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PEST MANAGEMENT DECISION GUIDE: GREEN LIST

Damping off on tomatoes

Phytophthora, Pythium, Rhizoctonia, Fusarium spp.
  • This disease is caused by different fungi that live in damp wet soils
  • Plant certified seeds that have been fungicide-treated (e.g. copper oxychloride).
  • Sterilize the soil by burning plant debris on the nursery site before seeding and incorporating the hot materials into the soil surface. Or, in hot weather, cover the site with black plastic sheets for a week to heat up the soil and kill the pathogen.
  • Plant disease-free seedlings
  • Avoid planting in previously affected areas
  • Avoid planting tomatoes in periods of heavy rains
  • Select nursery sites far away from tomato fields which are not too shaded or humid
  • Ensure there is good soil drainage by elevating seed beds and mixing top soil with a thin coating of sand and gravel
  • Do not over water because this favours the disease
  • Minimise leaf wetness by irrigating early in the day and using a drip irrigation system instead of overhead irrigation
  • Maintain a low soil pH by encoporating organic matter into the soil, such as compost, composted manure or acidic mulches.
  • Apply a thin layer of sand, perlite or sphagnum peat moss on the soil surface to discourage fungi and bacteria.
  • Ensure aeration through spacing of seeds (>5 cm (2”) space) and staking of plants with wooden sticks.
  • Disinfect seedling pots and trays with bleach (=NaOCl) before storage. Wear gloves or wash hands with water afterwards.
  • Look for symptoms on seedlings every day during the first 3 weeks after sowing
  • When tomato seedlings reach the 3-leaf stage, they are less susceptible.
  • Search for areas of poor germination in seedbed, because this disease may rot seeds before or during germination.
  • Look out for:
    • Thin and tough stem of the seedline (wirestem) resulting in reduced seedling vigour
    • Dark, water-soaked, soft lesions on stem bases of seedlings. Seedlings wilt and fall over.
    • Fuzzy white substance on the surface of the damp soil
  • Consider taking action as soon as one plant is affected
  • It is easier to prevent this disease than to control it.
  • Move unaffected seedlings away from those that are showing symptoms in order to reduce spread.
  • Uproot diseased seedlings and young plants. Bury deeply (to at least 50 cm), or burn. Do not compost as the damping off fungi may stay alive and spread.
  • Drench with Trichoderma based products

CREATED/UPDATED: May 2018
PRODUCED BY: Plantwise

©CAB International. Published under a CC-BY-SA 4.0 licence.