Rice Panicle Mite
Feeding takes place behind the leaf sheath and can be detected by the presence of cinnamon to chocolate-brown blotches there. Mites can often be observed directly when the outer sheath is removed. The mites also feed on the developing panicles from the boot stage to the milk stage of heading. The damage causes the entry of opportunistic fungal pathogens into developing grains and the leaf sheath (e.g. that transmitting sheath rot). This results in spikelet infertility, plant sterility, straight-head, and a characteristic deformation of the grains called "parrot-beaking". It is the most important and destructive mite pest attacking the rice crop worldwide.
The symptoms are caused by the feeding activity of the rice panicle mite, Steneotarsonemus spinki. High temperatures and low rainfall are ideal for the development of large populations in the field. Optimal conditions are temperatures between 25.5 °C and 27.5 °C and humidities between 80 and 90%. Intensive, continuous rice culture and the sharing of equipment between fields is also conducive to population buildup. Rice plants can be infested throughout the entire year. However, populations are greatest at the booting stage and decline as the plant matures. Damage is often difficult to characterize because the mite is commonly interacting with other pests of rice such as Sarocladium oryzae (sheath rot) and Burkholderia glumae (bacterial panicle blight).
Make sure not to kill natural enemies on of S. spinki on paddy fields (spiders, endo-parasitoid wasp, etc.) through the overuse of insecticide.
Always consider an integrated approach with preventive measures together with biological treatments if available. In case of heavy infestations, use insecticidal sprays containing hexythyazox, quinalphos, sulphur, propargite or fenpropathrin. Before spraying, flood the field to make mites move up the plant increase the efficiency of the treatment.