Yuyong Liang

Habitat management using flowering plants on rice bunds and field ridges surrounding rice paddies can enhance conservation biological control by supporting beneficial predatory insects. However, multi-year field evidence for sesame (Sesamum indicum) when deployed as these bund-side flowering strips, and there is no molecular gut-content confirmation that the key predatory mirid bug Cyrtorhinus lividipennis preys upon rice planthoppers pests under field conditions. Over a two-year field experiment, we compared rice paddies with sesame-planted bunds against control paddies without bunds. We surveyed major piercing-sucking pests (brown planthoppers Nilaparvata lugens, white-backed planthoppers Sogatella furcifera, leafhoppers, and thrips) and their primary predator C. lividipennis throughout different rice phenological growth stages. PCR-based laboratory digestion assays were used to quantify the detectability of N. lugens DNA in the gut of laboratory-reared and field-collected C. lividipennis. Sesame-planted bunds significantly increased natural-enemy abundance (C. lividipennis) and reduced planthoppers, leafhopper, and thrips densities. Treatment effects varied by rice stage, with suppression mainly occurring from booting/heading to grain filling and no significant differences at tillering, and effects at maturity were weak. In the laboratory, N. lugens DNA detection declined from 68.75% at 0 h to 0% at 16 h after feeding. In the field, 37.5% of C. lividipennis from sesame-bund paddies tested positive for N. lugens DNA. These findings provide field and molecular evidence that sesame-planted bunds conserve C. lividipennis and contribute to suppression of piercing-sucking rice pests, supporting their use as an auxiliary habitat-management tactic in rice integrated pest management.

Maize is a major cereal crop worldwide, and its stable production is essential for national and global food security. Pests are among the key factors affecting the yield and quality of maize. Therefore, it is crucial to evaluate the yield recovery and quality losses after implementing control measures against pests during different periods. In this study, we investigated the population dynamics of the main maize pests in South China and assessed the yield and quality of maize treated with measures for the effective control of these pests during different periods. The results showed that the fall armyworm (FAW), Spodoptera frugiperda, was the most severe pest of autumn maize. There was a 10.02% decrease in ear weight when no control measures were taken at the fourth-leaf stage, and there were 80.45% and 76.09% increases in the damage index when no control measures were taken at the tasseling and blister stages, respectively. Additionally, the tannin content in maize kernels increased by 26.28% when no pest control measures were taken throughout the entire growing period. These findings will increase farmers’ knowledge regarding the detrimental effects of the FAW and provide a theoretical basis for the reasonable and timely control of maize pests.

Objective Spodoptera frugiperda is one of main pests damaging maize.It is the most economical and environmentally friendly strategy to control S. frugiperda by selecting and using resistant maize variety. Method In this study，the field resistance of 47 maize varieties to S. frugiperda was evaluated by leaf damage level and ear damage level under natural infection in the field；and the laboratory fitness of S. frugiperda fed on 4 maize varieties which field resistance varied greatly was detected；finally，biochemical substances content of these maize leave were determined and their correlation with leaf damage index and feeding fitness was analyzed. Result The results showed that the resistance of 47 maize varieties to S. frugiperda was different between seedling stage and earing stage.At the seedling stage，there were also 39 sensitive varieties and 7 highly sensitive varieties and only Jingke 968 reached the medium resistance level.At the ear stage，8 varieties showed high resistance，5 varieties reached the resistance standard，13 varieties were moderately resistant，7 varieties were sensitive，and 14 varieties were highly sensitive.The varieties with high resistance were Wanxiantian 159，Meiyushuangtiannuo 502，Guitian 571，Ganketian 9，Baimuda，Guitian 570，Zhengtian 68，Jingheng 18-1.The host suitability index of S. frugiperda fed on 4 maize varieties ranking from high to low were Ruiyu 926，Ganketian 8，Jingke 968 and Shuangcui 270，and host suitability index were 9.57，7.12，6.40，and 6.13，respectively.The leaf damage index in the field was positively correlated with reducing sugar content of maize leave（R=0.940，P=0.030），and the host suitability index was negatively correlated with tannin and total alkaloid content（tannin：R=-0.910，P=0.045；total alkaloid：R=-0.926，P=0.037），it was also negatively correlated with amylose and total sugar content，but there was no significant difference. Conclusion One maize variety with medium resistance in seeding stage and 8 maize varieties with high ear resistance were screened.Due to the poor resistance of different maize varieties to S. frugiperda under natural conditions，other green control technologies should be developed to reduce damage of this pest.This study also proved that the indoor fitness was different from the field resistance results.At the same time，it was found that reducing sugar，tannin and total alkaloid may be involved in maize defense pests，which provided a research basis for further screening of insect-resistant metabolites.

Fall armyworm (FAW) Spodoptera frugiperda is a major migratory and polyphagous pest. Overwintering, migrating and colonizing characters of FAW are closely related to vegetation and host adaptation. In this study, we investigated oviposition preference, feeding preference of FAW, as well as fitness, cold tolerance of FAW larvae fed on spring and summer crop (corn) and two winter crops (cabbage, Brassica campestris and rape, B. napus). The results showed that FAW could complete their life cycle by feeding on cabbage and rape, although fitness was not as good as corn. FAW fed on cabbage had higher survival, female pupal mass and host suitability index than rape while larvae preferred to feed on rape leaves and females preferred to lay eggs on rape plants. In addition, FAW larvae fed on cabbage had the shortest recovery time from chill coma compared to corn and rape, indicating that cold tolerance of FAW larvae was improved by feeding on cabbage. Consequently, cabbage could be an ideal host for FAW which needed to survive and reproduce in winter. These results improve our understanding of host selection and adaption of FAW, as well as lay a foundation for predicting winter breeding areas of FAW.

The rice stem borer, Chilo suppressalis (Walker), and the rice leaf folder, Cnaphalocrocis medinalis Guenée are two of the most destructive lepidopteran pests in rice. Since these two lepidopteran insects show occurrence laps in rice paddy fields, farmers prefer to set the pheromone-baited traps of C. suppressalis accompany with the pheromone traps of C. medinalis in the rice fields for convenient observation. However, our field observation demonstrated that no male of the rice stem borer was captured in the traps baited with commercial C. suppressalis sex pheromone (CCS) combined with commercial C. medinalis sex pheromone (CCM). To confirm the C. medinalis sex pheromone component(s) to interfere with the attraction of males of the rice stem borers to their conspecific female moths, the single component of C. medinalis sex pheromone combined with CCS in traps were tested in the laboratory and in the rice paddy field. The results revealed the two alcohol components in CM, i.e., (Z)-11-octadecen-1-ol (Z11-18:OH) and (Z)-13-octadecen-1-ol (Z13-18:OH) may cause a significant reduction in the captures by CCS to C. suppressalis males. We recommend against using these sex pheromones together in the field and suggested that Z11-18:OH and Z13-18:OH could be potential inhibitors or antagonists of C. suppressalis sex pheromone to control the rice stem borer in practice.

Transgene flow through pollen and seeds leads to transgenic volunteers and feral populations in the nature, and consumer choice and economic incentives determine whether transgenic crops will be cultivated in the field. Transgenic and non-transgenic plants are likely to coexist in the field and natural habitats, but their competitive interactions are not well understood. Field experiments were conducted in an agricultural ecosystem with insecticide spraying and a natural ecosystem, using Bt-transgenic rice (Oryza sativa) and its non-transgenic counterpart in pure and mixed stands with a replacement series. Insect damage and competition significantly decreased plant growth and reproduction under the coexistence of transgenic and conventional rice. Insect-resistant transgenic rice was not competitively superior to its counterpart under different densities in both agricultural and natural ecosystems, irrespective of insect infection. Fitness cost due to Bt-transgene expression occurred only in an agroecosystem, where the population yield decreased with increasing percentage of transgenic rice. The population yield fluctuated in a natural ecosystem, with slight differences among pure and mixed stands under plant competition or insect pressure. The presence of Chilo suppressalis infection increased the number of non-target insects. Plant growth and reproduction patterns, relative competition ability and population yield indicate that Bt-transgenic and non-transgenic rice can coexist in agroecosystems, whereas in more natural habitats, transgenic rice is likely to outcompete non-transgenic rice.