Development of method to forecast soybean leaf damage by common cutworm using entomological radar and searchlight trap

Abstract

To develop a method to forecast soybean leaf damage caused by larvae of the common cutworm, Spodoptera litura (Fabricius), insect dispersion was monitored with an x-band entomological radar and a searchlight trap during the summer soybean season in 2016 and 2017 in western Japan. The insect catch number in the searchlight trap and number of newly damaged leaves in a soybean field were compared to see how much soybean damage the insect's arrival caused. The 2016 results indicated that catch number peaks appeared 3–5 days before the peaks in the number of newly damaged leaves. The time lag corresponded to the egg period. Similar data were found in 2017. However, both the catch number and the number of newly damaged leaves were smaller that year, due to the lower occurrence of the insect. The radar observation showed dispersion at altitudes over the monitoring site when the peaks in insect catch number occurred. The insects often arrived under a northerly wind condition, from the mountainous area to the north. This study suggested that short-term forecasting of soybean leaf damage by radar and searchlight trap may be possible.

Keywords

• wind
• pest control
• crops
• horticulture
• soybean leaf damage
• common cutworm
• searchlight trap
• insect dispersion
• x-band entomological radar
• summer soybean season
• insect catch number
• newly damaged leaves
• soybean field
• soybean damage
• catch number peaks
• time 3.0 d to 5.0 d