Effect of rice whorl maggot damage on the yield of a modern cultivar [Philippines]
1989
Justo, H.D. Jr. | Rubia, E.G. | Estano, D.B. | Shepard, B.M.
Damage by the rice whorl maggot (RWM) Hydrellia philippina Ferino on IR72 and its effect on yield were evaluated at IRRI [International Rice Research Inst., Los Banos, Laguna, Philippines] farm in wet season 1988. Rice hills were scored for percentage of RWM damage and then tagged based on the following scale: I=control, II=1-10%, III=11-20%, IV=21-30%, V=31-40%, VI=41-50%, VII=51-60%, VIII=61-70%, IX=71-80%, X=81-90%, and XI=91-100%. A maximum of 40 randomly-selected hills was tagged per damage scale. Scoring for RWM damage and tagging were done at 21 DT. Tagged hills were then assessed at 29, 36, and 43 DT in order to determine further damage by or disappearance of symptoms from RWM attacks. Symptoms of RWM damage on rice hills with high initial damage score (50%) gradually disappeared, and rice hills with low initial damage score showed increased severity of damage during the first assessment and also gradually disappeared in subsequent assessment periods. Analysis of yield components showed no significant difference in the number of spikelets/panicle. However, variations in the number of panicle/sq.m. and percentage of filled grains were recorded, but can hardly be attributed to RWM damage. There was no correlation between yield and severity of RWM damage. No other pest that may cause yield loss was recorded.
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