Evaluating compatibility of Trichoderma asperellum with dimethomorph and fluazinam for integrated disease management in durian

Abstract

Importance of the work: Fungicide-biocontrol compatibility for sustainable durian
disease management remains underexplored.
Objectives: To evaluate the compatibility of Trichoderma asperellum with dimethomorph
and fluazinam for sustainable durian disease management.
Materials and Methods: Pathogens from diseased durian tissues were identified
morphologically and molecularly. Five Trichoderma isolates were screened; Tri-1 was
confirmed as T. asperellum. Dual culture, poisoned food and soil assays were used to
assess antagonistic activity and survival under fungicide treatments.
Results: Four pathogens (Phytophthora palmivora, Fusarium solani, Lasiodiplodia
theobromae, Phomopsis sp.) were isolated. Tri-1 achieved the highest inhibition
(up to 86.17% against Phomopsis sp.). Dimethomorph had no inhibitory effect on
T. asperellum, while fluazinam suppressed growth by up to 55.13%. In dual culture,
dimethomorph + Trichoderma achieved 90–100% pathogen inhibition, whereas fluazinam
reduced Trichoderma viability. Based on the soil assay results, the microbial population
was stable when dimethomorph was used (2.93 × 10³ colony-forming units (CFU)/g
soil–3.67 × 10³ CFU/g soil at 60 d), while it dropped sharply when fluazinam was used
(0.12 × 10³ CFU/g soil).
Main finding: Trichoderma asperellum was compatible with dimethomorph but was
inhibited by fluazinam, which should be useful information in guiding fungicide selection
for integrated durian disease management.