DAMPING-OFF CAUSED BY:
Damping-off is caused by a number of seed- and soil-borne fungi and funguslike oomycetes, including Rhizoctonia solani, Aphanomyces cochlioides, and species of Pythium, Phytophthora, Botrytis, Fusarium, Cylindrocladium, Diplodia, Phoma, and Alternaria.
DAMAGE SYMPTOMS:
Disease of nursery beds and young seedlings resulting in reduced seed germination and poor stand of seedlings. Very high seedling mortality 25-75%
Pre-emergence damping off: Seedlings disintegrate before they come out of soil surface leading to poor seed germination
Post-emergence damping off is characterized by development of disease after seedlings have emerged out of soil but before the stems are lignified
Water soaked lesion formation at collar region
Infected areas turn brown and rot
Plants shrivel and collapse as a result of softening of tissues
In Rhizoctonia solani attack infected stems become hard, thin (wire stem symptoms) and infected seedlings topple Disease appear in patches both in nursery and field beds.
SURVIVAL AND SPREAD:
Damping-off two types preemergence, in which sprouting seeds decay in soil and young seedlings rot before emergence; and postemergence, in which newly emerged seedlings suddenly wilt, collapse, and die from a soft rot at the soil line. Woody seedlings wilt and wither but remain upright; root decay often follows. Greatest losses occur in cold wet soils in which germination and emergence are slow, often in indoor conditions.
FAVOURABLE CONDITIONS:
Heavy rainfall, excessive and frequent irrigation, poorly drained soil and close spacing, high soil moisture with temp around 25-30 °C
For Rhizoctonia: High soil moisture with temp around 30 – 35 °C.
CONTROLS:
Use of biological fungicide Tricoderma viride as a seed treatment to prevent seed or soil-borne diseases.
Usage of organic and good quality potting soil.
Avoid overwatering of tender seedlings.
Several applications of the fungicide may be necessary, If the specific fungus causing damping-off is not known, one broad spectrum fungicide (captan or ferbam), two specific fungicides (benomyl plus, etridiazole or metalaxyl) or a prepared combination of fungicides (etridiazole + thiophanate methyl) should be used.
