Loss of leaf area in sunflower may be caused by different factors, among them by defoliating insects, which are generally controlled with insecticide applications. Artificial defoliation in plants of economic value is a useful methodology to simulate attacks of pests on crops aiming at determining levels of economic damage. The objective of this study was to evaluate production components of sunflower subjected to increasing levels of defoliation 0, 10, 25, 50, 75 and 100% in three different phenological crop stages: V6 (six leaves with minimum of 4.0 cm in length), R1 (when inflorescence surrounded by immature bracts becomes visible) and R5.5 (50% of the disk flowers are fertilized or in anthesis). The experiment consisted of 18 treatments, in a randomized block design with four replicates. There was significant effect of treatment interaction for all components of production evaluated (head diameter, total weight of seeds per plant and weight of one hundred seeds), showing that the effect of defoliation depends on the phenological stage of the plant. The R5.5 stage was more sensitive to defoliation, causing losses in all evaluated production components.
Greenhouse; phenological stage; defoliation level; Chlosyne lacinia saundersii; Helianthus annuus