Abstract
The reduction of foliar area can cause yield reduction in common bean crops. The objective of this work was to verify which is the effect of different defoliation levels realized in several development stages of common bean (Phaseolus vulgaris L. cv. Goytacazes) over yield, weight of 100 seeds and number of pods per plant. The experimental design was randomized blocks, in a split-plot arrangement with five replications. The plot corresponded to the five defoliation epochs (first trifoliate leaf, flowering, pods formation, pods filling, and dry pods). In each plot, the split plot was represented by the four defoliation levels (0%, 33%, 67% and 100%). It was observed a decrease of yield for all levels defoliation considering all development stages, except for dried pods. The highest decrease was detected for flowering and pods formation. Through the regression analysis got a greater reduction in yield with 100% defoliation made at 42 days after emergence. The evaluation parameter that showed better relation with yield was a number of pods per plant.
Highlights
In Brazil, there is a good availability of improved varieties of common bean and adapted to the different regions, which facilitates the development of the crop
There was a significant difference between the mean levels of defoliation (LD)
Productivity was linearly reduced as a function of LD at all stages of development (Figure 1)
Summary
In Brazil, there is a good availability of improved varieties of common bean and adapted to the different regions, which facilitates the development of the crop. Pest damage in bean crop can be observed from sowing until the beans are dry in the pods or even stored, and due to the diversity of species that occur, virtually all plant structures have been shown to be susceptible [5], especially if the occurrence of the pests coincides with the period from germination to flowering [2]. This is because the production is directly related to the photosynthetic capacity of the plants and, depending on the leaf area index [6] [7]. Plants subjected to defoliation may have reduced production, mainly due to the decrease in the number of pods [4] [8] [9] [10], in seed mass and grain weight [3] [11], which leads to losses in production from 30% to 90% [5]
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