Common crops affected
What is it?
Late blight is caused by Phytophthora infestans, a water mould (oomycete). It thrives in cool, wet, humid conditions and spreads explosively on wind and rain. It infects leaves, stems, fruit, and tubers, and can move through a crop with alarming speed once established.
How to identify it
- Large, irregular, water-soaked dark lesions on leaves and stems
- White fuzzy growth on the underside of lesions in humid conditions
- Rapid browning and collapse of foliage
- Firm brown rot on fruit and tubers
- Explosive spread in cool, wet weather
Damage and how it spreads
Late blight can wipe out a tomato or potato crop within days under favorable weather, and infected tubers rot in storage. Because it spreads so fast and so far, prevention and rapid response are critical — once it is established and widespread, it is extremely difficult to stop.
How to control it
- Choose resistant varieties and certified clean seed or tubers.
- Maximize airflow, avoid leaf wetness, and never work plants when wet.
- Remove and destroy infected plants immediately — do not compost.
- Apply protective natural fungicide ahead of and during cool, wet weather.
Recommended Vegalab solution: Spore Control
Vegalab Spore Control (Thymol) lists phytophthora among its targets; it forms a protective cuticle film and inhibits spore germination and mycelium proliferation. Late blight is best managed preventively — apply as a foliar spray ahead of cool, wet weather, diluted 1:1,000 (1 mL/L), with full coverage, and remove infected plants promptly. Pair with resistant varieties and strict sanitation for a robust program.
| Role | Product | Use |
|---|---|---|
| Primary control | Spore Control | Broad-spectrum protective fungicide |
| Companion / broader pressure | Armour Boost | Silica for tissue resilience |
Preventing it next season
Use resistant varieties and clean seed, maximize airflow, avoid leaf wetness, scout intensively in cool wet weather, and protect preventively before outbreaks. Vigorous, well-supported plants resist stress better with Armour Boost.
Claims and product availability vary by jurisdiction. Always read and follow the product label.