Comparison of Trapping Effects of Different Traps and Monitoring the Occurrence Dynamics of <i>Spodoptera litura</i> in Soybean Fields of Dangtu, Anhui Province, China

In order to clarify the trapping efficiency of different types of sex pheromone traps on populations of <i>Spodoptera litura</i> in soybean fields, three kinds of conventional traps, called YL-VT, YL-HEMT and YL-NMT, and types of traps equipped with a automatic catch monitoring mechanism, called AIM and AIM-lite-A, have been tested. These last two allow monitoring the diurnal and seasonal rhythms of the catches. From 5 August to 5 October 2020, each YL-VT trap caught an average of 84.4 heads of <i>S. litura</i> moths per day, which was significantly higher than the YL-HEMT (11.8 heads), YL-NMT (16.5 heads) and AIM (9.7 heads), which did not show significant differences between them. The half-life of pheromone attraction effect in YL-VT trap is about 17–20 days. Considering the number of trapping and the duration of pheromone attraction effect, YL-VT trap is the best. For efficient monitoring, the validity period is approximately 15 days. Among the causes that could explain its higher capture rate and efficiency, the YL-VT trap has the smallest and largest number of inlet devices, and in it, the lure core is located inside of the insect inlet device. Under different occurrence numbers of <i>S. litura</i>, the accuracy of the automatic count of AIM-lite-A is 90% greater than in the AIM trap. The diurnal rhythms of <i>S. litura</i> observed by AIM-lite-A show that <i>S. litura</i> have two active periods that are from 18:00 to 21:00 and from 23:00 to 4:00 at night and that the first active period may be affected by sunshine and temperature. The annual activity rhythm of <i>S. litura</i> monitored by AIM showed that the activity of <i>S. litura</i> was related to temperature, there were approximately 6 generations of <i>S. litura</i> in a year and that the activity peak was from August to September in Dangtu, China. AIM and AIM-lite-A can be used for the annual monitoring of <i>S. litura</i> population in soybean fields because of their automatic counting function. AIM can simultaneously record a variety of meteorological data, AIM-lite-A has higher accuracy and a lower cost, which can be selected according to different situations. In conventional traps, the trap YL-VT can be used for the population monitoring of <i>S. litura</i> in soybean fields and pest control in the field, especially in greenhouses and net rooms where organic soybeans are grown, due to its low cost and efficient trapping ability.