No, mold is simply one of the tools mother nature uses to decompose organic substrates. Mold growing inside a confined space, where we breath in the concentrated spores, is very potentially harmful. Absolutely mold growing in your home is not healthy. Plants growing in a bale with mold on it are completely unaffected and actually benefit from the mold as mold is a decomposer, helping to break down the substrate into soil. Plants don’t breathe in and out like we do, so the mold doesn’t affect them at all. Mold growing on a bale will usually be attacked and consumed by the bacteria present in the bale shortly after it gets established. If a gardener has serious allergies to mold, then I would recommend wearing gloves, and a mask when gardening period, with bales or regular soil. If allergies are bad enough then maybe gardening in general just isn’t for you, stay indoors where your less likely to suffer any encounters with mold spores. Soil generally contains lots of mold spores as well, as does most air outdoors in the summer. The concentration is much lower than indoor air can be in a moldy house however and the lower concentration of spores is typically never a concern for most people. I would not recommend eating vegetable leaves with mold on them, for instance if a lettuce leaf came into contact and was smeared with mold prior to harvesting it, then I would suggest washing it well before consuming it. We eat moldy cheese all the time, they even charge extra for the moldiest of cheeses. Most mold itself is pretty harmless, but less than tasty to eat. Think about your straw bales like cheese, the moldier the better. Stop worrying about what you assume is going to go so terribly wrong with your Straw Bale Garden, and just get started. You’ll see that most of these concerns you have about moldy bales are completely unwarranted in the end.
You started conditioning your bales, but were interrupted by Mother Nature. Snow, rain, cold, whatever has thrown a twist in your progress and you are now concerned that the bales will not be ready to plant on time. Relax, and just pick up wherever you left off or were interrupted, and continue the process. One tip for speeding up the process if you are concerned that the bales are not conditioning quickly enough for your planting schedule, is to cover the bales with some black plastic sheeting. This will help adsorb heat energy from the sun and hold in the heat promoting the growth of bacteria in the bales. This isn’t required but can be helpful if you are on a strict schedule and need to plant on a particular date.
It is true that if the air temperature is cooler, the bacteria will not grow as quickly. This is why we refrigerate our leftovers from dinner, or put stuff we want to preserve in the freezer. When bacteria are cooled or frozen they will not reproduce as quickly and their effective rate of decomposition of any substrate will slow dramatically. If the bales warm up to even a slightly higher than air temperature level, this means the bacteria are growing inside. Bacteria reproduce by expanding to a certain size and then splitting. During this magical splitting process, the cell will shake and vibrate and create friction, which raises the temperature inside the bales. If the air temperature outside is 40 degrees but the temperature inside your bales is 45 degrees, this is a great sign of bacteria development. If the air temperature is 75 then the inside of your bales may be 130 degrees or hotter. The differential in temperature will increase as the air temperature increases. Don’t expect too much if your bales are in the “refrigerator” or the “freezer” outside. When the days get warmer the bacteria will grow quickly. Plan to plant after you have been conditioning the bales for 12 days (when the temp is over 45 degrees). If you get a few colder days, just add a couple more days to the conditioning period, or cover with black plastic. A sunny day will really get things cooking under that plastic. It is NOT necessary for your bales to ever get HOT. Sometimes they don’t get so hot, but they will always get warm. If you measure the temp every day and the temp never goes above 80 or 90 degrees, don’t worry, they will be fine. If you put your hand into the bales and they feel cold, don’t worry, if you followed the conditioning recipe then the bales are ready to plant after 12 days (18 days for the organic treatment), so plant or seed right away. Don’t worry if it seems like the bales still look the same, they will not have changed much in appearance, but the bacteria will have grown and colonized much of the bale by then, so it is time to plant.