Seasonal incidence of sugarcane white grub at Tamil Nadu, India

Sugarcane, a vital commercial crop, faces significant pest pressure from white grubs (Coleoptera: Scarabaeidae). It is an emerging problem especially in Tamil Nadu, where it causes severe damage to sugarcane production. This study aimed to assess the distribution, seasonal incidence and damage caused by white grubs in six districts of Tamil Nadu (Tiruvannamalai, Kallakurichi, Dharmapuri, Namakkal, Trichy and Thanjavur) during 2023-2024. The survey focused on larval population dynamics and correlated them with weather parameters. Roving surveys in four districts, where significant infestations were noted, showed that larval population peaks occurred in the 37th and 35th Standard Meteorological Weeks (SMWs) of 2023 and 2024 respectively. Larval damage per clump peaked at 79.67 % (37th SMW) in 2023 and 73.66 % (33rd SMW) in 2024, with the highest damage observed in Tiruvannamalai (79.88 %) in 2023 and Kallakurichi (76.13 %) in 2024. A significant positive correlation found between larval population and maximum temperature (r = 0.193 to 0.973 across districts) and a negative correlation with rainfall. For adult beetles, the maximum mean population of 105.49 adults/trap/week was recorded in the 24th SMW at Tiruvannamalai, with a general emergence starting from the 15th SMW (April). A significant positive correlation was observed between adult emergence and rainfall (r = 0.647 to 0.898) and minimum temperature (r= 0.456 to 0.743). Conversely, maximum temperature showed a negative correlation with adult emergence. These findings provide valuable insights for the development of Integrated Pest Management (IPM) strategies and enabling timely interventions to mitigate crop damage.