White mould

Symptoms

• On young plants, the lower part of the stem near the root collar is affected. Diseased plants differ from healthy ones by their pale colour and wilted leaves.
• The affected stem cracks and partly breaks, and the whole plant dies and dries out.
• With later infection, the stem surface turns brown and becomes wet. The stems become soft and break, and sclerotia are easy to find inside them.
• White-brown spots form on the outside of the heads; the tissue becomes wet and is easily pressed in.

Signs of the pathogen

• White felty masses of mycelium appear on affected plant parts, and sclerotia form on this mycelium over time.
• Sclerotia form between the seeds and inside the head tissue. As they dry out, affected heads fray into shreds.
• The sclerotia are large and easy to spot against a light background.

When to look

• It can appear as early as the seedling stage, but most often during head formation and flowering.
• The first signs of the disease are found from flowering onwards, in the root-collar and stem forms.
• The first sunflower disease assessment is made after emergence, before thinning. Plants that died from white and grey rot, plants infected with rust and healthy plants are counted.
• At the third assessment, at flowering, sclerotinia is recorded. The flowering period is the point when the first, spring period of sunflower death from sclerotinia ends.
• Before harvest, crops are surveyed, among other things, for sclerotinia.

How to count

• During the survey, pay attention to dense crops, low-lying areas, slopes and the like.
• The percentage of seedlings killed by rots and of rust infection is determined. In 10 places along a diagonal or along two parallel lines, 50 consecutive plants are examined, 5 m in from the edge of the field.
• It is recommended to assess the intensity of head infection by rots, especially white and grey rot, on a five-point scale. 0 points: heads not infected. 1 point: small spots on the upper side of the heads covering up to 25 % of the surface.

No rate and no spray timing here: both come from the label and the register.

Favourable conditions

• In dry conditions, the disease does not develop on a mass scale.
• Mass appearance of the disease is linked to rainfall. On the heads it appears after flowering, especially during rain. In dry periods the disease does not develop.
• Rainy weather at the end of the growing season, during seed ripening, favours stronger disease development.
• With heavy downpours during budding, flowering and seed filling of sunflower, moderate to severe disease is possible.
• The rot appears and develops in winter and spring oilseed rape crops at 60–90% humidity, an air temperature of +17..+27 °C and where a source of infection is present.

Every fact rests on a quote from its source, and each quote was checked against the page it is printed on.

1. EPPO Global Database · European and Mediterranean Plant Protection Organization
2. Станкевич С. В., Положенець В. М., Немерицька Л. В., Журавська І. А., «Моніторинг хвороб сільськогосподарських культур», навчальний посібник, 301 с. · Інститут біоенергетичних культур і цукрових буряків НААН, Державний біотехнологічний університет; Житомир: Рута, 2022 · p. 174, 175, 176, 177, 178
3. Прогноз фітосанітарного стану агроценозів України та рекомендації щодо захисту рослин у 2025 році · Держпродспоживслужба, НААН, НАН · p. 110, 132
4. Photos: Rasbak, Wikimedia Commons, CC BY-SA 3.0 · Jie-Hao Ou, iNaturalist, CC BY 4.0