Activity of rubidium and cesium in soybean looper (Lepidoptera: Noctuidae): insect feeding on cotton and soybean measured by elemental markers

Uptake and translocation of the elemental markers rubidium (Rb) and cesium (Cs) within adult soybean looper, Pseudoplusia includens (Walker), were determined using atomic absorption spectrophotometry in the laboratory in various feeding and mating treatments. Neonates were tested to determine marker transfer from male and female adults fed rubidium chloride (RbCl)-treated artificial nectar, cesium chloride (CsCI)-treated artificial nectar, or both. All females contained detectable levels of Rb, Cs, or both, which were obtained either through direct feeding or via spermatophores. Rubidium was present in females at significantly greater levels than Cs. No significant differences in Rb levels were observed between feeding or spermatophore acquisitions. Most neonates had significantly higher levels of Rb than Cs. In a field cage study to evaluate adult feeding and oviposition behavior on blooming cotton and blooming soybean treated with RbCl and CsCl, respectively, more eggs contained Rb than Cs, indicating greater feeding on cotton nectar than soybean nectar, regardless of the host plant upon which eggs were laid. Females laid more eggs on blooming soybean than on blooming cotton. Higher levels of Rb in cotton than Cs in soybean were recorded and may be attributed to initial elemental marker quantities available to the insects. This study provides the support for the generalized observations that soybean looper infestations in soybean can be related to feeding activities by adults in cotton.     

绿盲蝽成虫对六种寄主及其挥发物的选择趋势

针对绿盲蝽Apolyguslucorum（Meyer-Dttr）6种主要寄主,分别于5～10叶期和花蕾期,采用室内“Y”型嗅觉仪和田间罩笼接虫方法,研究了绿盲蝽成虫对不同寄主及其挥发物的选择趋势。田间罩笼接虫试验结果表明：5—10叶期的茼蒿、国抗22及泗棉3号上绿盲蝽虫量居多,绿豆次之,大豆和豇豆上的较少;花蕾期的茼蒿、绿豆、国抗22及泗棉3号上绿盲蝽较多,而豇豆、大豆上较少。以5～10叶期和花蕾期的上述6种寄主为实验材料,以无寄主花盆为空白对照,每期各成对设置17个气源组合,采用室内“Y”型嗅觉仪测定绿盲蝽成虫对这6种寄主气源的选择趋性。不同气源组合测定结果表明,绿盲蝽对5—10叶期植物性气源的选择趋势为：国抗22〉茼蒿〉绿豆〉泗棉3号〉大豆〉豇豆;绿盲蝽对花蕾期植物性气源的选择趋势为：绿豆〉茼蒿〉国抗22〉泗棉3号〉豇豆〉大豆。上述不同选择性试验结果综合表明,绿盲蝽成虫对5—10叶期和花蕾期不同寄主的选择趋势基本一致。     

Dynamics and seasonal abundance of stink bugs (Heteroptera: Pentatomidae) in a cotton-soybean ecosystem

Two soybean varieties (early-maturing group V and late-maturing group VII) and two cotton varieties (conventional and transgenic (Bt) were grown in adjacent replicated large field plots (approximately 0.1 ha each) at two locations for 3 yr. The dynamics and relative abundance of phytophagous stink bugs within these two crops were observed. The most abundant pentatomid species in both crops for all 3 yr were Nezara viridula (L.), Acrosternum hilare (Say), and Euschistus servus (Say). Several other species also were commonly collected. This is the first record of Mormidea lugens (F.) on soybean and E. quadrator Rolston, E. obscurus (Palisot), Holcostethus limbolarius (St?l), and Oebalus pugnax (F.) on cotton. Stink bugs began arriving in soybean when plant growth stages ranged from pod formation to full seed development. Peak numbers of these insects were found in soybean from the time of full-size seeds in the pods until early maturity. The bugs were first attracted to the earlier maturing cultivar (group V), where they remained until plants began to mature (R7). The pentatomids then moved to the later-maturing cultivar (group VII) as it reached full pod to full seed. Stink bugs began arriving in cotton from the time of the earliest flowers until after the first bolls formed. Peak numbers in cotton occurred during the time when all stages of developing bolls were present. Stink bug numbers were much greater in soybean than in cotton over all three seasons. This preference for soybean over cotton indicates the potential use of soybean as a trap crop for attracting stink bugs away from cotton. Additionally, the coordinated use of early- and late-maturing soybean cultivars as a trap crop could minimize the area requiring insecticides, as well as the number of insecticide applications to cotton.     

Interaction of Anthonomus grandis and cotton genotypes: biological and behavioral responses

The boll weevil, Anthonomus grandisBoheman (Coleoptera: Curculionidae), is a key pest of cotton, Gossypium hirsutumL. (Malvaceae). Knowledge about boll weevil feeding and oviposition behavior and its response to plant volatiles can underpin our understanding of host plant resistance, and contribute to improved monitoring and mass capture of this pest. Boll weevil oviposition preference and immature development in four cotton genotypes (CNPA TB90, TB85, TB15, and BRS Rubi) were investigated in the laboratory and greenhouse. Volatile organic compounds (VOCs) produced by TB90 and Rubi genotypes were obtained from herbivore‐damaged and undamaged control plants at two phenological stages – vegetative (prior to squaring) and reproductive (during squaring) – and four collection times – 24, 48, 72, and 96 h following herbivore damage. The boll weevil exhibited similar feeding and oviposition behavior across the four tested cotton genotypes. The chemical profiles of herbivore‐damaged plants of both genotypes across the two phenological stages were qualitatively similar, but differed in the amount of volatiles produced. Boll weevil response to VOC extracts was studied using a Y‐tube olfactometer. The boll weevil exhibited similar feeding and oviposition behavior at the four tested cotton genotypes, although delayed development and production of smaller adults was found when fed TB85. The chemical profile of herbivore‐damaged plants of both genotypes at the two phenological stages and time periods (24–96 h) was similar qualitatively, with 30 identified compounds, but differed in the amount of volatiles produced. Additionally, boll weevil olfactory response was positive to herbivory‐induced volatiles. The results help to understand the interaction between A. grandis and cotton plants, and why it is difficult to obtain cotton genotypes possessing constitutive resistance to this pest.     

Ants as egg predators of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Australian cotton crops

Abstract Helicoverpa armigera is a major pest of Australian cotton crops. To assess the impact of ant predation on H. armigera populations, the behaviour of four common ant taxa was observed in cotton crops in northern New South Wales over the 1999−2000 and 2001−02 seasons. Areas of cotton were artificially stocked with H. armigera eggs prior to observation. Pheidole spp. were the most frequently observed ants within the crop canopy in 1999−2000 and took the most H. armigera eggs. Iridomyrmex spp. were more frequently observed than Pheidole spp. in 2001−02 and also took some H. armigera eggs. Neither Paratrechina spp. nor Rhytidoponera metallica (Smith) took any H. armigera eggs, although both were seen in the crop canopy. Irrigation, cultivation and insecticide application disrupted foraging ants and limited their impact on H. armigera populations.     

新疆超高产棉花冠层光分布特征及其与群体光合生产的关系

以新疆超高产棉田(皮棉产量在4000 kg·hm^-2以上)为研究对象,分析不同生育时期棉花冠层光分布、群体光合速率和干物质积累量的变化,研究不同产量水平棉田冠层的光环境变化特征及其与群体光合生产的关系.结果表明： 超高产田盛花期到盛铃后期冠层上、中、下层光吸收率的比例为2∶2∶1,呈均匀分布,群体散射辐射和直射辐射透过系数分别为0.20～0.55和0.22～0.56,处于较适宜范围,中、下层叶片受光良好,冠层各层次叶片群体光合速率差异较小.与高产(3500 kg·hm^-2)和一般高产(3000 kg·hm^-2)棉田相比,超高产田在盛铃前期具有较高的叶面积指数和群体光合速率峰值,在初絮期和盛絮期的叶面积指数下降缓慢,群体光合速率峰值仍保持较高值,非叶绿色器官对产量形成的光合贡献增大,群体干物质积累量较高.在栽培过程中,调节冠层结构,使垂直方向上光辐射和群体光合能力分布均匀是确保棉花高效利用光能、实现超高产的重要途径.     

Response of cotton to prebloom square loss

In 1996 and 1997, various intensities of prebloom square removal were applied to three cultivars of cotton grown in Mississippi. With the exception of one cultivar in 1997, all cultivars were B. thuringiensis (Bt)-transgenic cotton. At harvest, the number of bolls and seed cotton weight was recorded for all plants in each square removal treatment. All cultivars responded similarly to square loss. A yield increase (overcompensation) was observed in the treatment where all squares were removed from the plant one week after squaring began. Only the treatment where all squares were removed before bloom significantly reduced yield and caused a large (>7 d) delay in crop maturation. Otherwise, moderate levels of square removal (approximately 20-50% of prebloom squares) had little impact on overall lint production. However, the patterns of cotton production on the plants were significantly influenced by the square removal treatments. The removal of relatively more or larger squares increased seed cotton production in late-season fruiting cohorts and on 'vegetative' branches. Compensation for square loss occurred by increasing the relative number and weight of bolls produced subsequent to early-season square removal. Typically, early-season square loss increased the value of later-season fruiting cohorts, especially the midseason cohorts and bolls on vegetative branches. The implications of prebloom square loss, including the compensatory ability of the cotton plant, on insect management are discussed.     

Influence of the host plant on occluded virus production and lethal infectivity of a baculovirus

Intra- and inter-specific effects of cotton, soybean, and clover on the time until death of Helicoverpa zea (Boddie) and Heliothis virescens (F.) larvae lethally infected with H. zea nucleopolyhedrovirus (HzSNPV) were evaluated in the laboratory. In the first test, on second instar only, the time until death of lethally infected larvae of both species differed with the plant tissues (vegetative or reproductive) and plant species. The total viral activity produced per larva in LC(50) units (occluded viral bodies (OBs) per larva/LC(50) in OBs/mm(2) of diet surface) was greater from H. virescens larvae fed vegetative than reproductive tissues of all host plants, but from H. zea virus production was greater only when fed vegetative tissue of soybean. In a second test that compared second and fourth instar H. virescens on cotton, total viral activity from larvae treated in both instars was greater when fed vegetative than reproductive tissues. Results of these tests suggest that the ability of host plants to influence baculovirus disease is more complex than previously believed. When examining the epizootic potential of a baculovirus, more attention must be given to the effects of the host plant on the insect-virus interactions.     

Choosy egg parasitoids: Specificity of oviposition-induced pine volatiles exploited by an egg parasitoid of pine sawflies

Generalist parasitoids are well‐known to be able to cope with the high genotypic and phenotypic plasticity of plant volatiles by learning odours during their host encounters. In contrast, specialised parasitoids often respond innately to host‐specific cues. Previous studies have shown that females of the specialised egg parasitoid Chrysonotomyia ruforum Krausse (Hymenoptera: Eulophidae) are attracted to volatiles from Pinus sylvestris L. induced by the egg deposition of its host Diprion pini L. (Hymenoptera: Diprionidae), when they have previously experienced pine twigs with host eggs. In this study we investigated by olfactometer bioassays how specifically C. ruforum responded to oviposition‐induced plant volatiles. Furthermore, we studied whether parasitoids show an innate response to oviposition‐induced pine volatiles. Naïve parasitoids were not attracted to oviposition‐induced pine volatiles. The attractiveness of volatiles from pines carrying eggs was shown to be specific for the pine and herbivore species, respectively (species specificity). We also tested whether not only oviposition, but also larval feeding, induces attractive volatiles (developmental stage specificity). The feeding of D. pini larvae did not induce the emission of P. sylvestris volatiles attractive to the egg parasitoid. Our results show that a specialist egg parasitoid does not innately show a positive response to oviposition‐induced plant volatiles, but needs to learn them. Furthermore, the results show that C. ruforum as a specialist does not learn a wide range of volatiles as some generalists do, but instead learns only a very specific oviposition‐induced plant volatile pattern, i.e., a pattern induced by the most preferred host species laying eggs on the most preferred food plant.     

Colonization preference of Euschistus servus and Nezara viridula in transgenic cotton varieties,peanut, and soybean

Producers of Bt cotton, Gossypium hirsutum L. (Malvaceae), in the southeastern USA face significant losses from highly polyphagous stink bug species. These problems may be exacerbated by crop rotation practices that often result in cotton, peanut, Arachis hypogaea L., and soybean, Glycine max (L.) Merrill (both Fabaceae), growing in close proximity to one another. Because all of these crops are hosts for the major pest stink bug species in the region, we experimentally examined colonization preference of these species among the crops to clarify this aspect of their population dynamics. We planted peanut, soybean, Bt cotton, and glyphosate‐tolerant (RR) non‐Bt cotton at three sites over 3 years in replicated plots ranging from 192 to 1 323 m² and calculated odds ratios for colonization of each crop for Nezara viridula (L.) and Euschistus servus (Say) (both Hemiptera: Pentatomidae). In four of five experiments, both E. servus and N. viridula preferred soybean significantly more often than Bt cotton, non‐Bt cotton, and peanut. Neither N. viridula nor E. servus showed any preference between non‐Bt and Bt cotton in any experiment. Both species had higher numbers in Bt and non‐Bt cotton relative to peanut; this was not significant for any single experiment, but analyses across all experiments indicated that N. viridula preferred Bt and non‐Bt cotton significantly more often than peanut. Our results suggest that soybean in the landscape may function as a sink for stink bug populations relative to nearby peanut and cotton when the soybean is in the reproductive stage of development. Stink bug preference for soybean may reduce pest pressure in near‐by crops, but population increases in soybean could lead to this crop functioning as a source for later‐season pest pressure in cotton.     

Feeding and oviposition preference of Phyllophaga cuyabana (Moser) (Coleoptera: Melolonthidae) on several crops

Laboratory and greenhouse experiments were carried out to study food and oviposition preference by Phyllophaga cuyabana (Moser) on different plant species as Cajanus cajan L. (pigeon pea), Crotalaria juncea L. (sun hemp), Crotalaria spectabilis Roth (showy crotalaria), Crotalaria ochroleuca G. Don (slenderleaf rattlebox), Glycine max [L.] Merrill (soybean), Gossypium hirsutum L. (cotton), Helianthus annuus L. (sunflower), Stizolobium aterrimum [Mucuna aterrima] Piper Tracey (velvetbean) and Zea mays L. (mayze). In no-choice experiments, the number of eggs layed in sunflower, C. juncea and soybean was larger compared to cotton. Despite the fact that the adults did not discriminate among plants, in dual-choice test, the proportion of eggs layed and leaf consumption by P. cuyabana adults in soybean were significantly higher than in C. spectabilis. The larval distribution in the soil was at random in multiple-choice, without any trend of preference, but in dual-choice, when soybean was the control, larvae always preferred to feed on its roots. P. cuyabana adults had preference for more suitable hosts and that could stand their offspring survival. This behaviour can be usefully exploited in an integrated management program for this pest.     

QTLs conditioning early growth in a soybean population segregating for growth habit

 There are both economic and environmental reasons for reducing the use of herbicides for weed control in soybean [Glycine max (L.) Merr.] fields. Optimizing crop competitiveness can reduce reliance on chemical weed control. Fast and vigorous early growth and rapid canopy development can be effective in suppressing weed infestation of crop plants. The purposes of this study were to identify and molecularly map the quantitative trait loci (QTLs) conditioning soybean plant height and canopy width during the early vegetative stages of soybean growth. A restriction fragment length polymorphism (RFLP) linkage map was created using 142 markers and 116 F₂-derived lines from a cross of ‘S100’בTokyo’. The parents and the 116 F₂-derived lines were evaluated in the greenhouse and in the field at Athens, Ga., in 1996 and 1997. Combined over environments, Tokyo averaged 41 and 17% taller plants than S100 at the V7 and V10 stages of development. Transgressive segregation was observed among the progeny at both stages. Based on single-factor analysis of variance (ANOVA), three and four independent RFLP loci were associated with plant height at the V7 and V10 stages, respectively. All three loci detected [on linkage groups (LGs) C2 and F, and unlinked] at the V7 stage were also detected at the V10 stage along with one additional independent locus on LG E. The Tokyo allele contributed to increased plant height at all loci except at the unlinked locus. Three QTLs (on LGs C2, E, and F) were consistent across environments, three (on LGs C2 and F, and unlinked) were consistent across stages of plant development, and two (on LGs C2 and F) were consistent both across environments and stages of plant development. Within each stage of development, there was no interaction among the independent loci, and the respective loci together explained most of the variation in the traits. Three independent RFLP loci were associated with canopy width at the V10 stage, of which one was unique to the trait, while the remaining loci (on LGs C2 and F) were in common with the independent loci for plant height. Canopy width had a strong correlation (r=0.87) with plant height at the V10 stage. However, mature plant height, lodging, or seed weight had no phenotypic or QTL association with early plant height or canopy width. Received: 10 May 1998 / Accepted: 13 July 1998     

Protocol for assessing soybean antixenosis to Heliothis virescens

Larvae of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) often infest soybean crops, Glycine max (L.) (Fabaceae), causing significant yield losses in important soybean-producing regions. The use of soybean varieties resistant to lepidopteran larvae is a major approach in soybean integrated pest management. However, standardization and optimization of bioassays that are used to screen genotypes for insect resistance are essential for high-throughput phenotyping. Methodologies for screening were assessed to determine the most effective method for discriminating levels of antixenosis to H. virescens in soybean plants. Feeding and oviposition preference assays were performed to determine optimal densities of larvae and adults, and optimal plant structures and growth stages for conducting assays. In addition, trichome densities, and fiber and lignin contents were quantified in plant structures of soybean cultivars differing in resistance. Resistance levels of cultivars were best differentiated using nine neonate larvae and two 6-day-old larvae, and by using young leaves of plants at the vegetative stage. This was likely due to the more pronounced differences in lignin and fiber contents in young leaves of vegetative-stage plants. Density of adult pairs, plant structure, and growth stage did not affect ability to distinguish differences in oviposition preference by H. virescens. Higher numbers of eggs were found on the leaves, which were the plant structures that exhibited the lowest trichome densities. The protocol developed in this work will benefit future evaluations of soybean genotypes for antixenosis against H. virescens.     

Distribution of Bemisia tabaci within soybean plants and on individual leaflets

To control whiteflies on soybean crops in an effective and economically viable way, it is necessary to quantify the occurrence and density of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) on the leaflets. Estimating the number of B. tabaci cm^‐2 on leaflets is difficult, because its distribution pattern on the various parts of the plant canopy and on the leaflet surface is unknown. The aim of this study was to evaluate the distribution of B. tabaci nymphs on soybean plants and leaflets, under greenhouse and field conditions. One hundred soybean plants infested with all nymph stages were randomly selected in a greenhouse, and 25 in a field. Of each plant, a trifoliate leaf of the middle third of the plant’s height was selected and its central leaflet was collected (greenhouse experiment), or a trifoliate leaf of each third layer (upper, middle, and lower), of which the left, central, and right leaflets were collected (field experiment). The collected leaflets were divided into 32 sections (1 cm² per section), arranged in an array of eight rows and four columns to count whitefly nymphs. The Morisita index (I_δ), the negative binomial parameter k, and the dispersion index (I) were calculated for each leaflet, using the number of nymphs as variable. The highest population densities of whitefly nymphs were found in the middle third of the soybean plants. In leaflets from the middle third, the nymphs concentrated in the middle and bottom parts of the leaflets, whereas in the upper and lower thirds of the plant, they were randomly distributed on the leaflets.     

Spatio‐temporal variation in Helicoverpa egg parasitism by Trichogramma in a tropical Bt‐transgenic cotton landscape

• 1 Understanding the spatio‐temporal dynamics of insects in agroecosystems is crucial when developing effective management strategies that emphasize the biological control of pests.
• 2 Wild populations of Trichogramma Westwood egg parasitoids are utilized for the biological suppression of the potentially resistant pest species Helicoverpa armigera (Hübner) in Bt‐transgenic cotton Gossypium hirsutum L. crops in the Ord River Irrigation Area (ORIA), Western Australia, Australia.
• 3 Extensive, spatially‐stratified sampling during a season of relatively high Trichogramma abundance found that spatial patterns of pest egg parasitism in the ORIA tend toward heterogeneity, and do not necessarily coincide with host spatio‐temporal dynamics. Both patterns of host egg density and mean rates of parasitism are not good indicators of parasitoid spatio‐temporal dynamics in ORIA cotton crops.
• 4 Parasitism rates can be significantly higher within the middle strata of the cotton plant canopy before complete canopy closure, despite a similar number of host eggs being available elsewhere in the plant.
• 5 Spatial variation in egg parasitism by Trichogramma in Bt‐transgenic cotton is evident at the between‐field, within‐field and within‐plant scale, and is not solely driven by host spatial dynamics. These factors should be considered when estimating Trichogramma impact on pest species during biological control and spatio‐temporal studies of host‐parasitoid interactions in general.

     

间接性害虫为害与作物产量损失的关系Ⅰ.食叶害虫

本文将繁多的农作物害虫分为间接性害虫和直接性害虫.间接性害虫造成的作物的某类器官或组织的损失率小于产量损失率.食叶害虫是间接性害虫中的一大类.作物对叶面积损失的产量反应很不一致,从完全失收到增产10倍.影响叶面积损失与产量关系的首要因素通常是作物在受害时的生长阶段.在叶面积损失率一定时,处于生长中期(最终营养库迅速增大期)的作物出现最大程度减产.在损失率过大,上部功能叶受害,为害持续时间过长,作物矮秆紧凑,水、肥及气象条件不良以及损失的叶面积分布不均匀等情形下,叶片受害后易于减产;反之则减产较少甚至增产.从分散的材料中归纳出这一基本关系,对当前广泛开展的食叶害虫的产量损失评价工作可能有参考和改进意义.     

Influence of cotton fruit stages as food sources on boll weevil (Coleoptera: Curculionidae) fecundity and oviposition

Boll weevil, Anthonomus grandis grandis Boheman (Coloeoptera: Curculionidae), populations in the Lower Rio Grande Valley of Texas increase strongly during the squaring stage, and preemptive insecticide sprays at the pinhead square stage were designed to capitalize on that association. Laboratory assays showed that cotton plant volatiles, or leaves as a food source, do not elicit egg production in wild weevils. Boll weevils fed on large (5.5-8-mm diameter) squares for 7 d resulted in > or = 3.8-fold more gravid females that developed 4.8-fold more chorionated eggs per female than weevils fed on match-head-sized squares, or postbloom, young (5-10-d-old), or old (3-5-wk-old) bolls. When presented with a choice, nongravid females preferred to feed on young and old bolls 4.7- and 8.4-fold more, respectively, than on large squares. In the field, large squares had 7.8- and 25-fold more feeding punctures than match-head-sized squares and bolls, respectively. Oviposition increased > or = 2.7-fold when females fed on large squares compared with match-head-sized squares and bolls. Greater feeding on large squares during squaring and the associated greater fecundity explain rapid weevil population buildups shortly after large squares become well established.     

Host selection by the wheat stem sawfly in winter wheat and the role of semiochemicals mediating oviposition preference

The wheat stem sawfly (WSS), Cephus cinctus Norton (Hymenoptera: Cephidae), causes significant damage in cereal crops in the northern Great Plains of North America. This study assessed oviposition preference in winter wheat, Triticum aestivum L. (Poaceae), and investigated how it is affected by the emission of semiochemicals, with the overall goal of enhancing trap crop efficacy. We studied five winter wheat cultivars that could be recommended as trap crops for WSS and compared them with regards to agronomic characteristics influencing oviposition behavior and their emission of behaviorally active volatiles. Subsequently, we evaluated oviposition preference on three selected cultivars, ‘Norstar’, ‘Neeley’, and ‘Rampart’, using choice tests at two plant growth stages. Most eggs were found in Norstar at both stages tested when females were exposed to the three cultivars simultaneously making it the preferred choice for a trap crop. Norstar also emitted more behaviorally active volatiles, primarily (E)‐ and (Z)‐β‐ocimene. The results for the effect of main stem height or diameter on oviposition was inconsistent between infested vs. uninfested stems within cultivars, although there was a correlation between infestation and height for younger plants. These results show that these agronomic characteristics, typically viewed as explanatory, did not clearly explain oviposition preference and suggest a role of β‐ocimene in determining suitability for oviposition among these cultivars. This study supports previous findings suggesting oviposition preference in winter wheat involves several cues, including stem height and volatile attractants that may be important in determining suitability.     

棉红铃虫田间产卵规律的进一步研究

在棉株结铃前,红铃虫一代卵主要分布于棉株新展开叶上。在棉花单株结铃达2．5个左右时,红铃虫卵均集中分布于棉青铃上。红铃虫二、三代卵分别以由外到内第二、三和第三、四大铃圆锥体位上的青铃卵量分布最多,分别占全株卵量的58．56％和67．19％红铃虫在10天以上日龄的青铃上均可产卵,其中在20～34天日龄的青龄上产卵量最大,占青铃上总卵量的55．02％。一代和二、三代红铃虫卵常分别1～8粒和1～13粒聚产成堆,单个青铃上可同期产卵1～16粒。     

Impacts of herbaceous bioenergy crops on atmospheric volatile organic composition and potential consequences for global climate change

The introduction of new crops to agroecosystems can change the chemical composition of the atmosphere by altering the amount and type of plant‐derived biogenic volatile organic compounds (BVOCs). BVOCs are produced by plants to aid in defense, pollination, and communication. Once released into the atmosphere, they have the ability to influence its chemical and physical properties. In this study, we compared BVOC emissions from three potential bioenergy crops and estimated their theoretical impacts on bioenergy agroecosystems. The crops chosen were miscanthus (Miscanthus × giganteus), switchgrass (Panicum virgatum), and an assemblage of prairie species (mix of ~28 species). The concentration of BVOCs was different within and above plant canopies. All crops produced higher levels of emissions at the upper canopy level. Miscanthus produced lower amounts of volatiles compared with other grasses. The chemical composition of volatiles differed significantly among plant communities. BVOCs from miscanthus were depleted in terpenoids relative to the other vegetation types. The carbon flux via BVOC emissions, calculated using the flux‐gradient method, was significantly higher in the prairie assemblage compared with miscanthus and switchgrass. The BVOC carbon flux was approximately three orders of magnitude lower than the net fluxes of carbon measured over the same fields using eddy covariance systems. Extrapolation of our findings to the landscape scale leads us to suggest that the widespread adoption of bioenergy crops could potentially alter the composition of BVOCs in the atmosphere, thereby influencing its warming potential, the formation of atmospheric particulates, and interactions between plants and arthropods. Our data and projections indicate that, among at least these three potential options for bioenergy production, miscanthus is likely to have lower impacts on atmospheric chemistry and biotic interactions mediated by these volatiles when miscanthus is planted on the landscape scale.