Rice Grain Damage by Combination and Sequence Infestations by the Rice Leaffolder, Cnaphalocrocis medinalis Guenee(Lepidoptera: Pyralidae), and the White-Backed Rice Planthopper, Sogatella furcifera Horváth(Hemiptera: Delphacidae)

The rice leaffolder （RLF）, Cnaphalocrocis medinalis Guenée （Lepidoptera：Pyralidae）, and the white-backed rice planthopper （WBPH）, Sogatella furcifera Horváth （Hemiptera： Delphacidae）, are major insect pests in China and several other Asian countries. These two pests commonly occur simultaneously or in a temporal sequence. Thus, the investigation of the effect of complex infestations or temporal sequence infestations by these pests on rice yield has a practical signiifcance for the control of these pests. The present study comprised experiments with the following four different variables in potted rice at the tillering stage：single pest species infestation, complex infestation, complete combination infestation and temporal sequence infestation （C. medinalis infestation prior to S. furcifera and S. furcifera infestation prior to C. medinalis）. The results showed that the four infestations resulted in a signiifcant decrease in 1 000-grain weight （1 000GW） and rate of yield loss （RYL） but an increase in blighted grain rate （BGR）, with a signiifcant positive correlation with the infestation density. However, the inlfuences of the complex infestation, complete combination infestation or sequence infestation on the 1 000GW, BGR and RYL were greater than those of the single pest species infestations but did not have addition effects, i.e., the effects of the complex infestation and combination infestation or sequence infestation on the 1 000GW, BGR and RYL were less than the additive effects of the two single pest species infestations at the same densities. In the condition of the same total infestation pressure, no signiifcant differences in the 1 000GW, BGR and RYL were found between C. medinalis infestation prior to S. furcifera and S. furcifera infestation prior to C. medinalis as well as between the sequence infestation and the complex infestation.

Toxicity of Bacillus thuringiensis Crystal Toxins to Field Populations of Rice Leaf Folder, Cnaphalocrocis medinalis （Guenee） and Establishment of Baseline Susceptibility to Cry1Ab

Eight insecticidal crystal proteins of Bacillus thuringiensis, CrylAa, CrylAb, CrylAc, CrylB, Cry2Aa, CrylC, CrylDa and Cry 1Ea were assessed for toxicity against 1 st instar larvae of rice leaf folder, Cnaphalocrocis medinalis （Guenee） at 48 HAT and 72 HAT. Bioassay results depicted CrylAa was the most toxic （LCso 2.35 ppm） followed by CrylBa （LCso 8,50 ppm） and CrylAb （LCso 8.73 ppm） at 48 HAT, whereas, at 72 HAT CrylAb proved to be highly toxic （LC50 0.50 ppm） followed by CrylAa （LCso 4.07 ppm）, CrylAc （LCso 4,84 ppm） and CrylBa （LCso 6.42 ppm）. Toxins Cry2Aa, CrylCa, CrylDa and CrylEa did not resulted in any mortality at 48 HAT and 72 HAT, respectively. Baseline estimates for CrylAb against 1st instar larvae of C. medinalis sampled from seven geographical locations revealed variation in LC50＇s from 0.37 ppm to LC50 16.25 ppm at 48 HAT and LC50 0.50 ppm to LC50 6.49 ppm 72 HAT, respectively with relative resistance ratios of 44-fold and 13-fold at 48 HAT and 72 HAT over the susceptible population.

Carboxylesterase and Glutathione-S-Transferase （GST＇s） Induced Resistance to Bacillus thuringiensis Toxin CrylAb in Rice Leaf Folder, Cnaphalocrocis medinalis （Guenee） Populations

The rice leaf folder （RLF）, Cnaphalocrocis medinalis （Guenee） （lnsecta： Lepidoptera： Pyralidae）, is an important pest, widely distributed in many rice growing areas of Asia. The over-use of broad-spectrum chemical insecticides has been cited as a major cause of outbreaks of C. medinalis as excessive spraying of insecticide disrupts natural biological control insecticides still remain the major control tactics against leaf folder. Carbofuran and fenthion, bendiocarb, acephate, carbosulfan, quinolphos, monocrotophos, phosphamidon and fenvalerate are the common ones used against rice leaf folder. Genetically, modified rice lines expressing B. thuringiensis insecticidal crystal proteins produced are highly tolerant to leidopteran pests. Though economic and environmental benefits of GM crops is well established, the matter of concern is the possibility of target insect pest developing resistance to this B. thuringiensis insecticidal toxins, evident from many laboratory and field experiments against many insect pests. The involvement of GSH S-transferase, carboxylesterase, and microsomal monooxygenase in insecticide resistance has been reported in insecticide-resistant strains of many insect species. Hence, the present study was taken up to monitor for cross resistance between B. thuringiensis cry toxins and synthetic insecticides in larvae of leaf folder as it is mediated by carboxylesterase titre and other enzymes by bioassay for two selected rice leaf folder field populations at the Entomology division of Directorate of Rice Research which showed 2-fold resistance ratio. Qualitative and quantitative changes of carboxylesterase （CarE） and glutathione-s-transferase （GST＇s） were worked out with midguts extracts of the two C. medinalis populations in the presence of a-napthyl acetate and chlorodi-nitro benzene substrates.

Effect of chlorpyrifos and methyl chlorpyrifos on controlling rice ieaffolder(Cnaphalocrocis medinalis Guenee)in field

Rice leaffolder(Cnaphalocrocis medinalis Guenee) hasbecome a serious pest on rice in Jiangsu Province. The in-sect appeared in Jul and remained until Sep. A field trialwith 5 treatments and three replications was laid out in arandomized complete block design in a farm field in Jiang-su, China in 1993. The hybrid rice tested was transplantedinto 2×25m plots. Using a knapsack sprayer, we applied

稻纵卷叶螟(Cnaphalocrocis medinalis)迁飞的多普勒昆虫雷达观测及动态

在2007年7～9月江淮稻区稻纵卷叶螟大发生期间,利用多普勒昆虫监测雷达在南京市浦口区对稻纵卷叶螟成虫的迁飞活动进行了监测,结合大气风温场的数值模拟,研究了稻纵卷叶螟成虫的空中飞行参数和种群迁飞动态。结果表明:稻纵卷叶螟多选择在黄昏18:30以后大规模起飞,空中虫群密度在20:00～22:00时最大,迁飞过程可持续到次日5:00;稻纵卷叶螟主要选择在500m以下高度飞行。空中虫群具有聚集成层的现象,虫层多在100～500m高度之间形成,有时形成两个虫层,成层现象与低空急流关系密切,与温度没有直接关系。迁飞过程分析表明,浦口区的六(4)代稻纵卷叶螟在台风、副热带高压和江淮气旋的影响下,先后出现了多次迁入迁出过程。低压系统外围的下沉气流很可能是稻纵卷叶螟两次集中迁入的主要原因。

稻纵卷叶螟(Cnaphalocrocis medinalis(Gene))在水稻品种上的半自然种群生命表参数及对植株含糖量的影响

在排除天敌情况下,用生命表方法比较了稻纵卷叶螟在5个常用栽培水稻品种扬粳9538、淮稻9号、扬辐粳8号、扬稻6号和汕优63上的半自然种群生命表。结果表明,取食淮稻9号的稻纵卷叶螟种群趋势指数最低,表现为较强的抗耐性;扬辐粳8号的稻纵卷叶螟种群趋势指数最高;各品种间稻纵卷叶螟不同虫期的存活率、♀/♂、蛹重、产卵量、卷叶率有一定差异;稻纵卷叶螟为害后,植株内可溶性糖含量品种间无明显差异,但不同品种与对照(未接虫)相比含量有增有减;还原糖含量品种间差异显著。

Field effect of Cnaphalocrocis medinalis granulovirus (CnmeGV) on the pest of rice leaffolder

Rice leaffolder,Cnaphalocrocis medinalis(Guenée),has become a major pest throughout the rice cultivating areas of China and caused severe damage to rice production.Cnaphalocrocis medinalis granulovirus(CnmeGV),a naturally occurring baculovirus,is revealed as a potential microbial agent for the pest control.Field applications of CnmeGV were conducted against rice leaffolder larvae in rice paddies.CnmeGV infected the larvae not only in the current generation but also in the successive generation,resulting in a sustained infection in the larva population for at least 48 days.Under diferent concentrations of CnmeGV(7.5×1011 and 1.125×1012 occlusion body(OB)ha-1)at 30 days after spraying,larval population reduced up to 76.32%and rice leaf rolled rate kept in 15.42%.Simultaneously,CnmeGV had no impact on arthropod predators of C.medinalis,with abundances ranging from 2.39 to 3.79 per ten hills.These results revealed that CnmeGV is suitable as a bio-pesticide for rice leaffolder management in rice paddies.

Growth and Reproduction of Artificially Fed Cnaphalocrocis medinalis

The growth and reproduction of rice leaffolder,Cnaphalocrocis medinalis,fed on an artificial diet were studied.The results showed that the larvae were able to grow and pupate on the artificial diet.The durations of larvae and pupas of C.medinalis on the artificial diet were 28.1 d and 10.1 d,postponed 4.9 d and 1.7 d respectively,compared with those reared with rice leaves.The number of ovipositions was 41.6 per female,26.2% higher than that fed on rice leaves.Survival rate curve of larvae was a descent function of mortality-age,with no significant differences from the curve of larvae fed on rice leaves.The net reproductive rate （Ro）,intrinsic rate of increase （rm） and finite rate of increase （λ） of the population fed on diet were 17.6928,0.0884 and 1.0924,respectively,and the mean generation time （T） and double time （td） were prolonged 4.9 d and 1.3 d in comparison with the treatment of rice leaves.Population trend index （I） was 3.26,indicating a growing number of the population of C.medinalis fed on artificial diet.

Influence of Rice Genotypes on Folding and Spinning Behaviour of Leaffolder(Cnaphalocrocis medinalis) and Its Interaction with Leaf Damage

Folding and spinning behavior of Cnaphalocrocis medinalis （Guenee） （Lepidoptera： Pyralidae） in different categories of rice genotypes viz., resistant, susceptible, hybrid, scented, popular and wild rice genotypes were significantly different. Longer leaf selection time and folding time per primary fold; shorter primary fold and whole leaf fold; lower number of binds per primary fold and whole leaf fold were recorded in resistant and wild rice genotypes. In the correlation analysis, it was found that the leaf folding parameters were positively correlated to leaf folder damage whereas the leaf spinning parameters were negatively correlated. Similarly, the morphological characters differed significantly among the chosen genotypes and were related to leaffolder damage. The leaf width and total productive tiller number were positively correlated to leaffolder infestation. Results also indicated that the trichome density and length, leaf length and plant height might contribute to resistance whereas total number of green leaves had no effect on leaffolder infestation. In the scatter plot analysis between leaf folding and spinning characters and leaffolder damage, the genotypes were separated into four groups viz., resistant （TKM6, Ptb 33, LFR831311, Oryza rhizomatis and O. minuta）, moderately resistant （ASD16 and CORH1）, moderately susceptible （ADT36, Pusa Basmati and CB200290） and susceptible （IR36 and TN1）. The present investigation proved that the leaf morphology viz., leaf length and width, plant height and trichome density and length may play a vital role in resistance against rice leaffolder.

pH influences the profiles of midgut extracts in Cnaphalocrocis medinalis(Guenée) and its degradation of activated Cry toxins

Midgut extracts play crucial roles in food digestion and detoxification.We evaluated the effect of pH on the profiles of the midgut extracts in rice leaffolder,Cnaphalocrocis medinalis and the degradation of activated Bt-toxins by the midgut extracts under different pH conditions.Total protease activity increased slightly with the increase with the simulated pH in the midgut extracts and the maximal protease activity was observed at pH 10.5,while an upward trend was observed as the pH of reaction buffer increased.Activity of chymotrypsin-like enzymes increased with pH,both in the buffer and midgut extracts,while the activity of trypsin-like enzyme was unaffected.Degradation of the activated Cry2 A by the midgut extracts enhanced as the pH increased.Cry2 A was fully degraded into smaller segments at pH 9.0-10.5.Activated Cry1 C protein at pH 9.0-10.5 was partially degraded by the midgut extracts.Activated Cry1 Aa and Cry1 Ac were partially degraded into fragments by the midgut extracts at high pH.These results will facilitate our further understanding of the interactions between C.medinalis and the Cry toxin.

Selectiveness of Cnaphalocrocis medinalis to Host Plants

A field experiment was conducted to study the selectiveness of Cnaphalocrocis medinalis Guenee （commonly known as the rice leaffolder or rice leafroller） towards five rice varieties （Yangfujing 8, Yangdao 6, Shanyou 136, Huaidao 9 and Nin.gjing 1） and three weed species （Echinochloa crusgalli, Leptochloa chinensis and Leersia hexandra）. The results showed that the rice varieties carried significantly higher numbers of C. medinalis moths and eggs than the weed species. Among the rice varieties, Yangfujing 8 was associated with a higher moth number. However, there was little difference in the number of C. medinalis eggs among the rice varieties. Additionally, a laboratory experiment was performed to investigate the olfactory response of female C. medinalis towards volatile compounds from different rice varieties, as well as its oviposition preference towards these rice varieties. The volatiles of Yangfujing 8, Yangdao 6 and Shanyou 136 attracted C. medinalis similarly to those of TN 1. In contrast, the volatiles of Huaidao 9 and Ningjing 1 clearly deterred C. medinalis. Nevertheless, C. medinalis did not exhibit clear oviposition preference towards any of the five tested rice varieties.

Potential influence of carbohydrate and amino acid intake by adults on the population dynamics of Cnaphalocrocis medinalis(Lepidoptera: Crambidae)

Cnaphalocrocis medinalis is a key lepidopteran pest of rice. However, little is known about the nutritional requirements of the adult or the effects of adult-derived nutrients on reproduction. The aim of the present study was to evaluate the effects of carbohydrates and amino acids on the reproductive and demographic parameters of C. medinalis. Different feeding solutions significantly influenced adult survival and reproduction. All the sources of carbohydrates used in the treatments(fructose, glucose, and sucrose) were sufficient to increase adult longevity and fecundity, and benefited the development of ovaries in the adult stage. The positive impact of carbohydrates on lifetime fecundity was due to the prolonged oviposition period and the increased daily fecundity. The intrinsic rate of increase(rm) of C. medinalis increased from 0.103 in waterfed individuals to approximately 0.138 when adults were fed with solutions containing carbohydrates. In contrast, amino acid intake by adult insects exhibited no effect on the longevity, fecundity, ovarian development or population growth, even showing an impact of decreasing longevity of females. As nectar secreted by the flowering plant is generally rich in sugars, the potential effects of nectar on the adults of C. medinalis and other pests have to be considered during the development of biological control by applying flowering plants as a microhabitat and food source for natural enemies in rice fields.

Effect of Six-fourth Generation Cnaphalocrocis medinalis (Guenée) on Rice yield and Control Index

[Objective] The study aimed to find out effects of six-fourth generation Cnaphalocrocis medinalis （Guenée） on rice production in Yangzhou district and its control index. [Method] Through artificial control of insects in field, four different insect volume gradients were set, the effects of different C. medinalis amounts on leaf roll rate and yield loss of Wuyunjing No.23 were determined. [Result] The results showed that within the range of 0-20 head/hill, as the amounts of insect increased, rice yield decreased, leaf roll rate and rice yield loss rate increased. According to 3% economic permit loss rate, the control index of C. medinalis on Wuyunjing No.23 was 173 head/hill. [Conclusion] The study would provide theoretical basis for effective controlling of six-fourth generation C. medinalis in Yangzhou district.

Effects of inhibitors on the protease profiles and degradation of activated Cry toxins in larval midgut juices of Cnaphalocrocis medinalis (Lepidoptera:Pyralidae)

Midgut juice plays an important role in food digestion and detoxification in insects.In order to understand the potential of midgut juice of Cnaphalocrocis medinalis(Guenée)to degrade Bt proteins,the enzymatic activity of midgut juice and its degradation of Bt proteins(Cry2A,Cry1C,Cry1Aa,and Cry1Ac)were evaluated in this study through protease inhibitor treatments.The activities of total protease in midgut juices were significantly inhibited by phenylmethylsulfonyl fluoride(PMSF),tosyl-L-lysine chloromethyl ketone(TLCK),pepstatin A and leupeptin.The enzymatic activity of chymotrypsin was significantly inhibited by PMSF,and enzymatic activity of trypsin was significantly inhibited by ethylenediaminetetraacetic acid(EDTA),PMSF,tosyl phenylalanine chloromethyl ketone(TPCK),TLCK and trans-epoxysuccinyl-L-leucylamido-(4-guanidino)butane(E-64).EDTA could significantly inhibit the degradation of Cry2A by C.medinalis.EDTA,PMSF,TPCK,and TLCK could inhibit the degradation of Cry1C and Cry1Aa.EDTA,PMSF,TPCK,TLCK,and E-64 could inhibit the degradation of Cry1Ac.Our results indicated that some protease inhibitors hindered various enzymatic activities in the larval midgut of C.medinalis,which may reduce the insect’s ability to degrade Bt toxins.These findings may aid the application of protease inhibitors in the management of this insect pest in the future.

Cloning,Tissue Distribution,and Transmembrane Orientation of the Olfactory Co-Receptor Orco from Two Important Lepidopteran Rice Pests,the Leaffolder(Cnaphalocrocis medinalis) and the Striped Stem Borer(Chilo suppressalis)

In insects,the sense of smell is mainly mediated by olfactory receptors（Ors）.Olfactory co-receptor（Orco）,which is coexpressed with the Ors in almost all olfactory receptor neurons（ORNs）,is demonstrated to be an essential component in the insect olfactory system.It can be potential target for developing novel olfactory-disruption strategy to control insect pests.In this study,two full-length cDNA sequences encoding Orcos（CmedOrco and ChsupOrco） were cloned from two Lepidopteran rice pests,the rice leaffolder,Cnaphalocrocis medinalis and the rice striped stem borer,Chilo suppressalis.The amino acid sequences of CmedOrco and ChsupOrco showed high similarity to the previously identified Orcos from other insect species. Bioinformatic prediction and cellular immunofluorescence indicated that CmedOrco and ChsupOrco were both seven-transmembrane proteins with intracellular N-termini and extracellular C-termini.mRNA expression levels of the two Orcos were much higher in male and female antennae than those in non-olfactory tissues,and the ChsupOrco transcripts reached a peak level in adults compared to other life stages.Our results provide a foundation from which it will be possible to elucidate the roles of Orco in moth olfaction and for the development of environment-friendly management strategies of these two rice insect pests.

Species and Occurrence of Parasitoids of Cnaphalocrocis medinalis in Nanning,Guangxi,China

[ Objective] To specify the parasitoid species of Cnaphalocrocis medinalis in Nanning, Guangxi Zhuang Autonomous Region, and provide theoretic ref- erences for the reasonable utilization and using natural enemy. [ Method] Field investigation and indoor rearing observation were adopted to figure out species and quantity of parasitoids of C. medinalis in Nanning in 2011 -2013. [ Result] There are 19 parasitoid species of C. medinalis in Nanning, belonging to Ich- neamonoidea, Chalcidoidea. Of Ichneamonoidea, there are 11 species from Ichneumonidae and Braconidae. Of Chalcidoidea, there are 8 species from Chalcididae, Eulophidae, Elasmidae, Trichogrammatidae and Encyrtidae. Among these species, Stenomesius maculatus Liao and Apanteles cypris Nixon are dominant parasitoids in larval stage. In natural control conditions, S. maculatus Liao is most-widely distributed species with the most population, especially in the first half year, accounting for 89.7 % of the total parasitoid quantity ; in pesticide application field, the quantity of S. maculatus Liao accounts for 69.1% of the total parasitoid quantity, and in nonpesticide field, it accounts for 78.5%. [ Conclusion] Application of chemical pesticide has serious impact on the natural populations of parasitoids, therefore, chemical pesticides should be applied reasonably to ensure the survival of parasitoids.

氯虫苯甲酰胺与杀虫单复配处理水稻种子对稻纵卷叶螟的防效及持效机理

稻纵卷叶螟Cnaphalocrocis medinalis是水稻生产上重要的迁飞性害虫,为开发出适用于种子处理且可长效防控稻纵卷叶螟的复配药剂,通过室内内吸活性测定、田间防效验证及植株中药剂含量检测,研究了氯虫苯甲酰胺和杀虫单复配的最适比例及对稻纵卷叶螟的田间防治效果,初步明确了复配剂的持效机理。内吸活性测定结果表明,氯虫苯甲酰胺和杀虫单质量浓度比为2:3时,共毒系数最高,内吸能力最强。按照该配比制备的25%氯虫·杀虫单种子处理悬浮剂(FS,分别含10%氯虫苯甲酰胺和15%杀虫单)在7.5~15 g/kg (种子,以下同)剂量范围内进行拌种处理,对水稻发芽和出苗安全。田间试验表明,采用25%氯虫·杀虫单FS按7.5~15 g/kg剂量拌种处理,对田间稻纵卷叶螟具有较好的控制作用,且持效期长,播种后94 d仍有70%左右的保叶效果。植株中药剂含量检测结果表明,25%氯虫·杀虫单FS对稻纵卷叶螟的持效控害能力主要与叶片中氯虫苯甲酰胺的残留含量有关,复配剂中的杀虫单虽然降解较快,但其在苗期可提高水稻根部对氯虫苯甲酰胺的吸收率。本研究结果可为开发防治稻纵卷叶螟的种子处理药剂提供理论依据及技术参考。

益于螟蛉绒茧蜂而非稻纵卷叶螟的寡糖筛选

鳞翅目害虫及其寄生性天敌的成虫均能通过取食蜜源食物来提高生态适应性。为筛选出有利于螟蛉绒茧蜂Cotesia ruficrus但不使稻纵卷叶螟Cnaphalocrocis medinalis受益的寡糖,本研究以蜜源中常见的12种寡糖为材料,评估供试寡糖对稻纵卷叶螟寿命和繁殖力的影响,及对螟蛉绒茧蜂寿命的影响。结果显示取食供试寡糖对稻纵卷叶螟的寿命影响不大,雌雄成虫的寿命分别在6.2~8.0 d和5.0~7.9 d,仅取食葡萄糖显著提高雌成虫的寿命。但果糖(232.1)、葡萄糖(130.1)和蔗糖(186.1)可以显著提高稻纵卷叶螟的每雌产卵量,分别是取食清水(31.7)的7.3倍、4.1倍和5.9倍。与稻纵卷叶螟不同,取食果糖、半乳糖、葡萄糖、甘露糖、麦芽糖、蜜二糖、蔗糖、海藻糖和松三糖均可显著提高螟蛉绒茧蜂雌雄成虫的寿命,分别是取食清水的3.7倍、2.9倍、2.5倍、2.1倍、2.3倍、2.0倍、2.8倍、2.6倍和1.7倍。因此,半乳糖、甘露糖、麦芽糖、蜜二糖、海藻糖和松三糖可以显著提高螟蛉绒茧蜂的寿命但不会促进其寄主稻纵卷叶螟的寿命和繁殖力。

亚致死浓度阿维菌素和毒死蜱对经历寄主转换的稻纵卷叶螟生长发育和繁殖的影响

【目的】本研究旨在明确寄主转换经历是否会改变亚致死浓度杀虫剂对稻纵卷叶螟Cnaphalocrocis medinalis生长发育和繁殖的影响,为杀虫剂的合理使用及稻纵卷叶螟的综合治理提供理论依据。【方法】从稻纵卷叶螟水稻种群和小麦种群中收集卵,并将其分别转换寄主植物饲养至2龄,作为具有不同寄主转换经历处理的幼虫[以水稻为食的水稻种群(R-R)、以小麦为食的水稻种群(R-W)、以小麦为食的小麦种群(W-W)和以水稻为食的小麦种群(W-R)]。利用离体叶片浸渍法对这些幼虫在亚致死浓度(LC_(25))阿维菌素和毒死蜱浸渍下的水稻或小麦叶片处理后48 h,测定3-5龄幼虫生长发育及成虫繁殖能力和寿命。【结果】未经杀虫剂处理时,寄主转换显著影响稻纵卷叶螟3-5龄幼虫总历期、化蛹率和蛹重,但对水稻种群和小麦种群的影响相反。LC_(25)浓度阿维菌素和毒死蜱处理2龄幼虫,显著延长3-5龄幼虫总历期,但延长程度因寄主转换经历而异。LC_(25)浓度阿维菌素显著降低各寄主转换经历幼虫的化蛹率(R-R组除外)。LC_(25)浓度毒死蜱仅显著降低W-W组的化蛹率。在2龄幼虫暴露于LC_(25)浓度阿维菌素后W-W和W-R组的蛹重显著降低。水稻种群化蛹率和蛹重受寄主转换的影响在LC_(25)浓度阿维菌素处理后消失,而小麦种群化蛹率和蛹重受寄主转换的影响在LC_(25)浓度阿维菌素和毒死蜱处理后均消失。无论是何种寄主转换经历还是LC_(25)浓度阿维菌素和毒死蜱处理均未影响成虫羽化率、交配率和单雌产卵量。寄主转换处理只显著影响未经杀虫剂处理时水稻种群的卵孵化率,但卵孵化率均未受LC_(25)浓度阿维菌素和毒死蜱处理影响。与未经杀虫剂处理相比,LC_(25)浓度阿维菌素和毒死蜱处理均未影响雌成虫寿命,但LC_(25)浓度毒死蜱处理显著增加了W-W组雄成虫寿命。【结论】寄主转换经历会影响阿维菌素和毒死蜱对稻纵卷叶螟的亚致死效应。LC_(25)浓度阿维菌素和毒死蜱处理经历寄主转换的稻纵卷叶螟幼虫后,其幼虫和蛹生长发育均受到不同程度影响,但成虫繁殖和寿命所受影响较小。使用针对稻纵卷叶螟的杀虫剂时和进行毒理实验时应考虑到寄主植物的潜在影响。

四川省犍为县两种纵卷叶螟幼虫和蛹的寄生蜂种类及发生动态

本研究旨在明确稻显纹纵卷叶螟和稻纵卷叶螟幼虫和蛹寄生蜂种类和优势寄生蜂种类差异,为两种纵卷叶螟的种间竞争机制研究和生物防治提供理论依据。通过采集四川省犍为县两种纵卷叶螟幼虫和蛹,于室内饲养羽化并收集寄生蜂,鉴定寄生蜂种类和调查自然寄生情况。结果显示,稻显纹纵卷叶螟和稻纵卷叶螟幼虫和蛹的寄生蜂种类主要有8种。其中,在两种纵卷叶螟中均发现的寄生蜂为趋稻厚唇姬蜂Phaeogenes sp.,仅在稻显纹纵卷叶螟中发现的寄生蜂为无脊大腿小蜂Brachymeria excarinata(Gahan,1925)、粘虫广肩小蜂Eurytoma verticillata(Fabricius,1798)、黄眶离缘姬蜂Trathala flavo-orbitalis(Cameron,1907)、具柄凹眼姬蜂指明亚种Casinaria pedunculata(Szépligeti,1908)和稻苞虫兔唇姬小蜂Dimmockia secunda(Crawford,1910),仅在稻纵卷叶螟中发现的寄生蜂为棱角肿腿蜂Goniozus sp.和大螟钝唇姬蜂Eriborus terebrans。稻显纹纵卷叶螟的寄生蜂寄生率(0.01%~0.46%)比稻纵卷叶螟寄生率(0.34%~2.07%)低。大螟钝唇姬蜂为稻纵卷叶螟寄生蜂的丰富种且优势度指数最高,但无脊大腿小蜂是稻显纹纵卷叶螟中优势度指数最高的优势种寄生蜂。稻显纹纵卷叶螟的寄生蜂优势种随时间发生变化,7月和9月的优势寄生蜂为无脊大腿小蜂,而8月为趋稻厚唇姬蜂和黄眶离缘姬蜂。但是,10月采集的稻显纹纵卷叶螟没有发现寄生蜂寄生的现象。两种纵卷叶螟虽为近缘种,但二者寄生蜂种类和优势寄生蜂种类存在差异。