Studies were conducted to test the hypothesis, significant benefits can be achieved for the management of rice water weevil, Lissorhoptrus oryzophilus Kuschel, by the use of rice varieties with low levels of host plant resistance coupled with the judicious use of cultural practices and insecticides. Tolerant traits of a current commercial variety of rice, "Bengal", was manifested consistently over multiple years. Study on rice growth as effected by weevil injury showed that pruning of root systems by larvae of weevil resulted in a decrease in tiller number and shoot biomass of rice plants in the vegetative stage of growth. Yield losses were due to a combination of decreases in panicle densities, numbers of grains per panicle, and grain weights. Experiments on density-yield relationships documented that larval densities during earlier stages of rice growth were more strongly correlated with yield losses than were larval densities later in the growing season. Slopes of yield loss were greater negative for early-flood than for delayed-flood plots, and greater negative for susceptible varieties. A phenology model predicted that emergence of weevils occurred after the accumulation of 139.2 degree-days (°C * Day). Using a temperature threshold of 10°C, the total degree-days required for development of one generation is about 623.4 degree-days (from egg to pupation was 359.1 ± 19.4; pupal development was 264.3). Larval development did not differ between varieties with different resistant levels. In conclusion, this study showed that host-plant resistance, delayed-flooding and reduced insecticide can be integrated together. Although use of high rate of insecticide currently gives the best economic return, integrated control provides a combination of adequate control and environmental friendliness. The same economic return can be achieved using a more tolerant variety and delayed-flood without insecticide treatment.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-03172004-203127 |
| Date | 19 March 2004 |
| Creators | Zou, Li |
| Contributors | Michael J. Stout, Dennis R. Ring, Richard T. Dunand, T. E. Reagan, Seth Johnson, Zhijun Liu |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-03172004-203127/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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