First report of black pustule disease in sponge gourd (Luffa cylindrica) in northern Egypt and its biological management.

Abstract

Background: In October 2022, black pustules were observed on the lower surface of sponge gourd (Luffa cylindrica) leaves in Kafer El-Dawar, North Egypt. Symptoms included abundant black pustules containing fungal conidia on plant leaves, which eventually led to the infected leaves drying out and dying.

Results: Two causal fungi were isolated from symptomatic leaves and their pathogenicity was confirmed to induce typical disease symptoms. On the base on morphological features and further molecular identification, the isolated pathogens were identified as Alternaria alternata (accession No. PP197255), and Fusarium equiseti (accession No. PP197302). A survey was conducted to detect this disease on luffa plant leaves in northern Egypt, where luffa plants are cultivated. An attempt at biological control of this disease was made for two successive growing seasons under field conditions. BF, algae, Trichoderma harzianum and Bacillus subtilis were applied as seed treatments, and soil drenches were applied, followed by foliar spraying. Throughout the two seasons, the applied bioagent B. subtilis significantly reduced disease severity followed by the T. harzianum and algae treatments.

Conclusion: Seed treatment with two bioagents, T. harzianum and B. subtilis, had the greatest effect on disease severity, followed by soil drenching + foliar spray, soil drench only, and in that respective order. This is the first report of black pustules on the leaves of Luffa plants caused by Alternaria alternata and Fusarium equiseti in Egypt.