Nymphal Development Time Research Articles

Importance of wildflowers in Orius insidiosus (Heteroptera: Anthocoridae) diet

Abstract The addition of non-crop floral resources is known to improve the fitness of many beneficial arthropods. Orius insidiosus (Say; Heteroptera: Anthocoridae) is a predator of several economically important pests and is known to feed on pollen. Spanish needles, Bidens alba L., and Leavenworth’s tickseed, Coreopsis leavenworthii Torrey & Gray (both Asteraceae), are two Florida native wildflowers that may serve as sources of pollen beneficial to O. insidiosus. The current study investigated the effects of adding flowers from C. leavenworthii and B. alba to the diet of captive O. insidiosus on longevity, nymphal development time, and cannibalism. A mixed diet of flowers and thrips prey increased O. insidiosus adult female longevity. Nymphal development time was reduced when B. alba was added to thrips when compared to a diet of thrips alone. Interestingly, cannibalism was low in all instances, suggesting a negligible effect of cannibalism on O. insidiosus except perhaps in extreme situations. These results indicate that B. alba and C. leavenworthii flowers can increase longevity and fitness of O. insidiosus, thus providing support for the use of these plants to enhance natural enemy services.

Differential Effects of Two Tomato Begomoviruses on the Life History and Feeding Preference of Bemisia tabaci.

Tomato yellow leaf curl disease, caused by a group of closely related tomato yellow leaf curl viruses, is a major threat to tomato cultivation worldwide. These viruses are primarily transmitted by the sweet potato whitefly (Bemisia tabaci) in a persistent-circulative manner, wherein the virus circulates in the body of B. tabaci and infects its tissues. The complex relationship between viruses and whiteflies significantly influences virus transmission, with studies showing varying effects of the former on the life history and feeding preference of the latter. Whether these effects are direct or indirect, and whether they are negative, neutral, or positive, appears to depend on the specific interactions between virus and whitefly species. The tomato yellow leaf curl Thailand virus (TYLCTHV) and the tomato leaf curl Taiwan virus (ToLCTV) are two prevalent begomoviruses in fields in Taiwan. This study examined the direct and indirect effects of TYLCTHV and ToLCTV on the life history traits (longevity, fecundity, nymph survival, and nymph developmental time) and feeding preference of B. tabaci Middle East-Asia Minor 1 (MEAM1). The results revealed that TYLCTHV had no effects on these life history traits or the feeding preference of MEAM1 whiteflies. Although ToLCTV did not directly affect the longevity and fecundity of MEAM1 whiteflies, their fecundity and the nymph developmental time were negatively affected by feeding on ToLCTV-infected plants. In addition, ToLCTV infection also altered the feeding preference of MEAM1 whiteflies. The different effects of virus infection may contribute to the lower prevalence of ToLCTV compared to TYLCTHV in fields in Taiwan.

Life history responses of the small brown planthopper Laodelphax striatellus to temperature change

Temperature is a key environmental factor in ectotherms and influences many life history traits. In the present study, the nymphal development time, sex ratio and wing dimorphism of the small brown planthopper Laodelphax striatellus were examined under the conditions of constant temperatures, naturally varying temperatures (or different generations), and different temperatures combined with different photoperiod. The results showed that from 18 to 28 °C, the developmental time of nymphs was gradually shortened with the increase of temperature, whereas the high temperatures of 30 and 32 °C in the third to fifth instar nymphal stages and high summer temperature of 28.8 and 29.7 °C significantly delayed developmental time and resulted in higher mortality of nymphs. In all treatments, the developmental time was longer in females than males. The nymphs took significantly longer time to develop in the short daylength of 12 h than in longer daylengths of 13, 14, 15 and 16. Differences in developmental time were also found between wing morph, with long-winged individuals being significantly longer than the short-winged individuals at lower temperatures and significantly shorter than the short-winged individuals at higher temperatures. In all treatments, the sex ratio was stable, approaching 1:1, without being affected by temperature, generations and photoperiod. Photoperiod and temperature had significantly influence on the wing dimorphism. Long daylength combined with different temperatures resulted in significantly higher proportions of long-winged morph, whereas the low temperatures combined with the short daylengths in autumn and winter resulted in significantly high proportion of short-winged morph.This study broadens our understanding of the life-history traits of this planthopper and provides basic data for analyzing the effects of climate change on the planthopper reproduction.

Comparative bionomics and life table studies ofLipaphis erysimi pseudobrassicae(Davis) andMyzus persicae(Sulzer) (Hemiptera: Aphididae) on three cabbage varieties

Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) are important pests of brassica crops, causing significant yield losses on cabbage in Ghana. To inform the development of ecologically sound and sustainable pest management strategies for these pests, their biological and population growth parameters were studied on three cabbage varieties (Oxylus, Fortune, and Leadercross). The study was conducted in a screen house under ambient conditions at 30 ± 1°C and 75 ± 5% RH and 12:12 h photoperiod from September to November 2020. The parameters of the preadult developmental period, survival rates, longevity, reproduction, and life table were evaluated following the female age-specific life table. There were significant differences in the nymphal developmental time, longevity, and fecundity on the cabbage varieties for both aphid species. The highest population growth parameters, net reproductive rate (R0), intrinsic rate of increase r, and finite rate of increase (λ) were recorded on Oxylus variety for both L. e. pseudobrassicae and M. persicae. The lowest was recorded on Leadercross variety for L.e pseudobrassicae and Fortune for M. persicae. The results from this study suggest that Leadercross is a less suitable host for L. e. pseudobrassicae and Fortune for M. persicae, thus, should be considered as less susceptible varieties for use in primary pest management by small-scale farmers or as a component of an integrated pest management strategy for these pests on cabbage.

Differential Proteomics Analysis Unraveled Mechanisms of Arma chinensis Responding to Improved Artificial Diet.

Simple SummaryArma chinensis Fallou is a predaceous stink bug that can effectively control many kinds of agricultural and forest pests, such as fall armyworm, cotton bollworm and Colorado potato beetle. An insect-free artificial diet comprising chicken egg, tuna fish and raw pig liver was developed for A. chinensis. Several biological characteristics were diminished for A. chinensis reared on the artificial diet compared to the pupae of Chinese oak silk moth. Changes in the formulation of the diet were made in response to the transcriptome results and tested using biological characteristics. Several parameters were improved over 6 generations, although the improved artificial diet remained inferior to the pupae of Chinese oak silk moth regarding egg viability, fecundity, body weight, and nymphal development time. The current study reported the differential proteomic analysis revealing the mechanism of A. chinensis responding to the improved artificial diet. This information will be used to optimize the formulation of the artificial diet and decrease the cost of mass rearing in A. chinensis.The development of artificial diets could considerably simplify and reduce the cost of mass rearing of natural enemies compared to conventional rearing methods. However, improvement of artificial diets can be tedious, convoluted and often uncertain. For accelerating diet development, a better method that can offer informative feedback to target deficiencies in diet improvement is required. Our previous research demonstrated several biological characteristics were diminished in the insect predator, Arma chinensis Fallou, fed on an artificial diet formulated with the aid of transcriptomic methods compared to the Chinese oak silk moth pupae. The present study reports differential proteomic analysis by iTRAQ-PRM, which unravels the molecular mechanism of A. chinensis responding to improvements in the artificial diet. Our study provides multivariate proteomic data and provides comprehensive sequence information in studying A. chinensis. Further, the physiological roles of the differentially expressed proteins and pathways enable us to explain several biological differences between natural prey-fed and improved diet-fed A. chinensis, and subsequent proposed reformulation optimizations to artificial diets.

Evaluation of Artemia sp. (Branchiopoda, Artemiidae) as an alternative prey for laboratory rearing of Tupiocoris cucurbitaceus (Hemiptera: Miridae), a predator of horticultural pests

Tupiocoris cucurbitaceus (Spinola) (Hemiptera: Miridae) is a predator of whiteflies (Hemiptera: Aleyrodidae) present in several American countries. Rearing this bug requires the use of plants as ovipositional substrate and a prey to feed on to complete its development. Artemia sp. (Branchiopoda, Artemiidae) cyst, a crustacean tested for the laboratory rearing of other hemipteran species, could be used as food, being less expensive than the species commonly employed (Sitotroga cerealella [Olivier] [Lepidoptera: Gelechiidae]). The objective of the present study was to determine nymphal developmental time, nymphal mortality, fertility, and sex ratio of T. cucurbitaceus fed on Artemia sp. cysts. Three diets were used during the rearing of three generations: S. cerealella eggs, Artemia sp. cysts and a mix of both species. The nymphal developmental time (11 to 13 days), nymphal mortality (40 to 66 %), and adult fertility (74 to 101 nymphs / female) were similar for all diets. In all cases, the adults showed a high female proportion (0.67-0.97). In conclusion, Artemia sp. cysts are suitable for T. cucurbitaceus laboratory rearing at least for three generations.

A sublethal concentration of afidopyropen suppresses the population growth of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae)

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is an important insect pest of cotton crops worldwide. The objectives of this study were to determine the acute toxicity of afidopyropen and whether there are any effects of sublethal concentrations of afidopyropen on the biological characteristics of A. gossypii. The results showed that afidopyropen possesses high acute toxicity to adult A. gossypii with a 72 h LC50 value of 1.062 mg L–1. A sublethal concentration (LC10) of afidopyropen significantly decreased adult longevity, fecundity and oviposition days of female adults in both F0 and F1 generations. The total pre-adult survival of F1 progeny was also significantly reduced by 30% at the LC10 of afidopyropen. In addition, the nymph developmental time, pre-adult period, adult pre-reproductive period (APRP), and total pre-reproductive period (TPRP) of the F1 progeny were significantly prolonged compared with the control. Several population parameters, including the net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (λ) of F1 progeny were significantly decreased by a sublethal afidopyropen concentration exposure. These results indicated that sublethal concentration of afidopyropen can significantly suppress A. gossypii population growth. It would be useful for assessing the overall effects of afidopyropen on A. gossypii.

Fungal-Based Biopesticide Formulations to Control Nymphs and Adults of the Desert Locust, Schistocerca gregaria Forskål (Orthoptera: Acrididae): A Laboratory and Field Cage Study

This is the first field study in which we have tested the efficacy of four different entomopathogenic fungal (EPF) formulations together in single study—i.e., Green Muscle, Green Guard, Metarhizium anisopliae, and an isolate of Beauveria bassiana (isolate WG-11)—against nymphs and adults of the desert locust, Schistocerca gregaria Forskål (Orthoptera: Acrididae). We conducted several different studies: (a) lethal bioassay against the 3rd, 5th, and adult stages under laboratory conditions; (b) sublethal effects on the reproduction, diet consumption, fecal production, and weight gain; (c) a greenhouse trial; and (d) a field cage trial. Under laboratory conditions, all EPF formulations caused significant mortality, and the highest efficacy was observed with Green Muscle, followed by Green Guard, B. bassiana, and M. anisopliae. Susceptibility was found to be greatest in 3rd-instar nymphs, followed by 5th instars, and then adults. Along with lethal effects, sublethal doses of EPF reduced the number of egg pods per female, total eggs per pod, and egg hatching, while extending nymphal developmental time and reducing adult longevity; again, Green Muscle performed better. Sublethal doses not only retarded reproduction, but also caused behavioral changes, including reductions in food consumption, fecal production, and weight gain. All EPF formulations not only produced significant mortality in laboratory conditions, but also performed very well under the greenhouse and field conditions. The maximum mortality against 3rd-instar (81.7% and 74.0%), 5th-instar (73.3% and 65.1%), and adult locusts (67.5% and 58.9%) was observed when using Green Muscle under greenhouse and field trials, respectively. The current study showed that all of the EPF formulations have the potential to reduce pest populations, and could be used in the integrated pest management program.

The ecological fitness of the tomato potato psyllid after transferring from non-crop host plants to tomato and potato.

An insect’s fitness varies on different host plant species, and can be affected by previous host feeding experience. In New Zealand, Bactericera cockerelli (the tomato potato psyllid (TPP)) overwinter on various host species, and later migrate to annually grown crop host plants. How changing host plant species affects the insect’s fitness is unknown. This study evaluated if transferring adult TPP from non-crop to crop host species impacts the development and survival of their progeny. TPP were reared on non-crop host species, boxthorn, poroporo, and crop host species, potato and tomato. Adults were transferred from non-crop to the crop host species and allowed to oviposit for 48 hours before being removed. The eggs and nymphs were monitored every 24 hours for the development and survival of each life stage. The incubation period of eggs from adults transferred from poroporo to tomato was 6.9 days, and for boxthorn to tomato was 7.2 days, and was less than for eggs of adults moved from tomato to tomato (9.0 days) and potato to potato (9.2 days) (P < 0.05). Nymph developmental time was similar for all treatments. Total development time (egg to adult) was shorter for the progeny of adults from poroporo transferred to tomato (20.5 days) than those from tomato to tomato (23.2). The survival of eggs did not differ across treatments. Fewer nymphs survived when adults were transferred from tomato to tomato (50.4%) than those from poroporo to tomato (92.1%) (P < 0.05). Total survival (egg to adult) was higher for progeny of adults transferred from poroporo to tomato (80.0%) compared to boxthorn to potato (35.3%), boxthorn to boxthorn (40.7%), poroporo to potato (33.9%) and tomato to tomato (37.6%) (P < 0.05). The implications of this shift in fitness are discussed in relation to TPP management.

Serratia symbiotica Enhances Fatty Acid Metabolism of Pea Aphid to Promote Host Development.

Bacterial symbionts associated with insects are often involved in host development and ecological adaptation. Serratia symbiotica, a common facultative endosymbiont harbored in pea aphids, improves host fitness and heat tolerance, but studies concerning the nutritional metabolism and impact on the aphid host associated with carrying Serratia are limited. In the current study, we showed that Serratia-infected aphids had a shorter nymphal developmental time and higher body weight than Serratia-free aphids when fed on detached leaves. Genes connecting to fatty acid biosynthesis and elongation were up-regulated in Serratia-infected aphids. Specifically, elevated expression of fatty acid synthase 1 (FASN1) and diacylglycerol-o-acyltransferase 2 (DGAT2) could result in accumulation of myristic acid, palmitic acid, linoleic acid, and arachidic acid in fat bodies. Impairing fatty acid synthesis in Serratia-infected pea aphids either by a pharmacological inhibitor or through silencing FASN1 and DGAT2 expression prolonged the nymphal growth period and decreased the aphid body weight. Conversely, supplementation of myristic acid (C14:0) to these aphids restored their normal development and weight gain. Our results indicated that Serratia promoted development and growth of its aphid host through enhancing fatty acid biosynthesis. Our discovery has shed more light on nutritional effects underlying the symbiosis between aphids and facultative endosymbionts.

Influence of the eggs of Ephestia kuehniella (Lepidoptera: Pyralidae) reared on different diets on the performance of the predatory bug Orius laevigatus (Hemiptera: Anthocoridae)

The predatory bug, Orius laevigatus (Fieber, 1860) (Hemiptera: Anthocoridae), is an important biological control agent and widely used for augmentative biological control of the western flower thrips, Frankliniella occidentalis Pergande, 1895 (Thysanoptera: Thripidae) in greenhouse crops. This bug is generally reared using the Mediterranean flour moth, Ephestia kuehniella Zeller, 1879 (Lepidoptera: Pyralidae). The aim of this study was to determine the effects of E. kuehniella eggs produced by adult moths reared on different larval diets on the performance of O. laevigatus. The diets were 95% cornmeal + 5% yeast (CY diet), 53.3% cornmeal + 26.7% wheat bran + 15% Glycerine + 5% yeast (CBGY diet) and 53.3% wheat flour + 26.7% wheat bran + 15% Glycerine + 5% yeast (WBGY diet). Laboratory studies started with newly emerged nymphs of O. laevigatus kept in a climate chamber at 27°C, 60% relative humidity and a 14L :10D photoperiod. Eggs of E. kuheniella adults that were fed on one of the three different larval diets were provided to the nymphs as a source of food and bean pods of water. Following adult emergence, all individuals were sexed, and female and male pairs were put in plastic containers (30 cc) with eggs of E. kuehniella and bean pods. Nymphal development time, fecundity and longevity of O. laevigatus were not differently affected by feeding on the eggs of E. kuehniella reared on the three diets. In addition, the daily and total egg consumption of adults of O. laevigatus were similar. Because the CY diet eggs contain more nutrients, their consumption by nymphs was lower. This study indicates that the CY diet is an adequate diet for rearing E. kuehniella for producing eggs for rearing O. laevigatus.

Overwintering biology of the predatory bug, Orius vicinus (ribaut) (Hemiptera: Anthocoridae) under outdoor conditions in the eastern mediterranean region of Turkey

Overwintering biology of Orius vicinus (Ribaut) (Hemiptera: Anthocoridae) was investigated between November 2017 and April 2018 in the Balcali location of Adana Province, Turkey under outdoor conditions. The duration of egg and nymphal development time, pre-oviposition, oviposition and post-oviposition periods of females, the number of eggs laid and adults longevity were determined by the experiments performed in the first day of each experimental month under the outdoor conditions at the Department of Plant Protection, Faculty of Agriculture, University of Cukurova. The duration of egg hatching lasted between 5 and 10 days in all months of experiment and the tested eggs were hatched even at low temperature and under short day length conditions. More than half of the nymphs obtained from the tested eggs became adults in the winter months. Despite the nymph’s survival was affected negatively by the sudden changes in temperature, they were tolerant to the low temperatures and short-day lengths during the winter period. All females in the trials oviposited for about 30 days even in the coldest periods (approximately 15 °C). The females were not affected by the environmental conditions particularly in winter season, and they did not undergo reproductive diapause. The obtained data shed light on the overwintering biology of O. vicinus which may be helpful for their potential role in controlling the non-diapaused pest species such as pest thrips in the early spring season.

Morphology, development and reproduction of &lt;em&gt;Atractomorpha acutipennis&lt;/em&gt; (Guérin-Méneville, 1844) (Orthoptera: Pyrgomorphidae)

For a better knowledge of Atractomorpha acutipennis bio-ecology and to facilitate its identification, we studied the morphology, development and reproduction of this grasshopper on Manihot esculenta under laboratory conditions. Five hundred and fifty-one first nymphal stages obtained in the laboratory were reared in cages. Some body parts allowed a clear identification of different nymphal instars. Post-embryonic development passed through six stages (males) and seven stages (females). Mean nymphal development time was 17.14 ± 0.62, 12.91 ± 0.62, 13.45 ± 0.69, 13.80 ± 0.68, 15.23 ± 0.55 days respectively in males nymphal instars 1 to 5 and 16.18 ± 0.54, 13.13 ± 0.59, 12.49 ± 0.42, 13.19 ± 0.58, 14.58 ± 0.61, 16.57 ± 0.68 days respectively, in females nymphal instars 1 to 6. Adult females deposited an average of 3.67 ± 2 egg pods each comprising 30.77 ± 10.5 eggs. First mating was observed 18 ± 15.42 days after the last moult. Oviposition occured on average 19.33± 5.33 days after the first mating. This study provides important information about the biology of A. acutipennis, which could help in developing control methods against this grasshopper in southern Cameroon.

In-vitro Response of Cereal Aphid Sitobion avenae (Homoptera: Aphididae) against some Selected Botanical Extracts

Cereal aphid, Sitobion avenae (Homoptera: Aphididae), is one of the destructive pests of wheat and other crops around the globe. Irrational utilization of highly toxic synthetic chemicals against this particular pest has led to several issues of health and environment. In such case, there is a need to find out the control measures, which are less toxic and friendly to environment. The present study was aimed to evaluate the effectiveness of aqueous extracts of four indigenous plants, i.e. akk (Calotropis procera), lemon (Citrus limon), neem (Azadirachta indica) and dhatura (Datura alba), against S. avenae in laboratory conditions. Toxicity bioassays were conducted according to Completely Randomized Design using 2% aqueous extracts with three replications. Results showed a differential response of aphids to all botanical extracts. Aphid mortality increased with the exposure time with maximum values (i.e. 39.52, 31.75, 26.76 and 24.07% for A. indica, C. procera, C. limon and D. alba extracts, respectively) recorded at 72 h posttreatment. Similarly, A. indica extract exhibited minimum fecundity (2.67 offspring per adult) and adult body weight (340.09 µg) and maximum nymphal development time (9.32 days), followed by C. procera, C. limon and D. alba. Overall study results suggest that A. indica and C. procera extracts would be effective botanical options for combating aphid infestations on wheat and other cereal crops

Biocontrol Potential of Purified Elicitor Protein PeBL1 Extracted from Brevibacillus laterosporus Strain A60 and Its Capacity in the Induction of Defense Process against Cucumber Aphid (Myzus persicae) in Cucumber (Cucumis sativus).

The Cucumber aphid (Myzus persicae), a destructive cucumber aphid usually managed by chemical pesticides, is responsible for enormous annual agricultural losses. A protein elicitor, PeBL1, was investigated in the present work for its ability to induce a defense response against M. persicae in cucumber. The rates of population growth (Intrinsic rate of increase) of M. persicae (second and third generations) decreased with PeBL1-treated cucumber seedlings as compared to positive (water) and negative 70.58 μg mL−1 controls (50 mM Tris-HCl, pH 8.0). In an assay on host selection, M. persicae had a preference for colonizing control plants as compared to the PeBL1-treated cucumber seedlings. The nymphal development time of the aphid was extended with the PeBL1-treated cucumber seedlings. Likewise, fecundity was reduced, with less offspring produced in the PeBL1-treated cucumber seedlings as compared to the positive (water) and negative 70.58 μg mL−1 controls (50 mM Tris-HCl, pH 8.0). The cucumber leaves treated with PeBL1 had a hazardous surface environment for M. persicae, caused by trichomes and wax formation. Jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) levels were significantly higher, exhibiting significant accumulation in the PeBL1-treated cucumber seedlings. The following results showed that PeBL1 considerably altered the height of the cucumber plant and the surface structure of the leaves to minimize M. persicae reproduction, and it prevented colonization. Defensive processes also included the activation of pathways (JA, SA, and ET). This study provides evidence of biocontrol for the use of PeBL1 in cucumber defense against M. persicae.

Reduced Mythimna separata infestation on Bt corn could benefit aphids.

Use of genetically engineered plants that express insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) have been proven efficacious for managing lepidopteran pests. However, in some cases herbivores that are not targeted by the Bt trait have increased in importance. It has been suggested that reduced caterpillar damage to Bt crops could lead to decreased levels of induced plant defensive compounds which might benefit other non-target herbivores. Here we investigated the potential effect of reduced damage by larvae of Mythimna separata on aphid populations in Bt corn. We compared the performance of Rhopalosiphum maidis feeding on non-Bt corn plants that had been infested by M. separata larvae or were uninfested. The results showed that caterpillar-infested corn plants significantly reduced the fitness of R. maidis leading to a prolonged nymphal development time, reduced adult longevity and fecundity compared to uninfested plants. Consequently, the population growth rate of corn aphids feeding on caterpillar-infested corn plants was significantly lower than on uninfested plants. As expected, the aphids performed significantly better on Lepidoptera-resistant Bt corn than on non-Bt corn when plants were infested with M. separata, since the caterpillars caused very little damage to the Bt plants. The current findings indicate that reduced M. separata infestation could benefit aphid development in Bt corn. Bt corn has the potential to be commercialized in China in the near future and aphids and other non-target pests should be monitored in the farming fields.

Evaluation of plant quality by Corythucha marmorata (Hemiptera: Tingidae) mothers: relationship between oviposition preference and nymphal performance on four sweet potato cultivars and goldenrod

In novel plant–insect relationships, oviposition preference and nymphal performance determine host range evolution. Corythucha marmorata, native to North America and specialist on asteraceous plants, has been reported to exploit sweet potato (Convolvulaceae) in Japan. Here we examined the capability of females to oviposit and of nymphs to grow on both a conventional host (goldenrod, Solidago altissima) and novel hosts (four sweet potato cultivars), of which the test insects had virtually no experience of contact at the population level. We then tested whether female preference and offspring performance were correlated. Nymphal survival and development time were always significantly greater on goldenrod, followed by sweet potato cultivars Caroline Lea, Benisengan, Narutokintoki, and Beniazuma in that order. Female oviposition preferences showed a similar order. On higher-ranked plants, the females accepted the plant faster and had higher fecundity. When goldenrod was included in the analysis, nymphal development time and survival rate were significantly related to preoviposition period. When goldenrod was excluded, nymphal survival rate was still significantly related to preoviposition period. These results support the theory that females lay their eggs on the most suitable host to maximize offspring fitness, even though C. marmorata had no experience with sweet potato cultivars. As C. marmorata is a hemimetabolous insect, in which adults and nymphs have a similar feeding habit and exploit the same habitat, this relationship seems plausible.

MAMP-triggered resistance induced by elicitor protein PeBA1 derived from Bacillus amyloliquefaciens NC6 in common bean (Phaseolus vulgaris L.) against green peach aphid (Myzus persicae Sulzer)

Bacterial microbe-associated molecular patterns (MAMPs) play an important role in innate plant immunity. This in vitro study evaluated the putative role of protein elicitor PeBA1 derived from Bacillus amyloliquefaciens NC6 strain in eliciting induced resistance type responses in common bean (Phaseolus vulgaris) plants against green peach aphid Myzus persicae. Nymphal developmental time of aphids was significantly prolonged and the fecundity was significantly reduced by different concentrations of PeBA1 elicitor (i.e. 40.51, 24.91 and 16.38 µg mL-1) applied at three different temperature regimes (i.e. 21, 27 and 30 °C). Moreover, foliar application of PeBA1 elicitor protein strongly up-regulated the expression levels of salicylic acid (SA) pathway-associated genes, while the expression levels of jasmonic acid (JA) pathway-associated genes exhibited a moderate induction. Quantification by LC/MSMS revealed a linear increase of both SA and JA plant defense hormones along with the time of exposure. Our findings suggest that the bacterial elicitor protein PeBA1 could be used as an effective biological pest management tool against phloem-feeding insect pests such as green peach aphids M. persicae.

Gluten hydrolase gene silencing using RNAi and its effect on the Sunn pest growth and development

RNAi technology has been described as a tool to study gene function and is of great potential as a next-generation biopesticide. Thus, in the present study, we identified and sequenced the Sunn pest Gluten hydrolase (GH) gene partially. Then, evaluated GH-dsRNA effects on the GH expression of the fifth instar nymphs and adults, as well as, on the insect growth and development using topical and injection assays. Results indicated that the topical application of GH-dsRNA on the fifth instar nymph caused a severe reduction (99.9%) of gut GH expression in comparison with control and, at the same time, high induction of the salivary gland’s expression profile. Gene upregulation indicates that the insect compensates for the reduction of the one gene expression with the induction of a gene in the other tissue to meet its demand. Also, the GH expression profile in the gut and salivary glands were evaluated 6, 12, and 21-hour post injections. Results revealed that the GH expression profile of both gut and salivary glands was reduced early hours after injection, but their expression profile was recovered 21-hour post-treatment. Thus, the results showed that dsRNA does not have a systemic effect since gene knockdown was not persistent. GH-dsRNA also affected nymphal development time, adult weight, survivability, and adult emergence. These effects indicated that the GH gene plays an essential physiological role(s) in addition to having a role in food digestion. Therefore, RNAi technology has the potential to be used to develop novel strategies for Sunn pest IPM programs.

Biological and Molecular Studies on an Invasive Insect Pest, Lygus hesperus (Hemiptera: Miridae), in the Taif Region, Saudi Arabia1

The tarnished plant bug, Lygus hesperus (Heteroptera: Miridae) is a pest on more than 150 plant species including field, fruit and vegetable crops. Our investigation on rose plants at Taif, Saudi Arabia observed that there are individuals of Lygus sp. during the flowering period. We morphologically identified these as Lygus hesperus. Consequently, this pest is considered as an exotic species in Saudi Arabia and it may be transformed from a minor to a major pest. We studied the length and sequencing of the ITS1 region and its flanking: 18S rRNA and 5.8S genes in this species. Biological and demographic parameters also were studied on two host plant species: green bean pods and rose flower buds. Sequencing of PCR product of ITS1 and its flanking in nine individuals of L. hesperus showed identical sequences for this fragment and obtained 743 bp for the complete ITS1. Biological data showed that the tested host source had an influence on all biological parameters except sex ratio, male longevity, preoviposition and postoviposition periods for females. The green bean pods as a host resulted in higher hatchability, shorter egg duration and nymphal development time, higher survival and fecundity, and longer female longevity. Therefore more favorable demographic parameters of L. hesperus were achieved on green bean pods where it had the shortest T and DT values as well as the highest GRR, rm, λ and R0 values. Additional biological data will be required on other plant hosts in the laboratory or field to estimate population growth and pest potential of L. hesperus in Saudi Arabia. Surveying of parasitoids and predators associated with this invasive insect pest are also desirable.