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• Panicle Rice Mite

Panicle Rice Mite Background

Background

The rice mite, Steneotarsonemus spinki ( S. spinki ) has been considered a serious rice pest in several Asian tropical regions. However, it was in the Americas that S. spinki assumed its largest economic importance. Yield losses in Central America have ranged from 30 to 90%. Until the present, S. spinki had not been found in rice crops in North America.

On July 13, 2007, USDA confirmed the detection of panicle rice mite (PRM), Steneotarsonemus spinki , at a rice research facility in Alvin, Brazoria County, Texas. Interceptions of this pest have been reported at greenhouses in Ohio and Texas during the last 10 years. S. spinki has also been confirmed in Puerto Rico.

Biology/Life Cycle

Under laboratory conditions (about 24°C), this mite multiplies rapidly; the duration of the life cycle varies from 5 to 9 days from egg to adult.

This mite is parthenogenetic. All the descendants of virgin females were males, but the mother female could mate with its male offspring and then produce both females and males. Virgin females in mite-free rice seedlings could develop an average of 79.4 mites in 17 days. Along with results on life cycle duration (13.6 to 8.5 days at 25°C to 30°C), this study showed that this mite has a high potential for population growth (Xu et al. 2001).

• Eggs: The eggs of these mites are a translucent white; they are also ovoid and elongated.
• Larvae: Like the eggs the larvae are a translucent white. The larvae are elongated.
• Inactive Larvae: This phase is also a translucent white. The larvae which will become adult females are transported by the (adult) males, as is common in other species in the Family Tarsonemidae.
• Adult Males: The body of the male is elongated and broadest in the anterior region of the hysterosoma.
• Adult Females: The body of the female is elongate and broadest in the region of the hysterosoma.

Hosts

There are two main reported hosts of RPM: Rice, Oryza sativa,and the weedy red rice, Oryza latifolia. 

Distribution

The rice panicle mite has been found in some areas the following countries: Asia, Japan, Phillippines, Caribbean (Cuba, Dominican Republic, Haiti, South America (Colombia, Venezuela), North America.

Dispersal Pathways

Some pathways for PRM are: rice seeds, wind dispersed, greenhouse and field workers, agricultural machinery, plant to plant transmission, hitchhiking on insects and birds, and floating on debris on flooded fields.

Symptoms

The symptoms vary depending upon the host country. In India, rice plants that had poorly exserted earheads and necrotic leaf sheaths were found to have rice panicle mites between the stem and the leaf sheath. In Korea, feeding by this mite caused the following symptoms deformed panicles and inflorescences, lesions on the inner surfaces of leaf sheaths, and browning of rice hulls. In Taiwan, the mite, in addition to its direct damage, usually carries spores of rice sheath rot fungus ( Acrocylindrium oryzae Sawada), which causes brownish spots on rice sheath and grains, damage termed “sterile grain syndrome.”