PSOs may have the potential to be integrated into pest management programme targeting H. armigera and O. nubilalis on cotton and maize crops, respectively.     

Effects of different potato cultivars on life history and demographic parameters of Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae)

Potato tuber worm, Phothorimae operculella Zeller (Lepidoptera: Gelechiidae) is a common pest of potato which causes a heavy loss in yield either in fields or storage. The effect of six potato cultivars (Agria, Florida, Impala, Picasso, Satina, and Sprint) were evaluated on the life history, life table and demographic parameters of P.operculella under laboratory conditions, which could be appropriate indices in resistance and susceptibility evaluation of potato cultivars. The longest development time was on Picasso (28.76 ± 0.36d) cultivar. The male longevity ranged from 4.83 ± 0.44d on Sprint to 7.45 ± 0.60d on Picasso. Impala and Satina with 53.22 ± 7.78 and 28.74 ± 3.54 eggs/individual had the highest and the lowest net reproductive rates (R₀). The highest values for the intrinsic rate of increase (r_m) and finite rate of increase (λ) were on Impala (r_m: 0.119 day^?1, λ: 1.75 day^?1), and the lowest value was on Sprint (r_m: 0.090 day^?1, λ: 1.01 day^?1). The results indicated that Sprint was the most resistant cultivar for the feeding of P.operculella, which could be useful in the development of integrated pest management programs for this pest.     

Seed structure and germination in Discaria toumatou (Rhamnaceae)

Data collected from field trials carried out in different years and environments were used to determine competitive ability and threshold levels of Ammi majus L., Chenopodium album L. and Sinapis arvensis L. The hyperbolic model showed a good fit to the experimental data. The three broadleaf weeds showed low and similar competitive indices (i ranging from 1–08 to 1–75), supporting the hypothesis of a high sunflower competitive ability. The economic threshold was four to six plants m^?2 for all three weeds in the case of weed control by hoeing and about six plants m^?2 for S. arvensis in the case of a postemergence treatment with imazamethabenz. Limitations and approximations in estimating competitive parameters are pointed out and discussed. Aptitude à la compétition et seuils de nuisibilité de trois mauvaises herbes dicotylédones dans le tournesol Des données recueillies dans des expérimentations au champ conduites dans différents environnements et au cours de différentes années ont été utilisées pour déterminer l'aptitude à la compétition et les seuils de nuisibilité de Ammi majus L., Chenopodium album L. et Sinapis arvensis L. Le modéle hyperbolique fournissait un bon ajustement aux données. Les trois mauvaises herbes avaient des indices de compétition bas et similaires (i de 1,08 à 1,75) ce qui conforte l'hypothèse d'une forte aptitude à la compétition du tournesol. Les seuils économiques étaient 4–6 plantes m^?2 pour toutes les mauvaises herbes dans le cas de désherbage mécanique et environ 6 plantes m^?2 pour S. arvensis dans le cas de traitement de post-levée avec l'imazaméthabenz. Les limitations et les approximations dans l'évaluation des paramètres de la compétition sont identifiés et discutés. Konkurrenzkraft und Schadensschwellen von drei dikotylen Unkrautarten in Sonnenblume Anhand von Ergebnissen aus Freilandversuchen in verschiedenen Jahren auf verschiedenen Standorten wurden die Konkurrenzkraft und die Schadensschwellen von Ammi majus L., Chenopodium album L., und Sinapis arvensis L, bestimmt. Die Ergebnisse ließen sich mit einer hyperbolischen Gleichung gut beschreiben. Die Konkurrenzindices i von 1,08 bis 1,75 waren fur alle 3 Arten ahnlich niedrig, worin sich die starke Konkurrenz der Sonnenblume widerspiegelt. Bei mechanischer Unkrautbekampfung lagen die Schadensschwellen fur alle 3 Unkrauter zwischen 4 und 6 Pflanzen m^?2, fur Nachauflaufbehandlung mit Imazametabenz fur Sinapis arvenis bei 6 Pflanzen m^?2. Grenzen und Annaherung der Bestimmung von Konkurrenzparametern werden eingehend diskutiert.     

丛枝菌根真菌和甜菜夜蛾的相互作用

为探索丛枝菌根(arbuscular mycorrhiza,AM)真菌与植食性昆虫的相互作用,将摩西管柄囊霉(Funneliformis mosseae BEG167,Fm)、根内球囊霉(Glomus intraradices BEG141,Gi)和地表球囊霉(Glomus versiforme Berch,Gv)3种AM真菌以及甜菜夜蛾Spodoptera exigua分别接种至花生和番茄上,通过测定AM真菌的侵染定殖和甜菜夜蛾的生长发育指标分析AM真菌与甜菜夜蛾的相互作用。结果显示,甜菜夜蛾取食菌根花生植株后,Fm、Gv和Gi的侵染率和泡囊数均有增加,侵染率分别是未取食的1.15、1.10和1.11倍,而Fm的泡囊数增加最显著,是未取食的1.27倍。在菌根番茄植株上,Fm和Gv的侵染率显著增加,分别是未取食的1.24倍和1.94倍,Fm、Gv和Gi的泡囊数均显著增加,分别是未取食的1.50、1.98和1.42倍。甜菜夜蛾取食菌根花生和菌根番茄植株后,幼虫存活率下降,幼虫历期和蛹期明显延长;Fm对其影响最显著,甜菜夜蛾在花生上的存活率、幼虫历期和蛹期分别为26.67%、26.78 d和10.67 d,在番茄上分别为35.52%、24.33 d和10.39 d,与取食非菌根植株处理差异显著。表明甜菜夜蛾能在一定程度上促进AM真菌的侵染和定殖,而AM真菌能抑制甜菜夜蛾的生长和发育,但其影响因AM真菌种类而不同。     

Assessing host specialization of Botrytis cinerea on lettuce and tomato by genotypic and phenotypic characterization

This study tested the hypothesis that Botyrtis cinerea shows host specialization on tomato and lettuce, using phenotypic and genotypic tools. Strains were isolated from tomato and lettuce grown together in the same greenhouse. Forty‐four lettuce strains and 42 tomato strains were investigated for their genetic diversity and their aggressiveness. Both gene diversity and allelic richness were significantly higher in lettuce strains than in tomato strains (P = 0·01). Cluster analysis revealed a clear division of the strains under study into two clusters. However, this structure did not separate the strains according to their host of origin. Tomato strains were significantly more aggressive than lettuce strains when inoculated on tomatoes (P = 0·001), but no significant differences in aggressiveness were observed when the strains were inoculated on lettuce (P = 0·17) or on apple (P = 0·87). The results suggest an absence of clear host specialization of B. cinerea on tomato and lettuce.     

Effect of host plants on developmental and population parameters of invasive leafminer, <Emphasis Type="Italic">Tuta absoluta</Emphasis> (Meyrick) (Lepidoptera: Gelechiidae)

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most serious pests of tomato, capable of causing 100% crop losses under favourable conditions. We studied the effect of different host plants on developmental and population parameters of this pest at 25?±?0.5 °C temperature, 70?±?5% relative humidity and 12 L: 12D photoperiod. Host plant had significant effect on the developmental biology and the population growth parameters of the pest. The leafminer developed fastest on tomato leaves and slowest on potato tubers. Population growth parameters like intrinsic rate of increase, net reproductive rate, finite rate of increase, doubling time and weekly multiplication rate of T. absoluta were highest on tomato leaves and lowest on potato tubers. Mean generation time was minimum on tomato leaves and maximum on potato tubers. Females developed on tomato leaves were more fecund than other hosts. Though, tomato was found to be the most suitable host plant of T. absoluta, yet, the pest developed and grew successfully on other alternate hosts like potato (Solanum tuberosum L.), brinjal (Solanum melongena L.) and pepino (Solanum muricatum Aiton). These hosts can, therefore, play an important role in the survival, population build up and overwintering of the miner. Further, under favourable conditions the miner can become a serious pest on these crops and need to be monitored on these crops as well.     

Taxonomy,distribution and biology of lettuce powdery mildew (Golovinomyces cichoracearum sensu stricto)

This paper reviews the taxonomy, biology, importance, host–pathogen interactions and control of lettuce powdery mildew. The main causal agent of this disease, Golovinomyces cichoracearum s.s., is an important powdery mildew pathogen of many members of the family Asteraceae. The pathogen is distributed worldwide and occurs on Lactuca sativa as well as wild Lactuca spp. and related taxa (e.g. Cichorium spp.). Powdery mildew of lettuce can be a major problem in production areas with favourable environmental conditions for disease development (dry, hot weather). The fungus grows ectophytically and appears as white, powdery growth on both the upper and lower sides of leaves. There is rather limited information on the geographic distribution of powdery mildew on wild Lactuca spp. Most L. sativa cultivars have been found to be susceptible. Large variability in virulence was confirmed and existence of different races is supposed. Resistance in L. sativa and some related wild Lactuca spp. is characterized by race‐specificity, but the genetic background of resistance is poorly understood. Sources of resistance are known in L. saligna and L. virosa. Lettuce powdery mildew can be effectively controlled by common fungicides (e.g. sulphur, myclobutanil, quinoline, strobilurins, etc.) and protective compounds (e.g. extract of neem oil, Reynoutria sachaliensis extracts). However, fungicide resistance may arise. Non‐fungicidal activators of plant systemic acquired resistance (SAR) had no direct effect on the causal agent. Future issues regarding lettuce powdery mildew research are summarized.     

Optical brightener M2R destroys the peritrophic membrane of Spodoptera exigua (Lepidoptera: Noctuidae) larvae

Observations under an environmental scanning electron microscope showed that the peritrophic membrane (PM) of Spodoptera exigua (Hübner) was smooth without pores, but there were many pores and slits in the PM of larvae fed with 10 g L(-1) optical brightener Calcofluor white M2R. After incubation of S. exigua PM in vitro with 10 g L(-1) M2R, a significant amount of proteins was released from the PM structure. M2R disrupted the structure of larval PM, resulting in greatly increased permeability and increased larval susceptibility to Syngrapha falcifera multiple nucleopolyhedrovirus infection. Continuous feeding of larvae on a diet treated with a 10 g L(-1) M2R solution significantly retarded larval development and resulted in high mortality. The destructive effect of M2R on PM was transient and reversible, depending on the presence of M2R within the midgut.     

Effects of four host plants on susceptibility of Spodoptera litura (Lepidoptera: Noctuidae) larvae to five insecticides and activities of detoxification esterases

BACKGROUND: The tobacco cutworm, Spodoptera litura (F.), is one of the most destructive polyphagous pests worldwide. The susceptibility of S. litura larvae reared on tobacco, Chinese cabbage, cowpea and sweet potato to phoxim, chlorfenapyr, methomyl, fenvalerate and emamectin benzoate under laboratory conditions was determined. RESULTS: Spodoptera litura larvae reared on tobacco were most tolerant to all insecticides, whereas those that fed on sweet potato were most susceptible. When larvae were reared on each host plant for three generations, the susceptibilities to phoxim of larvae that fed on Chinese cabbage and cowpea were similar, whereas the susceptibility of larvae that fed on sweet potato decreased by the third generation, and on tobacco the susceptibility decreased in each consecutive generation. When nicotine was added to their diet for three consecutive generations, the tolerance of larvae to phoxim increased twofold, and to emamectin benzoate 3.1‐fold, but the tolerance of larvae to fenvalerate and chlorfenapyr did not change. The acetylcholinesterase activities of the larvae that fed on sweet potato and cowpea were greater than the activities of those that fed on Chinese cabbage and tobacco. In contrast, the carboxylesterase activities of the larvae that fed on tobacco and Chinese cabbage were greater than the activities of those that fed on sweet potato and cowpea. The glutathione S‐transferase activities of larvae were highest when they fed on tobacco, followed by Chinese cabbage and cowpea, and the lowest activities were observed when larvae fed on sweet potato. CONCLUSION: Feeding on tobacco or with nicotine added to the diet, the larvae became more tolerant to insecticides, especially to phoxim and emamectin benzoate. Copyright © 2010 Society of Chemical Industry     

亚洲玉米螟的寄主植物种类

为探明亚洲玉米螟Ostrinia furnacalis(Guenée)的寄主植物种类,对13科38种植物进行了田间笼罩接虫试验和室内生物测定,并通过组建实验种群生命表分析了不同寄主植物对亚洲玉米螟生长发育和繁殖的影响。田间试验结果表明,亚洲玉米螟寄主植物有8科20种,酸模叶蓼是最适宜寄主植物,其次为玉米、谷子、薏苡等;在酸模叶蓼、玉米等11种植物上还发现了第2代幼虫。室内试验结果表明,在室内饲养条件下,亚洲玉米螟能在9科25种寄主植物上完成生活史,其中以向日葵为寄主植物的亚洲玉米螟种群增长最快,其次为玉米。研究表明,亚洲玉米螟的寄主植物共有9科27种,较适宜寄主植物有酸模叶蓼、玉米、谷子、苍耳和葎草,其中在玉米上的生长发育和繁殖最佳。