First report of Steneotarsonemus spinki Smiley (Trombidiformes: Tarsonemidae) infesting greenhouse-grown rice (Oryza sativa L. ssp. indica cv. MR 297) in Malaysia

Abstract

In October 2024, unusual symptoms not previously associated with known rice diseases in Malaysia were observed in a greenhouse facility at the Malaysian Agricultural Research and Development Institute (MARDI), Serdang, Selangor. Initial signs, characterised by powdery white spots on the lower leaves and orange-yellow tip discolouration, were initially misdiagnosed as nutrient deficiency. Further inspection revealed a white residue and internal browning of the leaf sheath. Scanning electron microscopy (SEM) confirmed the presence of Steneotarsonemus spinki Smiley (panicle rice mite), marking the first confirmed occurrence of this pest in Malaysian greenhouse-grown rice. Treatment with the acaricide spiromesifen resulted in a significant reduction of mite populations within one week, confirming both the role of the mites in the observed damage and the effectiveness of the acaricide. Herbarium specimens of the infected rice panicles were prepared and deposited under voucher numbers MDI 12,564, MDI 12,565, and MDI 12,566. This study investigates and documents the infestation and damage caused by S. spinki, highlighting the pest’s potential threat to Malaysian rice production and the need for vigilant monitoring and management.