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Neonicotinoid insecticides are in widespread use around the world, cause pollinator decline. We used semi-field conditions to determine the effect of sublethal insecticide, thiamethoxam, exposure on orientation behavior and sugar responsiveness. Bees could not reject the non-treated flower or the insecticide or insecticide/fungicide treated flower. After bees consumed the insecticide or insecticide/fungicide treated nectar, they could not discriminate between a flower odor or blank control in a Y-maze when making a first choice. We also found that treated bees wander back and forth in both arms to make a final decision about food location, and used longer duration in the Y maze than the control group. Sugar responsiveness was also reduced after bees were fed with insecticide or insecticide/fungicide treated food, one week was needed for them to display the same level of responsiveness as the control group. The thiamethoxam or thiamethoxam/carbendazol treated crop field does not act as an olfactory repellent to the bee, but it does affect its post-consumption behavior.

Honeybees are major pollinators of agricultural crops and many other plants in natural ecosystems alike. In recent years, managed honeybee colonies have decreased rapidly. The application of pesticides is hypothesized to be an important route leading to colony loss. Herein, a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was used to determine eight highly detectable pesticides (carbendazim, prochloraz, pyrimethanil, fenpropathrin, chlorpyrifos, imidacloprid, thiamethoxam, and acetamiprid) in rape flowers. A field experiment was conducted at the recommended dose to evaluate the contact exposure risk posed to honeybees for 0–14 days after treatment. The initial residue deposits of neonicotinoids and fungicides among these compounds were 0.4–1.3 mg/kg and 11.7–32.3 mg/kg, respectively, and 6.4 mg/kg for fenpropathrin and 4.2 mg/kg for chlorpyrifos. The risk was quantified using the flower hazard quotient (FHQ) value. According to the data, we considered imidacloprid, thiamethoxam, chlorpyrifos, fenpropathrin, and prochloraz to pose an unacceptable risk to honeybees after spraying in fields, while fungicides (carbendazim and pyrimethanil) and acetamiprid posed moderate or acceptable risks to honeybees. Therefore, acetamiprid can be used instead of imidacloprid and thiamethoxam to protect rape from some insects in agriculture, and the application of prochloraz should be reduced.

Core Ideas The grain yield was highest in the Pot‐S treatment, followed by the Pot‐flat‐S treatment and the Flat‐S treatment.Insufficient sink size (number of effective panicles multiplied by number of spikelets per panicle) is the key factor in the grain yield reduction in the Flat‐S treatment.The spatial distribution characteristics of the first and second leaves were crucial for the high yield formation of mechanically transplanted rice. The objective of this 2‐yr field experiment was to compare the performance of three rice (Oryza sativa L.) cultivars grown in three different nursery trays and mechanically transplanted using compatible machinery. The three treatments were a blanket‐type nursery tray (Flat‐S treatment), a bowl‐type nursery tray (Pot‐S treatment), and a pot‐style/blanket‐type nursery tray (Pot‐flat‐S treatment). The net photosynthetic rate, leaf area index, dry matter accumulation, and matter translocation from the sheath at flowering to the kernel were significantly higher in the Pot‐S treatment than in other two treatments (p < 0.05). The highest grain yield was in the Pot‐S treatment (9.15–11.81 × 103 kg ha–1), followed by the Pot‐flat‐S treatment (8.84–10.62 × 103 kg ha–1), and then the Flat‐S treatment (8.3–9.78 × 103 kg ha–1). Low yields were attributed mainly to weak sink characteristics. The relative heights of the top three leaves on the plant were higher in the Pot‐S treatment than in the other two treatments, and there was more space between adjacent leaves at the top of the canopy in the Pot‐S treatment than in the other two treatments. The flag leaf area, the height difference between the first and third leaves (HDfirst‐third) and between the second and third leaves (HDsecond‐third), the relative height of the first leaf, and the droop angle of the first leaf significantly affected the source and sink traits. Moreover, HDfirst‐second and HDfirst‐third significantly and directly affected grain yield. Thus, the HDs of the top three leaves were crucial for high yields of mechanically transplanted rice.