Suitable Host Plants Research Articles

The Potential of Using Different Legume Species in a Push–Pull Approach to Manage Spodoptera frugiperda in Maize in China

ABSTRACTFall armyworm (FAW), Spodoptera frugiperda (Smith), a notorious pest native to the tropical and subtropical Americas, has recently invaded China, causing substantial damage to crops, particularly maize. The push–pull strategy has been reported to be an effective prevention measure for FAW in Africa, with maize–soybean intercropping significantly reducing FAW infestation. To assess the potential of legume hosts as ‘push’ or ‘pull’ plants to control FAW in maize, we employed life table analysis and indoor cage tests to investigate the offspring performance, feeding and oviposition preference of FAW on five selected legume species, namely mung bean (Vigna radiata L.), soybean (Glycine max L.), kidney bean (Phaseolus vulgaris L.), red bean (Vigna angularis Willd.) and cowpea (Vigna unguiculata L. Walp), with maize (Zea mays L.) as a control. Mung bean and cowpea were subsequently selected as repellent and attractant plant, respectively, to study FAW infestation levels in maize in the field. The results showed that maize was the most suitable host plant for FAW, as indicated by its shortest developmental duration and highest pupal weight. However, among all the tested legume species, cowpea was the best host for FAW, with shorter larval, pre‐adult and adult durations than on the leaves of the other legumes. Moreover, the feeding and oviposition preference tests revealed that FAW had a strong preference for maize and cowpea, but strongly rejected mung bean. Compared with that in the maize monoculture group, the total number of eggs laid in the maize–mung group decreased by 67.25%, whereas that in the maize–cowpea group significantly increased by 2.04‐fold in greenhouse tests. In the randomised block field experiment, the infestation of maize by FAW in the mung bean–cowpea system was significantly lower than that in the maize monoculture or in the system with maize surrounded only by cowpea. This study indicated that mung bean and cowpea are promising candidates as repellent plants (push) and attractant plants (pull), respectively, for intercropping with maize to reduce the damage caused by FAW.

The systemic herbicide glyphosate affects the sporulation dynamics of Rhizophagus species more severely than mechanical defoliation or the contact herbicide diquat.

Arbuscular mycorrhizal fungi (AMF) are totally dependent on a suitable host plant for their carbon resources. Here, we investigated under in vitro conditions, the impact of defoliation practices, i.e., mechanical defoliation or chemical defoliation with a contact herbicide (Reglone®, containing the active ingredient diquat) or systemic herbicide (RoundUp®, containing the active ingredient glyphosate),on the dynamics of spore production of Rhizophagus irregularis and Rhizophagus intraradices associated with Solanum tuberosum and/or Medicago truncatula. Glyphosate affected the spore production rate more rapidly and severely than diquat or mechanical defoliation. We hypothesize that this effect was related to disruption of the C metabolism in the whole plant combined with a possible direct effect of glyphosate on the fungus within the roots and/or perhaps in soil via the release of this active ingredient from decaying roots. No glyphosate could be detected in the roots due to technical constraints, while its release from the roots in the medium corresponded to 0.11% of the active ingredient applied to the leaves. The three defoliation practices strongly affected root colonization, compared to the non-defoliated plants. However, the amount of glyphosate released into the medium did not affect spore germination and germ tube growth. These results suggest that the effects of defoliation on the dynamics of spore production are mainly indirect via an impact on the plant, and that the effect is faster and more marked with the glyphosate-formulation, possibly via a direct effect on the fungus in the roots and more unlikely on spore germination.

Oviposition behaviour and larval attraction of the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) to different maize plant varieties for pest management in Nigeria

Phytophagous insects likely select suitable host plants for oviposition based on olfactory and tactile cues. However, details of how insects differentiate among different plant varieties are often unclear. The fall armyworm (Spodoptera frugiperda J. E. Smith) is a highly destructive pest on maize, but little is known about the attraction and oviposition preference of S. frugiperda to different maize varieties, particularly in the context of sub-Saharan Africa, where the insect is a major threat to maize production. We determined the oviposition preference of S. frugiperda females on six different maize plant varieties three of which were hybrid varieties and three were open-pollinated varieties, in multiple-choice and no-choice assays. We also evaluated the attraction preference of S. frugiperda larvae on these maize varieties, using an olfactometer bioassay. We found that S. frugiperda females oviposited significantly less egg masses on the hybrid varieties DEKAIB and 30Y87 than on the other varieties tested and that females oviposited less on the hybrid maize varieties compared to the open-pollinated maize varieties overall. Additionally, we found that S. frugiperda larvae were more attracted to the open-pollinated variety LMFP than to clean air, which was not the case for any of the other maize varieties tested. Taken together, our results show that S. frugiperda responds differentially to the different maize varieties and that hybrid maize varieties seem less attractive. Further investigating the chemistry of hybrid maize varieties like DEKAIB might yield clues on how to breed maize varieties with increased resistance against S. frugiperda infestation.

Pastoral grasses and legumes as potential host plants for fall armyworm Spodoptera frugiperda (J.E. Smith) development.

AbstractThe fall armyworm, Spodopterafrugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a highly polyphagous, migratory pest native to the tropical and subtropical region of Americas. Grass crops particularly corn have been most heavily impacted since S. frugiperda invaded Australia in 2020. In northern Western Australia, S. frugiperda is primarily a problem in dry season (May to October) crops when there are abundant host plants available in monocultures. During the wet season (November to April) it is not known what host plants may support larval growth and development. Accordingly, this present study undertook a no-choice feeding bioassay to assess larval and pupal development on several grasses and legumes that are present over the wet season in northern Western Australia to evaluate their potential as suitable host plants for S. frugiperda. Maize (control) and sorghum were the most suitable hosts for S. frugiperda development as they supported greater larval and pupal survival, heavier larvae and pupae, and shorter development period. Following maize and sorghum, pastoral grasses, particularly blue grass, and a weedy grass, barnyard grass, had comparable effects on larval and pupal development. Legume pastures (Cavalcade, butterfly pea, and siratro) were unsuitable hosts in this bioassay as very few larvae completed their development to adults. This study demonstrates the potential for rangeland pasture grasses and weedy grasses as wet season host plants for S. frugiperda. They provide the necessary green bridge for S. frugiperda populations to survive. It is recommended that pastoralists monitor their grass forage for S. frugiperda and consider management if significant reductions in biomass are detected.

Off-season survival and life history of beet armyworm, Spodoptera exigua (Hubner) on various host plants

The beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae), has become a significant pest of chickpea in recent years. The polyphagous nature allows it to survive on various hosts during the off-season, creating a great menace to the crop in the following season. To assess the incidence and document the alternate hosts of S. exigua, a rapid roving survey was conducted in 11 chickpea-growing areas of Prakasam district, Andhra Pradesh, India. Additionally, the life history traits of S. exigua were studied on major alternate host plants under laboratory conditions (27 ± 1 °C and 70 ± 2% RH) to understand the survival, life expectancy and potential contribution to future populations. The results show that, among the different crops surveyed, the maximum larval incidence was noticed in maize (1.93 larvae/plant), cowpea (1.73 larvae/plant), and sunflower (1.68 larvae/plant) during the off-season. Life history studies of S. exigua showed that highest larval survival percentage was observed on chickpea (83.6%), while the lowest was on maize (44.5%). The mean developmental time for larvae was longest on maize (27.1 days) and shortest on chickpea (14.9 days). Larvae did not develop beyond the third instar when fed with chilli. The growth index statistics showed chickpea (9.2) was the most suitable host plant, whereas maize (0.9) was the least suitable host. The age-stage-specific survival rate (Sxj) varied across developmental stages, and the survival curves overlapped, indicating different growth rates among individuals. The life expectancy (exj) at age zero was highest on groundnut (37.06 days). The intrinsic rate of increase (r) of S. exigua was lowest on maize (0.10 ± 0.0013) and highest on chickpea (0.22 ± 0.0010). Similarly, the net reproductive rate (R0) was highest on chickpea (846.39 ± 18.22) and lowest on maize (59.50 ± 2.06). The population doubled every 3.08 ± 0.011 days on chickpea compared to 7.22 ± 0.80 days on maize. The study conclusively indicates that chickpea and sunflower, primarily cultivated during the rabi season in India, are the most preferred hosts for S. exigua. In contrast, maize and cotton, mainly grown during the kharif season, are less preferred and merely support the pest's survival. Consequently, S. exigua switches hosts between different crops growing seasons, so effective management of S. exigua during the kharif season can help prevent pest outbreaks during the rabi season.

SCREEN-HOUSE REARING OF THE CASHEW MIRID HELOPELTIS SCHOUTEDENI REUTER (HETEROPTERA: MIRIDAE) ON THREE VEGETABLES FOR ITS MANAGEMENT ON CASHEW

Helopeltis schoutedeni (Heteroptera: Miridae) is a significant cashew and cotton pest in East and West Africa. To date, viable laboratory rearing and maintenance protocols have been lacking to facilitate biological investigations on the bug. This drawback has largely hindered its successful management. The potential of three vegetable intercrops, cucumber fruit (Cucumis sativus L.), fresh French bean (Phaseolus vulgaris L.) pods, and pigeon pea (Cajanus cajan L.) were the suitable host plants for establishing laboratory colonies of H. schoutedeni. The developmental time, survival, oviposition, and feeding behaviors of H. schoutedeni under screen-house conditions were monitored. Newly hatched nymphs reared on these substrates successfully developed into adults with varying average developmental times of 25.72, 25.81, and 33.26 days for French beans, pigeon peas, and cucumbers, respectively. Similarly, survival varied significantly on the different plants, with the highest survival occurring on pigeon pea seedlings (97-100%) and the lowest on cucumber (48-69%; P < 0.05). Significantly more feeding lesions were recorded on pigeon peas (349.6 ± 82.56) than on cucumbers (52.6 ± 13.62) in the feeding preference test. The proportion of adult feeding during the scotophase was significantly higher than in the photophase (Pigeon pea seedling: t = -3.545; df = 18; P < 0.05, French beans: t = -2.684; df = 28; P < 0.05 and Cucumber t = 3.713; df = 18; P < 0.05). Oviposition was only recorded on pigeon pea seedlings. Present findings demonstrate the potential for using specific vegetables as suitable host plants for H. schoutedeni under confined and open field settings to aid future research studies toward effective management.. KEYWORDS :Cashew, Helopletis Schoutedeni, Legumes, Pest Management, Rearing

Indirect effects of plasma-activated water irrigation on Tetranychus urticae populations

AbstractPlasma-activated water (PAW) is receiving increased attention as a booster of seed germination and seedling vigor, and some studies have described use of PAW to manage crop pathogens. Here, we examined physicochemical properties of two PAWs (referred to as PAW 6.0 and 9.4 min with atmospheric plasma jet) and assessed “their indirect effects” (applied as supplementary irrigation) on host suitability of tomato plants (Solanum lycopersicum L.) to two-spotted spider mites (Tetranychus urticae Koch). Exposure of water to cold plasma significantly lowered pH and increased concentrations of H2O2, NO2−, and NO3−. Supplementary PAW irrigations elicited significant increases in leaf composition of several elements (N, P, K S, Ca, and Mg), leaf reflectance, plant size, and trichome densities (except non-glandular trichomes on the adaxial surface). Preference bioassays revealed significant avoidance of settling and reduced oviposition by two-spotted spider mites on leaf discs from PAW-irrigated plants compared to those from untreated control plants. Performance bioassays showed a significant decrease in two-spotted spider mite populations on PAW-irrigated plants. Results presented in this study provide comprehensive support to the hypothesis that indirect effects of supplementary PAW irrigation significantly reduce host plant suitability to two-spotted spider mites. PAW 6.0 may be slightly better than PAW 9.4, and this difference in performance is discussed in this study. Applications of PAW as supplementary irrigation are likely highly compatible with other IPM tactics and should be considered an innovative and sustainable component in twenty-first-century pest management.

Characterization of arbuscular mycorrhizal fungal species associating with Zea mays.

Taxonomic identification of arbuscular mycorrhizal (AM) fungal spores extracted directly from the field is sometimes difficult because spores are often degraded or parasitized by other organisms. Single-spore inoculation of a suitable host plant allows for establishing monosporic cultures of AM fungi. This study aimed to propagate AM fungal spores isolated from maize soil using single spores for morphological characterization. First, trap cultures were established to trigger the sporulation of AM fungal species. Second, trap cultures were established with individual morphotypes by picking up only one spore under a dissecting microscope and transferring it to a small triangle of sterilized filter paper, which was then carefully inoculated below a root from germinated sorghum seeds in each pot and covered with a sterile substrate. All pots were placed in sunbags and maintained in a plant growth room for 120 days. Spores obtained from single spore trap cultures from each treatment, maize after oats (MO), maize after maize (MM), maize after peas (MP), and maize after soybean (MS), were extracted using the sieving method. Healthy spores were selected for morphological analysis. Direct PCR was conducted by crushing spores in RNAlater and applying three sets of primer pairs: ITS1 × ITS4, NS31 × AML2, and SSUmcf and LSUmBr. Nucleotide sequences obtained from Sanger sequencing were aligned on MEGA X. The phylogenetic tree showed that the closest neighbors of the propagated AM fungal species belonged to the genera Claroideoglomus, Funneliformis, Gigaspora, Paraglomus, and Rhizophagus. The morphological characteristics were compared to the descriptive features of described species posted on the INVAM website, and they included Acaulospora cavernata, Diversispora spurca, Funneliformis geosporus, Funneliformis mosseae, Gigaspora clarus, Gigaspora margarita, Glomus macrosporum, Paraglomus occultum, and Rhizophagus intraradices. These findings can provide a great contribution to crop productivity and sustainable management of the agricultural ecosystem. Also, the isolate analyzed could be grouped into efficient promoters of growth and mycorrhization of maize independent of their geographical location.

CULTURABLE ENDOSYMBIOTIC BACTERIA FROM THE INDIAN LAC INSECT, KERRIA LACCA (KERR)

The Indian lac insect, Kerria lacca (Kerr) (Coccoidea: Tachardiidae) is a commercially important phytosuccivorous and sessile scale insect. Lac insects are cultured on suitable host plants in India and some Southeast Asian countries to produce lac. The lac insect harbours a number of endosymbionts. Isolation of culturable microbial endosymbionts and their identification through 16S rRNA has revealed sex and host-related differences of microbial species. Bacillus boroniphilus, Enterobacter cloacae and Staphylococcus sp. were found only in the lac insects reared on the plant host Cajanus cajan, whereas Bacillus firmus, Lysinibacillus xylanilyticus, Bacillus horneckiae and Bacillus velezensis were recorded only from Flemingia macrophylla. B. firmus and L. xylanilyticus were female-specific and B. horneckiae and B. velezensis were male-specific with Flemingia macrophylla as host; E. cloacae was female-specific and Bacillus boroniphilus and Staphylococcus sp. were male specific with C. cajan. Biochemical characteristics of the isolates, their genetic relationship with their taxonomic kin and their probable role, based on the information available about these endosymbionts in other hosts, have been studied.

Negative association between host plant suitability and the fitness cost of resistance to Bacillus thuringiensis (Bacillales:Bacillaceae).

Transgenic crops producing Bacillus thuringiensis (Bt) toxins are commonly used for controlling insect pests. Nearby refuges of non-Bt host plants play a central role in delaying the evolution of resistance to Bt toxins by pests. Pervasive fitness costs associated with resistance, which entail lower fitness of resistant than susceptible individuals in refuges, can increase the ability of refuges to delay resistance. Moreover, these costs are affected by environmental factors such as host plant suitability, implying that manipulating refuge plant suitability could improve the success of the refuge strategy. Based on results from a previous study of Trichoplusia ni resistant to Bt sprays, it was proposed that low-suitability host plants could magnify costs. To test this hypothesis, we investigated the association between host plant suitability and fitness costs for 80 observations from 30 cases reported in 18 studies of 8 pest species from 5 countries. Consistent with the hypothesis, the association between plant suitability and fitness cost was negative. With plant suitability scaled to range from 0 (low) to 1 (high), the expected cost was 20.7% with a suitability of 1 and the fitness cost increased 2.5% for each 0.1 decrease in suitability. The most common type of resistance to Bt toxins involves mutations affecting a few types of midgut proteins to which Bt toxins bind to kill insects. A better understanding of how such mutations interact with host plant suitability to generate fitness costs could be useful for enhancing the refuge strategy and sustaining the efficacy of Bt crops.

Struggling to survive: A comparison of Vanessa cardui larval survivorship on putative host plants

AbstractThe painted lady butterfly (Vanessa cardui) is a generalist herbivore with a global distribution. In North America, over 100 species have been identified as V. cardui larval host plants. This cosmopolitan species is commercially available in all life stages and can be reared on an artificial diet. As a result, V. cardui commonly serves as a model organism for education and outreach. However, gaps in our knowledge remain with regard to V. cardui ecology and larval host plant suitability for supporting complete development of larvae to reproductive adulthood. In a laboratory setting, we tested host plant suitability of five reported host plants commonly found in California sage scrub ecosystems by assessing survival of V. cardui caterpillars in its entirety. We also assessed how commercially sourced larvae survived on artificial diet: both raising the caterpillars exclusively on artificial diet as well as switching diets from artificial to thistle (a commonly reported host plant) and switching from thistle to artificial diet. We found that all commercially sourced caterpillars exhibited both high larval mortality and low pupation rates when reared on host plants, although larvae reared on Malacothamnus fasciculatus and Sphaeralcea ambigua survived longest. Moreover, M. fasciculatus and S. ambigua were the only host plants tested that supported successful pupation. This contrasted with 63% higher survival of wild‐collected larvae. Our findings suggest that commercially obtained V. cardui may struggle to utilize wild host plants and that future investigations into host plant suitability in wild populations are needed. Additionally, future research using commercial larvae should consider the implications for interpreting host plant suitability as larvae may exhibit adaptations to artificial diet or the loss of adaptation to consuming plant material.

Electrophysiological and Behavioral Responses of Batocera horsfieldi Hope to Volatiles from Pistacia chinensis Bunge.

Following infestation by phytophagous insects, changes in the composition and relative proportion of volatile components emitted by plants may be observed. Some phytophagous insects can accurately identify these compounds to locate suitable host plants. We investigated whether herbivore-induced plant volatiles (HIPVs) generated by herbivory on Pistacia chinensis Bunge (Sapindales: Aceraceae) might be semiochemicals for the host location of Batocera horsfieldi Hope (Coleoptera: Cerambycidae). We performed two-choice bioassays (indoor darkroom, inside cages) on plants damaged by adult feeding and intact control plants. Volatiles from these plants were then collected and identified, and the response of adult antennae to these compounds was tested via electroantennography (EAG). The behavioral responses of B. horsfieldi to these compounds were finally assessed using a Y-tube olfactometer. Host plant choice tests show that B. horsfieldi prefers feeding-damaged P. chinensis over healthy trees. In total, 15 compounds were collected from healthy and feeding-damaged P. chinensis, 10 of which were shared in both healthy and feeding-damaged P. chinensis, among which there were significant differences in the quantities of five terpenes, including α-pinene, β-pinene, α-phellandrene, D-limonene, and β-ocimene. In EAG assays, the antennae of B. horsfieldi adults responded strongly to (Z)-3-hexen-1-ol, β-ocimene, 3-carene, γ-terpinene, D-limonene, myrcene, and α-phellandrene. The antennae of B. horsfieldi adults responded in a dose-response manner to these compounds. Y-tube behavioral experiments showed that four compounds attracted mated females ((Z)-3-hexen-1-ol, β-ocimene, 3-carene, and α-phellandrene), two compounds ((Z)-3-hexen-1-ol and α-phellandrene) attracted males, and adults of both sexes avoided D-limonene. Feeding bioassays showed that (Z)-3-hexen-1-ol and β-ocimene could promote the feeding of B. horsfieldi and that D-limonene inhibited this response. These results could provide a theoretical basis for developing attractants or repellents for B. horsfieldi.

Biology of the Endemic Endangered Swallowtail Butterfly, Papilio desmondi teita (Lepidoptera: Papilionidae), on Wild Citrus Species in Taita Hills, Kenya

The Taita Hills swallowtail butterfly, Papilio desmondi teita, was reared in captivity on wild citrus (Rutaceae), Toddalia asiatica and Clausena anisata, in Ngangao Forest, Taita Hills, Kenya. The butterflies were exposed to the host plants for oviposition inside the laying buckets under ambient laboratory conditions. Results revealed that P. desmondi teita could only complete development on T. asiatica and but not on C. anisata in both seasons. The egg incubation period on T. asiatica was significantly shorter ( P < 0.001) compared to C. anisata during the first season ( P = 0.595) but not in the second season. The development period of the butterfly in 1st and 2nd seasons on T. asiatica was 81.13 ± 0.44 days and 112.15 ± 1.20 days, respectively, while a female-biased sex ratio was observed in the first and second seasons. Findings from this study indicate that T. asiatica was the most suitable host plant for development of P. desmondi teita.

Adaptability of Toxoptera aurantii (Hemiptera: Aphididae) to Different Tea Cultivars

The adaptability of phytophagous insects to different host plants is a key determinant of their population propagation. Understanding the feeding behaviour and population dynamics of insects is crucial for elucidating host adaptability and screening for insect-resistant germplasms. Here, we investigated Toxoptera aurantii (Hemiptera: Aphididae) adaptability using electropenetrography and assessed its population growth on seven tea cultivars: Huangjinya (HJY), Qianmei601 (QM601), Fudingdabaicha (FD), Longjing43 (LJ43), Qiancha1 (QC1), Qiancha8 (QC8) and Qiancha10 (QC10). The results showed that the feeding behaviour of T. aurantii differed significantly depending on the tea cultivars. The initial probing of T. aurantii on HJY was the earliest among the seven host plants. Aphids on QC1 and QC10 displayed an increased duration of stylet probing and decreased ingestion of phloem sap, whereas a contrasting trend was observed for aphids on HJY. In addition, the mechanical resistance of T. aurantii fed on HJY and QM601 during the probing phase was significantly lower than that of aphids fed on other cultivars. Population dynamic parameters revealed that the growth rate of T. aurantii reared on HJY was the fastest, and its population quantity within 15 days was markedly higher than that of aphids fed on other cultivars. These findings demonstrate that HJY is the most suitable host plant, whereas QC1 and QC10 are less suitable hosts for T. aurantii, although the aphids successfully survived on all the selected tea cultivars. Our results provide valuable information for the biological control of T. aurantii using resistant tea varieties.

Diversity, Seasonal Dynamics and Host Plants of Butterflies in Forest Research Centre, Siddipet, Telangana, India

Aim: This study aims at bringing out butterfly diversity through species richness, seasonal distribution and suitable host plant preferences of identified butterflies in Forest Research Centre, Siddipet, Telangana, India.
 Study Design: Line Transect Method is followed.
 Place and Duration of the Study: The study was conducted in Forest Research Centre (FRC), Siddipet, Telangana, India during 2021-2022.
 Methodology: Five line transects are laid across the research centre which are surveyed both in morning and afternoon at 9-11AM and 4-6PM respectively across the season viz., rainy, winter and summer seasons. Species identification was done based on the visual and photographical observations.
 Results: The study revealed a butterfly species richness of 53, spanning 39 genera and distributed across five families. These families included Nymphalidae (23 species), Pieridae (12 species), Lycaenidae (10 species), Papilionoidae (6 species), and Hesperiidae (2 species). When it came to host plant preferences, the butterflies showed a preference for families such as Fabaceae (23%), Malvaceae (16%), Capparaceae (12%), Acanthaceae (11%), and Poaceae (8%). Additionally, several other families, including Apocynaceae, Aristolochiaceae, Rhamnaceae, and Rutaceae, were found to host a few butterfly species. Regarding seasonal distribution, the study noted that butterfly species were more abundant during the winter season, followed by the rainy season, with the summer season exhibiting a significant difference in distribution and occurrence compared to the other two seasons.
 Conclusion: From the study, it can be concluded that FRC reported a diverse range of butterflies distributed across all the seasons making it potential site for preservation and conservation of butterflies and its host species.

How host plants influence the life history and population growth of Myzus persicae (Hemiptera: Aphididae) and its parasitoid, Aphidius platensis (Hymenoptera: Braconidae)

ABSTRACT The effect of three host plants, sweet pepper, cucumber and eggplant, on the survival and fecundity of Myzus persicae (Sulzer) (Hem.: Aphididae) and population growth parameters of Aphidius platensis as a solitary endoparasitoid of green peach aphid were studied. The raw data were analysed using the age-stage, two-sex life table theory. The results showed that sweet pepper is the most suitable host plant for green peach aphid development and reproduction. The intrinsic rates of increase (r) of M. persicae reared on eggplant, sweet pepper and cucumber were 0.32 ± 0.01, 0.33 ± 0.01 and – 0.071 ± 0.06 d− 1, respectively. Furthermore, other population parameters of aphids raised on sweet pepper and eggplant were significantly higher than corresponding parameter values of aphids fed on cucumber plant. The intrinsic rate of increase (r) of A. platensis reared on sweet pepper was 0.29 ± 0.01 d− 1. The life expectancy (exj ) of A. platensis parasitised pepper raised green peach aphids was 21.08 days on the first day of emergence, and the maximum reproductive value of A. platensis females occurred on the 14th day. Our results showed that sweet pepper could serve as a suitable host plant for rearing M. persicae as a host for A. platensis within a biological control programme context according to the pre-adult period, survival, adult longevity and fecundity of M. persicae. This information could be useful for mass rearing of A. platensis in insectariums where the faster growth and development of aphids are desirable.

Host Suitability of Tobacco Leaf Eating Caterpillar (Spodoptera litura F.) under Laboratory Condition

A study was conducted at the Bidi Tobacco Research Station, AAU, Anand laboratory during kharif (June-October 2021) to determine the most suitable host plant of S. litura among the groundnut, tobacco and castor. A statistically designed lab experiment using Completely Randomized Design (CRD) having twenty-five Repetitions and three treatments was laid out. Total life span of S. litura was longer on castor followed by groundnut and least duration was observed on tobacco. The egg hatching % was found more or less similar in each of host crop. Eggs were clustered and covered in tiny buff-colored hairs that resembled hairs on the gravid female’s abdomen tip. The total larval period from the first to sixth instar was recorded longer on castor followed by on groundnut and tobacco. Last larval instar was very active and consuming prolifically on leaves, resulting in the whole leaf being fed with just the mid rib remaining. The pupal period was found similar on three different hosts. Pupa become shiny, greenish in color after that color change from greenish to brownish yellow to light brown to dark brown in color with shiny appearance. Adult longevity of both male and female was found to be longer on castor followed by groundnut and tobacco. Adult moths (both male and female) were yellowish brown in colour, with a prominent head and black compound eyes. The female was somewhat bigger and stouter than the male. Fecundity (egg masses female-1) of adult female was noticed similarly in different host crops. Sex ratio of S. litura on groundnut was 1:1, on castor 1:1.09 and on tobacco 1:1.38.

Chemical Ecology and Management of Dengue Vectors.

Dengue, caused by the dengue virus, is the most widespread arboviral infectious disease of public health significance globally. This review explores the communicative function of olfactory cues that mediate host-seeking, egg-laying, plant-feeding, and mating behaviors in Aedes aegypti and Aedes albopictus, two mosquito vectors that drive dengue virus transmission. Aedes aegypti has adapted to live in close association with humans, preferentially feeding on them and laying eggs in human-fabricated water containers and natural habitats. In contrast, Ae. albopictus is considered opportunistic in its feeding habits and tends to inhabit more vegetative areas. Additionally, the ability of both mosquito species to locate suitable host plants for sugars and find mates for reproduction contributes to their survival. Advances in chemical ecology, functional genomics, and behavioral analyses have improved our understanding of the underlying neural mechanisms and reveal novel and specific olfactory semiochemicals that these species use to locate and discriminate among resources in their environment. Physiological status; learning; and host- and habitat-associated factors, including microbial infection and abundance, shape olfactory responses of these vectors. Some of these semiochemicals can be integrated into the toolbox for dengue surveillance and control.

A Faboideae-Specific Floral Scent Betrays Seeds to an Important Granivore Pest.

Seed predation by insect herbivores reduces crop production worldwide. Foraging on seeds at pre-dispersal generally means that females need to find the suitable host plant within a relatively short timeframe in order to synchronize larval development with seed production. The mechanistic understanding of host finding by seed pests can be harnessed for more sustainable pest management strategies. We here studied the chemical communication between the bean bug Riptortus pedestris, a major pest of legumes, and several crop species and cultivars in the Fabaceae. Via a comparative chemical analysis, we found that 1-octen-3-ol is the principal constituent of the floral scents of most species tested in the subfamily Faboideae, including soybean and faba bean. With field trapping and laboratory bioassays, including electroantennography, we further revealed that this compound can be perceived, and stimulate attraction responses, by R. pedestris nymphs and adults. The addition of 1-octen-3-ol to pheromone traps might therefore improve trapping efficacy for controlling populations of this important granivore pest on legumes.

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.