YIELD LOSSES BY STEM BORER (Diatraea saccharalis Fab. 1794) (LEPIDOPTERA: PYRALIDAE) IN UPLAND RICE GENOTYPES
Keywords:
Upland rice, stem borer, sampling, genotype evaluationAbstract
The impact of the Diatraea saccharalis natural infestation on yield of 24 genotypes of upland rice was studied in an experiment carried out in field conditions. The attack of D. saccharalis on stems and its effect on spikelet weight was determined using a yield loss index and by regression analysis. The index used quantifies the spikelet mass loss per bored stem in relation to spikelet mass no bored stem. The estimates obtained with these two methods were different. Less than 10% of genotypes showed a linear relationship between the infestation and stem borer damage. Estimated yield losses based on the index seemed more appropriate to the conditions of the experiment. Infestations by D. saccharalis did not visibly affect the weight of spikelets of five genotypes, caused a small reduction in two genotypes, and caused economic losses in the most of them (17 genotypes). The CNAs9023 genotype was the least infested and presented the highest weight of spikelets, and showed more resistance than CNAs9028, which was more infested and produced less.
KEY-WORDS: Upland rice; stem borer; sampling; genotype evaluation.
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