# Effectiveness of Repellent Plants for Controlling Potato Tuber Moth (Symmetrischema tangolias) in the Andean Highlands

## TL;DR

This study shows that using dried leaves from local plants like wormwood and muña can effectively protect stored seed potatoes from moth damage in the Andean highlands.

## Contribution

The study demonstrates that locally available aromatic plants can significantly reduce potato tuber moth damage, offering a low-cost alternative to chemical insecticides.

## Key findings

- All four tested plants reduced internal damage and live larvae in stored potatoes compared to untreated controls.
- Wormwood and muña were the most effective, reducing damage by up to 80–90% in warmer regions and completely preventing larvae in cooler regions.
- The method is a promising, low-cost complement to integrated pest management in highland storage systems.

## Abstract

Farmers in the Andean highlands face persistent losses of stored seed potatoes due to moth infestations that deteriorate tuber quality and reduce yields. Chemical insecticides are often used to control these pests, but their repeated application increases costs and poses health and environmental risks. In this study, we tested four locally available aromatic plants—Ambrosia peruviana, Eucalyptus globulus, Artemisia absinthium (wormwood) and Minthostachys verticillata (muña)—by layering dried leaves inside seed potato bags in two highland villages in Cajamarca, Peru, over a full storage season of 187 days under natural infestation. An entomologist examined the larvae and pupae recovered from damaged tubers and confirmed that all specimens belonged to S. tangolias. Compared with untreated bags, all four plants reduced internal damage and the number of live larvae, and wormwood and muña were consistently the most effective, often lowering damage to a small fraction of that observed in the control. These results suggest that a very simple practice—placing modest amounts of dried leaves from locally known plants in seed bags—can help farmers protect their seed potatoes from S. tangolias and may reduce the need for synthetic insecticides in highland storage systems.

Postharvest losses from potato tuber moth severely constrain seed quality in Andean smallholder systems. This study evaluated four locally available repellent plants—Ambrosia peruviana, Eucalyptus globulus, Artemisia absinthium, and Minthostachys mollis—applied as dried leaves layered within seed bags of INIA 302 ‘Amarilis’ under farmer-like storage at two highland sites in Cajamarca, Peru (Huaytorco, 3350 m; Samaday, 2750 m), over 187 days. Within each site, a Completely Randomized Design with three bag-level replicates per treatment was used, and damage was assessed after 187 days as incidence of attacked tubers, internal damage severity and live larval counts. Endpoint data were analyzed separately by site using Kruskal–Wallis tests followed by Dunn’s post hoc test with Šidák correction (α = 0.05). Across both sites, all botanicals significantly reduced damage severity and live larval counts relative to the untreated control. At the warmer, lower site, A. absinthium and M. verticillata achieved large effect sizes, with severity and larval numbers reduced by roughly 80–90% compared with the control, while at the cooler, higher site, larvae were not detected in any botanical treatment. These findings indicate that simple layering of dried leaves from locally available plants, particularly wormwood and muña, can substantially mitigate S. tangolias damage in highland seed potato stores and represents a promising, low-cost complement to integrated pest management, although multi-season and dose-response studies are still needed to confirm and refine this approach.