Impact of reassociation with a coevolved herbivore on oviposition deterrence in a hostplant

Although selection by herbivores for increased feeding deterrence in hostplants is well documented, selection for increased oviposition deterrence is rarely examined. We investigated chemical mediation of oviposition by the parsnip webworm (Depressaria pastinacella) on its principal hostplant Pastinaca sativa to determine whether ovipositing adults choose hostplants based on larval suitability and whether hostplants experience selection for increased oviposition deterrence. Webworms consume floral tissues and florivory selects for increased feeding deterrents; moths, however, oviposit on leaves of pre-bolting plants. Exclusive use of different plant parts for oviposition and larval feeding suggests oviposition should select for increased foliar deterrents. Recent webworm colonization of New Zealand (NZ) allowed us to assess phenotypic changes in foliar chemicals in response to webworm oviposition. In a common garden experiment, we compared NZ populations with and without a history of infestation from 2004 to 2006 for changes in leaf chemistry in response to oviposition. Three leaf volatiles, cis- and trans-ocimene, and β-farnesene, elicit strong responses in female moth antennae; these compounds were negatively associated with oviposition and are likely oviposition deterrents. Leaf β-farnesene was positively correlated with floral furanocoumarins that deter florivory; greater oviposition on plants with low floral furanocoumarins indicates that moths preferentially oviposit on parsnips most suitable for larval growth. Unlike florivory, high oviposition on leaves did not lower plant fitness, consistent with the fact that NZ parsnip foliar chemistry was unaffected by 3–6 years of webworm infestation. Thus, in this system, selection by ovipositing moths on foliar chemistry is weaker than selection by larvae on floral chemistry.     

Infanticide Avoidance by the Granary Weevil, <Emphasis Type="Italic">Sitophilus granarius</Emphasis> (L.) (Coleoptera: Curculionidae): The Role of Harbourage Markers,Oviposition Markers,and Egg-Plugs

In dual choice experiments, adult female granary weevils, Sitophilus granarius L. (Coleoptera: Curculionidae), demonstrated no feeding preference for wheat that had been previously exposed to male and female conspecifics but avoided feeding on grain parasitized with related or unrelated conspecific eggs. Feeding avoidance was lost if egg-parasitized grains possessed an additional unsealed oviposition cavity. Females also preferred to consume artificially damaged grains over undamaged grains. These results suggest that a harbourage-derived feeding deterrent does not exist but an oviposition-derived feeding deterrent does, and that this deterrent protects S. granarius conspecifics from infanticide regardless of their relationship to the adult insect. Egg-plugs may also serve to reduce infanticide by preventing the release of phagostimulatory compounds from oviposition-damaged wheat.     

The resistance of Pteridium aquilinum (L.) Kuhn to insect attack by Trichoplusia ni (Hübn.)

Summary Resistance of Pteridium aquilinum to insect attack was studied by incorporating air dried bracken leaf meal and extracts of bracken leaf meal into an artificial diet for Trichoplusia ni (Lepidoptera: Noctuidae). When larvae are reared on diets containing 6% bracken leaf meal, they do not mature past the second instar and after 16 days the average weight is approximately 1 mg compared to 70 mg for control larvae. Feeding initiation studies indicate that a feeding deterrent is present in bracken fern but feeding rates and food utilization efficiency studies suggest that either the deterrent or another compound also functions as a toxin. This toxin does not affect growth, feeding rates, or utilization efficiency for the first 4 days after third instar larvae are transferred to a diet containing the water extract of bracken leaf meal; thereafter growth is terminated and feeding is greatly reduced. The active factor is water soluble, heat labile, and non-volatile and this partial characterization indicates that neither the bracken ecdysones or the anti-thiamine factor of bracken is involved in the resistance of this fern to insect attack by T. ni.     

Deterrent effect of soybean meal on feeding of the silkworm, Bombyx mori

The occurrence of a factor in soybean which deters feeding of the silkworm was demonstrated. The deterrent was not extractable with ether or ethanol, but was extracted with 90% ethanol or hot water. Preliminary experiments showed that the deterrent was adsorbed on charcoal, but neither on activated alumina nor in a steam distillate. Autoclaving did not inactivate the deleterious effect. A crude extract of the deterrent showed a marked negative feeding response by including 0·4 mg/g of the dry diet.Inclusion of the crude extract in the diet retarded the growth of larvae, whereas larvae grew well when receiving the 90% ethanol-washed meal. Feeding response for various soybean meals and proteins were compared, and better larval growth has generally obtained when the feeding response was more positive. It is, however, inconclusive whether or not the deleterious principle possesses some physiologically toxic effect.The feeding behaviour of newly hatched larvae was observed in the presence of favourable and/or unfavourable diets, and a brief discussion is made concerning the feeding behaviour of this insect.     

Preimaginal conditioning does not affect oviposition preference in the diamondback moth

Abstract.  1. In holometabolous insects, learning has been demonstrated in both larval and adult stages. Whether learning can be retained through metamorphosis from larva via pupa to adult has long been a subject of debate. The present study is designed to distinguish between preimaginal and imaginal conditioning in the diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) using oviposition preference tests on females exposed to various types of learning experiences during immature and adult stages.
2. Cohorts of test insects were reared from egg to pupa on an artificial diet, or on one of two host plants, Chinese cabbage, Brassica campestris L. ssp. pekinensis , and common cabbage, Brassica oleracea L. var. capitata . The ensuing females reared on the three kinds of food showed similar oviposition preference between the two plants. A brief experience of the less preferred host, common cabbage, by adults slightly increased their preference for this plant.
3. Cohorts of test insects were reared from egg to pupa on an artificial diet with or without the addition of a neem-based oviposition deterrent (Neemix^® 4.5). Larval feeding experience did not alter oviposition response to the deterrent. However, emergence conditioning and early adult learning, achieved through experience of a residue of the deterrent carried over from the larval food on pupal cuticle and cocoons, altered oviposition preference significantly.
4. The combined results revealed no evidence of preimaginal conditioning in this insect but a strong effect of emergence conditioning and early adult learning on oviposition preference.     

Retention of Memory through Metamorphosis: Can a Moth Remember What It Learned As a Caterpillar?

Insects that undergo complete metamorphosis experience enormous changes in both morphology and lifestyle. The current study examines whether larval experience can persist through pupation into adulthood in Lepidoptera, and assesses two possible mechanisms that could underlie such behavior: exposure of emerging adults to chemicals from the larval environment, or associative learning transferred to adulthood via maintenance of intact synaptic connections. Fifth instar Manduca sexta caterpillars received an electrical shock associatively paired with a specific odor in order to create a conditioned odor aversion, and were assayed for learning in a Y choice apparatus as larvae and again as adult moths. We show that larvae learned to avoid the training odor, and that this aversion was still present in the adults. The adult aversion did not result from carryover of chemicals from the larval environment, as neither applying odorants to naïve pupae nor washing the pupae of trained caterpillars resulted in a change in behavior. In addition, we report that larvae trained at third instar still showed odor aversion after two molts, as fifth instars, but did not avoid the odor as adults, consistent with the idea that post-metamorphic recall involves regions of the brain that are not produced until later in larval development. The present study, the first to demonstrate conclusively that associative memory survives metamorphosis in Lepidoptera, provokes intriguing new questions about the organization and persistence of the central nervous system during metamorphosis. Our results have both ecological and evolutionary implications, as retention of memory through metamorphosis could influence host choice by polyphagous insects, shape habitat selection, and lead to eventual sympatric speciation.     

食物对棉铃虫生长发育及繁殖的影响

用棉花、花生、玉米及人工饲料作为食料,模拟幼虫田间取食习性,同时为雌蛾设立补充和无补充营养两个处理,研究了食物对棉铃虫 Helicoverpa armigera (Hübner) 生长发育及繁殖的影响。4种食料组幼虫历期之间有显著差异;雌、雄蛹重花生组显著小于其余三组。雌蛾腹部干重及其脂肪百分含量与雌蛹体重的排列顺序一样,雌蛾腹部干重人工饲料组显著大于棉花组和花生组。雌蛾寿命和繁殖受幼虫食料和成虫食物的双重影响。喂10%蜂蜜时,雌蛾寿命、交配率和产卵量在四个幼虫食料组之间没有显著差异。但喂以清水时,花生组雌蛾均未交配,寿命和产卵量显著小于其余三组。从同种幼虫食料来看,除人工饲料组外,其余3组雌蛾喂清水时的产卵量和寿命均比喂10%蜂蜜溶液时的显著下降。基于这些结果,作者认为棉花、玉米比花生更适合于棉铃虫的生长发育和繁殖。在田间自然栽培状态下,不同食料植物的糖分含量对棉铃虫生长发育和繁殖影响较大,含氮量的变化影响小。     

甘蔗、玉米气味对亚洲玉米螟成虫产卵和幼虫取食的影响

【目的】农作物间套作对害虫的影响很大程度上取决于害虫的行为反应,通过研究玉米/甘蔗套作系统中植物气味对亚洲玉米螟Ostrinia furnacalis(Guenee)行为的影响,将为利用化学生态手段防治套作田中的害虫提供依据。【方法】通过昆虫触角电位实验、成虫产卵和幼虫取食实验,测定了甘蔗、玉米植株及二氯甲烷漂洗物对亚洲玉米螟成虫产卵、幼虫取食的影响。【结果】亚洲玉米螟成虫在甘蔗植株上的落卵量(卵粒数、卵块数)与玉米植株差异不显著,取食甘蔗植株的幼虫数量显著低于玉米植株。亚洲玉米螟对甘蔗、玉米叶片漂洗物均可产生EAG反应,且在同一浓度下的反应值之间无显著差异。成虫产卵量(卵粒数、卵块数)在0.1 gE/mL浓度的甘蔗和玉米漂洗物间差异不显著;幼虫对经甘蔗叶片漂洗物处理过的饲料的相对取食率均低于65.00%,显著低于玉米漂洗物处理的饲料。【结论】甘蔗和玉米气味对亚洲玉米螟产卵的影响没有差异,但甘蔗气味会导致初孵幼虫表现出很强的逃逸行为。     

Oviposition and feeding behavior of the maize borer,Chilo partellus,in response to eight essential oil allelochemicals

Eight essential oil compounds were evaluated against the maize borer, Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae), to determine their influence on oviposition and feeding behavior. Thymol was the most active compound against C. partellus when evaluated as an oviposition deterrent (ODI₅₀ = 1.36 mg ml^?1), an ovicide (LC₅₀ = 2.06 mg ml^?1), or a feeding deterrent (FI₅₀ = 141.8 μg cm^?2) in laboratory experiments. The results corroborated with greenhouse experiments, in which egg laying on maize plants was inhibited significantly when the treatment was 15 times the concentration used in the laboratory experiments. However, there was neither any correlation between oviposition deterrence and feeding inhibition, nor between oviposition deterrence and ovicidal action. Apparently, toxicity per se or ovicidal action does not play any role in choice of oviposition in C. partellus. This was more obvious when the efficacy of compounds was compared in greenhouse experiments where ODI values and number of eggs laid on the treated leaves did not differ significantly in choice and no‐choice situations. Apparently, toxicity plays an important role in predicting host plant choice, but behavioral response in terms of oviposition preference is independent of toxic action, particularly for non‐host toxins. Thus, the same compounds affecting oviposition behavior on the one hand and having ovicidal or feeding deterrent properties on the other could be useful in field situations in any area‐wide integrated pest management model.     

紫茎泽兰粗提物对草地贪夜蛾生长发育及繁殖的影响

为明确紫茎泽兰粗提物对草地贪夜蛾生长发育及繁殖的影响,在实验室条件下分别利用4个不同稀释浓度（20、15、10、5倍）的紫茎泽兰粗提物处理玉米叶片后喂养草地贪夜蛾初孵幼虫,记录各虫态的发育历期、存活率、重量、成虫寿命以及后代性比、F2代卵孵化率、F2代卵的发育历期。结果表明,随着紫茎泽兰粗提物浓度的升高,草地贪夜蛾各虫态的发育历期延长,5倍稀释液处理下蛹的发育历期最长,达20.27 d,10倍稀释液处理下幼虫的发育历期最长,为21.46 d;随着处理浓度的增加,各虫态的重量逐渐降低,且存活率呈下降趋势,其中粗提物对蛹存活率的影响最大,对1~3龄幼虫存活率的影响较小;随着处理浓度的升高成虫的寿命均缩短,且雌成虫寿命长于雄成虫;随着处理浓度的升高,草地贪夜蛾的产卵前期和F2代卵发育历期延长,产卵期缩短;单雌产卵量、后代性比和卵的孵化率降低。总的来说,紫茎泽兰粗提物对草地贪夜蛾的生长发育及繁殖均造成消极影响。5倍稀释液对草地贪夜蛾的生长发育及繁殖的影响最显著,可作为草地贪夜蛾防治研究中的重要植物源杀虫剂材料。     

Preference of Bt‐resistant and susceptible Busseola fusca moths and larvae for Bt and non‐Bt maize

The sustainability of genetically engineered insecticidal Bacillus thuringiensis Berliner (Bt) maize, Zea mays L. (Poaceae), is threatened by the evolution of resistance by target pest species. Several Lepidoptera species have evolved resistance to Cry proteins expressed by Bt maize over the last decade, including the African maize stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae). The insect resistance management (IRM) strategy (i.e., the high‐dose/refuge strategy) deployed to delay resistance evolution is grounded on certain assumptions about the biology and ecology of a pest species, for example, the interactions between the insect pest and crop plants. Should these assumptions be violated, the evolution of resistance within pest populations will be rapid. This study evaluated the assumption that B. fusca adults and larvae select and colonize maize plants at random, and do not show any preference for either Bt or non‐Bt maize. Gravid female B. fusca moths of a resistant and susceptible population were subjected to two‐choice oviposition preference tests using stems of Bt and non‐Bt maize plants. Both the number of egg batches as well as the total number of eggs laid on each stem were recorded. The feeding preference of Bt‐resistant and susceptible neonate B. fusca larvae were evaluated in choice test bioassays with whorl leaf samples of specific maize cultivars. Although no differential oviposition preference was observed for either resistant or susceptible female moths, leaf damage ratings indicated that neonate larvae were able to detect Bt toxins and that they displayed feeding avoidance behaviour on Bt maize leaf samples.     

Continuous exposure to the deterrents cis‐jasmone and methyl jasmonate does not alter the behavioural responses of Frankliniella occidentalis

Behavioural responses of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), a generalist, cell sap‐feeding insect species with piercing‐sucking mouthparts, after continuous exposure to two deterrent secondary plant compounds are investigated. We compared in choice assays on bean leaf discs, the settling, feeding, and oviposition preferences of F. occidentalis females that had no experience with the two fatty acid derivatives methyl jasmonate and cis‐jasmone before testing (naïve thrips) vs. females that had been exposed to the deterrent compounds before testing (experienced thrips). The thrips were exposed to the deterrents at low or high concentrations for varied time periods and subsequently tested on bean leaf discs treated with the respective deterrent at either a low or a high concentration. Frankliniella occidentalis females avoided settling on the deterrent‐treated bean leaf discs for an observation period of 6 h, independent of their previous experience. Our results demonstrate that feeding and oviposition deterrence of the jasmonates to the thrips were not altered by continuous exposure of the thrips to the jasmonates. Habituation was not induced, neither by exposure to the low concentration of the deterrents nor by exposure to the high concentration. These results indicate that the risk of habituation to two volatile deterrent compounds after repeated exposure is not evident in F. occidentalis. This makes the two compounds potential candidates to be integrated in pest management strategies.     

Potato proteins, and other plant proteins, as potential transgenic resistance factors to pollen beetles in oilseed rape

Proteinase inhibitors (PIs), lectin and patatin purified from potato tubers were tested in no‐choice feeding assays with pollen beetle larvae (Meligethes spp.). The idea was to search for resistance factors possible to introduce into oilseed rape (Brassica napus) by genetic engineering. The larval diet was prepared by soaking oilseed rape anthers in protein solutions of known concentrations. Potato lectin was the most potent in that it was the only of these proteins that reduced both larval survival and growth rate, while cysteine, aspartic and metallo PIs and patatin only reduced larval growth rate. Serine PIs had no significant effect on larval performance. Subsequently, the effect of potato lectin was compared to that of lectins from other food or feed crops, resulting in the following mortality‐ based ranking of activity: Con A from jackbean > wheat germ lectin > potato lectin > peanut lectin. In choice tests, larvae did not discriminate between Con A‐ and control‐diets. These results suggest that the effect of Con A on larvae is toxic, not deterrent. Adult response was stronger to Con A than to potato lectin in no‐choice tests, just as it was in larvae. However, adult survival rate and weight was not affected by Con A but the lectin significantly reduced adult feeding as well as oviposition rates. A resistance factor that suppresses adult feeding on flower buds is important for reduced impact of the pollen beetle on the Brassica oilseed crop.     

The angiotensin converting enzyme inhibitor captopril reduces oviposition and ecdysteroid levels in Lepidoptera

The role of angiotensin converting enzyme (ACE, peptidyl dipeptidase A) in metamorphic- and reproductive-related events in the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera, Noctuidae) was studied by using the selective ACE inhibitor captopril. Although oral administration of captopril had no effect on larval growth, topical administration to new pupae resulted in a large decrease of successful adult formation. Oviposition and overall appearance of adults emerging from treated larvae did not differ significantly from those emerging from non-treated larvae. In contrast, topical or oral administration of captopril to newly emerged adults caused a reduction in oviposition. By evaluating the effect of captopril on ecdysteroid titers and trypsin activity, we revealed an additional physiological role for ACE. Captopril exerted an inhibitory effect on ecdysteroid levels in female but not in male adults. Larvae fed a diet containing captopril exhibited increased trypsin activity. A similar captopril-induced increase in trypsin activity was observed in female adults. In male adults, however, captopril elicited reduced levels of trypsin activity. Our results suggest that captopril downregulates oviposition by two independent pathways, one through ecdysteroid biosynthesis regulation, and the other through regulation of trypsin activity. Apparently, fecundity is influenced by a complex interaction of ACE, trypsin activity, and ecdysteroid levels.     

Oviposition deterrent effect of Spodoptera littoralis (Boisd.) larval frass to adult females of two major noctuid insect pests

Water extract of fresh frass of Spodoptera littoralis larval instars (L_1–3, L₄, L₅ and L₆) fed on Castor oil leaves was prepared by soaking at concentration (20?g frass/50?ml distiled water) followed by steering before filtration. Oviposition deterrent activity of the extract to S. littoralis and A. ipsilon adult females was evaluated as the mean number of laid eggs in treatments in comparison with control under laboratory conditions. Total amount of phenols and flavonoids in larval frass was determined. Extraction of L₆ frass obtained complete oviposition deterrent to S. littoralis adult moths and the minimum number of laid eggs by A. ipsilon adult females (11.8?eggs/female) in comparison with control (1026.0 and 848.2?eggs/female respectively). Maximum number of laid eggs by S. littoralis females was 361.0/f at treatment with L_1–3 frass extract and 748.0/adult female of A. ipsilon at treatment with L₄ frass extract. Low amount of phenols and/or flavonoids in frass extract of L₆ increased the oviposition deterrent effect while high amount of them as obtained in L₄ frass extract (3.504 and 1.610%, respectively) decreased the effect at both of tested insects.     

Feeding responses of specialist herbivores to plant extracts and pure allelochemicals: effects of prolonged exposure

We investigated the possibility of decreased feeding deterrent response following prolonged exposure in three specialist herbivores, Plutella xylostella (larvae), Pseudaletia unipuncta (larvae), and Epilachna varivestis (adults) through leaf disc choice and no‐choice tests. Neonate larvae (<24 h old) of the three species were reared on their host plants sprayed with the antifeedants until tested. Our results demonstrated that Ps. unipuncta did not show a decrease in feeding deterrent response to extracts of Melia volkensii (choice and no‐choice tests) or oregano (Origanum vulgare) (choice test) following prolonged exposure. Plutella xylostella exhibited a decrease in feeding deterrent response to M. volkensii in a choice test only, but not to oregano. Although not significant, we did find a trend toward decreasing feeding deterrent response to M. volkensii by both species in no‐choice tests. However, both species exhibited a significant decrease in feeding deterrent response to pure allelochemicals (Ps. unipuncta to thymol, and P. xylostella to thymol and toosendanin) compared with the naïve groups, following prolonged exposure in leaf disc choice tests. Epilachna varivestis showed a significant decrease in feeding deterrent responses to both oregano and thymol in leaf disc choice tests. We conclude from our present and previous studies that not only are there interspecific differences between generalist and specialist species but also among specialist species.     

番茄抽提物对小菜蛾的忌避,拒食及抑制产卵作用

在自然变温条件下,研究了番茄抽提物对小菜蛾成虫的忌避、幼虫的拒食作用及成虫繁殖力的影响。试验表明：番茄抽提物对小菜蛾成虫具有很强的忌避作用;用番茄抽提物处理过的包菜叶饲喂小菜蛾幼虫,其拒食率达５３％;番茄提物对小菜蛾成虫产卵也有明显抑制作用,产卵量下降６０％;番茄与包菜间种能明显地抑制小菜蛾种群数量的增长。其种群可下降５０％以上。     

棉铃虫成虫对两种关键花香气味的联系性学习

为了明确棉铃虫对苯乙醛和乙酸苯甲酯两种关键花香气味的联系性学习行为,在室内分别测定了不同学习训练的棉铃虫雌雄成虫对两种关键花香气味的选择偏好性反应和雄成虫的触角电位反应。偏好性测定结果表明,无花香气味接触经历的棉铃虫对苯乙醛和乙酸苯甲酯的选择频次均无显著差异,且单纯的花香气味接触经历也不能诱导棉铃虫气味偏好性的显著改变,唯有花香气味接触经历伴随蔗糖溶液进行强化训练时,才能诱导气味偏好性的显著性改变。从对两种花香气味的联系性学习看,棉铃虫更容易将苯乙醛与蔗糖溶液进行联系性学习,而不容易将乙酸苯甲酯与蔗糖溶液进行联系性学习。从性别差异看,雌虫比雄虫具有更强的将花香气味与蔗糖溶液进行联系性学习的能力。触角电位测定结果表明,不同学习训练的棉铃虫雄成虫对两种花香气味和绿叶气味顺-3-己烯-1-醇的EAG反应值之间不存在显著性差异。总之,花香气味伴随食物资源的联系性学习经历,能够明显提高棉铃虫成虫对花香气味的选择偏好,可以此为基础进一步优化花香引诱剂的配方设计和应用技术。     

Behavioural responses of diamondback moth Plutella xylostella (Lepidoptera: Plutellidae) to extracts derived from Melia azedarach and Azadirachta indica

The impact of three different doses of botanical insecticide derived from the syringa tree, Melia azedarach and the neem tree, Azadirachta indica was tested on the behaviour of the diamondback moth, Plutella xylostella (Linnaeus). Both botanical insecticides had a significant impact on larval behaviour. At higher doses the extracts showed feeding deterrent activity, with larvae preferring the untreated sides of cabbage leaves and consuming less of the treated half of cabbage leaves. The botanical insecticides had less of an effect on the oviposition behaviour of P. xylostella moths. In laboratory and glasshouse trials, significantly fewer eggs were oviposited on the plants that had been treated with syringa extracts. Therefore, the syringa extracts appear to have a repellent effect. In contrast, when exposed to the neem extracts the moths did not discriminate between control plants and treated plants. Behavioural observation indicated that, despite the lower number of eggs oviposited on cabbage treated with syringa extracts, the moths chose cabbage treated with the highest dose of syringa more often than they chose control cabbage plants. Similar observations were found in cabbage plants treated with neem, moths chose the medium dose more often than they chose the control. Oviposition and feeding deterrent properties are important factors in pest control, and results from this study indicate that botanical insecticides have the potential to be incorporated into control programmes for P. xylostella in South Africa.