Greenhouse disease update for Thielaviopsis black root rot

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Black root rot is a serious threat to pansies, petunias and vinca. Black root rot is caused by the fungus, Thielaviopsis, and may also infect cyclamen, poinsettia, primula, impatiens, snapdragon, verbena, phlox, begonia and nicotiana.Plants with black root rot often show symptoms that mimic nutrient deficiencies such as stunting with older leaves shriveling. Leaves may turn yellow and the youngest leaves become stunted and tinged with red.In mild infections, older leaves are yellow-green with the veins retaining their green color. Black root rot may also affect the lower stem on crops such as poinsettia, causing cracks that appear black. Sanitation is the best preventive measure against black root rot.Once this fungus is established in a crop or in a greenhouse, an effective fungicide program is needed.

Evaluation of fungicides for the control of Thielaviopsis root rot on pansy

Disease pressure was severe in this trial with 62.5 percent of the untreated inoculated plants dead by the last rating date. Experimental product Pageant 38WG (all rates) was not effective against Thielaviopsis, with all treatments having plant health and death (percentage) comparable to that of the untreated inoculated. Two biopesticides, Endorse and ZeroTol, were included in this trial.Endorse WP was moderately effective with plant health ratings significantly better than the untreated inoculated throughout the trial. ZeroTol was not effective in limiting disease in this trial. The experimental BAS 595 16F was one of only two treatments (the other being commercial standard OHP 6672 4.5L) to completely prevent plant death in this trial.

Thielaviopsis
Thielaviopsis

Acknowledgements

This research was funded in part by Floriculture Nursery and Research Initiative of the Agricultural Research Service under Cooperative Agreement #59-1907-5-553 and by the American Floral Endowment.

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Dr. Hausbeck’s work is funded in part by MSU‘s AgBioResearch.

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