Plant propagation can be challenging enough without the onset of disease, but warm and humid conditions necessary for seed germination or rooting cuttings also favor pathogens. Germinating seeds and newly-emerging roots and hypocotyls are often attacked by soil-borne plant pathogens that can cause major losses due to post and preemergence damping off, or low-quality plants and poor performance.Pathogens – Fusarium spp., Pythium spp. and Rhizoctonia solani are the primary culprits, but any pathogens present in the growing medium (i.e. Phytophthora, Botrytis and Thielaviopsis) are capable of attacking young plants.
Symptoms – Pre-emergence damping off occurs below the soil, where the pathogen attacks the emerging root or hypocotyl before full emergence, and results in poor stands. Post-emergence damping off results in rotten discolored stems at or near the soil line and root decay. Affected seedlings often appear shriveled brown, collapsed or stunted.
Host range – Seedling disease pathogens are widely distributed and are capable of attacking all stages of propagation material in greenhouses and nursery crops, including annuals, perennials, foliage plants and woody ornamentals.
Cultural control – Seedling diseases are difficult to control curatively, so the best approach is prevention. Follow strict sanitation measures and choose resistant plant varieties when available. Propagation areas should be weed free. Avoid overwatering and bedding mixes that retain water.
Chemical control – Preventative fungicide applications are almost essential under the conditions for propagation. Iprodione and Trifloxystrobin can be used for control of both Rhizoctonia and Fusarium. Flutolanil is excellent for Rhizoctonia and fosetyl-Al, Propamocarb hydrochloride and fenamidone are effective for controlling Pythium (refer to product labels for directions).
Always read and follow label instructions. Not all products registered in all states.