Flood and Planthopper Damage to Crops during Kyoho 17 (1732) and How Information on the Oiling Method was Circulated

Abstract

The rainy season in 1732 persisted for some 50 days. In the intercalary month of May, it rained day after day. Around May 10th, there was heavy rainfall resulting in extensive flood damage. Fortunately however, as the rain fell comparatively early, it was possible to minimize the damage by replanting the seedlings and also by switching to dry field farming. Following the rainy season, rainfall was moderate but the weather was unstable with thunderstorms, mixed sunshine and rain, and drizzles frequently occurring, lowering temperatures. The presumption is that the unfavorable conditions which had continued since the planting of the rice plants resulted in their feeble growth.There was an abnormal outbreak of planthoppers immediately following the end of the long rainy season and it was widely believed that this outbreak of planthoppers was related to the prolonged rains. However, recognition of the insect outbreak was based on theories of natural causes and the “In-yo-Gogyo-setsu” (Yin-yang and the Five Elements). Naturally, it was concluded that the extended rain had caused air borne planthoppers to arrive in great numbers. The presumption is now that the scant sunshine and high humidity prevailing during June and July, together with the growing conditions of rice plants, resulted in even heavier damage by the planthoppers.In the Kyushu, Chugoku and Shikoku districts, all private and Shogunate domains sent in urgent warnings (notifications) concerning the outbreak of planthoppers to the Shogunate government. Even when we examine the detached territories, we find that it was only the Mimasaka domain of the Annaka Clan that failed to send in a notification. In the Kinki district, 21 private clan domains (out of 57) and 11 magistrates' offices of the Shogunate domains (out of 15) sent in urgent warnings. The majority of the private domains in Kyushu also sent in their notifications at an early date. With respect to the private domains in Chugoku and Shikoku, the periods when notifications were sent in differed between the western and eastern halves of the districts assuming that a line is drawn from north to south down the center of these two districts. Notifications from private domains in the eastern parts of the Chugoku and Shikoku districts were sent in a at a later date as was the case with the Kinki district. Their notifications were sent in late because it was after harvesting that they realized than the damage was far worse than first expected.In Kyushu, abnormal insect damage caused by white-backed rice planthoppers occurred from the beginning of June. The Omura domain suffered severe damage in early June, and similar damage, the “Kabudae” phenomenon, struck the Isahaya and Saeki domains in mid-June with the result that these three domains resorted to switching to dry field farming. In Westen Japan, abnormal insect damage had occurred in almost all areas by mid-July. Particularly in villages in the Suo Hagi and Aki Hiroshima domains, rice crops were completely destroyed in a matter of a few days around July 15th. This date coincided with the period when late rice formed ears. The damage suffered during this period was that caused mainly by brown rice planthoppers. Shiinoki Village of the Chikuzen Akizuki domain experienced damage from both white-backed planthoppers and brown rice planthoppers. However, around July 11th the principal cause of rice plant damage changed from white-backed to brown rice planthoppers.Discovery of the oiling method to exterminate planthoppers marks an epoch in the history of agriculutral techniques of the modern age, but there is as yet no established theory concerning this method. Information on the oiling method spread primarily around the Fukuoka domain, the Omura domain and the territory controlled by Hitadaikan. In the Fukuoka domain, the villages were notified to adopt the oiling method as a “divine message from the Tenman-sama.”