Cnaphalocrocis medinalis is a key lepidopteran pest of rice.  However, little is known about the nutritional requirements of the adult or the effects of adult-derived nutrients on reproduction.  The aim of the present study was to evaluate the effects of carbohydrates and amino acids on the reproductive and demographic parameters of C.?medinalis.  Different feeding solutions significantly influenced adult survival and reproduction.  All the sources of carbohydrates used in the treatments (fructose, glucose, and sucrose) were sufficient to increase adult longevity and fecundity, and benefited the development of ovaries in the adult stage.  The positive impact of carbohydrates on lifetime fecundity was due to the prolonged oviposition period and the increased daily fecundity.  The intrinsic rate of increase (r_m) of C.?medinalis increased from 0.103 in water-fed individuals to approximately 0.138 when adults were fed with solutions containing carbohydrates.  In contrast, amino acid intake by adult insects exhibited no effect on the longevity, fecundity, ovarian development or population growth, even showing an impact of decreasing longevity of females.  As nectar secreted by the flowering plant is generally rich in sugars, the potential effects of nectar on the adults of C.?medinalis and other pests have to be considered during the development of biological control by applying flowering plants as a microhabitat and food source for natural enemies in rice fields.

The fall armyworm (FAW) Spodoptera frugiperda, which originated in the Americas, is advancing across China and threatening the nation’s maize crops.  Currently, one widely used tool for its control is genetically modified (GM) Bacillus thuringiensis (Bt) maize.  Sufficient content of Bt protein in appropriate plant parts is crucial for enhancing resistance against insect pests.  In this study, we conducted a systematic investigation of Cry1Ab levels in Chinese domestic GM maize DBN9936, which has recently obtained a biosafety certificate, and evaluated its efficacy against FAW.  Quantification of expression levels of Cry1Ab, via ELISA, indicated a spatio-temporal dynamic, with significant variation of mean Cry1Ab, ranging from 0.76 to 8.48 μg g^–1 FW with the Cry1Ab protein level ranked as: V6–V8 leaf>R1 leaf>R4 leaf>R1 silk>VT tassel>R4 kernel.  Among the nine locations, the Cry1Ab levels in DBN9936 of the Xinxiang, Langfang, and Harbin fields were significantly lower than those from Wuhan and Shenyang, and were slightly, but not significantly lower than those from the other four fields.  Furthermore, the artificial diet–Cry1Ab mixture and plant tissue feeding bioassays revealed that DBN9936 has high efficacy against FAW.  The insecticidal efficacy of different tissues against FAW larvae reached 34–100% with a descending order of lethality as follows: VT leaf>R4 leaf>R1 husk>R1 silk>VT tassel>R4 kernel.  Taken together, our results showed that Bt-Cry1Ab maize DBN9936 has potential as a promising strategy to manage FAW.

 

Three transgenic maize events (IE09S034, Shuangkang 12–5 and C0030.3.5) produced Cry1Ie, Cry1Ab/Cry2Aj and G10-EPSPS, Cry1Ab and EPSPS, respectively, all of which target the Asian corn borer.  The oriental armyworm Mythimna separata (Walker) is the secondary target.  In this study, the effects of the three Bt maizes on the development and survival of armyworm were studied.  The results showed that IE09S034 had insecticidal activity against 1st instar larvae, and the survival rate of armyworm fed with Bt maize for 10 days was 46.2%, significantly lower than that of the control.  The larvae at 3rd–6th instar were more tolerant of the Bt toxin than the early instar larvae.  However, Shuangkang 12-5 had good insecticidal activity against 1st–5th instar larvae.  The mortality was nearly 100% when the larvae were fed with Shuangkang 12-5 before 3rd instar, and the toxin had quick-acting efficacy.  This event significantly inhibited the development of armyworm; that is, the larval duration of the 3rd and 4th instar larvae fed with Shuangkang 12-5 was prolonged by 4.5 and 3.0 days, respectively.  The pupal weight and egg number were also significantly lower than those of the control.  For C0030.3.5, it could control 1st–5th instar larvae effectively.  The mortality rates were all over 50% if 1st–3rd larvae were fed with this event.  The pupal weight of 4th–6th instar larvae fed with Bt maize were only 53.9, 56.8 and 54.6%, respectively, compared to that of the control.  The number of eggs laid was significantly less than the control.  The results indicate that all three transgenic maize events exhibit the potential to provide effective control of early instar larvae of armyworm, which can be commercialized in future to control lepidoptera pests such as Asian corn borer and armyworm.

 

The multicolored Asian lady beetle, Harmonia axyridis (Coleoptera: Coccinellidae), is a common generalist predator in China and is occasionally found gathering on the Chinese pagoda tree, Sophora japonica, in summer.  In a field investigation, we found that H. axyridis adults preferred S. japonica during its flowering period even though their optimal prey (aphid) is absent at this time.  In addition, male and female adults were attracted to S. japonica flowers to a similar extent in a Y-tube olfactometer assay.  Using coupled gas chromatography-electroantennogram detection (GC-EAD), we identified a flower odor component (nonanal) that elicited a significant electrophysiological response in H. axyridis.  Electroantennogram (EAG) dose-dependent responses revealed that the amplitude of the adult beetle’s EAG response increased with increasing concentration of nonanal, peaking at 10 mg mL^–1.  In Y-tube olfactometer behavioral tests, H. axyridis adults preferred a 10 mg mL^–1 nonanal source over a 100 mg mL^–1 diluent.  Under field conditions, the adults were significantly attracted to both concentrations (10 and 100 mg mL^–1), and high concentrations generally had greater attraction.  All these results suggest that nonanal, a volatile compound of S. japonica flowers, greatly attracts H. axyridis adults.  This study provides a basis for the development of synthetic attractants of H. axyridis, with the potential to promote biocontrol services of this generalist predator in the native area (e.g., China) and to suppress its population by mass trapping in its invasive areas. 

Heavy metals have been found to be endocrine disruptors in invertebrates.  Lead is one of the most widespread elements of contamination, but there has been no research about the effects of lead stress on vitellogenin (Vg) gene expression in insects exposed to lead over multiple generations.  In this paper, the effects of different concentrations of lead (0, 0.3, 4.8 and 76.8 mg kg^–1) on the expression of Vg in the beet armyworm over five successive generations were studied.  The results showed that lead stress had significant effects on Vg expression in a dose-dependent manner.  For females at the larval and adult stages, as lead concentration increased, Vg expression was significantly inhibited; for males at these two developmental stages, Vg expression was induced and increased as lead concentration increased.  In addition, with the increase over stressed generations, inhibited effects for females and induced effects for males at the larval and adult stages became increasingly more obvious.  However, at the pupal stage, Vg expression in the two genders was different from that at the larval and adult stages.  The results indicate that lead stress can upregulate Vg expression in males which should be a useful indicator for environmental risk assessment.