A method to estimate the damage of Diabrotica speciosa larvae on potato tubers

Abstract

The marketable value of potato tubers is affected by damage caused by Diabrotica speciosa, whose larvae create holes on the tubers’ skin and internal feeding tunnels. The estimation of potato tuber damage is usually performed by assessing the external damage to the detriment of feeding tunnels caused by larvae. Thus, we propose a method to estimate the damage caused by D. speciosa larvae, considering the external and internal aspects of the tubers separately. For that, potato plants cv. Agata were grown under different infestations of larvae, measuring the area occupied by the holes and the volume of internal feeding tunnels, relating these data to the total area and volume of the tuber. The methodology used allowed us to characterize an increase in damage in tubers with the highest infestation of larvae. The correlation between internal and external damage caused by D. speciosa larvae was not significant, indicating that external damage alone is not an adequate parameter for the diagnosis of overall tuber quality. However, the method proposed here provides information regarding the volume of pulp consumed by the larvae, the extent of the galleries formed, and the relative volume of damage concerning the total tuber. Moreover, the method proposed here contemplates a more precise analysis of the external area damaged by herbivory relative to the total area of the tuber, which is not commonly considered in studies of underground plant structures.

Performance of potato cultivars grown in the organic production system

“…Besides these, plant architecture and depth of tuber formation have been reported as relevant factors that may reduce the ability of insects to reach the tubers (Pelletier et al, 2010). Among the genetic materials evaluated here, 'Catucha' stands out for its reduced sugar content (Barbosa et al, 2021), a characteristic that may be associated with lower internal damage intensity caused by D. speciosa larvae. When external damage is analyzed, the intrinsic mechanisms to explain the and climate conditions have a significant effect on the performance of cultivars in an organic system, corroborating with the study of Zarzýnska & Pietrasko (2015) and Passos et al (2017).…”

“…The tubers' dimensions (length and width) were recorded with the aid of a universal pachymeter. Thus, it was possible to estimate the area and volume of the tuber, which was considered an ellipsoid according to the methodology established by Barbosa et al (2021). Therefore, we estimated the internal and external damage based on volume and area, respectively, using this method.…”

“…The resistance factors of potato cultivars to rhizophagous insects are poorly known, although some are considered important, such as periderm thickness, pulp texture or fiber percentage, glycoalkaloid content, soluble sugar (°Brix) content, acidity and levels of nutrients and toxins present in the tubers (Barbosa et al, 2021). Besides these, plant architecture and depth of tuber formation have been reported as relevant factors that may reduce the ability of insects to reach the tubers (Pelletier et al, 2010).…”