Skip to main content
ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #158822
Title: EVALUATION OF FUNGAL PATHOGENS AS BIOLOGICAL CONTROL AGENTS FOR COGONGRASS

Author
item Ables, Camilla
item CHARUDATTAN, R. - UNIV. OF FLORIDA
item SHILLING, D. G. - UNIV. OF FLORIDA

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2005
Publication Date: 7/1/2005
Citation: Yandoc, C.B., Charudattan, R., Shilling, D.G. 2005. Evaluation of fungal pathogens as biological control agents for cogongrass (Imperata cylindrica). Weed Technology. 19(1):19-26.

Interpretive Summary: Two fungal pathogens, Bipolaris sacchari and Drechslera gigantea, were evaluated in the greenhouse and in the field for their potential as biological control agents of cogongrass. Greenhouse experiments showed that application of B. sacchari and D. gigantea caused foliar lesions and severe blight on cogongrass and that formulation of spores in oil emulsion enhanced their control efficacy. Field experiments showed that the application of a large inoculum volume (200 ml/0.25 m2) containing 105 or 106 spores/ml of either fungus formulated with 18% or 26% oil and applied with a hand-pumped sprayer produced the highest disease severity levels (>70%) during the 6-week experimental period. The level of injury caused by these fungi is sufficient to support their use as components for integrated management of cogongrass

Technical Abstract: Based on field surveys and evaluations in the greenhouse, two fungal pathogens, Bipolaris sacchari and Drechslera gigantea, were identified as promising biological control agents for cogongrass. In greenhouse trials, the application of spore suspensions of these fungi containing 105 spores/ml in a 1% aqueous gelatin solution resulted in high disease severity or DS (42 to 49 %, based on a rating scale for southern corn leaf blight with 50% as the maximum DS rating). Disease symptoms on cogongrass ranged from discrete lesions to complete blighting of leaves. Formulation of the spores in an oil emulsion composed of 4% horticultural oil, 10% light mineral oil, and 86% water resulted in higher DS regardless of the length of dew exposure after inoculation. Results from field trials showed a significant interaction effect of spore concentration, oil concentration, and application volume of the spore and oil emulsion mixture on the efficacy of B. sacchari and D. gigantea. Field application of a large inoculum volume (200 ml/0.25 m2) containing 105 or 106 spores/ml of either fungus formulated with 18% or 26% oil and applied with a hand-pumped sprayer produced the highest DS levels (>70%) during the 6-week experimental period. Although B. sacchari and D. gigantea were capable of controlling cogongrass by causing foliar blight, the regenerative ability of the rhizomes allowed cogongrass to recover from the damage caused by these fungi. However, the level of injury caused by these fungi is sufficient to support their use as components for integrated management of cogongrass.