Brown rot / blossom blight
A spring fungal disease that kills almond flowers and young twigs in cool, wet weather, leaves gummy cankers behind, and can go on to rot maturing nuts — protection depends on spraying right at bloom, not after symptoms show.
- Pathogen
- Monilinia laxa (fungus)
- Infects
- Open blossoms, twigs, later maturing nuts/fruit
- Favoured by
- Cool, humid, foggy or rainy bloom-time weather
- Main risk
- Flower & twig death; cankers; fruit rot later
Overview
Brown rot, caused by the fungus Monilinia laxa, is one of the most serious blossom-time diseases of almond and other stone fruit. Spores infect open flower parts — the petals, pistils and stamens — during cool, humid or rainy weather at bloom, and the infection quickly kills the flower and moves back into the twig it is attached to, killing that twig as well. Infected twigs develop cankers that often exude a gummy substance, and during continued foggy or humid weather the dead flowers and cankers can develop grey-to-tan spore masses that go on to infect still more blossoms nearby.
The same fungus can also infect and rot maturing nuts and fruit later in the season, particularly where they are wounded or in prolonged wet weather, though the blossom-time phase (blossom blight) is what does the most damage to almond in most Indian growing seasons. Because infection happens fast during a narrow bloom window and high humidity or slow-drying conditions after rain make it much worse, the whole management approach centres on a fungicide spray timed to pink bud and full bloom — waiting until blighted flowers or twig cankers are obvious means the damage for that season is already done.
How to identify it
- Open flowers turn brown, wilt and die quickly, often still hanging on the twig rather than dropping.
- The infection moves back from a killed flower into its twig, killing the twig and forming a canker.
- Cankers on infected twigs often ooze a gummy substance and, in continued humid weather, develop grey-to-tan spore masses.
- Later in the season, maturing nuts and fruit can show a soft, spreading brown rot, especially where the skin is wounded.
What causes it and when
- The fungus Monilinia laxa, which infects through the petals, pistils and stamens of open flowers.
- Strongly favoured by cool, humid, foggy or rainy weather right at bloom — the wetter and slower-drying the bloom period, the worse the outbreak.
- Spores from infected flowers and twig cankers spread on wind and splashing rain to infect further blossoms nearby.
- Nut and fruit infection later in the season is worse where the fruit surface is wounded or where wet weather persists as they mature.
Cultural & organic control
- Prune out and remove infected twig cankers during the dormant season, before the next bloom, to cut the amount of spore-bearing material carried over.
- Thin the canopy for better air movement and faster drying after rain or dew, since prolonged wetness is what lets the fungus establish.
- Remove mummified fruit left on the tree or ground from a previous season, since these also carry the fungus over winter.
- Avoid wounding fruit during thinning, handling or bird/insect damage where possible, since wounds are an easy entry point later in the season.
Chemical control
- A protectant fungicide spray timed to pink bud and repeated at full bloom is the single most important control measure — trials consistently show the full-bloom spray matters most.
- A further spray may be justified if wet, humid weather continues through and after bloom, since conditions that favour infection can persist over several weeks.
- Spraying after flowers are already blighted or twig cankers have formed does not reverse that season's damage — the value of the spray is preventive.
- Confirm the current recommended fungicide, timing and dose for almond brown rot with your local KVK or SKUAST-Kashmir's horticulture advisory.
Prevent it coming back
- Build the pink-bud and full-bloom spray timing into the orchard's fixed annual calendar rather than reacting to a wet spring after the fact.
- Prune out cankers and remove mummified fruit every dormant season so less inoculum survives to the next bloom.
- Keep the canopy open enough to dry quickly after rain, and avoid unnecessary fruit wounding through the season.
- Watch the weather forecast around bloom time and be ready to spray ahead of a predicted cool, wet spell rather than after it arrives.
Crops most at risk
Where this problem is called out in our crop guides — open a crop for the full package of practices.
Varieties to consider
Named seed varieties whose resistance or susceptibility to this problem is documented on their own variety page.
Frequently asked questions
My almond blossoms turned brown and died right after a spell of cool, damp weather. What happened?
That is the classic sign of brown rot (blossom blight), caused by the fungus Monilinia laxa, which infects open flowers fastest in cool, humid or rainy bloom-time weather. Once a flower is infected there is no rescuing it, and the infection often moves back into the twig, killing that too. The lesson for next year is to spray a protectant fungicide at pink bud and again at full bloom, rather than waiting to see if the weather turns wet.
Why does spraying after I see blighted flowers or twig cankers not help?
Because by the time flowers are visibly blighted or a twig canker has formed, the fungus has already killed that tissue — a fungicide cannot reverse damage that has already happened. The spray's job is to protect healthy, still-open flowers before infection occurs, which is why the pink-bud and full-bloom timing matters so much more than spraying reactively once symptoms appear.
Can brown rot affect the almond nuts themselves, not just the flowers?
Yes — the same fungus that causes blossom blight can also infect and rot maturing nuts and fruit later in the season, especially where the surface is wounded or the weather stays wet as they mature. In most Indian almond-growing seasons the blossom-time phase does the most economic damage, but avoiding fruit wounding and removing mummified fruit each season also helps limit this later-season infection.
Symptoms and control measures follow ICAR, KVK and state agricultural-university package-of-practices; any named chemical is a registered use. Always read the product label and confirm the dose for your crop and zone. editorial policy.