Yield components and quality of rice in response to graminaceous weed density and rice stink bug populations

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Field experiments were conducted in 2002 and 2003 to investigate weed density, its relationship to rice stink bug (Oebalus pugnax, F.) populations, and damage to rice caused by stink bugs. Graminaceous weeds examined were barnyardgrass, Echinochloa crus-galli Beauv., Amazon sprangletop, Leptochloa panicoides (Presl.) Hitchc., broadleaf signalgrass, Brachiaria platyphylla Nash., and large crabgrass, Digitaria sanguinalis, (L.). Rice seed weight, percent filled seed, percent pecky rice, milling quality, and yield were measured. Data showed that 13-23 weeds/1 m2 was associated with an increase of one rice stink bug per plot. Weeds served as hosts of rice stink bugs prior to panicle emergence of rice; consequently, rice stink bugs infested rice early in the grain filling process and reduced the percentage of filled seeds. One hundred weeds/1 m2 caused a 1% increase in pecky rice, and for every 1% pecky rice, milling quality was reduced by 0.5%. Plots not treated with insecticide had significantly more non-filled seeds, pecky rice, and broken kernels than treated plots. Neither weeds nor insects at the densities observed in this test appeared to effect seed weight. Rice stink bug damage did not significantly contribute to yield losses greater than weeds in the absence of rice stink bugs. Rice stink bugs had more of an affect on the quality of rice rather than the yield. Results reported here suggest that late season weed control may be important in terms of indirect losses in grain quality associated with increased populations of rice stink bug. © 2005 Elsevier Ltd. All rights reserved.

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Crop Protection

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