Silver Nanoparticles and Acetic Acid Show Strong Potential Against Complex Crown Gall and Root-Knot Disease in Guava

A newly published study has characterized and evaluated management strategies for one of the most destructive disease complexes affecting guava plants: the simultaneous infection by Agrobacterium tumefaciens (crown gall bacterium) and Meloidogyne incognita (root-knot nematode). The research, conducted on guava orchards in Egypt’s Beheira Governorate, shows significant promise for silver nanoparticles and acetic acid as effective tools for controlling this dual infection.

The study isolated four virulent A. tumefaciens strains (RAt1, RAt2, RAt3, and EAt4) from guava roots and confirmed their identity through pathogenicity tests and PCR using tms2, virD2, and 16S rRNA gene markers. Simultaneously, the root-knot nematode population was identified as M. incognita based on classical perineal pattern analysis.

Researchers tested a range of treatments—including three silver nanoparticle formulations, antibiotics, commercial chemicals, synthetic nematicides, and biological agents—to assess their antibacterial and nematicidal activity. The results highlight three key findings:

Silver nanoparticles exhibited strong antimicrobial activity.
AgNP/CMC, AgNP/chitosan/OLE, and AgNP/chitosan/OLE/acetic acid produced bactericidal or bacteriostatic effects on the bacterial isolates and caused up to 90% juvenile nematode mortality within 24 hours, reaching 100% mortality by 48 hours.
Acetic acid was the most effective commercial chemical.
A 9% acetic acid solution completely inhibited all A. tumefaciens isolates and caused total egg mass destruction and 100% mortality of nematode juveniles.
Streptomycin was the only antibiotic to show bactericidal action on the more resistant isolate (EAt4).
Other antibiotics produced only bacteriostatic effects.

Synthetic nematicides achieved complete juvenile mortality but did not suppress A. tumefaciens. Biological agents (Trichoderma album and Bacillus megaterium) allowed nematode survival for up to 48 hours.

The study concludes that silver nanoparticles, acetic acid, sodium hypochlorite, Clorox, and streptomycin are promising tools for managing this challenging disease complex, providing a framework for further development of integrated control strategies for guava production.

Reference

Elsaedy, M.A., Osman, K.A., Younis, A.M. et al. Characterization and management of crown gall bacterium and root-knot nematode as a complex disease infecting guava plants. Discov. Plants 2, 326 (2025). https://doi.org/10.1007/s44372-025-00419-6