Mineral and natural films change the physical-chemical properties of grapes and modulate oviposition behaviour of Ceratitis capitata Wiedemann (Diptera: Tephritidae)

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the main pests of fruit, worldwide, and the use of population suppression method with low environmental impact is an increasingly strong requirement of the consumer market. The aim of this study was to evaluate the effect of mineral and natural films on the physical-chemical properties of grapes (Vitis vinifera L.), cultivar Itália, and oviposition behaviour of C. capitata. Fruits were immersed in suspensions (100 and 200 g L-1) of mineral (kaolin Surround®WP, kaolin 607, kaolin 608, kaolin 611 and talc) and natural films (chitosan, cassava starch, potato starch and guar gum 5.0 g L-1) and distilled water (control). After drying, fruits were exposed to C. capitata pairs of males and females for 24 h in choice and non-choice tests; the number of punctures with and without eggs, eggs per fruit and behavioural response of fly to treated and untreated fruits were recorded. Results obtained in this study are promising, given the scientific evidence that films of mineral particles such as kaolin (Surround®, 607, 608 and 611) changed the firmness, luminosity, chroma and hue angle of grapes and reduced the oviposition of C. capitata. In addition, our results also showed that natural polymers do not deter C. capitata females, but rather seem to stimulate oviposition.

Potential roles of selected forage grasses in management of fall armyworm (Spodoptera frugiperda) through companion cropping

Production of maize, Zea mays L. (Poaceae), in sub-Saharan Africa is threatened by a new invasive pest, fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae). To mitigate this threat, push-pull companion cropping, a system originally developed for management of lepidopteran stemborers, may be used to control FAW. The original system involved trap crops that functioned as a 'pull' component to attract moths away from the main crop. How grass species can be used as trap crops in a push-pull system to control FAW is a question that remains to be answered, because maize is already a highly preferred host plant. Therefore, we tested oviposition preference of FAW female moths in no-choice and two-choice experiments and larval performance on six selected grasses (Poaceae) to assess their roles as trap crop 'pull' plants in the system. In no-choice tests, numbers of eggs deposited on Brachiaria brizantha (Hochst. ex A. Rich.) R. Webster cv. 'Piata', cv. 'Mulato II', and cv. 'Xaraes', and Napier grass (Pennisetum purpureum K. Schumach) cv. 'South Africa' were not statistically different from those deposited on maize. In two-choice tests between grasses and maize, there were no significant differences in number of eggs laid when the plants were of the same size. However, in two-choice tests with maize plants half of the size of the grasses, significantly more eggs were laid on B. brizantha cv. Xaraes and P. purpureum cv. South Africa than on maize, suggesting that crop phenology could make a difference. Numbers of larvae arrested on grass leaf cuts were considerably lower than those on maize leaf cuts after 48 h. In two-choice tests with maize, molasses grass (Melinis minutiflora P. Beauv.) was the only grass that was significantly preferred to maize for larval settlement after 24 h. After 48 h in the two-choice test, it was the only grass that retained larvae, although the larval count was significantly lower than on maize. Our data show that none of the grasses tested were strongly preferred to maize, but the results indicate plants attractive to FAW adults and larvae that could be utilized in a multiple trap crop approach to target various stages of the pest. Furthermore, results indicate the importance of planting these companion plants earlier than maize.

Efficacy and Cost-Effectiveness of Phenotyping for Rice Resistance and Tolerance to Planthoppers

Simple Summary

Rice in Asia is damaged by a range of sap-sucking planthoppers. For the last 50 years, the main focus for integrated management of these insects was to develop resistant rice varieties. A single, bulk phenotyping test, known as the standard seedling seedbox test (SSST) was used to inform the majority of genetics and breeding programs for planthopper-resistant rice. However, there has been much debate over the efficacy of this test. We compared results from the SSST against those from a range of other phenotyping tests to assess how antibiosis and tolerance (the ability of rice to compensate for damage) affect test results, and how phenotyping might be improved to capture information regarding plant traits that are otherwise overlooked by the SSST. Based on the efficacy and costs of different tests, we recommend that breeding programs adopt a modified seedling seedbox test (MSST) when phenotyping 100s of rice lines but that insect performance tests that assess relative changes in planthopper biomass could be adopted when phenotyping fewer lines (e.g., <100 lines). The days-to-wilt (DTW) test was found to be particularly effective in segregating resistant/tolerant lines from susceptible lines.

Abstract

The standard seedling seedbox test (SSST) is the most prevalent phenotyping test in research on the genetics and breeding of planthopper-resistant rice. Using 16 rice lines that included plants susceptible, resistant and tolerant to the brown planthopper (Nilaparvata lugens), we compared the SSST to modified seedling seedbox tests (MSSTs) and the days-to-wilt (DTW) test. We also conducted a series of performance tests to assess nymph survival and development; adult longevity and egg-laying; egg survival; honeydew production; and plant weight loss. We also assessed the relative costs of the different phenotyping tests to better recommend test protocols that are suitable for high-throughput phenotyping. The SSST was found to be highly robust but fails to identify late-stage resistance; tolerance; or ovicidal responses. MSSTs improved phenotyping by identifying plants with low damage from planthoppers at later growth stages. Herbivore performance tests such as population or biomass build-up tests reduce space requirements and reduce setup and evaluation costs compared with bulk tests. They can also facilitate the assessment of plant tolerance; albeit with added costs. The DTW test most clearly segregates resistant and susceptible plants, thereby facilitating gene discovery and marker-assisted selection. We recommend that bulk testing be improved by switching from the SSST to a suitable MSST and that donor variety and pre-release lines be assessed for the nature of rice–planthopper interactions using biomass build-up tests—including the DTW test.

Ovitrap Preference in the Black Soldier Fly, Hermetia illucens (L.) (Diptera: Stratiomyidae)

&lt;b&gt;Background and Objective:&lt;/b&gt; The adult female of the Black Soldier Fly (BSF) usually performs oviposition near decaying organic matter in cracks found in dry areas. In mass-rearing facilities or on a laboratory scale, females usually lay eggs on the provided ovitrap which is made of various types of materials. This study was aimed to observe the female preferential behaviour for ovitrap types during the oviposition period. &lt;b&gt;Materials and Methods:&lt;/b&gt; The study was conducted in a semi-outdoor screen house with direct sunlight. The ovitrap materials used were: Dry leaves, wood, cardboard and plastic (infraboard). The parameters calculated in this study were ovitrap preference, oviposition duration, the number and weight of the eggs, fertility of eggs, development time and mortality of offspring. &lt;b&gt;Results:&lt;/b&gt; The BSF females preferred the wood ovitrap to other ovitrap types. This was indicated by the high number of females visits, the number of egg-laying females and the total number of eggs on the wood ovitrap. Eggs found in the plastic ovitrap had the highest mortality compared to eggs found in the other ovitraps. &lt;b&gt;Conclusion:&lt;/b&gt; The difference of ovitrap material affected female visitation preferences, the oviposition frequency and the duration of egg-laying of female BSF but did not affect offspring development time in any of the stages (egg-adults).

The effect of chemical exudates of three larvivorous fish species on oviposition preference of Aedes aegypti and Aedes albopictus (Diptera: Culicidae)

Mosquito species Aedes aegypti and Aedes albopictus are vectors of dengue worldwide. Mosquito vector control through maintaining larvivorous fish in water bodies is generally suggested, however, its underlying role towards oviposition preference of these dengue vectors is unknown in the Sri Lankan context. The current study investigated the effect of chemical exudates from larvivorous fish species Poecilia reticulata, Rasbora daniconius and Applocheilus dayi on the oviposition preference of Aedes mosquitoes. The number of eggs laid by each mosquito species was determined using ovitraps that contained water conditioned by the fish species both separately and in combination. The ovitraps were placed inside insect cages containing engorged gravid Aedes females. Both the mosquito species had the least preference of oviposition in water conditioned by A. dayi followed by R. daniconius. The highest preference of oviposition was shown for water conditioned by P. reticulata. The current study indicated that oviposition site selection in Ae. aegypti and Ae. albopictus was reduced by A. dayi and R. daniconius, however, it was not influenced by the fish combinations used. Further studies are warranted to understand the chemical cues associated with larvivorous fish towards the oviposition preference in Aedes mosquitoes.

Evaluation of large volume yeast interfering RNA lure-and-kill ovitraps for attraction and control of Aedes mosquitoes

Aedes mosquitoes (Diptera: Culicidae), principle vectors of several arboviruses, typically lay eggs in man-made water-filled containers located near human dwellings. Given the widespread emergence of insecticide resistance, stable and biofriendly alternatives for mosquito larviciding are needed. Laboratory studies have demonstrated that inactivated yeast interfering RNA tablets targeting key larval developmental genes can be used to facilitate effective larvicidal activity while also promoting selective gravid female oviposition behaviour. Here we examined the efficacy of transferring this technology toward development of lure-and-kill ovitraps targeting Aedes aegypti (L.) and Aedes albopictus (Skuse) female mosquitoes. Insectary, simulated field and semi-field experiments demonstrated that two mosquito-specific yeast interfering RNA pesticides induce high levels of mortality among larvae of both species in treated large volume containers. Small-scale field trials conducted in Trinidad, West Indies demonstrated that large volume ovitrap containers baited with inactivated yeast tablets lure significantly more gravid females than traps containing only water and were highly attractive to both A. aegypti and A. albopictus females. These studies indicate that development of biorational yeast interfering RNA-baited ovitraps may represent a new tool for control of Aedes mosquitoes, including deployment in existing lure-and-kill ovitrap technologies or traditional container larviciding programs.

Detecting the Conspecific: Herbivory-Induced Olfactory Cues in the Fall Armyworm (Lepidoptera: Noctuidae)

The fall armyworm (FAW), Spodoptera frugiperda (Smith), is a polyphagous pest whose larval feeding threatens several economically important crops worldwide with especially severe damage to corn (Zea mays L.). Field-derived resistance to several conventional pesticides and Bt toxins have threatened the efficacy of current management strategies, necessitating the development of alternative pest management methods and technologies. One possible avenue is the use of volatile organic compounds (VOCs) and other secondary metabolites that are produced and sequestered by plants as a response to larval feeding. The effects of conspecific larval feeding on fall armyworm oviposition preferences and larval fitness were examined using two-choice oviposition experiments, larval feeding trials, targeted metabolomics, and VOC analyses. There was a significant preference for oviposition on corn plants that lacked larval feeding damage, and larvae fed tissue from damaged plants exhibited reduced weights and head capsule widths. All larval feeding promoted significantly increased metabolite and VOC concentrations compared to corn plants without any feeding. Metabolite differences were driven primarily by linoleic acid (which is directly toxic to fall armyworm) and tricarboxylic acids. Several VOCs with significantly increased concentrations in damaged corn plants were known oviposition deterrents that warrant further investigation in an integrated pest management context.

Egg retention, viviparity and ovoviviparity in Paraneoptera

This article is a second part of the themed issue "Aberrant cytogenetic and reproductive patterns in the evolution of Paraneoptera insects", prepared by the Russian-Bulgarian research team. Here, analysis of aberrations related to the egg development is provided based on literature data and the author's own investigations. Evolutionary aspects of ovoviviparity/viviparity are also briefly discussed. Material and methods, terminology and nomenclature of taxonomic names are listed in the first paper of the issue (Gavrilov-Zimin et al. 2021).

Microorganisms Associated with Mosquito Oviposition Sites: Implications for Habitat Selection and Insect Life Histories

Mosquitoes are considered one of the most important threats worldwide due to their ability to vector pathogens. They are responsible for the transmission of major pathogens such as malaria, dengue, zika, or chikungunya. Due to the lack of treatments or prophylaxis against many of the transmitted pathogens and an increasing prevalence of mosquito resistance to insecticides and drugs available, alternative strategies are now being explored. Some of these involve the use of microorganisms as promising agent to limit the fitness of mosquitoes, attract or repel them, and decrease the replication and transmission of pathogenic agents. In recent years, the importance of microorganisms colonizing the habitat of mosquitoes has particularly been investigated since they appeared to play major roles in their development and diseases transmission. In this issue, we will synthesize researches investigating how microorganisms present within water habitats may influence breeding site selection and oviposition strategies of gravid mosquito females. We will also highlight the impact of such microbes on the fate of females' progeny during their immature stages with a specific focus on egg hatching, development rate, and larvae or pupae survival.

Domestication of Chili Pepper Has Altered Fruit Traits Affecting the Oviposition and Feeding Behavior of the Pepper Weevil

The pepper weevil, Anthonomus eugenii, Cano (Coleoptera: Curculionidae), is one of the most destructive pests of chili pepper. It causes extensive damage on varieties selected for consumption. However, the occurrence of this pest on wild and ornamental peppers remains unknown. We investigated the consequences of chili domestication on the feeding and oviposition of A. eugenii on fruits and flowers. We used plants of one wild accession, Bird Eye Pepper, five ornamental varieties (Pops Yellow, Black Pearl, Sedona Sun, Chilli Chilli, and Salsa Deep), and two domesticated varieties selected for consumption (Scotch Bonnet and Jalapeño). First, we characterized the plants according to their fruit and flower sizes, pericarp thickness, capsaicin level, fruit position, and flower color. Then, we evaluated the susceptibility of fruits and flowers to A. eugenii. Overall, domestication increased fruit and flower sizes and pericarp thickness, altered capsaicin levels, and altered fruit position and flower color. Weevils laid more eggs and caused more feeding damage on varieties selected for consumption than on wild and ornamental plants. Our results add to the growing literature on the consequences of crop domestication on herbivores. This knowledge could be integrated into breeding programs to select varieties resistant against the pepper weevil.

Development and lifespan of Culicoides obsoletus s.s. (Meigen) and other livestock-associated species reared at different temperatures under laboratory conditions

Culicoides Latreille (Diptera: Ceratopogonidae) transmit arboviruses affecting wild and domestic ruminants such as bluetongue (BTV) and Schmallenberg virus (SBV). The sub-adult development and lifespan of Culicoides obsoletus s.s. (Meigen), Culicoides circumscriptus Kieffer and Culicoides paolae Boorman were examined at three different temperatures under laboratory conditions. Insects were collected from field between spring and autumn 2015 in two livestock farms located in Majorca (Spain). Gravid females were held individually at 18, 25 or 30 °C. Low temperatures increased the adult lifespan, time to oviposit and rate of development, whereas high temperatures increased the number of eggs, successful pupation and adult emergence as well as the larvae growth rate. The results showed that C. obsoletus s.s. have optimum development at 18 °C, whereas the optimal rearing temperature for C. circumscriptus and C. paolae was under warmer conditions of 25-30 °C. Variations in temperature/humidity and assays with different materials and substrates for oviposition should be considered in future studies. Understanding the requirements of the different species of Culicoides optimizing the results should be of special interest for predicting environmental change effects on these species, in addition to determining the rearing conditions for candidate Culicoides vectors.

Elucidating the Fitness of a Dead-End Trap Crop Strategy against the Tomato Fruitworm, Helicoverpa armigera

Simple Summary

The tomato fruitworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), is a destructive polyphagous insect pest of tomatoes and its control largely depends on chemical pesticides. However, indiscriminate use of chemical pesticides has resulted in the development of resistance and posed serious environmental problems. Alternatively, in search of environmentally friendly pest management techniques, the use of trap crops has recently gained more attention. In this study, we compared different accessions of S. viarum to investigate which of them have the highest potential as a dead-end trap crop for H. armigera. Results from the laboratory experiment showed a significant variation among the S. viarum accessions in terms of H. armigera oviposition, and exhibited a higher level of resistance against H. armigera larvae compared to the tomato plants. Under the semi-field condition, trap cropping of S. viarum significantly reduces the total egg-laying of H. armigera on tomato. This study provides important information about the abilities of S. viarum plants to influence the life parameter of H. armigera and highlighted the possibilities to use S. viarum as a dead-end trap crop for the management of H. armigera. However, the efficacy of S. viarum needs to be tested under large, open-field conditions.

Abstract

Solanum viarum has been proposed as a potential dead-end trap crop for the management of Helicoverpa armigera because of its unsuitability for larval growth and survival despite being overwhelmingly preferred for oviposition. This study delved into the different S. viarum accessions for ovipositional preference and non-suitability for larval growth and survival of H. armigera. Besides, foliage trichomes, acylsugars, and phenolic content of S. viarum plants were assessed and compared with tomato. Since there is no significant variation in the ovipositional preference and larval performance of H. armigera, our result revealed that all those evaluated accessions of S. viarum have the potential to be used as a dead-end trap crop for the management of H. armigera. However, significant variation among the S. viarum accessions in terms of H. armigera oviposition was also evident in a no-choice experiment. Because of high-density glandular trichomes, acylsugars, and phenolic content, S. viarum significantly impaired H. armigera larval growth and survival compared to the tomato. Hence, our study elucidated that the S. viarum plant fits with the criteria for dead-end trap crop, and has the potential as a dead-end trap crop for the H. armigera, which needs to be tested under large, open-field conditions.

Bioacaricidal Potential of Moringa oleifera Ethanol Extract for Tetranychus merganser Boudreaux (Acari: Tetranychidae) Control

The Tetranychidae family includes mites causing severe damage to agricultural fields. The red spider mite, Tetranychus merganser Boudreaux (Acari: Tetranychidae), causes severe damage to several plant species grown as cash crops. Current red spider mite control depends mainly on chemical insecticides. There is a need for alternate control measures that are environmentally friendlier than chemical pesticides. The aim of the study was to assess the effects of Moringa oleifera leaf ethanolic extract at different concentrations (0.1, 0.5, 1, 5, 10, 15, and 20% (v/v)) against T. merganser females. Such effects can serve as a basis to include this compound in integrated pest management programs for the control of red spider mites. Mites treated with 20% (v/v) killed 86.67%, 13.70%, and 96.30% at 24, 48, and 72 h, respectively, as compared to the control treatment. Oviposition, egg hatching, and the damage caused by red spider mites were all reduced at high concentrations. Moringa oleifera leaf ethanolic extract can be used as a powerful bioacaricide for the control of T. merganser.

Evaluation of Ethanol Extract of Moringa oleifera Lam. as Acaricide against Oligonychus punicae Hirst (Trombidiformes: Tetranychidae)

Tetranychidae family is a major group of mites causing serious damage in agricultural, vegetable and ornamental crops. Avocado bronze mite (ABM), Oligonychus punicae Hirst (Acari: Tetranychidae) causes major crop damage, defoliation and fruit abortion. At present, the control of this mite depends mainly on agrochemicals. Therefore it is necessary to find alternatives to synthetic pesticides that can help minimize environmental impact and health risks for the consumers. The aim of this research was to assess the effect of different concentrations (0.1, 0.5, 1, 5, 10, 15 and 20% (v/v)) of ethanolic extract of Moringa oleifera leaves against adult ABM females. Mites treated with 0.1 and 20% (v/v) of the extract showed mortality of 0.00% and 46.67%, 6.67% and 86.67%, 13.70% and 96.67%, at 24, 48 and 72 h, as compared to the control treatment, respectively. The number of eggs laid and hatch, as well as ABM feeding rates, depended on the extract concentration, which led to a reduction in the growth rate. M. oleifera leaf ethanolic extract has potential to control O. punicae.

Comparison of novaluron, pyriproxyfen, spinosad and temephos as larvicides against Aedes aegypti in Chiapas, Mexico

OBJECTIVE

To compare the efficacy of three modern larvicides with the organophosphate temephos for control of Aedes aegypti in water tanks in Chiapas.

MATERIALS AND METHODS

Trials were performed to compare the efficacy of pyriproxyfen, novaluron, two formulations of spinosad (granules and tablets) and temephos in oviposition traps and domestic water tanks.

RESULTS

Pyriproxyfen and temephos provided 2-3 weeks of complete control of larvae in oviposition traps, whereas spinosad granules and novaluron provided 7-12 weeks of control. Treatment of water tanks resulted in a significant reduction in oviposition by Ae. aegypti in houses (p<0.001). Higher numbers of larvae were present in temephos and pyriproxyfen-treated water tanks compared to novaluron and spinosad tablet treatments during most of the study.

CONCLUSIONS

Spinosad formulations and novaluron were effective larvicides in this region. The poor performance of temephos may be indicative of reduced susceptibility in Ae. aegypti populations in Chiapas.

Fitness Costs of Chlorantraniliprole Resistance Related to the SeNPF Overexpression in the Spodoptera exigua (Lepidoptera: Noctuidae)

Spodopteraexigua, a multifeeding insect pest, has developed a high level of resistance to chlorantraniliprole, which is a benzoylurea insecticide that targets the ryanodine receptors (RyRs). Herein, the resistant strain (SE-Sel) and sensitive strain (SE-Sus) were obtained by bidirectional screening for six generations. The potential oviposited eggs and oviposition rate of the SE-Sel strain were dramatically lower than those of the SE-Sus strain; on the contrary, the weights of prepupae and preadult were significantly increased. As a post-mating response, the higher number of non-oviposited eggs in the SE-Sel strain was caused by a lower mating rate. In addition, the expression levels of vitellogenin (SeVg) and its receptor (SeVgR) in the SE-Sel strain were consistently lower than those in the SE-Sus strain. An RyR^I4743M mutation, contributing to the resistance to chlorantraniliprole, was located in the S3 transmembrane segments and might have affected the release of calcium ions; it led to the upregulated expression of the neuropeptide SeNPF and its receptor SeNPFR, and the mating and oviposition rate were significantly recovered when the SeNPF was knocked down though RNA interference (RNAi) in the male adult of the SE-Sel strain. Moreover, the expression of the juvenile hormone-binding proteins SeJHBWDS3 and SeJHBAN in the male adult of the SE-Sel strain was significantly decreased, which proved the existence of a fitness cost from another angle. Therefore, these results indicate that the fitness cost accompanied by chlorantraniliprole resistance in S. exigua may be related to the decrease in mating desire due to SeNPF overexpression.

Sex-Dependent Effects of the Microbiome on Foraging and Locomotion in Drosophila suzukii

There is growing evidence that symbiotic microbes can influence multiple nutrition-related behaviors of their hosts, including locomotion, feeding, and foraging. However, how the microbiome affects nutrition-related behavior is largely unknown. Here, we demonstrate clear sexual dimorphism in how the microbiome affects foraging behavior of a frugivorous fruit fly, Drosophila suzukii. Female flies deprived of their microbiome (axenic) were consistently less active in foraging on fruits than their conventional counterparts, even though they were more susceptible to starvation and starvation-induced locomotion was notably more elevated in axenic than conventional females. Such behavioral change was not observed in male flies. The lag of axenic female flies but not male flies to forage on fruits is associated with lower oviposition by axenic flies, and mirrored by reduced food seeking observed in virgin females when compared to mated, gravid females. In contrast to foraging intensity being highly dependent on the microbiome, conventional and axenic flies of both sexes showed relatively consistent and similar fruit preferences in foraging and oviposition, with raspberries being preferred among the fruits tested. Collectively, this work highlights a clear sex-specific effect of the microbiome on foraging and locomotion behaviors in flies, an important first step toward identifying specific mechanisms that may drive the modulation of insect behavior by interactions between the host, the microbiome, and food.

Interactions of Helicoverpa punctigera (Lepidoptera: Noctuidae) Larvae and Adults With Four Native Host Plants Relative to Field Use Patterns

Generalist insect herbivores may be recorded from a great variety of host plants. Under natural conditions, however, they are almost invariably associated with a few primary host species on which most of the juveniles develop. We experimentally investigated the interaction of the generalist moth Helicoverpa punctigera Wallengren (Lepidoptera: Noctuidae) with four of its native host plants, two designated primary hosts and two secondary hosts (based on field observations). We tested whether primary host plants support higher survival rates of larvae and whether they are more attractive to ovipositing moths and feeding larvae. We also evaluated whether relative attractiveness of host plants for oviposition matches larval survival rates on them-the preference-performance hypothesis. Moths laid significantly more eggs on two of the four host plant species, one of them a primary host, the other a secondary host. Larvae developed best when reared on the attractive secondary host, developed at intermediate levels on the two primary hosts, and performed worst on the less attractive secondary host. Relative attractiveness of the four host plants to caterpillars differed from that of the moths. Neither adult nor larval attraction to host plants fully supported the preference-performance hypothesis, but oviposition was better correlated with larval survival rates than was larval attraction. Our results suggest the relative frequency at which particular host species are used in the field may depend on factors not yet considered including the long-distance attractants used by moths and the relative distribution of host species.

Using an artificial neural network to predict the probability of oviposition events of precision-fed broiler breeder hens

Identifying daily oviposition events for individual broiler breeders is important for bird management. Identifying non-laying birds in a flock that might be caused by improper nutrition or diseases can guide diet changes or disease treatments for these individuals. Oviposition depends on follicle maturation and egg formation, and follicle maturation can be variable. As such, the day and time of oviposition events of individual birds in a free-run flock can be hard to predict. Based on a precision feeding (PF) system that can record the feeding activity of individual birds, a recent study reported a machine learning model to predict daily egg-laying events of broiler breeders. However, there were 2 limitations in that study: 1) It could only be used to identify daily egg-laying events on a subsequent day; 2) The prediction outputs that were binary labels were unable to indicate more details among the outputs with the same label. To improve the previous approach, the current study aimed to predict and output the probability of daily oviposition events occurring using a specific time point in 1 day. In the current study, 706 egg-laying events recorded by nest boxes with radio frequency identification of hens and 706 randomly selected no-egg-laying events were used. The anchor point was newly defined in the current study as a specific time point in 1 day, and 26 features around the anchor point were created for all events (706 egg-laying events and 706 no-egg-laying events). A feed-forward artificial neural network (ANN) model was built for prediction. The area under the receiver operating characteristic (ROC) curve was 0.9409, indicating that the model had an outstanding classification performance. The ANN model could predict oviposition events on the current day, and the output was a probability that could be informative to indicate the likelihood of an oviposition event for an individual breeder. In situations where total egg production was known for a group, the ANN model could predict the probability of daily oviposition events occurring of all individual birds and then rank them to choose those most likely to have laid an egg.

Adulticidal Efficacy and Sublethal Effects of Metofluthrin in Residual Insecticide Blends Against Wild Aedes albopictus (Diptera: Culicidae)

Field development for optimizing the use patterns of spatial repellents are an ongoing research need. To investigate volatile pyrethroids in blends containing multiple active ingredients, metofluthrin was formulated into a vegetation spray for application to foliage and mosquito harborage. Metofluthrin was compared by itself and in combination with Sector (permethrin), Hyperion (sumithrin), Onslaught Fast Cap (s-fenvalerate, prallethrin), and against a benchmark for comparison, OneGuard (λ-cyhalothrin, prallethrin, pyriproxyfen). Field sites with established Aedes albopictus (Skuse) (Diptera: Culicidae) populations were allocated as control and treatment and surveilled with both adult traps and oviposition cups before and after treatment. Adult mosquito reductions were consistently higher over 4 wk in the combination treatments and were comparable to OneGuard. In contrast, efficacy provided by metofluthrin alone or the standalone existing product (Sector, Hyperion, Onslaught) by were consistently less effective than OneGuard and the comparative blends. Additionally, poorly melanized and collapsing eggs were identified from mosquito adults collected at treated field sites. A 20-50% significant decrease in nonviable mosquito eggs, a 50% or more reduction in total eggs and an 80% or more reduction in adult mosquitoes collected at the local field sites was demonstrated across all metofluthrin-containing treatments. Metofluthrin applications both supplemented the adulticidal control of the selected pyrethroid-containing products and provided significant reduction in egg laying frequency and viability during monitoring of areas adjacent to the treated vegetation. Metofluthrin, and possibly other volatile ingredients, appears to have complex interactions for mosquito control in the field and could be unique as a supporting ingredient to other insecticides.

Experimental field evidence shows milkweed contaminated with a common neonicotinoid decreases larval survival of monarch butterflies

Neonicotinoid insecticides are the most widely used class of insecticides in the world and can have both lethal and sub-lethal effects on non-target organisms in agricultural areas. Monarch butterflies Danaus plexippus have experienced dramatic declines in recent decades and, given that a large proportion of milkweed on the landscape grows in agricultural areas, there is concern about the negative effects of neonicotinoids on this non-target insect. In the field, we exposed common milkweed Asclepias syriaca, an obligate host plant of monarch butterflies, to agriculturally realistic levels of clothianidin, a widely used neonicotinoid insecticide. We tested whether this treatment influenced the number of eggs laid and larval survival over 2 years. Milkweeds were transplanted into 60 experimental plots alongside a corn crop planted with a clothianidin seed coat and 60 control plots alongside an untreated corn crop. The number of eggs, larvae at each stage (first to fifth instar), and the presence of other arthropods were recorded weekly from June to the end of August and survival from egg to fifth instar was estimated using a Bayesian state-space statistical model. We counted more eggs in treated plots compared to control plots, suggesting a preference for treated milkweed. The number of plots with arthropods did not differ between treatments, but within treated plots, there was a greater decrease in the number of arthropods throughout the season. There was no evidence that monarchs selected plots with fewer arthropods for oviposition. Larval survival was lower in clothianidin-treated plots compared to control plots. Our results suggest milkweed near clothianidin-treated crops can reduce larval survival of monarch butterflies. While we provide some evidence that clothianidin could also act as an ecological trap for this species, further work is needed to identify additional components of fitness, including individual egg-laying rates and survival beyond the pupal stage. Our findings add to a growing body of evidence that neonicotinoids can negatively affect non-target organisms. ​.

Influence of Vertebrate Excreta on Attraction, Oviposition and Development of the Asian Tiger Mosquito, Aedes albopictus (Diptera: Culicidae)

Simple Summary

Commonly known as the Asian tiger mosquito, Aedes albopictus is a vector of dengue worldwide. Knowledge of the behavior of dengue vectors facilitates effective vector control. This is the first comprehensive analysis of selected vertebrate excreta of goat, cow and pig to identify the oviposition attraction and growth performance of Ae. albopictus in Sri Lanka. The current study revealed that Ae. albopictus gravid females are significantly attracted to goat excreta but are repelled by pig excreta. The oviposition preference was highest for the cow excreta and lowest for the pig excreta. For excreta combinations, the Cow+Goat combination increased the oviposition while the Pig+Goat combination reduced the oviposition. The oviposition preference of Ae. albopictus increased with the rate of fermentation. The pig excreta increased the Ae. albopictus larval mortality, larval and pupal duration and reduced adult fecundity, whereas the cow excreta positively affected all these aspects. Additionally, our findings suggest that a high abundance of Ae. albopictus in rural areas of Sri Lanka is possibly due to its oviposition attraction and the growth performance of the vertebrate excreta.

Abstract

Aedes albopictus is an important vector of dengue worldwide. Eliminating dengue in Sri Lanka depends entirely on controlling the vector and human-vector contact. Thus, studying the bionomics and behavior of Ae. albopictus is paramount. The objective of this study was to evaluate the effect of the excreta of cow, goat and pig on the attraction, oviposition and development of Ae. albopictus. Bioassay chambers determined the mosquito stimulatory response. Ovitraps determined Ae. albopictus oviposition preference to excreta singly, in combination and on fermentation. The excreta effect on larval development was also determined. The results revealed that Ae. albopictus gravid females were significantly attracted to goat excreta but were repelled by pig excreta. The oviposition preference was highest for cow excreta and lowest for pig excreta. For excreta combinations, the Cow+Goat combination increased the oviposition while the Pig+Goat combination reduced the oviposition. The oviposition preference of Ae. albopictus increased with the rate of fermentation. The pig excreta increased the Ae. albopictus larval mortality, larval and pupal duration and reduced adult fecundity, whereas the cow excreta positively affected all these aspects. Our findings additionally suggest that a high abundance of Ae. albopictus in rural areas of Sri Lanka may be due to its oviposition attraction and growth performance for vertebrate excreta.

Symbiotic bacteria attenuate Drosophila oviposition repellence to alkaline through acidification

Metazoans harbor a wealth of symbionts that are ever-changing the environment by taking up resources and/or excreting metabolites. One such common environmental modification is a change in pH. Conventional wisdom holds that symbionts facilitate the survival and production of their hosts in the wild, but this notion lacks empirical evidence. Here, we report that symbiotic bacteria in the genus Enterococcus attenuate the oviposition avoidance of alkaline environments in Drosophila. We studied the effects of alkalinity on oviposition preference for the first time, and found that flies are robustly disinclined to oviposit on alkali-containing substrates. This innate repulsion to alkaline environments is explained, in part, by the fact that alkalinity compromises the health and lifespan of both offspring and parent Drosophila. Enterococcus dramatically diminished or even completely reversed the ovipositional avoidance of alkalinity in Drosophila. Mechanistically, Enterococcus generate abundant lactate during fermentation, which neutralizes the residual alkali in an egg-laying substrate. In conclusion, Enterococcus protects Drosophila from alkali stress by acidifying the ovipositional substrate, and ultimately improves the fitness of the Drosophila population. Our results demonstrate that symbionts are profound factors in the Drosophila ovipositional decision, and extend our understanding of the intimate interactions between Drosophila and their symbionts.

Diversity of bacteria in different life stages and their impact on the development and reproduction of Zeugodacus tau (Diptera: Tephritidae)

Fruit flies usually harbor diverse communities of bacteria in their digestive systems, which are known to play a significant role in their fitness. However, little information is available on Zeugodacus tau, a polyphagous pest worldwide. This study reports the first extensive analysis of bacterial communities in different life stages and their effect on the development and reproduction of laboratory-reared Z. tau. Cultured bacteria were identified using the conventional method, and all bacteria were identified by high-throughput technologies (16S ribosomal RNA gene sequencing of V3-V4 region). A total of six bacterial phyla were identified in larvae, pupae, and male and female adult flies, which were distributed into 14 classes, 32 orders, 58 families and 96 genera. Proteobacteria was the most represented phylum in all the stages except larvae. Enterobacter, Klebsiella, Providencia, and Pseudomonas were identified by conventional and next-generation sequencing analysis in both male and female adult flies, and Enterobacter was found to be the main genus. After being fed with antibiotics from the first instar larvae, bacterial diversity changed markedly in the adult stage. Untreated flies laid eggs and needed 20 days before oviposition while the treated flies showed ovary development inhibited and were not able to lay eggs, probably due to the alteration of the microbiota. These findings provide the cornerstone for unexplored research on bacterial function in Z. tau, which will help to develop an environmentally friendly management technique for this kind of harmful insect.