State of pesticide residue in litchi orchard soils in Guangxi and Fujian, China

Litchi, a famous (sub)tropical fruit, originated in South China. After Guangdong Province, Guangxi is the second largest litchi production base, and Fujian is also another main litchi production base in China. The state of pesticide residue in litchi fruit has been of great concern to researcher and consumers. In fact, the state of pesticide residue in litchi orchard soils has been related to the quality and safety of litchi fruit. This work therefore investigated the state of common pesticide residues in Guangxi and Fujian litchi orchards to guide safe production of the crop in these regions. A total of 210 soil samples were collected in litchi orchards in Guangxi and Fujian after harvest. The samples were analyzed for commonly used pesticides, including metalaxyl, mancozeb, carbendazim, deltamethrin, cypermethrin, cyhalothrin, dipterex, dimethoate and dichlorvos. Based on the results, carbendazim was the most frequently detectable pesticide in litchi orchards in both Guangxi and Fujian. The detection rates of carbendazim in Guangxi and Fujian litchi orchard soils were 48.1% and 84.0%, respectively. While mancozeb, dipterex and dimethoate were not detected in Guangxi orchard soils, the detection rates of the other five pesticides were less than 10%. Metalaxyl and cypermethrin were observed in 24.0% of the soil samples from Fujian orchards. The other six pesticides were at least not detectable. Litchi orchards numbered with zero or one detectable pesticide accounted for 48.6% and 38.4% of the total litchi orchards in Guangxi, and 56.0% and 8.0% in Fujian, respectively. Litchi orchards with two detectable pesticides accounted for 11.4% and 32.0% of the total investigated litchi orchards in Guangxi and Fujian respectively. The pesticide with the highest mean concentration in orchard fields of Guangxi was cypemethrin (5.0 μg·kg^-1), followed by dichlorvos (1.9 μg·kg^-1). The concentrations of the other detectable pesticides were less than 1.0 μg·kg^-1. The ranked order of average detectable pesticides was carbendazim (0.77 μg·kg^-1) > metalaxyl (0.65 μg·kg^-1) > cypermethrin (0.48 μg·kg^-1) in Fujian. Although higher concentrations and detection rates of pesticides were detected in Fujian, the state of pesticide residues in both Fujian and Guangxi was still minimal. Hence, soil pesticide residues in litchi orchards posed no harm to litchi quality in both Guangxi and Fujian.