Abstract
Simulation of the attack of defoliating insects provides a measurement of the level of damage that the crop can support at a given developmental stage and also allows to quantify the loss of productivity. This study evaluated the effects of increasing levels of artificial defoliation in upland rice plants under field conditions, on grain production at three phenological stages, vegetative stage V8 (collar formation in the 8th leaf of the main stem), vegetative stage V12 (formation of the flag leaf) and reproductive stage R3/R4 (liberation of the panicle or anthesis). The percentage of damage at all stages increased significantly from 25% defoliation, and was higher when defoliation occurred in V8 and V12. Defoliation levels up to 50% in the reproductive stage did not influence the quantity of filled grains, total spikelets per panicle and weight of filled grains per panicle, and thus the pest control is not required. The data show that the control of leaf-chewing insects in upland rice should be restricted to the vegetative stage.
Highlights
Rice (Oryza sativa L.) is one of the most ancient cultivated plant species and currently occupies 10% of the agricultural lands of the planet (CHANG, 2003)
This study evaluated the effects of increasing levels of artificial defoliation in upland rice plants under field conditions, on grain production at three phenological stages, vegetative stage V8, vegetative stage V12 and reproductive stage R3/R4
The data show that the control of leaf-chewing insects in upland rice should be restricted to the vegetative stage
Summary
Rice (Oryza sativa L.) is one of the most ancient cultivated plant species and currently occupies 10% of the agricultural lands of the planet (CHANG, 2003). In this study increasing levels of artificial defoliation was simulated at different phenological stages of upland rice to estimate the damage caused by defoliating insects on grain production. The results for total spikelets showed significant difference for the isolated factors (phenological stage - DF= 2; F= 77.6750; P< 0.001 and percentage of defoliation Df= 4, F= F= 46.0361; P< 0.001).
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