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.

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.

Nontarget impacts of six transgenic Bt rice lines (expressing the Cry1Ab or Cry1Ab/Cry1Ac protein) on the thrips, Stenchaetothrips biformis (Bagnall)

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.

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, EF1β, 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 EF1β, PGK, and RPL18, related to developmental stages; RPS3 and RPL18 in larval tissues; EF1β and PGK in larvae feeding on different rice varieties; EF1α, EF1β, 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.