The Effects of Temperature and Humidity on a Field Population of Bradysia odoriphaga (Diptera: Sciaridae)

Impacts of climate change and host plant availability on the potential distribution of Bradysia odoriphaga (Diptera: Sciaridae) in China

BACKGROUND

Chinese chives (Allium tuberosum Rottler ex Sprengel) are favored by consumers because of its delicious taste and unique fragrance. Bradysia odoriphaga (Diptera: Sciaridae) is a main pest that severely harms Chinese chives and other Liliaceae's production. Climate change may change the future distribution of B. odoriphaga in China. In this study, the CLIMEX was employed to project the potential distribution of B. odoriphaga in China, based on China's historical climate data (1987-2016) and forecast climate data (2021-2100).

RESULTS

Bradysia odoriphaga distributed mainly between 19.8° N-48.3° N and 74.8° E-134.3° E, accounting for 73.25% of the total mainland area of China under historical climate conditions. Among them, the favorable and highly favorable habitats accounted for 30.64% of the total potential distribution. Under future climate conditions, B. odoriphaga will be distributed mainly between 19.8° N-49.3° N and 73.8° E-134.3° E, accounting for 84.89% of China's total mainland area. Among them, the favorable and highly favorable habitats will account for 35.23% of the total potential distribution, indicating an increase in the degree of fitness. Areas with relatively appropriate temperature and humidity will be more suitable for the survival of B. odoriphaga. Temperature was a more important determinant of the climatic suitability of the pest B. odoriphaga than humidity. Host plants (Liliaceae) availability also had impact on climate suitability in some regions.

CONCLUSIONS

These projected potential distributions will provide supportive information for monitoring and early forecasting of pest outbreaks, and to reduce future economic and ecological losses. © 2024 Society of Chemical Industry.

Biological and physiological responses of two Bradysia pests, Bradysia odoriphaga and Bradysia difformis, to Dinotefuran and Lufenuron

Bradysia odoriphaga and Bradysia difformis are destructive root maggots that cause severe losses to vegetables, flowers and edible fungi. Due to the long-term dependence on single pesticides, Bradysia resistance to insecticides has increased, and field control efficacy has decreased obviously. To screen alternative insecticides, and compare the insecticide susceptibility of these two species, we tested the toxicity of eight insecticides to B. odoriphaga and B. difformis, and measured the sublethal effects of Dinotefuran and Lufenuron on life-history parameters and detoxification enzyme activities. Bioassay results indicated that Dinotefuran and Lufenuron had relatively higher toxicity to B. odoriphaga and B. difformis compared to other neonicotinoid and insect growth regulator insecticides, respectively. Significant adverse impacts caused by sublethal concentrations (LC₂₀) of Dinotefuran and Lufenuron on the life-history parameters of F0 and F1 generations of B. odoriphaga and B. difformis were observed. These included reduced survival, prolonged larval development and reduced adult longevity and fecundity. B. odoriphaga had greater resistance and adaptation to insecticides than B. difformis, and an LC₂₀ concentration of Dinotefuran stimulated the reproduction of B. odoriphaga F1 generation and increased the life table parameters. Detoxifying enzymes (CarE and GSTs) and P450 activities fluctuated after a sublethal concentration (Dinotefuran and Lufenuron) treatment, and at the peak value of enzyme activities, the enhancement of detoxifying enzymes of B. odoriphaga was significantly higher than that of B. difformis. These results indicated that Dinotefuran and Lufenuron should be considered as alternatives to other insecticides for control of root maggots. B. odoriphaga exhibited stronger adaptation to insecticides than B. difformis. These data provide guidance for control of root maggots, and the basic information presented here can help reveal the differences in adaptive mechanisms between B. odoriphaga and B. difformis.

Identification and Pathogenicity of a New Entomopathogenic Fungus, Mucor hiemalis (Mucorales: Mucorales), on the Root Maggot, Bradysia odoriphaga (Diptera: Sciaridae)

Bradysia odoriphaga Yang and Zhang (Diptera: Sciaridae), the Chinese chive root maggot, is a destructive pest of Allium vegetables and flowers that causes severe losses in northern China. Novel biological control technologies are needed for controlling this pest. We identified a new entomopathogenic fungus isolated from infected B. odoriphaga larvae and evaluated the susceptibility of the biological stages of B. odoriphaga and the effects of temperature on fungus growth and pathogenicity. Based on morphological characteristics and molecular phylogeny, the fungus was identified as Mucor hiemalis BO-1 (Mucorales: Mucorales). This fungus had the strongest virulence to B. odoriphaga larvae followed by eggs and pupae, while B. odoriphaga adults were not susceptible. A temperature range of 18-28°C was optimum for the growth and sporulation of M. hiemalis BO-1 and virulence to B. odoriphaga larvae. At 3 and 5 d after inoculation with 105 spores/ml at 23°C, the survival rates were 24.8% and 4.8% (2nd instar larvae), respectively, and 49.6% and 12.8% (4th instar larvae), respectively. The potted plant trials confirmed that M. hiemalis BO-1 exerted excellent control efficiency against B. odoriphaga larvae, and the control exceeded 80% within 5 d when the spore concentration applied exceeded 107 spores/ml. In conclusion, these findings supported the hypotheses that this fungus could serve as an effective control agent against B. odoriphaga larvae and is worth being further tested to determine its full potential as a biocontrol agent.

Impacts of Non-Lethal High-Temperature Stress on the Development and Reproductive Organs of Bradysia odoriphaga

Simple Summary

Bradysia odoriphaga is a soil-dwelling insect native to China, and its preferred host is Chinese chives. In this study, non-lethal high-temperature as an important limiting factor to affect the population and development of B. odoriphaga was assessed. Meanwhile, the physiological mechanism on non-lethal high-temperature to reduce the population was also identified. These would lay a key theoretical foundation for the future development of high-temperature products for environment friendly pest control strategies.

Abstract

Bradysia odoriphaga is an agricultural pest in China’s vegetable industry. In this study, pupae and adults were exposed to various non-lethal high-temperatures. The results demonstrated a decreased rate of eclosion once the pupae were exposed to temperatures exceeding 37 °C for 1 h. No effect on the lifespan of unmated female adults was observed after exposure to temperature stress, while unmated male adult lifespan decreased (>37 °C for 2 h). The size of the testis and ovaries for unmated male and female adults decreased, as did the fecundity and egg hatching rate for mated females. Compared with the control group (25 °C), the testis size of unmated male adults decreased after high-temperature stress followed by recovery at 25 °C for 1 h, though the size of the ovaries of female adults did not change. Additionally, the size of the testis and ovaries for unmated male and female adults decreased following high-temperature stress and 24 h of recovery at 25 °C. High temperatures affected males more than females; 37 °C is the critical temperature to control the population of B. odoriphaga. These results lay the foundation for the future development of environmentally friendly high-temperature prevention and pest-control strategies.

The Thermoperiod Alters Boper Gene Expression and Thereby Regulates the Eclosion Rhythm of Bradysia odoriphaga (Diptera: Sciaridae)

In most organisms, various physiological and behavioral functions are expressed rhythmically. Previous studies have shown that thermoperiod is an important factor affecting circadian clock-related genes that regulate insect locomotor activity. Bradysia odoriphaga Yang & Zhang is an underground pest that attacks more than 30 crops but is especially damaging to Chinese chives. In this study, we analyzed the adult eclosion time and period (Boper) gene expression in B. odoriphaga as affected by temperature (cycling vs constant temperature), insect stage, and tissue specific. We found that the eclosion time and expression of the Boper gene changed during the temperature cycle but not under a constant temperature. Silencing of Boper expression significantly decreased the adult eclosion rate and significantly increased adult mortality and malformation. The findings indicate that thermoperiod alters Boper expression and regulates the eclosion rhythm.