Characterization of pests, pest losses, and production patterns in rainfed lowland rice of the Mekong River Delta [Viet Nam]
1995
Pinnschmidt, H.O. | Nguyen Dang Long | Tran Tan Viet | Le Dinh Don | Teng, P.S. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Holistic field surveys with integrated crop-protection treatments were conducted at four rainfed lowland rice sites in the Mekong River Delta (Southern Vietnam) in 1992. Data on crop development, yield, dynamics of disease and pest severities, weather, water conditions, physicochemical soil properties, and crop-and pest-management practices were collected. High yields were closely associated with high soil productivity as indicated by high soil carbon content, high fertilizer input, and high pest-management intensity; low occurrence of vegetative drought stress; and high pest and disease severities whereas low yields were associated with the opposite conditions. The total yield-gap was estimated to range from about 20 percent to 70 percent and be due mainly to N-limitation: less than 10 percent was attributed to pests and diseases. Intensification of chemical pest control significantly increased yield and pest-induced yield losses estimated at the field level were between about 10 percent and 20 percent with highest values at low-yielding sites. Chemical control did not significantly affect overall disease- and pest-severity levels. Disease and pest severities did not consistently positively correlate with yield-loss estimates adjusted for N-limitation or maximum yield per field. Key pests with regard to observed disease- or damaged-severity level were sucking insects on panicles, the dirty panicle complex, stem rot, weeds, stem borers, other tiller-damaging pests, and brown spot. Leaf yellowing was only severe at Long An whereas root rot was severe at all sites except Soc Trang
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