Sap-sucking Pests Research Articles

Shifts in Pseudomonas species diversity influence adaptation of brown planthopper to changing climates and geographical locations

SummaryThe brown planthopper (BPH) is a monophagous sap-sucking pest of rice that causes immense yield loss. The rapid build-up of pesticide resistance combined with the ability of BPH populations to quickly overcome host plant resistance has rendered conventional control strategies ineffective. One of the likely ways in which BPH adapts to novel environments is by undergoing rapid shifts in its microbiome composition. To elucidate the rapid adaptation to novel environments and the contributions of Pseudomonas toward insect survival, we performed Pseudomonas-specific 16S rRNA gut-microbiome profiling of BPH populations. Results revealed the differential occurrence of Pseudomonas species in BPH populations with changing climates and geographical locations. Further, the observed variation in Pseudomonas species composition and abundance correlated with BPH survivability. Collectively, this study, while adding to our current understanding of symbiont-mediated insect adaptation, also demonstrated a complex interplay between insect physiology and microbiome dynamics, which likely confers BPH its rapid adaptive capacity.

Control of a sap-sucking insect pest by plastid-mediated RNA interference

Expression of double-stranded RNAs in plastids offers great potential for the efficient control of chewing insects. However, many insect pests do not consume plant tissue but rather feed on the host plant by sucking sap from the vascular system. Whether or not plastid-mediated RNA interference (RNAi) can be employed to control sap-sucking insects is unknown. Here, we show that five species of sap-sucking hemipteran insects acquire plastid RNA upon feeding on plants. We generated both nuclear transgenic and transplastomic tobacco plants expressing double-stranded RNAs targeting the MpDhc64C gene, a newly identified efficient target gene of RNAi whose silencing causes lethality to the green peach aphid Myzus persicae. In a whole-plant bioassay, transplastomic plants exhibited significant resistance to aphids, as evidenced by reduced insect survival, impaired fecundity, and decreased weight of survivors. The protective effect was comparable with that conferred by the best-performing nuclear transgenic plants. We found that the proportion of aphids on mature leaves of transplastomic plants was significantly lower compared with that of nuclear transgenic plants. When aphids were allowed to infest only the mature leaves, transplastomic plants grew significantly faster and were overall better protected from the pest compared with nuclear transgenic plants. When monitored by electrical-penetration-graph analyses and aphid avoidance response experiments, the insects displayed remarkable alterations in feeding behavior, which was different in nuclear transgenic and transplastomic plants, likely reflecting specific avoidance strategies to toxic RNA molecules. Taken together, our study demonstrates that plastid-mediated RNAi provides an efficient strategy for controlling at least some sap-sucking insect pests, even though there is most likely no or only very little chloroplast RNA in the sap.

Reactive Oxygen Species Initiate Defence Responses of Potato Photosystem II to Sap-Sucking Insect Feeding.

Simple SummaryPotato is one of the most universally cultivated horticultural crops and is vulnerable to a range of herbivorous insects. One of them is the brown marmorated stink bug, an invasive polyphagous sap-sucking agricultural insect pest that penetrates the phloem to sieve elements and removes sap via a specialized mouthpart, the stylet. By using the chlorophyll fluorescence imaging methodology, we examined potato photosystem II (PSII) photochemistry responses in the area of feeding on the whole leaf area. Highly increased reactive oxygen species (ROS) generation was observed as rapidly as 3 min after feeding to initiate defence responses and can be considered the primary plant defence response mechanism against herbivores. Our experimental results confirmed that chlorophyll fluorescence imaging methodology can detect spatial heterogeneity of PSII efficiency at the whole leaf surface and is a promising tool for investigating plant response mechanisms of sap-sucking insect herbivores. We suggest that PSII responses to insect feeding underlie ROS-dependent signalling. We conclude that the potato PSII response mechanism to sap-sucking insect herbivores is described by the induction of the defence response to reduce herbivory damage, instead of induction of tolerance, through a compensatory photosynthetic response mechanism that is observed after chewing insect feeding.Potato, Solanum tuberosum L., one of the most commonly cultivated horticultural crops throughout the world, is susceptible to a variety of herbivory insects. In the present study, we evaluated the consequence of feeding by the sap-sucking insect Halyomorpha halys on potato leaf photosynthetic efficiency. By using chlorophyll fluorescence imaging methodology, we examined photosystem II (PSII) photochemistry in terms of feeding and at the whole leaf area. The role of reactive oxygen species (ROS) in potato’s defence response mechanism immediately after feeding was also assessed. Even 3 min after feeding, increased ROS generation was observed to diffuse through the leaf central vein, probably to act as a long-distance signalling molecule. The proportion of absorbed energy being used in photochemistry (ΦPSII) at the whole leaf level, after 20 min of feeding, was reduced by 8% compared to before feeding due to the decreased number of open PSII reaction centres (qp). After 90 min of feeding, ΦPSII decreased by 46% at the whole leaf level. Meanwhile, at the feeding zones, which were located mainly in the proximity of the leaf midrib, ΦPSII was lower than 85%, with a concurrent increase in singlet-excited oxygen (1O2) generation, which is considered to be harmful. However, the photoprotective mechanism (ΦNPQ), which was highly induced 90 min after feeding, was efficient to compensate for the decrease in the quantum yield of PSII photochemistry (ΦPSII). Therefore, the quantum yield of non-regulated energy loss in PSII (ΦNO), which represents 1O2 generation, remained unaffected at the whole leaf level. We suggest that the potato PSII response to sap-sucking insect feeding underlies the ROS-dependent signalling that occurs immediately and initiates a photoprotective PSII defence response to reduce herbivory damage. A controlled ROS burst can be considered the primary plant defence response mechanism to herbivores.

Insecticidal and Enzyme Inhibition Activities of Leaf/Bark Extracts, Fractions, Seed Oil and Isolated Compounds from Triadica sebifera (L.) Small against Aphis craccivora Koch.

Aphid, Aphis craccivora Koch (Hemiptera: Aphididae), is a major sap-sucking insect pest of leguminous crops and also transmits plant viruses, leading to economic yield loss. Indiscriminate and repeated use of insecticides for control of aphid leads to the development of resistance, and is harmful to the environment, non-target organisms, etc. Plant-based extracts/seed oils (SO) are the best alternatives to insecticides. Insecticidal activities of Triadica sebifera have not been reported against A. craccivora and other insect pests to date. In the current study, the main objective was to study the insecticidal activities of leaf/bark extracts/fractions, seed oil, isolated compounds, and their combinations against A. craccivora. Results showed that, among the extracts, ethanolic bark extract 80% (LC50 = 5115.98 mg/L) was more effective against A. craccivora. Among fractions, the n-hexane fraction of leaves (LC50 = 425.73 mg/L) and the ethyl acetate fraction of bark (LC50 = 813.45 mg/L) were promising. Among compounds, gallic acid was the most effective (LC50 = 1303.68 mg/L) compared to shikimic acid and quercetin. SO (LC50 = 850.94 mg/L) was superior compared to extracts/fractions/compounds. All the combinations showed toxicity and synergistic activity. Leaf/bark extracts and SO significantly inhibited the AChE and GST activity in A. craccivora. Based on field bio-efficacy, the leaf extract/SO or their combinations can be recommended for the control of aphids.

Biological evidences for successive oogenesis and egg-laying of Matsumurasca onukii.

Tea plant (Camellia sinensis) is one of the most important horticultural cash crops, and tea green leafhopper (Matsumurasca onukii) is an extremely harmful sap-sucking pest of tea plant. Serious generation overlapping, which is mainly caused by the long oviposition period, leads to poor control effect of pesticides on this pest in the tea plantation. But the intuitive evidences of continuous oogenesis and egg-laying of this pest are still lacking, which seriously hindered the development of genetic control methods. Here, we clarified the main structures of the inner reproductive system of tea green leafhopper female adult. Oviposition behaviors were monitored as well, and six oviposition steps were recorded. According to the maturity of oocytes, the maturity stages of the reproductive system under different copulation periods were classified into 4 stages. For female adults at stage IV, mature and immature oocytes were presented simultaneously, and the developmental levels of oocytes were asynchronous among different ovarioles. The proportion of gravid females with mature oocytes significantly increased when the continuous copulation time was prolonged. In sync with the development of the ovary maturity, female adults started to slightly deposit eggs at the 5th day, and then increased dramatically. In addition, we found that, whether mature or immature, oocytes in the ovarioles always emitted green fluorescence under blue light excitation, which in turn provide solid proof for the new egg detection method from the insect physiology point of view.

Multiple factors mediate insecticide toxicity to a key predator for cotton insect pest management.

Mortality of agricultural pests caused by arthropod predators is a valuable ecosystem service for crop production. The earwig, Euborellia annulipes (Lucas), attacks different pest species in various crop ecosystems, including larvae and pupae of the boll weevil, Anthonomus grandis grandis (Boh.). In this study, multiple factors were assessed to measure the selectivity of insecticides used against sap-sucking and chewing cotton pests for two E. annulipes populations. Nymphs and adults of E. annulipes were exposed to the insecticides in two ways: ingestion of contaminated prey, and contact with dried residues on either inert surfaces or treated plants bearing prey. Pymetrozine, chlorantraniliprole, and spinetoram had little effect on the predator regardless the tested earwig population, life stage with developmental time and survival, or the route of exposure (ingestion and residual). Cyantraniliprole dried-residue impeded nymph to complete development and only 27% of adults survived until 20 days after exposure. Pyriproxyfen was harmless through acute toxicity to nymphs and adult earwigs (70-100% survival 72 h after exposure), but prevented normal development of nymphs to adults causing chronic toxicity. Chlorfenapyr, indoxacarb, lambda-cyhalothrin, chlorpyrifos, dimethoate, and malathion were harmful to the predator regardless life stage or method of exposure. The negative impact of thiamethoxam, lambda-cyhalothrin and indoxacarb was diminished when exposure occurred on plants with predator allowed to shelter in the soil. The results indicate that insecticide selectivity outcome varies by the insecticide, predator life stage and the predator's behavior. Therefore, testing different predator life stages via several routes of exposure, without denying the insect the opportunity to engage in its normal behavior can provide better estimates of insecticide selectivity.

Fighting off the sucking pests of soybean: managing stink bugs and whiteflies

Stink bugs and whiteflies are major concerns for pest management in Brazilian soybean fields, causing severe economic losses to soybean growers and leading to excessive insecticide applications per crop cycle. Despite biological differences, these two sap-sucking pests often co-occur in soybean fields and can be successfully managed with the same insecticide spray, reducing operational costs to the growers. The aim of this work was to evaluate the efficacy of eleven insecticides in the control of stink bugs and whiteflies. Two insecticide sprays were made with an interval of 14 days between them. The results from ANOVA and Tukey post-hoc test (P≤0.05) revealed significant differences among treatments. Acetamiprid + bifenthrin (75 + 75 g a.i. ha-1) was the most efficient treatment for the control of stink bugs, reaching 97.8% of insect mortality. Cyantraniliprole + bifenthrin (50 + 50 g a.i. ha-1) was the most efficient treatment for the control of whiteflies, reaching 78.8% of insect mortality. This treatment also presented the highest combined control of stink bugs and whiteflies, reaching 83.5% of insect mortality

Priming of rice defense against a sap-sucking insect pest brown planthopper by silicon

Priming of rice defense against a sap-sucking insect pest brown planthopper by silicon

Inheritance and molecular tagging of genes introgressed from Gossypium arboreum to G. hirsutum for leafhopper tolerance

Cotton cultivation is conquered by transgenic Bt upland cotton hybrids in India. Bt gene does not provide resistance against sucking insect pests. Due to the inherent vulnerability of extant Bt cotton hybrids to sap-sucking insect pests including leafhopper, upland cotton cultivation is seriously threatened by surging populations of these pests. Consistent and extensive screening of upland cotton germplasm over the years has revealed absence of adequate resistance against leafhopper. Here, we report introgression of leafhopper tolerance from a diploid A-genome cotton species, Gossypium arboreum into G. hirsutum. The dominance of leafhopper tolerance was observed over its susceptibility. Genetic analysis revealed that tolerance to leafhopper was inherited in a simple Mendelian fashion and was controlled by two genes, either singly or in combination. Using bulked segregant analysis, two simple-sequence repeat markers, namely NAU 922 and BNL 1705, located on chromosomes A5 and A11 respectively, were tagged with leafhopper tolerance. To the best of our knowledge, this is the first report of molecular tagging of leafhopper tolerance introgressed from G. arboreum into G. hirsutum. A significant negative association was observed between leaf trichome density and leafhopper nymph population.

A New Mitochondrial Genome of Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) and Mitogenome-Wide Investigation on Polymorphisms.

Simple SummaryWe completed one mitogenome of white-backed planthopper (WBPH), Sogatella furcifera (Horváth), with finding heteroplasmy phenomenon confirmed by PCR reaction and Sanger sequencing method. This heteroplasmy was not observed in WBPHs (n = 24) collected from the fields, suggesting that it may be uncommon in fields. We also analyzed single nucleotide polymorphisms, insertion and deletions, and simple sequence repeats among three currently available WBPH mitogenomes of Korea and China, suggesting that identified intraspecific variations could be potential candidates for developing markers to distinguish geographical populations of WBPH including Korean and Chinese. Phylogenetic analysis of 32 mitogenomes of Delphacidae including the three WBPH mitogenomes suggested that Delphacinae seems to be monophyletic and Sogatella species including WBPH are clearly formed as one clade.White-backed planthopper (WBPH), Sogatella furcifera (Horváth), is one of the major sap-sucking rice pests in East Asia. We have determined a new complete mitochondrial genome of WBPH collected in the Korean peninsula using NGS technology. Its length and GC percentages are 16,613 bp and 23.8%, respectively. We observed one polymorphic site, a non-synonymous change, in the COX3 gene with confirmation heteroplasmy phenomenon within individuals of WBPH by PCR amplification and Sanger sequencing, the first report in this species. In addition, this heteroplasmy was not observed in wild WBPH populations, suggesting that it may be uncommon in fields. We analyzed single nucleotide polymorphisms, insertion, and deletions, and simple sequence repeats among the three WBPH mitogenomes from Korea and China and found diverse intraspecific variations, which could be potential candidates for developing markers to distinguish geographical populations. Phylogenetic analysis of 32 mitogenomes of Delphacidae including the three WBPH mitogenomes suggested that Delphacinae seems to be monophyletic and Sogatella species including WBPH are clearly formed as one clade. In the future, it is expected that complete mitogenomes of individuals of geographically dispersed WBPH populations will be used for further population genetic studies to understand the migration pathway of WBPH.

Impact of sublethal and low lethal concentrations of flonicamid on key biological traits and population growth associated genes in melon aphid, Aphis gossypii Glover

Flonicamid (N-cyanomethyl-4-trifluoromethylnicotinamide) is a novel systemic insecticide that shows high insecticidal toxicity against sap-sucking pests. However, little is known about the sublethal effects of flonicamid on melon aphid, Aphis gossypii Glover, a serious insect pest of many vegetables. Herein, the toxicity of flonicamid to A. gossypii was determined using the leaf-dipping method, and the sublethal effects of this insecticide on biological traits of A. gossypii were evaluated using age-stage, two-sex life table method. The results showed that the LC50 value of flonicamid to A. gossypii adults was 7.177 mg L−1. The sublethal (LC5) and low lethal (LC15) concentrations of flonicamid reduced the fecundity of the F0 generation aphids. Moreover, the intrinsic rate of increase (r) and finite rate of increase (λ) of F1 generation were also significantly decreased in the flonicamid treatment groups, while the mean generation time (T) of the F1 generation was significantly prolonged compared to the control. In addition, the expression levels of juvenile hormone epoxide hydrolase (JHEH), vitellogenin (Vg), and ultraspiracle protein (USP) significantly increased in surviving adult aphids that were exposed to LC5 and LC15 of flonicamid in the F0 generation. The data demonstrate that sublethal and low lethal concentrations of flonicamid could suppress the growth of A. gossypii, and the differential expression of development- and reproduction-related genes might be involved in the sublethal effects of flonicamid on A. gossypii.

Leafhopper (Idioscopus spp.) excreted honeydew distracts honey bees (Apis spp.) from visiting mango (Mangifera indica L.) flowers: an indirect loss inflicted by the sucking pests hitherto unaccounted

Honeydew is a sugar-rich sweet substance excreted by the phloem-feeding herbivorous insects like aphids, leafhoppers, mealybugs and scales of the Order Hemiptera. The honeydew is generally deposited on the surface of leaves and other plant parts and serves as a food source to other nectar feeders including honey bees. There is a possibility that the presence of honeydew might distract honey bees from visiting flowers, leading to depriving them of adequate pollination services. In order to establish this hypothesis, field studies were conducted for two consecutive flowering seasons (2017 and 2018) in a mango orchard at Bengaluru, India to assess the effect of honeydew excreted by leafhoppers (Idioscopus spp.), a serious sap-sucking pest of mango (Mangifera indica L.), on honey bee visitation to mango flowers. The number of bees foraging on the inflorescence of mango trees which were allowed to have hopper infestation and subsequent honeydew on foliage was compared with those on trees which were maintained free from leafhoppers incidence and honeydew. The mean number of bees of all three species of Apis foraging on mango flowers on trees maintained free from hopper infestation was significantly higher (4.58/10 panicles/5 min) compared to that on trees with leafhopper infestation and subsequent honeydew deposits on leaves (1.98), which translates to a very considerable 55.53% reduction. Since mango is a cross-pollinated crop, the fruit set is directly proportional to the extent of pollinator activity. This study highlights a different ecological implication of honeydew excreted by a sucking pest of a fruit crop.

Comprehensive characterization of Allium cepa leaf lectin (ACAL1) for its potential use against sap-sucking plant pests: in silico study

Comprehensive characterization of Allium cepa leaf lectin (ACAL1) for its potential use against sap-sucking plant pests: in silico study

Potential Global Distribution of Daktulosphaira vitifoliae under Climate Change Based on MaxEnt.

Simple SummaryDaktulosphaira vitifoliae (Fitch) or grape phylloxera is a small, invasive, and sap-sucking insect widely distribution in most viticultural areas of the world. In the current study, the potential distribution ranges of the leaf-feeding population under current and future environmental conditions were simulated by MaxEnt software. The highly suitable ranges of D. vitifoliae mainly focus on Europe, East and North China, Japan, the Eastern USA, Uruguay, and the Southeast of South America under current climatic conditions. The highly suitable ranges were obviously increased under future climate conditions.Grape phylloxera, Daktulosphaira vitifoliae, is a small, invasive, sap-sucking pest that is widely present in most viticulture regions all over the world. It is originally from North America and feeds on grapevine roots and leaves. In the current study, the potential distribution area of the leaf-feeding population was investigated with MaxEnt based on population occurrence data under different environmental variables. Results suggested that under current climatic conditions, Europe, East and North China, Japan, the Eastern USA, Uruguay, and the Southeast of South America are highly suitable areas for the occurrence of phylloxera leaf populations. The results showed that isothermality and precipitation of coldest quarter were major factors which contribute more than 60% of the model under current climate conditions. Our results provide important information for governmental decision makers and famers to develop control and management strategies against D. vitifoliae, and can also be used as a reference for studies on other invasive pest.

The Efficiency of Plant Defense: Aphid Pest Pressure Does Not Alter Production of Food Rewards by Okra Plants in Ant Presence.

Pearl bodies are produced by some plant species as food reward for ants and in exchange, ants defend these plants against insect pests. Sap-sucking pests such as aphids also excrete honeydew as food reward for ants, leading to potential conflict where ants could preferentially defend either the plant or the aphid. How pest insects might influence plant pearl body production, is yet to be investigated. Okra is a widely consumed vegetable worldwide and is attacked by the ant-tended cotton aphid. The plants produce pearl bodies, which are predominantly found on the underside of the leaves and formed from epidermal cells. We conducted a set of field and greenhouse experiments to explore plant-aphid-ant interactions, their influence on pearl body production and resulting performance of okra plants, across okra varieties. We found that ants of Pheidole genus, which are dominant in okra fields, preferred pearl bodies over aphid honeydew; although, their highest abundance was recorded in presence of both these food rewards, and on one okra variety. Removal of pearl bodies from the plants increased their production; however, plant growth and chlorophyll content were negatively associated with pearl body replenishment. Potentially to mitigate this resource cost, plants developed such a novel defense response because we found that aphid presence reduced pearl body production, but only when there were no ants. Finally, aphids negatively affected plant performance, but only at very high densities. As aphids also attract ants, plants may tolerate their presence at low densities to attract higher ant abundances. Our study highlights that plants can adapt their defense strategies in pest presence for efficient resource use. We suggest that understanding pearl body associated interactions in crop plants can assist in using such traits for pest management.

Direct and Indirect Effect via Endophytism of Entomopathogenic Fungi on the Fitness of Myzus persicae and Its Ability to Spread PLRV on Tobacco.

Simple SummaryAphids are major crop pests that are feeding on plant sap and transmitting plant viruses, thus inducing high yield losses worldwide. As chemical pesticides are decreasingly used in plant protection, fungi that cause disease to insects (entomopathogenic fungi) are one of the promising alternatives. They are commonly applied by spraying plants to protect them against herbivores. When applied, some fungi penetrate and live within plant tissues, thus helping to internally protect from insect attacks and other plant diseases. The aim of our study was to assess the effects of entomopathogenic fungi (EPF) applied firstly by contact after insect direct spraying, secondly by endophytic plant inoculation, and thirdly by associated both methods assessing the green peach aphid performances. The impact of the presence of endophytic entomopathogenic fungi (EEPF) in plant tissues on virus transmission by aphids was also considered. We found that the EPF Beauveria bassiana killed the green peach aphid and reduced its fecundity regardless of the application method. On fungal-inoculated plants, there was also a high mortality of aphid nymphs and infection by the potato leafroll virus (PLRV) was delayed by about a week with the EEPF treatment compared to fungal-free plants. This study showed that spraying plant leaves with EPF not only has a direct insecticidal effect against insects but could also have beneficial side effects for the plant against viruses.Aphids are major crop pests that transmit more than half of all insect-vectored plant viruses responsible for high yield losses worldwide. Entomopathogenic fungi (EPF) are biological control agents mainly used by foliar application to control herbivores, including sap-sucking pests such as aphids. Their ability to colonize plant tissues and to interact with diverse plant pathogenic microorganisms have been reported. In our study, we evaluated the effectiveness of Beauveria bassiana ((Balsamo-Crivelli) Vuillemin) directly applied by contact or/and indirectly via endophytism in tobacco plants (Nicotiana tabacum L.) against the virus vector Myzus persicae (Sulzer) carrying the Potato leafroll virus (PLRV) or not. We found that both contact treatment and endophytic colonization of leaves significantly increased aphid mortality and decreased the fecundity rate when compared to control plants. In addition, on fungal-colonized leaves, viruliferous aphids were more negatively impacted than virus-free ones and nymph mortality was significantly higher than on fungal-free plants. Furthermore, we assessed PLRV transmission by M. persicae on tobacco plants inoculated with either B. bassiana or Metarhizium acridum ((Driver and Milner) JF Bischoff, Rehner, and Humber) as source or/and recipient plants. Myzus persicae was found to acquire and transmit PLRV regardless of the treatment. Nevertheless, the infection rate of endophytically colonized plants was lower at a seven-day incubation period and had increased to almost 100% after fifteen days. These results suggest that B. bassiana is effective against aphids, both by contact and via endophytism, and both B. bassiana and M. acridum delayed PLRV infection in tobacco.

Efficacy of rice straw mulch for the sustainable production and insect pest management in okra (Abelmoschus esculentus)

With an aim to utilize rice straw for crop mulching purpose and prevent environmental damage caused due to its burning, the efficacy of rice straw mulching was compared with the standard practice of silver colored polyethylene mulch and without mulch in okra (Abelmoschus esculentus (L.) Moench) for the crop growth, yield and for the reduction of insect pest population. The trials were performed during the rabi season with two sprays each of neem (Agroneem®@ 2 ml/l), imidacloprid (Confidor®@ 0.5 ml/l) and their combination. Plant growth and yield was significantly higher in silver mulch and straw mulch compared to the control. The yield of okra was maximum in silver colored polythene mulch along with the application of insecticide imidacloprid. The yield were 23.89, 16.08 and 15.80 t/ha respectively during the years, 2015-16, 2016-17 and 2017-18. The yield observed in straw mulch was slightly lower than silver colored polythene mulch, but higher than control. The straw mulch was found at par with silver colored polythene mulch in reducing population of sap sucking insect, pests, aphids, thrips, leafhoppers and whiteflies. Among the treatments, spray of imidacloprid (@ 0.5 ml/l) was found best for reducing pest population. The results indicated the utility of rice straw mulching as an organic option for the okra cultivation, which is otherwise burnt every year creating huge environmental problem in India

Fitness cost of imidacloprid resistance in the cotton-staining bug, Dysdercus koenigii

Dysdercus koenigii, a serious cotton-staining insect pest in many countries, has shown high resistance to imidacloprid, a systemic neonicotinoid insecticide used to control sap-sucking pests. With the aim of creating an effective management strategy, the biological traits of susceptible (SS) and imidacloprid-resistant (Imida-RS) D. koenigii, as well as their reciprocal crosses (CR1 and CR2), were investigated here using a life table established on age, stage, and two-sex patterns. Compared with SS D. koenigii, Imida-RS and CR1 strains had lower relative fitness (0.80 and 0.47, respectively) and fecundity (eggs per female); prolonged egg duration and a prolonged adult preoviposition period; shorter nymphal duration, male/female total longevity, and oviposition days, and a shorter total preoviposition period. However, there were no differences among strains in nymphal survival rates and female ratio. The CR2 D. koenigii had similar relative fitness value (1.09), suggested no fitness cost in most of the parameters. Demographic parameters, including net reproductive rate, were lower in the Imida-RS strain than in SS and CR2 D. koenigii. Similarly, the Imida-RS and CR1 strains had shorter generation time and doubling time, lower reproductive value and life expectancy relative to the SS and CR2 D. koenigii. In addition, age-specific fecundity was negatively affected in the CR1 strain compared with the other strains. These findings could help facilitate the development of rational D. koenigii control strategies.

Effects of nitrogen fertilization and some non-conventional insecticides on sap sucking pests and yield of transgenic Bt cotton in Sudan

Integrated management of BT cotton pests was carried in field experiments during the seasons; 2016/2017 (Season I) and 2017/2018 (Season II) in the experimental research farm of Kassala University, Sudan. Four insecticides (imidacloprid, abamectin, profenofos and lufenuron) and three levels of soil applied nitrogen; 43.81 kgha−1, 87.62 kgha−1 and 131.43 kgha−1 were tested at recommended doses. Seven weekly counts of abundant pests (whitefly, jassid, aphid, and mealybug) were done starting 4 weeks before spraying. Post spray counts were done after 3, 10 and 17 days from spraying. Seed cotton yield of various treatments was recorded and economic analysis of the package was calculated. Results indicated that increasing the nitrogen dose result in significant increase in population of sap sucking pests during the pre-spray counts while insecticide treatments significantly reduced the infestation level in the post spray counts. Aphid was found in season I while mealybug was found in season II only in contrast to whitefly and jassid which were found in both seasons. Imidacloprid was the most effective insecticide causing reduction in the level of infestation by the various sap sucking pests in the range of 11.20% -71.66%, followed by lufenuron (with reduction in infestations level ranging between 8.12% to 69.11%) and profenofos (with infestation reduction ranging between 9.88% to 66.74%). On the other hand abamectin was the least effective treatment causing the least infestation reduction in the population of sap sucking pests (ranging between 8.38% to 66.45%). No significant interactions were found between nitrogen and insecticide treatments. Highest seed cotton yield and revenue was associated with imidacloprid combined with various nitrogen levels (causing 46%–63% increase), followed abamectin nitrogen treatments (7%–22%), profenofos and lufenuron nitrogen combinations. Generally, seed cotton yield increases by the increase of nitrogen dose, while the revenue (net benefit) depends on the price of the insecticide used.

Host-induced gene silencing of brown planthopper glutathione S-transferase gene enhances rice resistance to sap-sucking insect pests

Host-induced gene silencing (HIGS) of insect growth and development is a promising measure for pest control in practice; the feasibility of disarming insect detoxification of toxic phytochemicals via HIGS of insect detoxification enzymes remains largely unexplored. In this study, a HIGS system was applied to interfere with glutathione S-transferase (GST) gene expression in brown planthopper (BPH, Nilaparvata lugens), a key insect pest in rice of Asia, and regulate rice resistance to the insect. The recombination vector in transgenic plants was expressed in almost all organs, especially in vascular bundle tissues, mesophyll, epidermal cells and leaf sheath sap, but not in xylem. Target BPH NlGST1-1 was successfully integrated into rice genome, the resultant transgenic rice lines harbored a single-copy of BPH NlGST1-1 dsRNA, and expression of NlGST1-1 dsRNA was detected in leaves and leaf sheaths of transgenic lines. However, the content of phytochemical gramine, an inherent alkaloid in gramineous plants, did not change in these transgenic plants. BPH nymphs reared on the transgenic rice expressing NlGST1-1 dsRNA displayed significant reductions in NlGST1-1 transcript expression and GST activity. The transgenic plants significantly retarded relative growth rate of the nymphs and the insect female fecundity, the plants also showed enhanced resistance when attacked by BPH. Our study demonstrated the feasibility of reinforcing gramine-mediated plant defense via HIGS of GSTs in herbivorous insects. HIGS-mediated suppression of the herbivore adaptive mechanism has significant implications for efficiently managing BPH and other pests in rice.