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.

Assessing the effects of Cry1C rice and Cry2A rice to Pseudogonatopus flavifemur, a parasitoid of rice planthoppers.

Transgenic rice producing insecticidal proteins from Bacillus thuringiensis (Bt) could help protect the plants from damage by lepidopteran pests. However, one concern is the potential of Bt rice to harm non-target natural enemies, which play a vital role in pest control. In the present study, the potential effects of Cry1C rice and Cry2A rice on different life-table parameters and population dynamics of Pseudogonatopus flavifemur, a parasitoid of rice planthoppers, were evaluated under laboratory and field condition. The exposure of P. flavifemur to plant-produced Bt proteins was also analyzed. Results indicated that direct feeding on rice plants was the main exposure pathway of P. flavifemur to the Cry1C and Cry2A proteins. No significant difference on the development, survival, longevity, fecundity, and prey consumption of P. flavifemur was detected over two generations between the Bt and non-Bt rice treatments. Furthermore, the population dynamics of P. flavifemur were not affected by Cry1C rice and Cry2A rice. In conclusion, the tested Cry1C rice and Cry2A rice do not appear to harm the parasitoid P. flavifemur.

Effects of Transgenic Rice Infected with SRBSDV on Bt expression and the Ecological Fitness of Non-vector Brown Planthopper Nilaparvata lugens.

The susceptibility of rice lines, T1C-19, T2A-1, and MH63 to SRBSDV infection are similar and the contents of cry protein in T2A-1 and T1C-19 do not change significantly. The survival rates of BPH nymphs feeding on SRBSDV-infected T1C-19, Bt T2A-1, or MH63 rice plants were not significantly different. The developmental stages of female BPH fed on T1C-19 plants infected with SRBSDV were significantly shorter than those fed on uninfected rice, while the males showed no significant difference. The duration of BPH feeding on SRBSDV-infected T2A-1 and MH63 also showed no significant difference in comparison with the respective control groups. Longevities of BPH adults feeding on SRBSDV-infected T1C-19, T2A-1 or MH63 were also not significant. However, the longevity of male adult BPH feeding on un-infected MH63 was significantly reduced in comparison with that of adult males feeding on un-infected T1C-19 and T2A-1 rice. In addition, the different rice lines and the rice plants infected and uninfected with SRBSDV did not significantly affect the sex ratio, female body weight, longevity, fecundity, or egg hatchability of BPH. In general, transgenic Bt rice infected with SRBSDV had little effect on the ecological adaptability of BPH.

The Effects of Temperature and Host Age on the Fecundity of Four Trichogramma Species, Egg Parasitoids of the Cnaphalocrocis medinalis (Lepidoptera: Pyralidae).

The Cnaphalocrocis medinalis (Guenée) is one of the most important rice pests in Asia and is difficult to control by chemical insecticides due to its rapid development of resistance. To screen potential species for biological control of C. medinalis, we investigated the effects of temperature (20, 24, 28, 32, and 36 °C) and host age (1-, 2-, 3-, and 4-d-old) on the fecundity of four Trichogramma spp. on C. medinalis eggs. Our results indicated that C. medinalis eggs were acceptable to T. japonicum, T. chilonis, T. dendrolimi, and T. ostriniae, though no eggs were parasitized at 36 °C. There were no significant differences in parasitism among the four Trichogramma species under the tested temperature regions, except at 20 °C where parasitism by T. japonicum was significantly higher than that by T. chilonis and T. ostriniae. However, T. japonicum had significantly more progeny than the other three Trichogramma species at 32 °C. All four Trichogramma species performed well on 1-, 2-, and 3-d-old C. medinalis eggs, but parasitism on 4-d-old eggs was significantly reduced. Trichogramma japonicum parasitized the highest number of C. medinalis eggs on different aged hosts and had more progeny than the other Trichogramma species, especially on 3-d-old hosts. In conclusion, T. japonicum exhibited better performance on C. medinalis eggs than the other three Trichogramma species and could be considered as our most suitable Trichogramma candidate for control of C. medinalis.

[A banker plant system of 'Leesia sayanuka-Nlilaparvata muiri-Tytthus chinensis' to control rice planthoppers]. / "秕谷草-伪褐飞虱-ä¸­åŽæ·¡ç¿ ç›²è½"载体植物系统的可行性.

In order to clarify the feasibility of the banker plant system "Leesia sayanuka-Nlilaparvata muiri-Tytthus chinensis" to control rice planthooper, the effects of the combination of rice, L. sa-yanuka, N. lugen and N. muiri on the adult morphology, population growth, oviposition and feeding selectivity of T. chinensis were carried out in the present study. The results showed that the body size of male and female adults of T. chinensis rice population (feeding on N. lugens eggs) were significantly larger than those of T. chinensis population (feeding on N. muiri eggs). Population growth parameters including fecundity, net productive rate, innate capacity for increase, finite rate of increase of L. sayanuka feeding on N. lugens eggs were significantly higher than those of L. sayanuka feeding on N. muiri eggs. However, the population growth ability of L. sayanuka feeding on N. muiri was still high enough to expand the population. For the oviposition selection, both rice population and L. sayanuka population preferred laying eggs on rice than on L. sayanuka. Meanwhile, there was no significant difference in the predation of females, males and nymphs to N. lugens eggs or N. muiri eggs between rice population and L. sayanuka population. At last, based on our results, we discussed the feasibility of establishing the banker plant system "L. sayanuka-N. muiri-T. chinensis" in rice fields.

Different Performance of Two Trichogramma (Hymenoptera: Trichogrammatidae) Species Feeding on Sugars.

Most parasitoids depend on carbohydrate-rich foods to maximize their longevity and reproduction potential. These food resources are commonly from floral nectar, extra-floral nectar, and honeydew, which contain monosaccharides, disaccharides, and oligosaccharides. Here, we report an experiment to explore the effects of 12 naturally occurring sugars on the gustatory response, longevity, and fecundity of Trichogramma japonicum and Trichogramma chilonis These two parasitoid species differed in their responses to the tested sugars. Trichogramma japonicum showed a high gustatory response to eight sugars, but T. chilonis to only six. However, only fructose, glucose, and sucrose increased the longevity of T. japonicum, and only glucose enhanced the fecundity. For T. chilonis, fructose, galactose, gluctose, maltose, melibiose, sucrose, and melezitose prolonged the longevity and increased fecundity. Furthermore, female T. japonicum benefitted much less from the ingestion of sugars when compared with female T. chilonis For T. japonicum, feeding on suitable sugars, longevity was increased by a factor of 1.8-2.0, and fecundity by a factor of 1.5. In T. chilonis, longevity increased by a factor of 2.9-5.2 and fecundity by 2.7-4.0. Thus, providing the right sugars to the parasitoids will help to enhance the biological control efficacy of Trichogramma, and T. chilonis in particular.

[Effects of plant viruses on vector and non-vector herbivorous arthropods and their natural enemies: a mini review].

Plant viruses transmitted by arthropods, as an important biotic factor, may not only directly affect the yield and quality of host plants, and development, physiological characteristics and ecological performances of their vector arthropods, but also directly or indirectly affect the non-vector herbivorous arthropods and their natural enemies in the same ecosystem, thereby causing influences to the whole agro-ecosystem. This paper reviewed the progress on the effects of plant viruses on herbivorous arthropods, including vector and non-vector, and their natural enemies, and on their ecological mechanisms to provide a reference for optimizing the management of vector and non-vector arthropod populations and sustainable control of plant viruses in agro-ecosystem.

Mechanisms for flowering plants to benefit arthropod natural enemies of insect pests: prospects for enhanced use in agriculture.

Reduction of noncrop habitats, intensive use of pesticides and high levels of disturbance associated with intensive crop production simplify the farming landscape and bring about a sharp decline of biodiversity. This, in turn, weakens the biological control ecosystem service provided by arthropod natural enemies. Strategic use of flowering plants to enhance plant biodiversity in a well-targeted manner can provide natural enemies with food sources and shelter to improve biological control and reduce dependence on chemical pesticides. This article reviews the nutritional value of various types of plant-derived food for natural enemies, possible adverse effects on pest management, and the practical application of flowering plants in orchards, vegetables and field crops, agricultural systems where most research has taken place. Prospects for more effective use of flowering plants to maximize biological control of insect pests in agroecosystem are good but depend up on selection of optimal plant species based on information on the ecological mechanisms by which natural enemies are selectively favored over pest species.

Influence of rice black streaked dwarf virus on the ecological fitness of non-vector planthopper Nilaparvata lugens (Hemiptera: Delphacidae).

Rice black streak dwarf virus (RBSDV) is transmitted by the small brown planthopper (SBPH), Laodelphax striatellus (Fallen). Non-vector rice brown planthopper (BPH), Nilaparvata lugens (Stål), shares the same host rice plants with SBPH in paddy fields. The changes in nutritional composition of rice plants infected by RBSDV and the ecological fitness of BPH feeding on the infected plants were studied under both artificial climate chamber and field conditions. Contents of 16 detected amino acids and soluble sugar in RBSDV infected rice plants were higher than those in the healthy ones. On the diseased plants BPH had significantly higher nymphal survival rates, nymphal duration of the males, weight of the female adults, as well as egg hatchability compared to BPH being fed on healthy plants. However, there was no obvious difference in female nymph duration, longevity and fecundity. Defense enzymes (superoxidase dismutase, SOD and catalase, CAT) and detoxifying enzymes (carboxylesterase, CAE and glutathione S-transferase, GST) in BPH adults fed on diseased plants had markedly higher activities. The results indicate rice plants infected by RBSDV improved the ecological fitness of the brown planthopper, a serious pest but not a transmitter of the RBSDV virus.

[Ecological responses of brown planthopper, Nilaparvata lugens, to triazophos and deltamethrin on transgenic Bt rice lines and their non-Bt parental rice].

In this study, the brown planthopper (BPH), Nilaparvata lugens (Hemiptera: Delphacidae), cultured on Bt rice lines (T1C-19 with cry1C gene and T2A-1 with cry2A gene) and their parental rice MH63, were treated with a series of concentrations of triazophos and deltamethrin when they developed up to the third instar for the evaluation of the effects of Bt rice on BPH resurgence induced by pesticides. The results indicated that BPH nymphal duration decreased with the increasing concentration of deltamethrin, while no significant differences of BPH nymphal duration were observed on the same rice variety treated with the different concentrations of triazophos. Furthermore, the survival rate of BPH significantly declined and their fecundity significantly increased with the increasing concentration of insecticides. However, ecological fitness parameters of BPH including nymphal duration, survival rate, female adult mass, fecundity and egg hatchability were not significantly different among Bt and non-Bt rice varieties when they treated with the same concentration of insecticide. These results implied that no significant difference in the BPH resurgence induced by pesticides was observed among the two tested Bt rice varieties and their non-Bt parental rice variety.

[Interactive effects of temperature and nitrogen fertilizer on the survival, development, and reproduction of brown planthopper Nilaparvata lugens].

A laboratory study was made on the interactive effects of temperature (20 degrees C, 23 degrees C, 26 degrees C, 29 degrees C, and 32 degrees C) and nitrogen fertilization level (0 and 250 kg x hm(-2)) on the survival, development, and reproduction of brown planthopper (BPH) Nilaparvata lugens. With increasing temperature from 20 degrees C to 29 degrees C, the egg hatchability, nymphal survival, and adult fecundity of BPH increased and the developmental duration of all stages shortened; while at 32 degrees C, it was in adverse. At all test temperatures, the BPH on rice plants treated with 250 kg N x hm(-2) had higher egg hatchability, nymphal survival and adult fecundity, and shorter developmental duration of eggs and nymphs, compared with no nitrogen fertilization, which suggested that high level nitrogen fertilization enhanced the ecological adaptability of BPH to stress conditions. There were significant interactive effects of temperature and nitrogen fertilizer on the egg hatchability, nymphal duration, and adult fecundity of BPH, implying that global warming and long-term high level application of nitrogen fertilizer could be responsible for the outbreaks of BPH in recent years.