Effect of dew temperature, post-inoculation condition, and pathogen dose on suppression of scentless chamomile byColletotrichum truncatum

Abstract

Scentless chamomile, a noxious weed in western Canada, has a high natural tolerance to many herbicides. Colletotrichum truncatum , a host specific fungal pathogen, is suppressive to scentless chamomile when applied inundatively. A broadcast application was used at 200 L ha (1 to evaluate biocontrol potential of this pathogen under a range of dew temperatures (DT), postinoculation conditions (PIC), and pathogen doses (PD). A DT between 20 and 258C was more conducive to infection, resulting in higher levels of disease and weed suppression as compared to 15 and 308C. Under similar post-inoculation temperature regimes, disease was only slightly more severe in growth chambers than in the greenhouse. There was a positive linear relationship between the PD and weed suppression. An inoculum concentration /1)/10 8 spores mL (1 reduced plant fresh weight by approximately 50% when compared to untreated controls. These results indicate that biocontrol of scentless chamomile using C. truncatum in the semi-arid Canadian prairies will likely encounter frequent non-favourable field conditions.

Effect of plant stage, Colletotrichum truncatum dose, and use of herbicide on control of Matricaria perforata

“…These mixtures were then applied to scentless chamomile at 8-and 11-leaf stages. The 2 Â 10 6 spores/ml concentration represented the minimum dose required to cause measurable freshweight reduction on scentless chamomile at the 8-leaf stage (Graham et al, 2006a) and 20 Â 10 6 spores/ml was the highest possible dose for the study due to limited spore-production capacity. The material volume required for applications using the cabinet sprayer was about 100 ml per treatment per trial.…”

Interactions ofColletotrichum truncatumwith Herbicides for Control of Scentless Chamomile (Matricaria perforata)

“…Several strains of Colletotrichum truncatum obtained from diseased scentless chamomile plants were found moderately efficacious against the weed when high inoculum doses were applied (Peng et al 2005a). At 200 L/ha application volume (5 ϫ 10 7 spores/ml), Colletotrichum truncatum reduced fresh weight of scentless chamomile by 50% when compared to nontreated controls (Graham et al 2006). Although 50% suppression is believed to be insufficient for practical weed control, few herbicides offer more efficacious solutions.…”