“Bud blast” is a term used to describe the situation in which a plant seems to be growing well, but the flower buds fail to fully develop and open. There are many possible reasons for that, but all are caused by an undue stress being put on the plant.
Insect or mite damage is a common cause of bud blast, as they suck the juices out of the buds or help introduce pathogens that cause them to die. Both may be controlled through the proper use of an appropriate pesticide, and mite infestation can often be prevented by maintianing a decent humidity level in the growing area.
Low humidity, by itself, is another common cause of bud blast, as the buds may lose water more rapidly than it can be “pumped” into them by the plant. This can be made worse by blasts of air from forced-air heating or air conditioning systems.
A sudden change in conditions – even briefly – can also lead to bud blast. I cannot tell you how many times I’ve purchased a budded plant at a show, only to have some, if not all of the buds fail because of a very brief chill when moving from the car into the house or greenhouse. Hot air coming from a room heater can be another culprit.
Improper watering may also play a role. Underwatering is a direct cause of bud blast – the plant draws water out of its tissues in order to stay alive, with the sensitive buds losing out quickly. Overwatering is an indirect cause of bud blast, as suffocation of the root system weakens its functioning, so the plant is unable to take up sufficient water.
A change in lighting can lead to bud blast, whether that be too much or too little. If the flower buds are exposed to unusually bright light, they can become warm and desiccated, so will fail to develop. A plant that should be in bright light may abort the buds if moved into shade before they open. Flowers are how pollinators are attracted, and as each plant’s pollinators are unique to the plant’s growing environment, a change may suggest that pollination is unlikely, so the plant aborts the attempt in order to save resources.
Spraying pesticides might also be a culprit, especially if they are oil based, such as Ultrafine or neem oils. They don’t even need to be sprayed on the buds for there to be an issue.
Another, often overlooked category of bud blast initiators is chemical vapors in the air. Exposure to fumes from paints and solvents seems fairly obvious, but we should not overlook gas stoves and heaters or ripening fruit. Ethylene is released by incomplete combustion of hydrocarbon fuels, so keeping burners clean and tuned to burn efficiently is the key to prevention. Ripening fruits also emit ethylene gas, so if you have a bowl of apples nearby, or tomatoes ripening in a windowsill, they might be the source of bud blast issues, as well.
Similarly, it is a good idea to avoid wetting flower buds when watering, feeding, or applying other treatments. Fertilizer are mineral salts that may extract moisture from the buds, for example. Even if the material isn’t directly damaging to the buds, and water left standing around the buds might favor the growth of pathogens.
Least likely is genetics – a plant may have a tendency to blast its buds, even under ideal conditions, due to a defective gene. This is rare among cultivated plants. Not many want to buy an orchid that cannot bloom, so they they get culled pretty readily by the breeder or grower.
Unfortunately, once a bud starts to fail, there is nothing that can be done to reverse it, so my only advice is “do what you can to prevent it from happening”.