Sublethal and transgenerational effects of lufenuron on biological characteristics and expression of reproductive related genes in the fall armyworm, Spodoptera frugiperda.

The fall armyworm, Spodoptera frugiperda, is a notorious polyphagous pest that causes serious economic losses in crucial crops and has invaded Africa and Asia. Lufenuron is widely used for controlling S. frugiperda in China, owing to its high toxicity against this key pest, and less pollution and little impact on natural enemies. In the present study, the sublethal and transgenerational effects of lufenuron on S. frugiperda were investigated to provide in-depth information for the rational use of lufenuron. Results showed that the development time and pupae weight were not significantly affected following exposure of females to LC10 and LC25 and male S. frugiperda to the LC10 of lufenuron. However, LC25 exposure significantly reduced pupal and total development time and pupae weight of male S. frugiperda. The longevity of S. frugiperda adults was prolonged by lufenuron and the fecundity of S. frugiperda treated with LC10 of lufenuron was significantly increased by 40% compared to the control. In addition, our study demonstrated that the LC25 of lufenuron had transgenerational effects on the progeny generation. The development time of female S. frugiperda whose parents were exposed to LC25 of lufenuron was significantly decreased compared to the control. And then, the expression profiles of Vg, VgR, JHEH, JHE, JHAMT, JHBP, CYP307A1, CYP306A1, CYP302A1 and CYP314A1 genes involved in insect reproduction and development were analyzed using Quantitative Real-Time PCR (RT-qPCR). Results showed that Vg, VgR, JHE, JHAMT, and CYP306A1 were significantly upregulated at the LC10 of lufenuron, which revealed that these upregulated genes might be linked with increased fecundity of S. frugiperda. Taken together, these findings highlighted the importance of sublethal and transgenerational effects under laboratory conditions and these effects may change the population dynamics in the field. Therefore, our study provided valuable information for promoting the rational use of lufenuron for controlling S. frugiperda.

The interaction of two-spotted spider mites, Tetranychus urticae Koch, with Cry protein production and predation by Amblyseius andersoni (Chant) in Cry1Ac/Cry2Ab cotton and Cry1F maize.

Crops producing insecticidal crystal (Cry) proteins from the bacterium, Bacillus thuringiensis (Bt), are an important tool for managing lepidopteran pests on cotton and maize. However, the effects of these Bt crops on non-target organisms, especially natural enemies that provide biological control services, are required to be addressed in an environmental risk assessment. Amblyseius andersoni (Acari: Phytoseiidae) is a cosmopolitan predator of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), a significant pest of cotton and maize. Tri-trophic studies were conducted to assess the potential effects of Cry1Ac/Cry2Ab cotton and Cry1F maize on life history parameters (survival rate, development time, fecundity and egg hatching rate) of A. andersoni. We confirmed that these Bt crops have no effects on the biology of T. urticae and, in turn, that there were no differences in any of the life history parameters of A. andersoni when it fed on T. urticae feeding on Cry1Ac/Cry2Ab or non-Bt cotton and Cry1F or non-Bt maize. Use of a susceptible insect assay demonstrated that T. urticae contained biologically active Cry proteins. Cry proteins concentrations declined greatly as they moved from plants to herbivores to predators and protein concentration did not appear to be related to mite density. Free-choice experiments revealed that A. andersoni had no preference for Cry1Ac/Cry2Ab cotton or Cry1F maize-reared T. urticae compared with those reared on non-Bt cotton or maize. Collectively these results provide strong evidence that these crops can complement other integrated pest management tactics including biological control.

Eliminating host-mediated effects demonstrates Bt maize producing Cry1F has no adverse effects on the parasitoid Cotesia marginiventris.

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an important pest of maize in the United States and many tropical areas in the western hemisphere. In 2001, Herculex I(®) (Cry1F) maize was commercially planted in the United States to control Lepidoptera, including S. frugiperda. In 2006, a population of S. frugiperda was discovered in Puerto Rico that had evolved resistance to Cry1F maize in the field, making it the first well-documented case of an insect with field resistance to a plant producing protein from Bacillus thuringiensis (Bt). Using this resistant population, we conducted tri-trophic studies with a natural enemy of S. frugiperda. By using resistant S. frugiperda, we were able to overcome possible prey-mediated effects and avoid concerns about potential differences in laboratory- or field-derived Bt resistance. We used the Cry1F-resistant S. frugiperda to evaluate effects of Cry1F on Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae), a larval endoparasitoid of S. frugiperda, over five generations. Our results clearly demonstrate that Cry1F maize does not affect development, parasitism, survivorship, sex ratio, longevity or fecundity of C. marginiventris when they parasitize Cry1F maize-fed S. frugiperda. Furthermore, the level of Cry1F protein in the leaves was strongly diluted when transferred from Bt maize to S. frugiperda and was not detected in larvae, cocoons or adults of C. marginiventris. Our results refute previous reports of C. marginiventris being harmed by Bt proteins and suggest that such results were caused by prey-mediated effects due to using Bt-susceptible lepidopteran hosts.

Southern rice black-streaked dwarf virus (SRBSDV) directly affects the feeding and reproduction behavior of its vector, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae).

BACKGROUND: Southern rice black-streaked dwarf virus (SRBSDV) is a recently discovered member of the genus Fijivirus and it is transmitted by the rice whitebacked planthopper (WBPH), Sogatella furcifera (Horváth). It was found that SRBSDV infected vectors might contribute negatively to the WBPH population, although the longer nymphal period might benefit viral acquisition, transmission and increase infection rate. The interaction between SRBSDV and its vector need to be further explored to gain better understanding of the dispersal of WBPH and the spread of virus disease, in particular the feeding and reproduction behavior of viruliferous WBPH. METHODS: Newly hatched nymphs of WBPH were fed on healthy rice plant after feeding on SRBSDV-infected rice plants for 2 h, and newly emerged adults were numbered and tested. Feeding behaviors of WBPH adults were monitored electronically within a Faraday cage using a Giga-4 DC EPG amplifier. The newly emerged adults were paired, and the fecundity and egg hatchability were investigated. WBPH was molecularly identified for SRBSDV when they dead. According to the identification results, data on viruliferous and non-viruliferous WBPH were collected and analyzed. RESULTS: Feeding behavior of viruliferous WBPH was different from those of non-viruliferous WBPH. Frequency of phloem sap ingestion of viruliferous WBPH increased significantly, however the total feeding duration did not increase markedly. When both WBPH parents were infected with SRBSDV, their fecundity and hatchability of the eggs produced were significant lower than those of normal WBPH parents. However, if only one of the parents was viruliferous, fecundity and egg hatchability were only slightly affected. CONCLUSIONS: Viruliferous WBPH fed on the phloem more frequently than non-viruliferous WBPH and can thus contribute to virus transmission. When both vector parents are viruliferous fecundity and hatchability of the eggs were significantly reduced. However when only one of the parents WBPH was viruliferous, there were no significant effects.

Effects of Bt cotton on Thrips tabaci (Thysanoptera: Thripidae) and its predator, Orius insidiosus (Hemiptera: Anthocoridae).

Laboratory studies were conducted to investigate tritrophic transfer of insecticidal Cry proteins from transgenic cotton to an herbivore and its predator, and to examine effects of these proteins on the predator's development, survival, and reproduction. Cry1Ac and Cry2Ab proteins from the bacterium Bacillus thuringiensis (Bt) produced in Bollgard-II (BG-II, Event 15985) cotton plants were acquired by Thrips tabaci Lindeman (Thysanoptera: Thripidae), an important sucking pest of cotton, and its generalist predator, Orius insidiosus (Say) (Hemiptera: Anthocoridae). The average protein titers in BG-II cotton leaves were 1,256 and 43,637 ng Cry1Ac and Cry2Ab per gram fresh leaf tissue, respectively. At the second trophic level, larvae of T. tabaci reared on BG-II cotton for 48-96 h had 22.1 and 2.1% of the Cry1Ac and Cry2Ab levels expressed in leaves, respectively. At the third trophic level, O. insidiosus that fed on T. tabaci larvae had 4.4 and 0.3% of the Cry1Ac and Cry2Ab protein levels, respectively, expressed in BG-II plants. O. insidiosus survivorship, time of nymphal development, adult weight, preoviposition and postoviposition periods, fecundity, and adult longevity were not adversely affected owing to consumption of T. tabaci larvae that had fed on BG-II cotton compared with non-Bt cotton. Our results indicate that O. insidiosus, a common predator of T. tabaci, is not harmed by BG-II cotton when exposed to Bt proteins through its prey. Thus, O. insidiosus can continue to provide important biological control services in the cotton ecosystem when BG-II cotton is used to control primary lepidopteran pests.

Tri-trophic studies using Cry1Ac-resistant Plutella xylostella demonstrate no adverse effects of Cry1Ac on the entomopathogenic nematode, Heterorhabditis bacteriophora.

The potential impacts on natural enemies of crops that produce insecticidal Cry proteins from Bacillus thuringiensis (Bt) are an important part of an environmental risk assessment. Entomopathogenic nematodes are important natural enemies of lepidopteran pests, and the effects of Bt crops on these nontarget organisms should be investigated to avoid disruption of their biological control function. The objective of this study was to investigate the effects of Cry1Ac-expressing transgenic Bt broccoli on the entomopathogenic nematode, Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae), under tri-trophic conditions. Using CrylAc-resistant Plutella xylostella L. (Lepidoptera: Plutellidae) larvae as hosts, we evaluated the potential impact of Cry1Ac-expressing Bt broccoli on several fitness parameters of H. bacteriophora. Virulence, reproductive potential, time of emergence, and preference of H. bacteriophora for the host (P. xylostella) were not significantly affected when CrylAc-resistant P. xylostella larvae were reared on leaves of Cry1Ac or non-Bt broccoli. Also the aforementioned parameters of the subsequent generation of H. bacteriophora did not differ between nematodes obtained from P. xylostella reared on CrylAc broccoli compared with those obtained from P. xylostella reared on non-Bt broccoli. To the best of our knowledge, the current study provides the first clear evidence that Cry1Ac does not affect important fitness parameters of H. bacteriophora.

Decrease of insecticide resistance over generations without exposure to insecticides in Nilaparvata lugens (Hemipteran: Delphacidae).

The brown planthopper, Nilaparvata lugens (Stål), is one of the most important insect pests on paddy rice in tropical and temperate Asia. Overuse and misuse of insecticides have resulted in the development of high resistance to many different insecticides in this pest. Studies were conducted to evaluate the change of resistance level to four insecticides over 15 generations without any exposure to insecticides in brown planthopper. After 15 generations' rearing without exposure to insecticide, brown planthopper could reverse the resistance to imidacloprid, chlorpyrifos, fipronil, and fenobucarb. The range and style of resistance reversal of brown planthopper differed when treated with four different insecticides. To monitor potential changes in insect physiological responses, we measured the activity of each of the three selected enzymes, including acetylcholinesterases (AChE), general esterases (EST), and glutathione S-transferases. After multiple generations' rearing without exposure to insecticide, AChE and EST activities of brown planthopper declined with the increased generations, suggesting that the brown planthopper population adjusted activities of EST and AChE to adapt to the non-insecticide environment. These findings suggest that the reducing, temporary stop, or rotation of insecticide application could be incorporated into the brown planthopper management.

Using field-evolved resistance to Cry1F maize in a lepidopteran pest to demonstrate no adverse effects of Cry1F on one of its major predators.

Spodoptera frugiperda (JE Smith) represents the first documented case of field-evolved resistance to a genetically engineered crop expressing an insecticidal protein from Bacillus thuringiensis (Bt). In this case it was Cry1F-expressing maize (Mycogen 2A517). The ladybird beetle, Coleomegilla maculata, is a common and abundant predator that suppresses pest populations in maize and many other cropping systems. Its larvae and adults are polyphagous, feeding on aphids, thrips, lepidopteran eggs and larvae, as well as plant tissues. Thus, C. maculata may be exposed to Bt proteins expressed in genetically engineered crops by several pathways. Using Cry1F-resistant S. frugiperda larvae as prey, we evaluated the potential impact of Cry1F-expressing maize on several fitness parameters of C. maculata over two generations. Using Cry1F resistant prey removed any potential prey-mediated effects. Duration of larval and pupal stages, adult weight and female fecundity of C. maculata were not different when they were fed resistant S. frugiperda larvae reared on either Bt or control maize leaves during both generations. ELISA and insect-sensitive bioassays showed C. maculata were exposed to bioactive Cry1F protein. The insecticidal protein had no effect on C. maculata larvae, even though larvae contained 20-32 ng of Cry1F/g by fresh weight. Over all, our results demonstrated that the Cry1F protein did not affect important fitness parameters of one of S. frugiperda's major predators and that Cry1F protein did not accumulate but was strongly diluted when transferred during trophic interactions.

Bt rice expressing Cry1Ab does not stimulate an outbreak of its non-target herbivore, Nilaparvata lugens.

In this study, the non-target effects of Bt rice "KMD2" expressing a Cry1Ab protein on the performance of the brown planthopper (BPH), Nilaparvata lugens, over multiple generations were evaluated under laboratory and field conditions. In the laboratory, BPH was reared to observe the impact of the Bt rice as compared to its parental non-Bt cultivar Xiushui 11, while the population dynamics and oviposition performance of BPH were investigated in the field. The survival of BPH nymphs fed Bt and non-Bt rice did not differ significantly. The nymph developmental duration of BPH was significantly delayed by the Bt rice by comparison with the non-Bt rice for the 1st and 2nd but not the 4th generation. Most importantly, the fecundity of BPH on the Bt rice was significantly decreased in every generation when compared with the non-Bt rice. In the field investigations, the population density of BPH nymphs was significantly lower in the Bt rice field. However, the temporal pattern of population dynamics of BPH adults was similar between the Bt and non-Bt rice, presumably due to migratory interference of the adults. In the Bt rice field, the percentage of tillers with eggs and the number of eggs per tiller were also significantly lower from tillering to mature stage. Additionally, Cry1Ab protein could not be detected in guts from single BPH adults. In general, our results suggest that the Bt rice "KMD2" could not stimulate an outbreak of BPH.

Two P450 genes, CYP6SN3 and CYP306A1, involved in the growth and development of Chilo suppressalis and the lethal effect caused by vetiver grass.

Chilo suppressalis is a widely distributed pest occurring in nearly all paddy fields, which has developed high level resistance to different classes of insecticides. Vetiver grass has been identified as a dead-end trap plant for the alternative control of C. suppressalis. In this study, two cytochrome P450 monooxygenase (P450) genes, CsCYP6SN3 and CsCYP306A1, were identified and characterized, which are expressed at all developmental stages, with the highest expression in the midguts and fat bodies of 3rd instar larvae. Vetiver significantly inhibited the expression levels of CsCYP6SN3 and CsCYP306A1 in 3rd larvae after feeding. RNA interference showed that silencing CsCYP6SN3 and CsCYP306A1 genes dramatically reduced the pupation rate and pupa weight. Feeding on vetiver after silencing CsCYP6SN3 and CsCYP306A1 led to higher mortality compared with feeding on rice. In conclusion, these findings indicated that the expression levels of CsCYP6SN3 and CsCYP306A1 were associated with the lethal effect of vetiver against C. suppressalis larvae and functional knowledge about these two detoxification genes could provide new targets for agricultural pest control.

Reference Genes for Expression Analysis Using RT-qPCR in Cnaphalocrocis medinalis (Lepidoptera: Pyralidae).

Cnaphalocrocis medinalis is a destructive migratory rice pest. Although many studies have investigated its behavioral and physiological responses to environmental changes and migration-inducing factors, little is known about its molecular mechanisms. This study was conducted to select suitable RT-qPCR reference genes to facilitate future gene expression studies. Here, thirteen candidate housekeeping genes (EF1α, AK, EF1ß, GAPDH, PGK, RPL13, RPL18, RPS3, 18S rRNA, TBP1, TBP2, ACT, and UCCR) were selected to evaluate their stabilities under different conditions using the ∆CT method; the geNorm, NormFinder, BestKeeper algorithms; and the online tool RefFinder. The results showed that the most stable reference genes were EF1ß, PGK, and RPL18, related to developmental stages; RPS3 and RPL18 in larval tissues; EF1ß and PGK in larvae feeding on different rice varieties; EF1α, EF1ß, and PGK in larvae temperature treatments; PGK and RPL13, related to different adult ages; PGK, EF1α, and ACT, related to adult nutritional conditions; RPL18 and PGK, related to adult mating status; and, RPS3 and PGK, related to different adult take-off characteristics. Our results reveal reference genes that apply to various experimental conditions and will greatly improve the reliability of RT-qPCR analysis for the further study of gene function in this pest.

Resistance of Lepidopteran Egg Parasitoids, Trichogramma japonicum and Trichogramma chilonis, to Insecticides Used for Control of Rice Planthoppers.

Trichogramma wasps are commonly used as biocontrol agents to manage lepidopteran rice pests in rice fields. However, lepidopteran pests synergistically occur with rice planthoppers which are not targeted by Trichogramma. The use of Trichogramma parasitoids in field-based pest control efforts is greatly affected by the application of insecticides targeting planthoppers. As such, insecticide-resistant strains of Trichogramma are urgently needed for the incorporation of these beneficial natural enemies into integrated pest management programs in rice agroecosystems. In the present study, Trichogramma japonicum Ahmead (Hymenoptera: Trichogrammitidae) and Trichogramma chilonis Ishii (Hymenoptera: Trichogrammitidae) were treated with sublethal doses of four insecticides which target rice planthoppers, to generate tolerant strains in the laboratory. The resistance rate of T. japonicum to imidacloprid was the highest (17.8-folds) after 10 successive treatments and experienced 2.5, 4.72, and 7.41-fold increases in tolerance to thiamethoxam, buprofezin, and nitenpyram, respectively. Tolerance of T. chilonis to imidacloprid, thiamethoxam, buprofezin, and nitenpyram were 8.8, 6.9, 4.43, and 5.67-fold greater, respectively. The emergence and deformity (without spreading wings or short wings) rates of T. japonicum and T. chilonis gradually recovered with an increased exposure time of treatments. The fecundity of T. japonicum treated with thiamethoxam was significantly higher than that of the control and T. chilonis treated with thiamethoxam and nitenpyra. Our results demonstrate that screening for insecticide-tolerant/resistant Trichogramma strains was feasible, especially in the pairing of T. japonicum and imidacloprid, which could provide a valuable biological control tool that can be combined with traditional chemical control strategies for use in IPM of rice agroecosystems.

Application of a novel method PCR-ligase detection reaction for tracking predator-prey trophic links in insect-resistant GM rice ecosystem.

Insect-resistant genetically modified (IRGM) rice is on the verge of commercial release in China, however, its potential non-target effect on non-target insect natural enemies remains controversial. Tracking trophic interactions between predators and preys in IRGM rice ecosystem can provide new insights into better understanding of the ecological risks of IRGM rice. In the present study, a novel method based on ligase detection reaction (LDR), PCR-LDR was introduced to track 15 prey species in the gut of a predaceous spider Pirata subpiraticus, a dominant natural enemy in rice field. Our results indicated that PCR-LDR could provide high specificity and sensitivity in tracking prey-predator interactions in rice ecosystems. PCR-LDR could detect as little as 1,000 th of DNA mixture. Reliable detection of DNA samples of prey species using PCR-LDR could be significantly affected by digestion time and prey species. In the analysis of 200 field-collected P. subpiraticus and 105 field-collected Tetragnatha maxillosa individuals using PCR-LDR, prey remains were identified in 78.3 and 74.3% of the individuals, respectively, from which significant predation differences between the two spider species were observed. Predation behavior of the spider species was not significantly different between Bt and non-Bt control rice lines. These results indicated that PCR-LDR can be used as an important tool for ecological studies, especially on the interactions between predators and preys in IRGM rice or other similar ecosystems.

Use of safflower as a trap crop for managing the mirid bug, Lygus pratensis Linnaeus (Hemiptera: Miridae), in cotton fields.

BACKGROUND: Cotton has been increasingly harmed by the mirid bug (Lygus pratensis Linnaeus) in Xinjiang Uyghur Autonomous Region, China. Using trap plants within or around the border of the cotton may be a beneficial management strategy for this pest of cotton. RESULTS: The potential of safflower (Carthamus tinctorius Linn) as a trap plant for managing L. pratensis was evaluated in laboratory and field experiments. Y-tube olfactometer assays demonstrated that L. pratensis was highly attracted to volatiles derived from safflower. Field experiments showed that safflower plots hosted more L. pratensis (adults and nymphs) than cotton plots. Early-sown safflower had more L. pratensis than mid-sown or late-sown safflower, and was more conducive to the settlement and reproduction of L. pratensis. The density of L. pratensis on safflower trap crops in three sowing patterns was significantly higher than on adjacent cotton. The pattern of intercropping safflower trap crops was more effective at reducing densities of L. pratensis on cotton than placing safflower as 'spot' trap crops or peripheral trap crops. However, this result also may be related to the overall area of the safflower trap crops. With regular chemical control of L. pratensis on safflower trap crops, the number of cotton bolls was increased by 10.04%, whereas the rate of boll damage was reduced by 33.44%, compared to cotton without safflower trap crops and insecticide sprays. CONCLUSION: Safflower shows promise as an effective trap crop for L. pratensis, and may contribute to controlling L. pratensis in cotton. © 2020 Society of Chemical Industry.

Transgenic rice plants expressing a fused protein of Cry1Ab/Vip3H has resistance to rice stem borers under laboratory and field conditions.

Six transgenic rice, Oryza sativa L., lines (G6H1, G6H2, G6H3, G6H4, G6H5, and G6H6) expressing a fused Cry1Ab/Vip3H protein, were evaluated for resistance against the Asiatic rice borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae), and the stem borer Sesamia inferens (Walker) (Lepidoptera: Noctuidae) in the laboratory and field. The bioassay results indicated that the mortality of Asiatic rice borer and S. inferens neonate larvae on six transgenic lines from seedling to filling stage was up to 100% at 168 h after infestation. The cumulative feeding area by Asiatic rice borer neonate larvae on all transgenic lines was significantly reduced compared with the untransformed parental 'Xiushui 110' rice. A 2-yr field evaluation showed that damage during the vegetative stage (deadheart) or during the reproductive stage (whitehead) caused by Asiatic rice borer and S. inferens for transgenic lines was much lower than the control. For three lines (G6H1, G6H2, and G6H6), no damage was found during the entire growing period. Estimation of fused Cry1Ab/Vip3H protein concentrations using PathoScreen kit for Bt-Cry1Ab/1Ac protein indicated that the expression levels of Cry1Ab protein both in main stems (within the average range of 0.006-0.073% of total soluble protein) and their flag leaves (within the average range of 0.001-0.038% of total soluble protein) were significantly different among six transgenic lines at different developmental stages. Both laboratory and field researches suggested that the transgenic rice lines have considerable potential for protecting rice from attack by both stem borers.

Response of Trichogramma spp. (Hymenoptera: Trichogrammatidae) to Insecticides at Concentrations Sublethal to Cnaphalocrocis medinalis (Lepidoptera: Pyralidae).

Trichogramma japonicum Ashmead (Hymenoptera: Trichogrammatidae) and Trichogramma dendrolimi Matsumura (Hymenoptera: Trichogrammatidae) are important parasitoids of Lepidopteran pests and are used for biological control in rice fields. In this study, the response of two of these parasitoids to four insecticides (chlorpyrifos, chlorantraniliprole, emamectin benzoate, and spinosad) were evaluated at target sublethal concentrations (TSC10 and TSC25, representing the LC10 and LC25 to the target pest) of the important rice pest, Cnaphalocrocis medinalis (Guenée). Each of the insecticides led to the mortality of adult T. japonicum and T. dendrolimi at TSC10 and TSC25, whereas no significant differences in the mortality of T. japonicum between TSC10 of chlorantraniliprole and control groups occurred. The parasitic capacity increased at F0 of T. japonicum at the two TSCs of spinosad treated host eggs, whereas the TSC10 was lower for emamectin benzoate at F1 for T. japonicum. The TSCs of chlorpyrifos treated host eggs negatively influenced the emergence rates of T. japonicum at F1. Emamectin benzoate with TSC10 reduced the female ratio of T. japonicum at F1. For T. dendrolimi, the TSCs of chlorpyrifos treated host eggs negatively influenced the emergence rates at F1. These findings indicate that T. japonicum and T. dendrolimi are affected by insecticides at TSCs, and among the four insecticides, chlorantraniliprole had the lowest mortality rates for T. japonicum and T. dendrolimi at TSCs.

Screening Sugars Can Benefit the Parasitoid Cotesia chilonis (Hymenoptera: Braconidae) Without Benefiting Its Host, Chilo suppressalis (Lepidoptera: Crambidae).

Most adult parasitoids depend on carbohydrate-rich food as an energy source for longevity, fecundity, and mobility. Thus, providing sugars has been proposed as a technique to maximize the biological control efficacy of parasitoids. However, the sugars provided for parasitoids need to be carefully selected because herbivore hosts might also benefit. Here we explore the effects of 12 naturally occurring sugars on the longevity and fecundity of the rice pest, Chilo suppressalis, and the longevity of its parasitoid, Cotesia chilonis, as well as the effect of sugars on sugar consumption of C. chilonis. Results showed that none of the tested sugars significantly impacted the longevity of C. suppressalis, but fructose, glucose, maltose, and sucrose significantly increased its fecundity. The longevity of C. chilonis was significantly increased when fed fructose, glucose, sucrose, maltose, trehalose, and melezitose. Our data suggest that C. chilonis consumed larger quantities of glucose, fructose, and sucrose followed by maltose, melezitose, and trehalose and the longevity of C. chilonis was positively correlated to sugar consumption. Our data also suggest that the herbivore C. suppressalis and its parasitoid C. chilonis responded differently to trehalose and melezitose. Although additional studies are needed, our data suggest that these sugars could be considered as candidate components for sugar sprays to enhance the activity and efficacy of C. chilonis, but without benefiting its pest host.

Bt cotton producing Cry1Ac and Cry2Ab does not harm two parasitoids, Cotesia marginiventris and Copidosoma floridanum.

Cabbage looper, Trichoplusia ni (Hübner) is an important lepidopteran pest on many vegetable and greenhouse crops, and some field crops. Although there are no commercial transgenic Bt vegetable or greenhouse crops, T. ni is a target of Bollgard II cotton, which produces Cry1Ac and Cry2Ab. We expand on previous work that examined the effect of Bt crops on parasitoids using Bt-resistant lepidopteran populations as hosts. Cry1Ac/Cry2Ab-resistant T. ni larvae were used to eliminate host quality effects and to evaluate the direct effects of Bt cotton on the parasitoids Copidosoma floridanum (Ashmead) and Cotesia marginiventris (Cresson). These tri-trophic studies confirm that Bt cotton had no significant impact on development, success of parasitism, survival and adult longevity of C. marginiventris when using Bt-resistant T. ni fed on Bt cotton. Similarly, this Bt cotton had no significant impact on the development, mummy weight and the number of progeny produced by C. floridanum. Our studies verified that lyophilized Bt crop tissue maintained its insecticidal bioactivity when incorporated into an artificial diet, demonstrating that hosts and parasitoids were exposed to active Cry proteins. The egg-larval parasitoid C. floridanum, or similar species that consume their entire host, should be considered useful surrogates in risk assessment of Bt crops to non-target arthropods.

The rice planthopper parasitoid Anagrus nilaparvatae is not at risk when feeding on honeydew derived from Bacillus thuringiensis (Bt) rice.

BACKGROUND: Honeydew is a sugar-rich excretion produced by sap-feeding Sternorrhyncha and is an important source of carbohydrates for natural enemies, especially for parasitoids. Honeydew derived from genetically modified (GM) crops can contain amounts of the transgene product. Thus, it is a possible route of exposure for natural enemies feeding on honeydew. In the present study, the potential effects of Nilaparvata lugens honeydew derived from Cry1C and Cry2A rice on different life-table parameters and parasitism dynamics of the egg parasitoid Anagrus nilaparvatae were evaluated under laboratory and field conditions. Furthermore, the Bacillus thuringiensis (Bt) levels and the sugar and amino acid composition of honeydew were analyzed. RESULTS: Results indicated that A. nilaparvatae was exposed to Bt proteins by feeding on N. lugens honeydew produced from Bt rice. However, honeydew derived from the tested Cry1C and Cry2A rice lines did not affect the development, longevity, emergence rate and fecundity of A. nilaparvatae. Also, the parasitism dynamics in the field remained unaffected. In addition, the sugar and amino acid composition of N. lugens honeydew was not significantly altered for the tested Bt rice lines compared with the parental non-Bt plant. CONCLUSION: The quality of honeydew derived from the tested Bt rice lines as a food resource for natural enemies was maintained. © 2018 Society of Chemical Industry.

Variation among conventional cultivars could be used as a criterion for environmental safety assessment of Bt rice on nontarget arthropods.

The current difficulty facing risk evaluations of Bacillus thuringiensis (Bt) crops on nontarget arthropods (NTAs) is the lack of criteria for determining what represents unacceptable risk. In this study, we investigated the biological parameters in the laboratory and field population abundance of Nilaparvata lugens (Hemiptera: Delphacidae) on two Bt rice lines and the non-Bt parent, together with 14 other conventional rice cultivars. Significant difference were found in nymphal duration and fecundity of N. lugens fed on Bt rice KMD2, as well as field population density on 12 October, compared with non-Bt parent. However, compared with the variation among conventional rice cultivars, the variation of each parameter between Bt rice and the non-Bt parent was much smaller, which can be easily seen from low-high bar graphs and also the coefficient of variation value (C.V). The variation among conventional cultivars is proposed to be used as a criterion for the safety assessment of Bt rice on NTAs, particularly when statistically significant differences in several parameters are found between Bt rice and its non-Bt parent. Coefficient of variation is suggested as a promising parameter for ecological risk judgement of IRGM rice on NTAs.