Efecto de la Plutella xylostella (Lepidoptera: Plutellidae) sobre el rendimiento del cultivo de colza

In Uruguay, rapeseed (Brassica napus, Linnaeus, 1753; Brassicales: Brassicaceae) cultivation has become highly important within the agricultural system, establishing itself as one of the main winter crops. Its inclusion contributes to diversifying crop rotations, reducing the dominance of grasses and promoting the sustainability of the production system. Furthermore, it has significant value for the oilseed industry due to the high quality and oil content of its grain. Among the pests that affect this crop, Plutella xylostella (Linnaeus, 1758; Lepidóptera Plutellidae) is a defoliating larva that has been frequently observed, potentially affecting yield and grain quality parameters. The objective of this study was to evaluate the effect of Plutella xylostella larvae on rapeseed cultivation. Three experimental trials were conducted, two under field conditions and one in the laboratory. The first field trial aimed to evaluate the damage caused by P. xylostella larvae on rapeseed leaves through controlled infestation at different larval densities. Simultaneously, mechanical defoliation of the leaves was carried out to achieve higher percentages of defoliation. The second field trial aimed to evaluate the potential impact of this pest on rapeseed pod dehiscence by individually inoculating each pod with larvae. Finally, the laboratory trial consisted of evaluating foliar consumption caused by P. xylostella larvae in the L2/L3 larval stages. The experiments were conducted at the Experimental Station EEMAC (Paysandú, Uruguay) during the 2025 growing season. The field trial included control plants, two densities of inoculated larvae (1 and 4 larvae per plant) at the C1 phenological stage of rapeseed, and three levels of mechanical defoliation (10, 50, and 80%) applied at stage E. Defoliation was monitored, yield components were estimated, and yield was determined by manual harvesting at physiological maturity. The results indicated no significant differences in yield among the treatments evaluated, except for the 80% mechanical defoliation treatment, which showed a significant yield reduction (p-value <0,0001). To evaluate the effect on silique dehiscence, two second or third instar larvae were inoculated into one silique per plant, confined in a cage, and siliques with cages but without larvae were used as a control. After physiological maturity, the siliques were harvested, dried, and subjected to mechanical agitation to determine their degree of dehiscence using a visual grain loss scale. Under the evaluated conditions, no effect of the larvae on silique dehiscence was observed (p-value 0,3614). Under controlled conditions, foliar consumption was assessed by placing a larval individual on a rapeseed leaf. Defoliation was quantified every 24 hours using BioLeaf software, with an estimated average consumption of 0.08 cm² per larva per day. Overall, this work provides information on the damage caused by P. xylostella in rapeseed under Uruguayan conditions, constituting a basis for decision-making in pest management.