Repellency of Silver-Gray Plastic Film on Megalurothrips usitatus (Thysanoptera: Thripidae) in Cowpea (Vigna ungiculata)

<i>Megalurothrips usitatus</i> (Bagnall) (Thysanoptera: Thripidae) is a serious insect pest, causing severe damage to crops in Southeast Asia and Hainan Province, China. The misuse of chemical pesticides has led to high resistance in pests to many pesticides. Physical control is an alternative method that is environmentally friendly. We investigated the effects of silver-gray plastic film on the behavior of <i>M. usitatus</i> on cowpea (<i>Vigna ungiculata</i>). The observations of behavior found that the silver-gray plastic film has different repellent effects on female and male thrips, with a repellency rate of over 90% for male thrips, while it repels female thrips at a rate of 85% in the laboratory. Field surveys have found that the number of <i>M. usitatus</i> arrived at the first peak at 7:00-9:00 a.m., and then gradually decreased, reaching its lowest point by noon, and then gradually increased to reach the second peak at 13:00-15:00 p.m. on a sunny day. In the climbing period of yardlong beans, before flowering, despite the increasing numbers of thrips, we found that the number of thrips in the silver-gray plastic film hanging area was significantly lower than that in the control area. During the early and late stages of flowering, the number of thrips in the silver-gray plastic film hanging area was significantly lower than that in the control area, but during the peak flowering period, there was no significant difference in thrips numbers between the areas with silver-gray plastic film and the control areas. These results indicate that the silver-gray plastic film is a potential method to decrease damage from <i>M. usitatus</i>, especially in the early stages of crop growth.