Mold can become a problem in any stage of growth and after harvest. Excess water on buds/foliage, overwatering and low air flow all cause mold. To prevent mold make sure their is always a lot of airflow in and around flowers and foliage. Also try and make sure the relative humidity never gets too high (above 75% ). This isn't really possible to control outdoors while the plants are growing, but when drying and curing it will be possible to control. Above all keep things clean, well ventilated and dry and you should avoid mold problems.