Behavioral mechanism of transfer and dispersal of Propylaea japonica in cotton adjacent to sorghum fields

Increasing crop biodiversity, such as by adjacent managed crops, is recognized as an effective biological control measure. However, few studies have focused on the mechanisms involved in how adjacent managed crops increase natural enemy populations, leading to reduced pest numbers. This study investigated the hypothesis that cotton grown adjacent to sorghum would positively influence the feeding and oviposition preferences of the ladybug Propylaea japonica, which predates cotton aphids, leading to enhanced pest control. The populations of Aphis gossypii were significantly lower and those of P. japonica were significantly higher in cotton grown adjacent to sorghum compared with monoculture cotton fields. Regardless of diet on which the larva of P. japonica were reared (Melanaphis sacchari, A. gossypii, and 50% M. sacchari + 50% A. gossypii), the adults always consumed significantly more M. sacchari compared with A. gossypii. P. japonica also showed significantly higher feeding and oviposition preferences for host plants bearing aphids to only host plants. P. japonica fed M. sacchari preferred to lay eggs on cotton, whereas those fed A. gossypii preferred to lay eggs on sorghum. These results suggest that the habitat of natural enemies can be expanded by influencing their feeding and oviposition preferences to achieve pest control in adjacent cropping systems. This research, which incorporates field and laboratory studies, suggests an approach for the successful conservation and biological control of cotton aphids using adjacent managed cotton and sorghum crops

Curative efficacy of entomopathogenic nematodes against white grubs in honeysuckle fields

Root-feeding white grubs are one of the most serious pests of honeysuckle trees (Lonicera japonica) in China, directly damaging their roots and facilitating infection by soil pathogens. Entomopathogenic nematodes (EPNs) are considered as potential control agents against soil-dwelling insect pests. This study aimed to identify effective EPN species against white grubs through bioassay and field experiments. Among the EPN species screened against Holotrichia oblita under laboratory conditions, Steinernema feltiae and Heterorhabditis indica had low virulence, while S. longicaudum, S. glaseri, and H. bacteriophora applied at a rate of 400 IJs/larva caused a higher corrected mortality (80.00 ± 5.77%), which screened them as good candidates for future applications. The field experiments showed that both S. longicaudum and H. bacteriophora were approximately as effective in reducing white grubs as the insecticide phoxim, whereas S. glaseri caused a significantly lower reduction compared with these two EPNs and phoxim. Plant mortalities obtained from S. longicaudum, H. bacteriophora and the insecticide treatment plots were significantly lower than those observed in the water-treated control plots. All EPNs examined could establish well in the treated honeysuckle fields for 42 d, confirmed by Tenebrio molitar larvae baiting technique. Our findings suggest that EPNs could provide curative efficacy against white grubs and significantly reduce plant death in honeysuckle fields

An Analysis of the Factors Affecting Hyporheic Exchange based on Numerical Modeling

The hyporheic zone is a transition zone for the exchange of matter and energy between surface water and subsurface water. The study of trends and sensitivities of bed hyporheic exchanges to the various influencing factors is of great significance. The surface−groundwater flow process was simulated using a multiphysics computational fluid dynamics (CFD) method and compared to previous flume experiments. Based on that, the single-factor effects of flow velocity (u), water depth (H), dune wave height (h), and bed substrate permeability (κ) on hyporheic exchange in the bed hyporheic zone were investigated. The sensitivity analysis of various factors (H, u, dune wavelength (L), h, bed substrate porosity (θ), κ, and the diffusion coefficient of solute molecules (Dm)) in the surface−subsurface water coupling model was done using orthogonal tests. The results indicated that u, h, and κ were positively related, whereas H was negatively related to hyporheic exchange. H and u showed large effects, whereas κ, Dm, and θ had moderate effects, and L and h showed small effects on hyporheic exchange. This study provides valuable references for the protection and recovery of river ecology

Sublethal effects of imidacloprid on the performance of the bird cherry-oat aphid Rhopalosiphum padi.

The bird cherry-oat aphid, Rhopalosiphum padi (L.), is a major insect pest of cereal crops in many countries. Imidacloprid has been widely used for controlling piercing-sucking insect pests worldwide, but its sublethal effects on R. padi have not been well addressed. In this study, we investigated the sublethal effects of imidacloprid on biological parameters and five enzyme activities of R. padi. The LC10, LC20, and LC25 of imidacloprid to adult aphids were 0.0053, 0.0329 and 0.0659 mg L-1, respectively. These concentrations significantly decreased pre-adult survival rate, but prolonged the development duration of 1st instar nymphs, pre-oviposition period, and adult longevity. Adult oviposition period was also extended by LC20. The intrinsic rate of increase (r), net reproductive rate (R0), and finite rate (λ) decreased at all three concentrations, whereas mean generation time (T) increased. Moreover, LC20 and LC25 significantly inhibited superoxide dismutase (SOD) activity, but increased catalase (CAT) activity. Acetylcholinesterase (AChE) activity also increased at LC20. However, cytochrome P450 enzyme and peroxidase (POD) activity did not differ between imidacloprid treatments and the control. In conclusion, the imidacloprid concentrations tested here have negative impacts on the performance of R. padi by reducing its nymphal survival, extending the development duration of some stages, decreasing the rate of population growth, and altering enzyme activities

Sublethal and transgenerational effects of sulfoxaflor on the demography and feeding behaviour of the mirid bug Apolygus lucorum.

Sulfoxaflor, the first commercially available sulfoximine insecticide, has been used for the control of sap-feeding insect pests such as plant bugs and aphids on a variety of crops. However, its sublethal effects on the mirid bug Apolygus lucorum, one of the key insect pests of Bt cotton and fruit trees in China, have not been fully examined. Here, we evaluated the demography and feeding behaviour of A. lucorum exposed to sulfoxaflor. The leaf-dipping bioassay showed that the LC10 and LC30 of sulfoxaflor against 3rd-instar nymphs of this insect were 1.23 and 8.37 mg L-1, respectively. The LC10 significantly extended the nymphal duration and decreased the oviposition period by 5.29 days and female fecundity by 56.99% in the parent generation (F0). The longer duration of egg, 5th-instar nymphs, preadult, and male adult longevity were observed in the F1 generation (F1) at LC10. At the LC30, the duration of egg and 1st-instar nymph, female adult longevity, and oviposition period of the F1 were significantly shorter, while the nymphal duration in the F0 and duration of 5th-instar nymphs, preadult survival rate, and male adult longevity in the F1 significantly increased. The net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) in the F1 were not significantly affected by these two concentrations, whereas the mean generation time (T) was lower at the LC30. Additionally, the probe counts and cells mixture feeding time were markedly lengthened by the LC10 and LC30, respectively, when A. lucorum nymphs exposed to sulfoxaflor fed on Bt cotton plants without insecticides. These results clearly indicate that sulfoxaflor causes sublethal effects on A. lucorum and the transgenerational effects depend on the tested concentrations