A hetero-chitooligosaccharide as plant defense elicitors against spider mites

The increasing challenges of pesticide resistance and environmental degradation in modern agriculture require sustainable pest management strategies. This study investigates the efficacy of a specific type of hetero-chitooligosaccharide called partially deacetylated chitooligosaccharide enriched in d-glucosamine (DACOS; 85.6% deacetylation, an average molecular mass of 1092.52 Da), as a plant defense elicitor against the two-spotted spider mite, Tetranychus urticae Koch.

In planta bioassays revealed suppression of mite performance on DACOS-treated leaves of kidney bean seedlings. Local effects were most pronounced at 80 mg L^-1 (ppm), which reduced mite survival by 30% and cumulative fecundity by 41% after 6 days. Systemic effects were strongest at 160 ppm, indicating distinct concentration requirements for local versus systemic defense induction. Behavioral choice assays revealed that DACOS-treated leaves induced 73% mite repellency. No direct acaricidal effects were observed, which confirms the role of DACOS as a plant defense elicitor. Metabolic profiling revealed enriched pathways (e.g., monoterpenoid biosynthesis and α-linolenic acid metabolism) that produce volatile organic compounds with repellent properties.

These findings suggest that DACOS is an environmentally friendly and non-biotic induced resistance stimulus that can enhance plant defense, bypass pesticide resistance, and promote the sustainability of crop production. © 2026 Society of Chemical Industry.