Oviposition Sites Research Articles

Alkaline water as a potential agent for biting midge control: Managing effectiveness and non-target organism impact evaluation.

Biting midge Forcipomyia taiwana is one of the common pests in East Asia. Their nuisance and blood-sucking behavior causes problems not only for human health but also for some industries. This study aims to evaluate the effectiveness of spraying alkaline water on controlling biting midge population and potential side effects of such approach on non-target organisms. Laboratory experiments were conducted to evaluate the effect of alkaline water on oviposition site preference of female biting midges as well as crickets. Effect of alkaline water on distribution pattern of earthworms was also examined. Besides, we also performed field manipulative studies by long term spraying of alkaline water to evaluate the effects on biting midge density, microalgae abundance and ground arthropod communities. The results of laboratory experiments showed that female biting midges laid significantly fewer eggs in surface treated with alkaline water. However, alkaline water treatment did not significantly affect the oviposition site choice of crickets and distribution pattern of earthworms. Result of field manipulations showed that long-term spraying of alkaline water could significantly reduce the abundance of soil microalgae and density of biting midges, but did not affect the diversity of non-target ground arthropods. These results demonstrate that long-term spraying of alkaline water could decrease biting midge density without harming co-existing non-target organisms and therefore is a potentially eco-friendly approach to control such pest.

Micro-habitat features determine oviposition site selection in High Brown and Dark Green Fritillaries

The survival of butterfly populations depends on successful oviposition strategies. The limited mobility of early life stages requires females to select sites that reflect larval requirements. However, as land use and climate changes are altering habitat conditions and micro-climate, some species may adapt ovipositing strategies and flourish while others, with narrow niche requirements, may be unable to respond. Oviposition site selection and micro-habitat niche is examined for two closely related butterfly species—the specialist High Brown Fritillary (Fabriciana adippe) and relative generalist Dark Green Fritillary (Speyeria aglaja) through field observations of egg-laying females and analysis of micro-habitat characteristics. A total of 104 oviposition behaviour observations across both species were recorded in 69 1 m2 quadrats, with the habitat characteristics compared to randomly selected quadrats in the same area. Results show that higher host plant density was a positively significant factor for oviposition site selection only for the High Brown Fritillary. Moreover, the cover of live Bracken (Pteridium aquilinum) and grass were important for site selection in both species, with High Brown Fritillaries tolerating less live Bracken and grass cover than Dark Green Fritillaries. This confirms the more specific requirements and narrower micro-habitat niche of the High Brown Fritillary, which appears to be more sensitive to micro-habitat cooling.Implications for insect conservationThe management of Bracken mosaic habitats for these two species should aim to supress grass growth and maintain Bracken density within limits, by opening the Bracken canopy on a rotation through grazing or manual cutting, ensuring a continuous supply of suitable micro-habitat.

Odour-mediated oviposition site selection in Aedes aegypti depends on aquatic stage and density

BackgroundOlfaction plays an important role in the selection and assessment of oviposition sites by mosquitoes. Volatile organic compounds (VOCs) associated with potential breeding sites affect the behaviour of gravid mosquitoes, with VOCs from aquatic stages of conspecific mosquitoes influencing and regulating oviposition. The purpose of this study was to conduct a systematic analysis of the behavioural response of gravid Aedes aegypti to conspecific aquatic stage-conditioned water, to identify the associated bioactive VOCs and to determine how blends of these VOCs regulate oviposition site selection and stimulate egg-laying.MethodsUsing a multi-choice olfactory oviposition assay, controlling for other sensory modalities, the responses of individual females to water conditioned with different densities of conspecific aquatic stages were assessed. The conditioned water samples from the most preferred density of each aquatic stage were subsequently compared to each other using the same oviposition assay and analysed using an analysis of variance (ANOVA) followed by a Tukey post-hoc test. Using combined gas chromatography and electroantennographic detection or mass spectrometry, bioactive VOCs from the preferred density of each aquatic stage were identified. Synthetic blends were prepared based on the identified ratios of bioactive VOCs in the aquatic stages, and then tested to determine the oviposition choice of Ae. aegypti in a dose-dependent manner, against a solvent control, using a dual-choice assay. This dataset was analysed using nominal logistic regression followed by an odds ratio comparison.ResultsGravid Ae. aegypti responded stage- and density-dependently to water conditioned with eggs, second- and fourth-instar larvae, and pupal exuviae, but not to water conditioned with pupae alone. Multi-choice assays demonstrated that gravid mosquitoes preferred to oviposit in water conditioned with fourth-instar larvae, over the other aquatic stage-conditioned water. Gravid Ae. aegypti were attracted, and generally stimulated, to oviposit in a dose-dependent manner to the individual identified synthetic odour blends for the different aquatic stages.ConclusionsIntraspecific VOCs regulate oviposition site selection in Ae. aegypti in a stage- and density-dependent manner. We discuss the need for further studies to evaluate the identified synthetic blends to modulate the odour-mediated oviposition of Ae. aegypti under field conditions.Graphical

A mosaic of endogenous and plant-derived courtship signals in moths

Insects rely on olfaction to guide a wide range of adaptive behaviors, including mate and food localization, mate choice, oviposition site selection, kin recognition, and predator avoidance.1 In nocturnal insects, such as moths2 and cockroaches,3 mate finding is stimulated predominantly by long-range species-specific sex pheromones, typically emitted by females. During courtship, at close range, males in most moth species emit a blend of pheromone compounds from an everted, often large, pheromone gland. While long-distance communication with sex pheromones has been remarkably well characterized in thousands of moth species,2,4 close-range chemosensory sexual communication remains poorly understood. We reveal that in the moth Chloridea virescens, the male pheromone consists of three distinct classes of compounds: de novo biosynthesized alcohols, aldehydes, acetates, and carboxylic acids that resemble the female's emissions; newly identified compounds that are unique to the male pheromone, such as aliphatic polyunsaturated hydrocarbons; and sequestered plant secondary compounds and hormone derivatives, including methyl salicylate (MeSA). Thus, males employ a mosaic pheromone blend of disparate origins that may serve multiple functions during courtship. We show that two olfactory receptors in female antennae are tuned to MeSA, which facilitates female acceptance of the male. Because MeSA is emitted by plants attacked by pathogens and herbivores,5 the chemosensory system of female moths was likely already tuned to this plant volatile, and males appear to exploit the female's preadapted sensory bias. Interestingly, while female moths (largely nocturnal) and butterflies (diurnal) diverged in their use of sensory modalities in sexual communication,6 MeSA is used by males of both lineages.

Behavioral responses of different reproductive statuses and sexes in Hermetia illucens (L) adults to different attractants.

The odor of various fermented organic materials acts as an attractant for oviposition by gravid females of the black soldier fly (BSF) to find larval food sources. Females display oviposition site selection on various organic materials, but little work has been done on the response to substrate attractants under caged conditions similar to those in a BSF farm production system. Fifty of each reproductive status (mated and virgin) and sex (males and females) of BSF adults were marked and then exposed to one of five different oviposition attractants in a transparent acrylic chamber: no substrate (control) plus pineapple, mixed vegetables, okara, and fermented fish to represent fruit-, vegetable-, plant protein-, and animal protein-based substrates, respectively. The frequency of the perching activity on the oviposition apparatus and flying behavior under the LED illumination, including the laid egg weight, were recorded. The sexually-related activities of BSF adults were clearly observed. A majority of the females preferred to perch on the oviposition apparatus and fly around the illuminated area compared to the very low activities of the mated males. The BSF adults displayed different behavioral responses to the different tested attractants. While active flying was common when using plant protein- and animal protein-based substrates, mated females showed the greatest perching preference for plant-based substrates (fruit and vegetables) and this correlated with the laid egg weight. Egg-laying was more likely to happen on the plant-based substrate than on the animal protein-based substrate. However, the strong smell of the animal protein-based substrate could strongly trigger lekking behavior, which is an important part of mating behavior. This knowledge can support egg trapping in nature and also improve the efficiency of egg production in mass-rearing facilities.

Predators as biocontrol agents of mosquito larvae in small and large habitats in Chiang Mai, Thailand.

Controlling mosquito-borne disease is a major global challenge due to the rise of insecticide-resistant mosquitoes. In response, we conducted a study in Chiang Mai Province, Thailand, which is one of the largest and the most popular cities for tourists in Southeast Asia, to explore the potential of local species as biological control agents for mosquito larvae. Mosquito larvae and aquatic predators were sampled from large and small habitats, while relevant physico-chemical parameters were measured. The study identified 560 predators and 1,572 mosquitoes, with most mosquito species belonging to the genus Culex. Additionally, the study identified 16 predator taxa, including four fish taxa and 12 taxa of predatory aquatic insects belonging to four orders: Coleoptera, Hemiptera, Odonata, and Diptera. The study found that several locally occurring predator species, namely Poecillia, Laccophilus, Lutzia, Toxorhynchites splendens, Agrionoptera, and Pseudarion, shared habitats with mosquitoes, indicating their potential as effective biological control agents for mosquito control. Conductivity, dissolved oxygen, and pH were the important physico-chemical parameters that affect both predators and mosquito larvae. Consequently, promoting native predators and reducing mosquito larvae through habitat management would be a sustainable and ecologically friendly approach in large habitats where it is not possible to remove mosquito oviposition sites. In smaller habitats, releasing local aquatic predators and removing oviposition sites may be a suitable strategy.

A mosquito-specific antennal protein is critical for the attraction to human odor in the malaria vector Anopheles gambiae

Mosquitoes rely mainly on the sense of smell to decipher their environment and locate suitable food sources, hosts for blood feeding and oviposition sites. The molecular bases of olfaction involve multigenic families of olfactory proteins that have evolved to interact with a narrow set of odorants that are critical for survival. Understanding the complex interplay between diversified repertoires of olfactory proteins and ecologically-relevant odorant signals, which elicit important behaviors, is fundamental for the design of novel control strategies targeting the sense of smell of disease vector mosquitoes. Previously, large multigene families of odorant receptor and ionotropic receptor proteins, as well as a subset of odorant-binding proteins have been shown to mediate the selectivity and sensitivity of the mosquito olfactory system. In this study, we identify a mosquito-specific antennal protein (MSAP) gene as a novel molecular actor of odorant reception. MSAP is highly conserved across mosquito species and is transcribed at an extremely high level in female antennae. In order to understand its role in the mosquito olfactory system, we generated knockout mutant lines in Anopheles gambiae, and performed comparative analysis of behavioral and physiological responses to human-associated odorants. We found that MSAP promotes female mosquito attraction to human odor and enhances the sensitivity of the antennae to a variety of odorants. These findings suggest that MSAP is an important component of the mosquito olfactory system, which until now has gone completely unnoticed.

Artificial light at night has species‐specific effects on oviposition behavior of mosquitoes

AbstractArtificial light at night (ALAN) is a pervasive and growing issue worldwide. ALAN disrupts the physiology and natural crepuscular and nocturnal behavior of organisms, with widely observed effects on insects. Mosquitoes (Diptera: Culicidae) are disease vectors that evaluate and select freshwater habitats as oviposition sites. This behavior has both ecological and epidemiological implications. However, it is unknown how ALAN affects mosquito oviposition. We compared oviposition rates in outdoor mesocosms exposed to light‐emitting diodes (LED, 3000 K, ca. 13 lux) with dark controls. We assayed the oviposition behavior of natural populations of mosquitoes by quantifying mosquito eggs (Culex restuans Theobald and Ochlerotatus japonicus Theobald) deposited in the experimental mesocosms over 7 days. Mosquitoes had species‐specific responses to ALAN. Mean cumulative Cx. restuans egg raft deposition was greater in control pools than in ALAN pools (21 vs. 10 eggs). We observed no response of Oc. japonicus, potentially reflecting the risk associated with the alternative oviposition strategies of the two species (eggs rafts vs. skip oviposition). Our results show that ALAN has species‐specific effects on organisms, thereby complicating our understanding of the behavioral and potential ecological and epidemiological effects of this novel anthropogenic stressor.

Oviposition behavior is not affected by ultraviolet light in a butterfly with sexually-dimorphic expression of a UV-sensitive opsin.

Animal vision is important for mediating multiple complex behaviors. In Heliconius butterflies, vision guides fundamental behaviors such as oviposition, foraging, and mate choice. Color vision in Heliconius involves ultraviolet (UV), blue and long-wavelength-sensitive photoreceptors (opsins). Additionally, Heliconius possess a duplicated UV opsin, and its expression varies widely within the genus. In Heliconius erato, opsin expression is sexually dimorphic; only females express both UV-sensitive opsins, enabling UV wavelength discrimination. However, the selective pressures responsible for sex-specific differences in opsin expression and visual perception remain unresolved. Female Heliconius invest heavily in finding suitable hostplants for oviposition, a behavior heavily dependent on visual cues. Here, we tested the hypothesis that UV vision is important for oviposition in H. erato and Heliconius himera females by manipulating the availability of UV in behavioral experiments under natural conditions. Our results indicate that UV does not influence the number of oviposition attempts or eggs laid, and the hostplant, Passiflora punctata, does not reflect UV wavelengths. Models of H. erato female vision suggest only minimal stimulation of the UV opsins. Overall, these findings suggest that UV wavelengths do not directly affect the ability of Heliconius females to find suitable oviposition sites. Alternatively, UV discrimination could be used in the context of foraging or mate choice, but this remains to be tested.

Diamondback moth egg susceptibility to rainfall: effects of leaf surface properties on the direct and indirect impact of simulated rain

AbstractDiamondback moth (DBM), Plutella xylostella L. (Lepidoptera: Plutellidae), eggs are vulnerable to rainfall, but the impact is dependent on host plant properties and the nature of oviposition sites. The effects of host plants, common cabbage (Brassica oleracea L. var. capitata) and Chinese cabbage (Brassica rapa L. var. pekinensis) (Brassicaceae), and oviposition sites on the fate of eggs subjected to simulated raindrops were investigated in laboratory experiments. In oviposition studies, DBM deposited more eggs on leaf veins than on leaf laminas on both host plants. In common cabbage plants, eggs laid on lower leaves (leaf 2) were less susceptible to dislodgment by rainfall than eggs laid on upper leaves (leaf 6). Eggs laid on the veins on the abaxial surfaces of leaves 2 and 6 of common cabbage plants were less susceptible to dislodgment by raindrops than eggs laid at other sites on this host plant. In Chinese cabbage plants, eggs laid on the veins were less susceptible to dislodgment by raindrops than eggs laid on leaf laminas. When DBM laid eggs in clusters, eggs were less susceptible to dislodgment by raindrops. The presence of waxes on leaf surfaces and concave veins affected egg placement and the retention of eggs at oviposition sites when subjected to raindrops. Eggs were more resistant to raindrops on the concave veined and less waxy leaves of Chinese cabbage plants than on waxy surfaces of smooth common cabbage leaves. When epicuticular wax crystals were removed from common cabbage leaves before oviposition, eggs were more resistant to dislodgment by raindrops. Leaf orientation or angle (horizontal plane vs. an angle of 45°) did not affect the susceptibility of eggs to raindrops. However, eggs were affected indirectly, and vibrations caused by the impact of raindrops resulted in egg removal from both adaxial and abaxial surfaces. Overall, eggs were less likely to be dislodged by raindrops when laid on concave veins and less waxy leaf surfaces. In oviposition tests, DBM laid fewer eggs on plant parts from which they were most easily removed by raindrops, and when they did lay eggs at these sites, they often deposited them in clusters which were more resistant than single eggs to removal by raindrops. The study reiterates the species‐specific nature of DBM‐host plant interactions and shows that female DBM can modify their behaviour to improve the probability of egg survival when substrates available for oviposition are sub‐optimal.

A green leaf volatile, (Z)-3-hexenyl-acetate, mediates differential oviposition by Spodoptera frugiperda on maize and rice

BackgroundInsects rely on chemosensory perception, mainly olfaction, for the location of mates, food sources, and oviposition sites. Plant-released volatile compounds guide herbivorous insects to search for and locate their host plants, further helping them to identify suitable positions for oviposition. The fall armyworm Spodoptera frugiperda (S. frugiperda) was found to invade China in 2019 and has since seriously threatened multiple crops, particularly maize and rice. However, the chemical and molecular mechanisms underlying oviposition preference in this pest are not fully understood. Here, the oviposition preference of S. frugiperda on maize and rice plants was investigated.ResultsGC-EAD and GC–MS/MS techniques were used to identify the antennally active volatiles from maize and rice plants. The attraction and oviposition stimulation of identified components to female adults were tested in both laboratory and field settings. The odorant receptors (ORs) on female antennae were expressed in Xenopus oocytes, and their functions evaluated by RNAi. Ten and eleven compounds of maize and rice plants, respectively, were identified to possess electrophysiological activity from headspace volatiles. Among these compounds, (Z)-3-hexenyl-acetate specifically presented in maize volatiles was found to play a critical role in attracting females and stimulating oviposition compared to rice volatiles. Among the cloned ORs on the antennae of both sexes, SfruOR23 with highly female-biased expression mediated the responses of females to (Z)-3-hexenyl-acetate. Knockdown of SfruOR23 using RNAi markedly reduced the electrophysiological response of female antennae and oviposition preference to the compound.Conclusions(Z)-3-Hexenyl-acetate is a key volatile mediating the host and oviposition preference of S. frugiperda on maize. The olfactory receptor of (Z)-3-hexenyl-acetate was identified to be SfruOR23, which is mainly expressed in the antennae of S. frugiperda.

Host plant selection by Cerambycidae in two different strata in association with seasonality and physical wood characteristics in a tropical dry forest

Abstract1. There is little information on tropical dry forests regarding cerambycids and their relationship with seasonality, vertical stratification, and physical characteristics of the wood they require to develop.2. In this work, we determined whether cerambycids in a tropical dry forest of central Mexico differed in the selection of oviposition sites in two different strata throughout two seasons; the relationship between the time of exposure of branches and the emergence of cerambycids; the emergence of these insects in relation to the physical characteristics of the wood and its relationship with stratification and seasonality; and if there was a seasonal shift between strata by cerambycids. Branch segments from 81 woody plant species were cut and exposed to allow the cerambycids to oviposit; the branches were harvested in four 2‐month periods and placed in emergence chambers. For each plant species, we measured the density, decomposition rate, and offered volume of wood.3. There was a greater quantity of generalist species of stratum (15) and season (12), and we found six important habitat indicator species: three species were significantly associated with the canopy and the dry season, two species preferred the dry season but not strata, and one species preferred both strata in the dry season and the ground during the rainy season. Cerambycid species generally selected soft and ephemeral wood resources.4. Branch selection by cerambycids in Central Mexico is not random choice; it is determined by season, stratum, density, and especially by host type, decomposition, and volume. Finally, there is a greater abundance of cerambycids in the ground and a greater richness of species in the canopy.

Eggs in faeces: defensive mechanisms and effects of faecal coating by a water scavenger beetle, Coelostoma stultum (Coleopterea: Hydrophilidae).

The egg stage in insect development is vulnerable to fluctuations in environmental conditions and attacks by natural enemies. Protective devices are effective means of avoiding both abiotic and biotic damage to eggs. Although some insects use their faeces as a protective device, few studies have focused on using faeces for egg protection, and studies that examined the mechanism are lacking. Females of a water scavenger beetle, Coelostoma stultum, typically lay eggs and coat them with cocoons and their faeces. The efficacy of a double defensive device, however, remains uncertain. Here, we conducted field observations and laboratory experiments to assess the protective effects of cocoons with faecal coating on eggs against predation and determine the duration and mechanisms of this defence. Our findings reveal that the faeces on the egg cocoon protected eggs from predation by the pill bugs, Armadillidium vulgare, and marsh slugs, Deroceras laeve. Laboratory experiments showed that the defensive effect of faecal coating was maintained for three days and decreased daily. The double protective traits with faecal coating on the egg cocoons protected the eggs from instense predation pressure in C. stultum. The behavioural patterns of the pill bugs and egg predation rates indicate that the faecal coating behaviour in C. stultum protects eggs with chemical compounds and textural camouflage in mud when the antennae of the pill bugs touch faeces. It is important to note that for this defence to be effective, the chemistry and texture of the faeces should be similar to that of the oviposition sites.

Oviposition Preferences of Aedes aegypti in Msambweni, Kwale County, Kenya.

Aedes aegypti is the primary vector of dengue fever virus (DENV) worldwide. Infusions made from organic materials have been shown to act as oviposition attractants for Ae. aegypti; however, studies on locally suitable infusion materials are lacking. The current study assessed the suitability of 4 locally available materials as oviposition infusions for use in surveillance and control of Ae. aegypti in Kwale County, Kenya. Oviposition infusion preferences were assessed in laboratory, semifield, and field conditions, using 4 infusions made from banana, grass, neem, and coconut. In addition, ovitrapping in wall, grass, bush, and banana microhabitats was done in 10 houses each in urban and rural coastal households to determine suitable oviposition microhabitats. Overall, the highest oviposition responses were observed for banana infusion, followed by neem and grass infusions, which were comparable. Coconut infusion resulted in the lowest oviposition response. Although female Ae. aegypti did not show preference for any microhabitat, the oviposition activity across all the microhabitats was highly enhanced by use of the organic infusions. Banana, neem, and grass infusions could be used to attract gravid mosquitoes to oviposition sites laced with insecticide to kill eggs. Additionally, banana plantings could be important targets for integrated vector control programs.

A predatory mite that suppresses Diaphorina citri populations on plants with pollen and oviposition sites

AbstractThe Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is the major citrus pest worldwide because it can transmit the bacteria associated with citrus greening disease (huanglongbing, HLB). The most common management strategy of this pest is chemical control, but this often results in pest resistance and threatens the sustainability of the citrus culture. There is therefore need for sustainable control strategies such as biological control. Previous experiments showed that the predatory mite Amblyseius herbicolus Chant (Acari: Phytoseiidae) is able to develop and reproduce on D. citri eggs. Here, we studied the population dynamics of this pest on plants with and without A. herbicolus on isolated orange jasmine plants, Murraya paniculata (L.) Jack (Rutaceae), an important host plant of the pest. Predatory mites were released 1 week before the release of D. citri and were provided with twines with pollen as oviposition sites and food source, respectively, to maintain populations of A. herbicolus in the absence of the pest. Densities of adults and nymphs of D. citri on plants with predators were about 85% lower than on plants without predators, showing that A. herbicolus is a potential biocontrol agent of D. citri. However, the stage structure of the D. citri populations at the end of the experiment did not differ significantly between control plants and plants with predators. This led us to investigate whether the predator attacked other stages besides eggs. Indeed, predators were able to feed and reproduce on first and second instar nymphs of D. citri, but not on instars 3–5. Concluding, the release of A. herbicolus with alternative food and oviposition sites can reduce infestations of D. citri. We suggest that field experiments should be done in areas where HLB occurs to test whether releases of this predator limit the spread of this devastating disease.

Life history and bionomics of Glycobius speciosus (Coleoptera: Cerambycidae: Cerambycinae: Clytini).

Glycobius speciosus (Say) was studied in New York State to elucidate poorly known aspects of its biology. Head capsule size from excavated larvae coupled with gallery lengths measured at the time of excavation was used to characterize larval development. Partial life tables indicated nearly 20% of G. speciosus survive to adulthood. Larvae experienced 30% of their mortality during early development, 27% during mid-larval development, and 43% during late larval development. Predation by hairy woodpeckers, Dryobates villosus (Linnaeus) (Piciformes: Picidae), the only unambiguous source of mortality, accounted for 43% mortality in naturally infested trees located and followed 2004-2009, and 74% late instar mortality. One parasitoid, Dolichomitus irritator (Fabricius) (Hymenoptera: Ichneumonidae), was recovered from a single larva. Beetles emerged between 316 accumulated DD (base 10 °C) and 648 DD. Males emerged prior to, or simultaneously with, females and lived longer. Female fecundity averaged 41.3 ± 6 eggs. Larval eclosion occurred 7-10 days after oviposition. Non-functional ovipositors observed in 16% of females represented an appreciable reproductive loss. In 77% of infested trees 1 oviposition site was located and in 70% of oviposition sites examined only 1 or 2 larvae successfully eclosed, penetrated the bark to the phloem-xylem interface, and began feeding. Beetles preferred southern and eastern aspects for oviposition which occurred preferentially on the lower bole (<20 cm). Male beetles had longer and wider antennae than females, pronotal pits containing gland pores, and a straight to concave posterior margin of the terminal sternite compared to the more rounded margin of females.

Evaluation of winter cover crop methods for management of flatheaded appletree borer (Coleoptera: Buprestidae).

Winter cover crops grown at the base of red maples (Acer rubrum L.) can reduce flatheaded appletree borer (Chrysobothris femorata Olivier; Coleoptera: Buprestidae; FAB) damage by both physically blocking preferred oviposition sites and altering the environment around them. However, cover crop competition negatively affects tree growth. To investigate long-term cover crop effects, trees grown with cover crop for 2 yr were transitioned to a standard herbicide practice. After 4 yr, trees in the initial 2 yr cover crop plots were 1 yr behind in growth compared to trees grown in bare rows for all 4 yr. Most growth reduction occurred in the first year following transplant. Additional borer losses of 1-2% per year were observed in production years 3 and 4. A second experiment answered 2 questions: Can killing the cover crop once it reaches maximal height protect trees from borers while also reducing competition and thereby increase tree growth? and Do herbicide applications increase borer attacks? In this experiment, red maples were grown with (i) a standard herbicide program, (ii) a mulch mat, (iii) a cover crop that was killed early, or (iv) a cover crop allowed to senesce naturally. Evaluations after 2 yr indicated early kill of the cover crop was not enough to improve tree growth. Further, trees in the early kill cover crop treatment had the most FAB attacks. Cover crops allowed to senesce naturally reduced FAB attacks in both studies; however, more work is needed to minimize disparities in tree growth during the initial year post-transplant and determine the causal relationship between herbicide use and borer attacks.

Larval and adult experience and ecotype affect oviposition behavior in a niche-expanding butterfly

AbstractLocal adaptation, early-developmental and behavioral plasticity have all been suggested to be underlying mechanisms of behavioral variation. They allow organisms to cope with resource heterogeneity in time and space. However, the relative contribution of each of these drivers on niche-expansion success is still unclear. We addressed this issue by studying oviposition behavior in a butterfly (Pararge aegeria) that used to be confined to forest, but recently colonized anthropogenic areas too. We caught females of either forest or agricultural ecotype and allowed their larval offspring to experience early-habitat cues in either open field or woodland conditions. For 110 females of this transplant experiment, we monitored all oviposition-related behaviors (i.e., site selection, searching, motivation, learning) using repeated trials in outdoor flight cages with naturally occurring host grasses. We observed changes in oviposition site preference, with increasing preference for semi-shaded host grass (by vegetation or vertical structures) over consecutive egg-lays. Motivation to oviposit was most affected by larval experience (in interaction with cage environment). We also show evidence for ecotypic differentiation with the agricultural ecotype showing reduced search effort during the first trial compared to the forest ecotype. We argue that females of agricultural landscapes with fragmented resource distributions adopt a more risk-aversive oviposition strategy. Our detailed behavioral tracking under ecologically relevant conditions, stresses the importance of considering different types of behavioral plasticity to unravel a species’ success during niche expansion.

Involvement of Holotrichia parallela odorant-binding protein 3 in the localization of oviposition sites

Organic fertilizers-derived volatiles attract Holotrichia parallela during oviposition. However, the mechanisms underlying the perception of oviposition cues in H. parallela remain unclear. Here, H. parallela odorant-binding protein 3 (HparOBP3) was identified as a key OBP. Bioinformatics analysis showed that HparOBP3 clustered together with Holotrichia oblita OBP8. HparOBP3 was mainly expressed in the antennae of both sexes. Recombinant HparOBP3 exhibited distinct binding affinities towards 22 compounds released by organic fertilizers. After 48 h of RNA interference (RNAi), the expression of HparOBP3 in male and female antennae was decreased by 90.77 % and 82.30 %, respectively. In addition, silencing of HparOBP3 significantly reduced the electrophysiological responses and tropism of males to cis-3-hexen-1-ol, 1-hexanol, and (Z)-β-ocimene as well as females to cis-3-hexen-1-ol, 1-hexanol, benzaldehyde, and (Z)-β-ocimene. Molecular docking indicated that hydrophobic residues Leu-83, Leu-87, Phe-108, and Ile-120 of HparOBP3 were important amino acids for interacting with ligands. Mutation of the key residue, Leu-83, significantly diminished the binding ability of HparOBP3. Furthermore, acrylic plastic arena bioassays showed that the attraction and oviposition indexes of organic fertilizers to H. parallela were reduced by 55.78 % and 60.11 %, respectively, after silencing HparOBP3. These results suggest that HparOBP3 is essential in mediating the oviposition behavior of H. parallela.

Chikungunya Virus Infection and Gonotrophic Cycle Shape Aedes aegypti Oviposition Behavior and Preferences.

Targeting gravid females through chemical lures is a promising strategy in vector control; however, it requires the understanding of the factors susceptible to alter female oviposition behavior. Here, we evaluated the effect of infection with chikungunya virus (CHIKV) and the number of gonotrophic cycles (GCs) on oviposition activity in A. aegypti. Dual choice oviposition assays were performed, where dodecanoic acid, pentadecanoic acid, n-heneicosane and a Sargasssum fluitans (Børgesen) Børgesen extract were tested in uninfected females and females infected with CHIKV, at the 1st and 2nd GC. Infected females displayed a lower percentage of oviposition and a higher number of eggs laid at the 1st GC. Then, the combined effects of GC and CHIKV were observed on oviposition preferences, with a chemical-dependent effect. For instance, the deterrent effect of n-heneicosane and pentadecanoic acid increased at the 2nd GC in infected females. These results allow for a deeper understanding of the mechanisms involved in oviposition site selection and highlight the need for taking into account physiological stage changes to increase the control programs' efficacy.